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Experimental atheoreticalcal study of a solar deslination system

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Experimental atheoreticalcal study of a solar deslination system
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Abbood, Husseun Abdulhasan ( author )
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English
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Saline water conversion ( lcsh )
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Review:
An innovative new concept of a solar water desalination system that uses PV panels and batteries was developed. The concept utilizes solar cells to collect solar radiation and uses them as an electrical source to supply power to the system thereby raising its efficiency. Batteries are also used in the proposed system to provide a stable power supply to the system as well as to store the energy supplied by solar cells. The battery gives continuity to the process in times when the system lacks solar energy. The system was constructed in three parts: electrical, thermal, and condensation. The uniqueness of this concept is that the PV solar panels and batteries create a stable desalination system for the production of fresh water and provides a higher rate of pure water production compared to thermal systems.
Review:
Additionally, in this research, Matlab Simulink was used to model a single slope solar still, and the model was composed of four groups. Fifteen equations were utilized in the simulation process, and they represent the second and third groups in the modeling, while part one and four are the input and output data. The input data includes the solar radiation intensity, water temperature, glass temperature data, and the depth of the salt-water inside the solar still. The output was the production of pure water.
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Thesis (M.S.)--University of Colorado Denver
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Includes bibliographical references.
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by Husseun Abdulhasan Abbood.

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University of Florida
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Full Text
EXPERIMENTAL AND THEORTICAL STUDY
OF A SOLAR DESALINATION SYSTEM by
HUSSEIN ABDULHASAN ABBOOD B.S., University of Basrah, 2007
A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Master of Science Mechanical Engineering Program
2017


11
2017
HUSSEIN ABDULHASAN ABBOOD
ALL RIGHTS RESERVED


This thesis for the Master of Science degree by Hussein Abdulhasan Abbood has been approved for the Mechanical Engineering Program By
Peter Jenkins, Chair Kannan Premnath
Maryam Darbeheshti


iv
Abbood, Hussein Abdulhasan (M.S., Mechanical Engineering Program)
Experimental and Theoretical Study of a Solar Desalination System Thesis directed by Professor Peter Jenkins
ABSTRACT
An innovative new concept of a solar water desalination system that uses PV panels and batteries was developed. The concept utilizes solar cells to collect solar radiation and uses them as an electrical source to supply power to the system thereby raising its efficiency. Batteries are also used in the proposed system to provide a stable power supply to the system as well as to store the energy supplied by solar cells. The battery gives continuity to the process in times when the system lacks solar energy. The system was constructed in three parts: electrical, thermal, and condensation. The uniqueness of this concept is that the PV solar panels and batteries create a stable desalination system for the production of fresh water and provides a higher rate of pure water production compared to thermal systems.
Additionally, in this research, Matlab Simulink was used to model a single slope solar still, and the model was composed of four groups. Fifteen equations were utilized in the simulation process, and they represent the second and third groups in the modeling, while part one and four are the input and output data. The input data includes the solar radiation intensity, water temperature, glass temperature data, and the depth of the salt-water inside the solar still. The output was the production of pure water.
The form and content of this abstract are approved. I recommend its publication.
Approved: Peter Jenkins


V
TABLE OF CONTENTS
CHAPTER
I INTRODUCTION................................................................... 1
H BACKGROUND, OBJECTIVES OF THE STUDY, AND SCOPE OF WORK............4
2.1 Water....................................................................4
2.2 Water Salinity...........................................................5
2.3 Desalination.............................................................6
2.4 Desalination Technologies................................................8
2.4.1 Thermal Processes and Membrane Processes.............................9
2.4.1.1 Multi-Stage Flash Desalination (MSF).............................9
2.4.1.2 Multi-Effect Boiling (MEB) Process..............................10
2.4.1.3 Vapor Compression (VC) .........................................11
2.4.1.4 Reverse Osmosis (RO)............................................11
2.4.1.5 Electrodialysis (ED)............................................12
2.4.1.6 Electrodialysis Reversal (EDR) .................................13
2.5 Solar Radiation.........................................................13
2.5.1 Solar Radiation Intensity on the Horizontal and Inclined Surfaces....13
2.5.2 Photovoltaic Solar Panels and the Method to Generate Power Using Solar
Cells.................................................................15
2.6 Solar Desalination Processes.............................................16
2.7 Objectives of This Research..............................................17
2.8 Scope of Work............................................................18


VI
in SOLAR DESALINATION SYSTEM DESIGN.............................................19
3.1 Description and Operating Principle of the Proposed System...............19
3.2 System Design..............................................................20
3.2.1 PV Panels..............................................................20
3.2.2 Batteries and Charge Controller........................................23
3.2.3 Coil Heater and Copper Pipe............................................24
3.2.4 Description of the Heat Transfer Equation Between the Coil Heater and the
Copper Tube............................................................24
3.2.5 Measuring Devices......................................................26
3.3 Description Modeling of Single Slope Solar Still Using Matlab Simulink...26
3.3.1 Description of Part 1 and Part 2 in the Modeling.....................27
3.3.2 Input and Output Data for Modeling.....................................29
3.4 Algorithm Flow Chart to Calculate the Water Production...................31
IV THERMAL ANALYSIS..............................................................32
4.1 Theoretical Analysis ofPV Solar Desalination System........................32
4.1.1 Radiation Heat Transfer Between the Coil Heater and Outer Pipe Wall....32
4.1.2 Conduction Heat Transfer Between Outer Tube Wall and Inner Tube Wall...34
4.1.3 Convection Heat Transfer Between the Water Surface and Inner Pipe Wall.35
4.1.4 Heat Transfer Between the Cold Water and the Steam Inside the Pipe.....37
4.1.5 Heat Transfer Between the Copper Tube and Air..........................39
4.2 Theoretical Analysis of Solar Still........................................39
4.3.1 The Energy Balance for Glass Cover.....................................40
4.3.2 The Heat Balance of the Bottom and Sides of the Basin..................43


vii
4.3.3 The Equations of Energy Balance on the Water Surface Inside the Basin.45
V RESULTS AND DISCUSSION........................................................47
5.1 Experimental Location...................................................47
5.2 Method to Obtain Measurements...........................................47
5.3 Results Obtained from Measurements......................................48
5.3.1 Experimental Measurements for Seawater on August 9....................48
5.3.2 Experimental Measurements for Salt-water on September 4...............52
5.3.3 Experimental Measurements for Tap water and Lake water on October 2 and
28....................................................................55
5.4 Salinity Measurements...................................................60
5.5 Theoretical Measurements for the Solar Still System.....................61
5.5.1 Input and Output Data of Solar Stills Modeling on August 9 When the Water
Depth Was 5 cm........................................................61
5.5.2 Input and Output Data of Solar Stills Modeling on October 2 When the Water
Depth Was 10 cm.......................................................63
5.5.3 Input and Output Data of Solar Stills Modeling on October 28 When the Water
Depth Was 15 cm.......................................................65
5.6 Comparison Between the Experimental Results and Theoretical Data........66
5.6.1 Comparison Between the Output Water of PV Solar Desalination System and
Solar Still on August 9 ..............................................66
5.6.2 Comparison Between the Output Water of PV Solar Desalination System and
Solar Still on October 2..............................................67
VI CONCLUSION AND RECOMMENDATION OF FUTURE WORK
68


Vlll
BIBLIOGRAPHY...............................................70
APPENDIX
A. EES PROGRAM (POWER CALCULATION)....................73
B. ITERATIONS (WATER TEMPERATURE).....................77


IX
LIST OF TABLES
TABLE
2.1 Percentage of water resources across the globe................................4
2.2 Composition of seawater with salinity of 36000ppm.............................6
2.3 Water desalination categories.................................................9
2.4 Indirect solar desalination system...........................................17
5.1 Salinity measurements for seawater, salt-water, tap water, and lake water.....61
5.2 Hourly variation of solar radiation, wind speed, ambient temperature, and water
temperature on August 9...........................................................62
5.3 Hourly variation of solar radiation, wind speed, ambient temperature, and water
temperature on October 2..........................................................63
5.4 Hourly variation of solar radiation, wind speed, ambient temperature, and water
temperature on October 28.........................................................65


X
LIST OF FIGURES
FIGURE
2.1 Global installed capacities of desalination.....................................8
2.2 Multi-stage flash desalination (MSF) process....................................10
2.3 Diagram of a multi-effect boiling (MEB) process.................................11
2.4 Schematic diagram of a reverse osmosis process..................................12
2.5 Direct radiation incident on the horizontal and inclined surfaces...............15
3.1 Schematic of the proposed system................................................20
3.2 A PV solar panel................................................................21
3.3 Mixed connection of batteries to generate 12 V and 24 V.........................24
3.4 Schematic of modeling the single slope solar sill...............................27
3.5 Schematic of part 1 for the modeling............................................28
3.6 Schematic of part 2 for the modeling............................................29
3.7 EES program to calculate the water and glass temperature........................30
4.1 Schematic of the heat transfer in the whole system..............................32
4.2 Heat transfer between the coil heater and copper tube...........................33
4.3 Heat transfer between the outer wall and inner wall of the copper tube..........34
4.4 Heat transfer between cold water and vapor......................................37
4.5 Heat transfer between the vapor inside the copper tube and air..................39
4.6 Energy balances for the whole solar still.......................................40
4.7 Energy balance for glass cover..................................................41
4.8 Energy balance for the bottom and side basin....................................44
4.9 Energy balance for seawater interface...........................................45


XI
5.1 Image of the location of the Boulder Creek Building, University of Colorado Denver
campus..................................................................................47
5.2 Hourly solar radiation values on a 30 tilted surface on August 9..................49
5.3 Comparison of the generated power and power consumed on August 9...................50
5.4 Hourly variation of the experimental desalinated water yield and ambient temperature
(seawater)..........................................................................51
5.5 Voltage, current, and power consumption on August 9 (seawater).....................51
5.6 Hourly solar radiation values on a 30 tilted surface on September 4...............52
5.7 Comparison of generated power and power consumed on September 4....................53
5.8 Hourly variation of the desalinated water and temperature (salt-water).............54
5.9 Voltage, current, and power consumption on September 4 (salt-water)................55
5.10 Hourly solar radiation values on 30stilted surface on October 2...................56
5.11 Hourly solar radiation values on 30stilted surface on October 28..................56
5.12 Comparison of generated power and power consumed on October 2.....................57
5.13 Comparison of generated power and power consumed on October 28....................58
5.14 Hourly variation of experimental desalinated water yield and temperature (tap water) .59
5.15 Hourly variation of experimental desalinated water yield and temperature
(lake water) ...........................................................................59
5.16 Hourly variation of theoretical desalinated water yield on August 9 (5 cm depth) .63
5.17 Hourly variation of theoretical desalinated water yield on October 2 (10 cm depth).64
5.18 Hourly variation of theoretical desalinated water yield on October 28 (15 cm depth) ...65
5.19 Comparison of the output water of PV solar desalination and solar still on August 9 ...66
5.20 Comparison of the output water of PV solar desalination and solar still on October 2 ..67


1
CHAPTER I INTRODUCTION
Currently, fresh water shortage is predicted to be the biggest problem of the world due to unsustainable water consumption rates and population growth. The United Nations Environment Programme (UNEP) stated that one-third of the worlds population lives in nations with insufficient fresh water to support the population and, by 2025, two-thirds of the world population will face water scarcity [39], The scarcity of pure water has become a major issue in several countries around the world. According to the World Bank, there are about eighty countries today that have water shortages that threaten the health and economies of their people, while 40% of the worlds population live in arid, remote areas and islands, and have no access to fresh water [42], In developing nations and in the Middle East, there are approximately 3 billion people who have no access to potable water sources, and approximately 1.76 billion people live in regions already facing a severe shortage of fresh water [34],
Water covers 70% of the earths surface, and the total amount of the global water reserves are approximately 1.4 billion cubic meters of water. Ocean water is estimated to be more than 97% from the total water reserves while 2.5% is fresh water on the surface of the earth. Rivers and lakes are the main sources of the fresh water, and it also exists in the atmosphere, as polar ice, and as groundwater [37],
The pollution of rivers, lakes, and underground water by industrial waste has increased the problem. In many countries around the world, the purity of rivers and lakes is threatened by overuse and pollution. Rivers and lake water are often no longer able to provide the pure water that people need while the impact of pests and diseases is increasing.


2
Moreover, powerful underground pumping(fracking) and long distance piping are depleting groundwater aquifers well beyond sustainable recovery levels. In many cases, this converts clean water to brackish water with high concentrations of dangerous minerals which result in health problems.
Besides the problems of water shortage and pollution, providing energy to desalinate water constitutes another challenge. The water desalination process requires the consumption of a large amount of energy. It was calculated that the production of 1 million m3/day of fresh water needs 10 million tons of oil per year [15], Therefore, many developing countries suffer from lack of fresh water due to fuel costs and poor infrastructure [34], Furthermore, most of the current desalination systems depend on conventional technologies which produce large amounts of waste and greenhouse gasses. They also cause environmental degradation and increase pollution in the atmosphere.
Renewable energy sources, such as solar energy and wind energy, have gained more attraction for use in desalination plants due to their ability to save conventional energy for other applications, reduce environmental pollution, and provide low maintenance. Solar energy systems can be classified into two main types: thermal systems and photovoltaic systems. The solar thermal system uses solar radiation to provide heat and uses solar collectors to harness the solar energy. The solar collector absorbs solar radiation through a heat transfer medium and converts it into useful energy. The Photovoltaic (PV) desalination system converts solar radiation directly into electricity, and it has a higher efficiency when compared to thermal systems. The proposed system in this research deals with the thermal solar water desalination system, and presents a desalination system that uses non-traditional and innovative technology.


3
This thesis is organized as follows. Chapter 2 provides background information about desalination, objectives of this research, and the scope of work. Chapter 3 describes the design of the solar desalination system and the operating principle of the proposed system and provides the description for modeling of single slope solar still. Chapter 4 shows the thermal analysis for every component in a PV solar and solar still system. Chapter 5 shows the experimental and theoretical data for the production of pure water in four days from the solar desalination system. Finally, chapter 6 provides conclusions and recommendations for future work in this area.


4
CHAPTER H
BACKGROUND, OBJECTIVES OF THIS RESEARCH, AND SCOPE OF WORK
2.1 Water
Water has unique chemical properties regarded as a part of the cycle and balance of life. Organisms need water for survival. The earths surface is 70% water, but only 2.5% is considered fresh water, and 80% of that fresh water is frozen in the ice caps of mountains or in the form of soil moisture [7], Water resources, volume, and percentage of water resources distributed on the earths surface are shown in Table 2.1.
Table 2.1 Percentage of water resources across the globe.
No. Resource Volume Fresh water percent Total water percentage
1 Atmospherics 12,900 0.001 0.01
2 Glaciers 24,064,000 1.72 68.7
3 Ground Ice 300,000 0.021 0.86
4 Rivers 2,120 0.0002 0.006
5 Lakes 176,400 0.013 0.26
6 Marshes 11,470 0.0008 0.03
7 Soil Moisture 16,500 0.0012 0.05
8 Aquifers 10,530,000 0.75 30.1
9 Lithosphere 23,400,000 1.68
10 Ocean 1,338,000,000 95.81
Total 1,396,513,390
Historically, rivers and lakes were the main sources of water that humans used. In recent history, aquifers have become one of those sources. However, with the growing human population, the demand for fresh water has increased dramatically. According to the US Census Bureau, the worlds population has grown from 3 billion to 6 billion between


5
1960 2000, and it will reach 9 billion in 2045 [3 8], The population has already grown rapidly, and the consumption of fresh water has increased while the amount of fresh water has remained constant. Therefore, the world is suffering from a shortage of fresh water, and this shortage is expected to increase in the future. Today, water shortage is estimated at approximately 40% and could grow to 60% by 2025 [7],
Population growth is not the only reason for water shortage. It can be attributed to changes in lifestyle, an increase in economic processes, and human activities. United States Geological Survey shows that the water consumption rate in the United States in 2010 is
306,000 million gallons per day fresh water and 48,300 million gallons per day saline water [41], Today, many countries suffer from water shortages that threaten their health and economies while clean water is unaccessible to 40% of the worlds population located in remote areas and islands[42],
2.2 Water Salinity
Water is classified based on salinity into three groups. The first group has a salinity range of 0.005- 1 ppt. This group includes water that is safe to drink, meets household requirements and is used in some industrial applications [7], The main sources of this type of water are rivers and lakes, or it can be generated by desalination. In fact, in desalination plants, the percentage of water salinity never exceeds 0.005 ppt [7], There are many uses for this type of water such as dairy, food, cooling, washing, and cleaning. Additionally, the low salinity level is used for ion exchangers that operate using desalinated water. Also, boilers and heat exchangers in industrial applications need less stringent water quality to operate [7], Water that contains a salinity range of 1- 3ppt falls within the scope of the second group of water, and it is suitable for irrigation and industrial cooling. The third group of


6
water that is above 10 ppt, and it is called high-salinity water. Seawater, which has a salinity range of 30 50ppt, is considered the largest source of the third water category. The average salinity of seawater is 34ppt, which varies depending on local ambient and topographical conditions [7], Seawater is a mixture of water, dissolved salts and minerals. The composition of seawater is shown in Table 2.2. Seawater also contains other suspended materials, such as sand, clay, microorganisms, viruses, and colloidal matter, and their size ranges from 5xl0"2 -0.15pm [7],
Table 2.2 Composition of seawater with salinity of 36000ppm
Compound Composition Mass Percent Ppm
Chloride ci- 55.03 19,810.80
Sodium Na+ 30.61 11,019.60
Sulfate (S04) 7.68 2,764.80
Magnesium Mg+ + 3.69 1,328.40
Calcium Ca+ + 1.16 417.6
Potassium K+ 1.16 417.6
Carbonic Acid (C03)" 0.41 147.6
Bromine Br 0.19 68.4
Boric Acid H3B03- 0.07 25.2
Strontium Sr+ + 0.04 14.4
Total 100 36,000
2.3 Desalination
Desalination is the process of separating the dissolved salts and minerals from the fresh water. Desalination processes are used in many applications, such as municipal, industrial, and commercial. Up until 1800, single stage stills that were used for water desalination were operated in the batch mode, and cook stoves or furnaces supplied the energy without recovering the heat of condensation. The real beginning of water desalination


7
was at the beginning of the twentieth century [7], In 1912, a six-effect desalination water plant was built in Egypt with a capacity of 75 m3/d. When the oil industry started during the period of 1929-1937, the total production capacity of water desalination increased [7],
During World War II, pure water supplies were limited, and there was a significant effort to convert salt water into clean water. In 1952, American Congress passed The Salt Water Act, and it provided federal support to develop water desalination processes. The initial development of technology for water desalination processes was between the 1950s and 1960s when the U.S. Department of the Interior, through the Office of Saline Water (OSW), provided funding. In 1961, the first modern desalination plant was built in Texas [17], With technological advancements, desalination processes have come to play a significant role in meeting the growing population needs.
However, water conservation has become one of the requirements of modem life. Many communities around the world entirely rely on desalinated water, and this is one of the main reasons for the survival of these countries. So, there are significant efforts to encourage people to conserve water before turning to desalination. There are different methods of water desalination used in various countries, and they depend on desalination sources and the geological region of the country. It has been observed that 48% of the global desalination production takes place in the Middle East. It is mostly concentrated in Gulf countries, while the US occupies second place with 19%. Asia, Europe, and Africa have 14%, 14% and 6% of global desalination production respectively [19], Furthermore, over the past decade, the number of desalination plants has increased almost twice much as their total capacity [19], In general, water desalination capacity grew approximately twenty percent every year from 1972 1999, and over 8,600 desalination plants had been built around the world (40). Figure


2.1 describes the desalination production capacity which exceeded 65 million m3 per day in 2008. It also shows the capacity of desalination plants continuously grew until reaching approximately 130 million m3 per day in 2016 [16],
1980 1984 1988 1992 1996 2000 2004 2008 2012 2016
Figure 2.1 Global installed capacities of desalination 2.4 Desalination Technologies
Desalination can be classified into two major categories: thermal and membrane. Thermal technology is based on the natural water processes of desalination and often involves heat transfer, while membrane technology is based on filtration through a membrane and often uses electricity as an energy source. Total dissolved solids of water produced by thermal technology are estimated at approximately 20ppm while, with membrane technology, around 100-500 ppm [18], Within these two main types, there are sub-categories as shown in Table 2.3, and they use various techniques to desalinate water. There are other desalination technologies, but they are either not very common or are currently under research. The overall capacity of both thermal and membrane technology is estimated to be 7 billion gallons per day (bgd) at the beginning of 2000, with each contributing 50% of the total


9
capacity [40],
Table 2.3 Water desalination categories
Thermal Technology Membrane Technology
Multi-Stage Flash Distillation (MSF) Electrodialysis (ED)
Multi-Effect Distillation (MED) Electrodialysis reversal (EDR)
Vapor Compression Distillation (VCD) Reverse Osmosis (RO)
2.4.1 Thermal Processes and Membrane Processes
The thermal desalination process includes multi-stage flash (MSF), multi-effect evaporation (MEE) and vapor compression (VC). Currently, almost all multi-effect evaporation processes are combined with vapor compression technologies. Membrane processes cover Reverse Osmosis (RO), Electrodialysis reversal (EDR), and Electrodialysis (ED).
2.4.1.1 Multi-Stage Flash Desalination (MSF)
Today, Multi-Stage Flash Desalination has become the most common technique for desalinating water and it uses a brine heater that heats and pressurizes salt-water, and the hot water flows into chambers or stages. The saltwater flashes and converts to vapor due to lower pressure in the stage. Seawater passes from one stage to another and the flashings are repeated without additional energy consumption. Flashing converts seawater to vapor and heat exchangers in each stage condenses the vapor and converts it to fresh water. The number of stages of a Multistage Flash Desalination process range from 4 40, and it operates at


10
temperatures ranging from 100 -110 C to produce 6-11kg of desalinated water per kg of steam applied [29], The life span of a MSF is expected to be 12 40 years [24], The maximum temperature level for Multi-Stage Flash Desalination is limited by the levels of salinity in the water to avoid scaling, and this limits the performance of this technology. A key design feature of Multistage Flash Desalination systems is bulk liquid boiling ,which alleviates problems with scale formation on the heat transfer tubes [32], Figure 2.2 illustrates
a Multi-Stage Flash Desalination process.
Figure 2.2 Multi-stage flash desalination (MSF) process 2,4,1,2 Multi-Effect Boiling (MEB) Process
The principles of the multi-effect boiling process are based on evaporation and condensation at different stages. In this technology, steam is condensed in one of the stages, and the heat loss is used to heat salt water in the next stage and is then converted to vapor. Seawater passes through multiple stages of boiling without requiring additional energy. The preheated steam from the boiler is fed into a series of tubes, and the vapor heats the tube and acts as a heat exchanger to evaporate incoming seawater from another channel. After that, the vapor is condensed into pure water. The system includes heat exchangers instead of a solar collector or heater, and it is used to preheat the feed water. Figure 2.3 described the Multi-


11
effect boiling process.
Figure 2.3 Diagram of a multi-effect boiling (MEB) process 2,4,1,3 Vapor Compression (VC)
One of the main advantages of the VC technology is that it does not require an external heat source. Vapor Compression technology has a similar operating principle to Multi-effect boiling except that this method generates heat. In VC technology, compression provides heat to vaporize the water while in MEB technology, a boiler heats the salt-water and converts it to vapor. Vapor Compression units are often built as relatively small units, and their capacity ranges from a few liters up to 3000m3 per day [22],
2,4,1,4 Reverse Osmosis (RO)
Membrane technology (Reverse Osmosis technology) is the fastest growing technology of all water desalination processes. Reverse osmosis technology uses pressure to force seawater through a membrane, and that results in obtaining pure water by separating the salt. In Reverse Osmosis, heating or phase changes are not required, and there is no energy consumption for heating. However, energy is needed to pressurize the feed water to pass through the membrane. In most ROs, the pressure needed to convert sea water to fresh


12
water ranges from 50 80 bars, while brackish water requires 10-25 bars. Most of Reverse Osmosis systems use turbines that recover most of the consumed energy. The energy required to desalinate sea water is 5 kWh/m3, while brackish water needs 3kWh/m3 [27], The cost of building Reverse Osmosis plants is low. Figure 2.4 shows a RO.
Pump Membrane Assembly
Figure 2.4 Schematic diagram of a reverse osmosis process [27]
However, maintenance costs are high due to the cost of membrane replacement and the parts used for energy generation. Also, the system requires intensive pre/post-treatment. The capacity of Reverse Osmosis systems ranges from 0.5m3 per day for a small system to 330,000m3 per day for the largest plant [27]
2,4,1,5 Electrodialysis (EDI
In the early 1950s, the first Electrodialysis system was introduced commercially, and this was ten years before the design of Reverse Osmosis [27], The operation of Electrodialysis technology systems is based on an electrical potential to move salts selectively through a membrane and obtain pure water from seawater. The higher salinity in the feed water consumes a greater amount of electrical energy and has a higher cost. The average energy consumption to produce fresh water with 500 ppm is about 1.5-4 kWh/m3 when the salinity level of the feed water ranges from 1500 3500 ppm [24], Figure 2.4 shows the ED system. The ED design has a high cost if it used for seawater desalination, and it does not have a barrier effect against microbiological contamination. Therefore, it is more


13
appropriate for brackish water. The capacity of Electrodialysis ranges from lm3 per day for the small system to 220.000 m3 for the largest ED plant.
2,4,1,6 Electrodialysis Reversal (EDR)
In the early 1970s, the EDR desalination system was introduced. Electrodialysis reversal system is based on the same principle that ED technology uses, except that both the product and concentrate channels are identical in construction. Also, the same membranes are used to provide a continuous self-cleaning ED process that uses periodic reversal of the DC polarity to allow systems to run at high recovery rates. [28]
2.5.1 Solar Radiation Intensity on the Horizontal and Inclined Surfaces
The intensity of solar radiation that falls on the earth's surface depends on the surface orientation and its inclination. Although surfaces that are perpendicular to the sun's rays receive the largest amount of sun radiation, the processes to track the sun are often expensive and impractical. As a result, the most appropriate solution is using inclined solar panels.
Thus, it was essential to calculate the incident of solar radiation on the inclined surfaces [28], Figure 2.5 shows the direct radiation that falls on horizontal and inclined panels surfaces. The intensity of the incident of solar radiation on the earth's surface on a clear day can be expressed in the following relationship [6],
WhereSc is the solar constant (1367 W/m2),

2.5 Solar Radiation
E = Sc l + 0.033cos
(2.1)
of the sun at solar noon, co is the hour angle which is the angular displacement of the sun east


or west of the local meridian due to rotation of the earth on its axis at 15 per hour, with morning negative and afternoon positive.
14
The daily theoretical solar radiation on a horizontal surface is obtained by [25],
(
24 x 3600 x Sc 1 + 0.033 cos
H
V
cos (ft cos 8 sin ats H-- cos (ft sin 8
(2.2)
o
180
n
In locations that often have a clear and dry atmosphere (high places or arid regions), the results from the previous relationship must be multiplied by the C factor. Similarly, in places that frequently have cloudy and wet weather, the C factor should be calculated when the amount of solar radiation incident is estimated.
Incident solar radiation on the inclined surface consists of three components: beam, diffuse, and ground- reflected radiation [25]
HbB is the daily beam radiation on an inclined surface, HdB is the daily diffuse radiation on an inclined surface, and Hr is the daily reflected radiation on an inclined surface. The daily beam radiation can be estimated as,
The diffuse component includes three subcomponents: Isotropic, which is received uniformly from all of the sky dome, Circumsolar diffuse, which results from forward scattering of solar radiation and is concentrated on the part of the sky around the sun, and the third part is concentrated near the horizon and is large in clear skies. Thus, the daily solar radiation incident on inclined surfaces is given in the following relationship [6]:
Ht=HbB+HdB+Hr
(2.3)
(2.4)
Ht=(H Hd)Rbm+Hd
2
2
(2.5)


15
The Hourly solar radiation incident on inclined surfaces is given in the following relationship
[6]:
!, =IbRb
1 + cos y
Hp
1 cos y
(2.6)
The Monthly solar radiation incident on inclined surfaces is given in the following relationship
Where Rbm is the monthly average daily geometric factor, and it is calculated by [6],
cos(cp y)cosS sin con
Rbm =
71
180
or.
1sin(cp y)sinS
coscp cosS sincos
71
180
orssincp sinS
(2.8)
2.5.1 Photovoltaic Solar Panels and the Method to Generate Power Using Solar Cells
PV cells are one of the best methods to convert solar energy into electrical energy. This method has several advantages compared with the thermodynamic method, such as high


16
reliability, different sizes and a variety of uses, and they can be composed of independent parts with productivity equal to the whole PV solar panel. Additionally, the design that uses this method is simpler than other methods because it includes portable panels which make it possible to reduce panels and sometimes dispense maintenance entirely.
Solar radiation passes through the surface of the cells when the sunlight falls on a PV panel. Part of it is absorbed by the first cell layer, which contains phosphorus, while the majority of the incident solar radiation is absorbed by the layer that includes silicone mixture with Boron. This process generates a free movement of electrons, and the free electrons flow through the electrical connector in cells. DC power will be generated, and an electrical load can be connected to the cell. Moreover, the movement of electrons increases with the increasing intensity of the incident solar radiation on the cell. Therefore, PV solar panels are directed at a suitably tilted angle to face the sun so that solar radiation falls vertically on it [23],
2.6 Solar Desalination Processes
One of the applications of solar energy is providing the required energy for a water desalination process either in the form of thermal or electric energy. Using solar energy in water desalination processes reduces the cost required to convert salt-water to drinkable water. Solar desalination processes can be categorized into two main parts indirect solar desalination systems and direct solar desalination systems. Indirect systems require two separate subsystems. A collector used to collect solar energy and a system that uses the collected solar energy to produce pure water [10], The indirect desalination system has been subjected to several analytical and experimental studies. The table 2.4 illustrates some of the studies that have analyzed this type of system. The indirect solar collector systems are


affected by several factors.
Table 2.4 Indirect solar desalination system
17
Collector types Desalination type Authors Title Source
photovoltaic Reverse osmosis Bendfeld, J., Broker, Ch., Menne, K., Ortjohann, E., Temme, L. Design of a PV-powered reverse osmosis plant for desalination of brackish water[5]
Parabolic trough collector ME Rodriguez and Camacho Conditions for economic benefits of the use of solar energy in multi-stage flash distillation,[9]
Evacuated tube ME El-Nashar, A.M An optimal design of a solar desalination plant,[8]
Hybrid system Reverse osmosis Joyce, A., Loureiro, D., Rodrigues, C., and Castro, S., Small reverse osmosis units using PV systems for water purification in rural places,[14]
Solar pond Multi-stage flash AlHawaj, 0., and Darwish, M.A., A solar pond assisted multi-effect desalting system, [2]
2.7 Objectives of This Research The objectives of this research are the following:
Conduct an experimental study for the PV solar desalination system, and compare the results with theoretical data obtain from modelling of a single slope solar still system.
Develop a theoretical model by using Matlab Simulink to simulate the performance of the single solar still.


18
Conduct a thermal analysis of a PV solar desalination system and a single slope solar still desalination system.
Perform numerical calculations using the EES program.
Compare the numerical and experimental results.
2.8 Scope of Work
The experimental study was conducted on a solar water desalination system by using new concepts to develop the performance of this system. Also, the simulation system was designed for solar stills. Through this research, the following tasks were performed:
The mathematical and thermal analysis was conducted for each component of both systems by using a coupled set of equations.
The Experimental work includes the following steps:
o The design, operation and testing the experimental system, o Testing the system on different days, o Collect and evaluate the results.
The theoretical work includes the following:
o Design a theoretical model of the system to simulate the performance of the system.
o Run the simulation model and collect the data.


19
CHAPTER HI
SOLAR DESALINATION SYSTEM DESIGN
3.1 Description and Operating Principle of the Proposed System
This research involved the development and study of a solar desalination system that used PV solar panels and batteries. The concept utilized solar cells to collect the largest possible amount of solar radiation and used it as an electrical source to supply power to the system. Batteries are also used in the proposed system to provide power as well as store the energy supplied by the solar cells. The uniqueness of this concept is that the PV solar panels and batteries in a desalination system create a stable production of fresh water and a higher rate of pure water production compared to the conventional thermal systems.
The system, as shown in Figure 3.1, was constructed with PV solar panels, and it consists of three parts: electrical, thermal, and condensation. The electrical part contains PV panels, a charge controller, batteries, and electrical connections. The thermal part includes a coil heater and a copper tube, while the condensation part includes a water container and cold water tap. The solar cells received the solar radiation and converted it to electrical power. PV panels were connected to the batteries that stored electrical energy from the PV panels as well as supplied power to the coil heater, a heat source for the system, which converted the water into steam. The coil heater received power from the batteries and generated heat to the water inside the copper tube. Furthermore, the system includes a water tank containing provisions to feed the cold salt-water directly from the external water source. The water tank was connected to a copper tube that absorbed the heat from the coil heater. The copper tube passed through another water tank that contained cold water, which worked as a condenser. The copper tube extended to the top, approximately 30-cm above the lower base of the


20
system, to allow the water vapor to rise and leave the salts. Then it lowered to about 10 cm and passed through the cold water.
Water tank
Batteries PV solar panel
Figure 3.1 Schematic of the proposed system
To start the operation, the water tank was filled completely with salt-water. The water was allowed to rise in the copper tube under the influence of pressure and created a water level in which the heat of the coil could reach. Depending on the water pressure, the water level raised to about 20 cm above the lower base of the system, and the coil heater was installed at the same level. When the batteries started to apply power to the coil heater, they provided the required heat to evaporate the salt-water to vapor. The water vapor would then rise inside the copper tube and pass through the cold water tank. Heat exchange took place between the vapor and the cold water. Consequently, the vapor was condensed, and fresh water was produced in a separate container.
3.2 System Design
3.2.1 PV Panels:


21
Two PV solar panels were utilized in this solar desalination system. Both of the PV panels had output power ratings of 320 watts, and they were connected in parallel as shown in Figure 3.2.
The maximum output power from the PV solar panels could be estimated depending on short circuit current, open circuit voltage, and fill factor, as well as the operating temperature. In fact, the operating temperature has an influence on the efficiency of a PV solar cell, and that can be traced to its effects on the current and the voltage. Both Voc and FF decrease substantially with an increase in temperature due to the thermally excited electrons dominating the electrical properties of the semiconductor. The Ics increases with temperature, but only slightly for C-Si solar cells[33]. The maximum output power from PV solar panel is given as,
Figure 3.2 PV solar panel
(3.1)
The fill factor can be calculated by two methods (actual and theoretical)[33]:
actual
[y.l,l-('n(y.,l + 0.72))]
(3.2)
V+l


22
V =
n x k x T / V
(3.3)
The theoretical fill factor can be calculated as,
V xl
1212 _ np mp
*\heo '
V0CxIsc
(3.4)
The maximum current and maximum voltage of PV panel can be estimated as,
^mp+l ^"mpi
/lO
TO
(35)
The Newton-Raphsons method was used to calculate Imp in the equation (3.5) in an iterative form, and the subscript i indicates the zth iteration [33]:
/0= 2-41,i + 2(l, +Io)^L + [ln(l,c+I0 -I,)-ln(lj]
,R
(3.6)
/(lnpi)=Inp+2(lsc+Io-Inp>np^ + (lmp-Isc-Io)+[ln(lsc+Io-Inp)-ln(lo)] = 0.
V,
(3.7)
Vmp=Vtln
(^c ^mp) |
I
R T
(3.8)
Furthermore, the relationship between the current and voltage for PV solar cells was illustrated by Wagner [33]as:
I =1,1-10
f V+IRS '\ V, 1
e 1 -1
(3.9)
V =Vt.ln
'(w + 0"

(3.10)
Where I;1 indicates the electric current generated by illumination, I0 denotes the diode


23
current and Rs is the resistance an approximately 0.03Q. Vt indicates the thermal voltage and can be estimated depending on the temperature (T) of the cells by using the following equation, Vt= (nkT/q). n indicates the diode factor, q is the charge (1.602x 10'19), and k
represents the Boltzmann constant (1.38/ 10'23JK'1 ).The diode current (I0) was calculated by measuring open circuit voltage with io = IN Voc / Vt.
3.2.2 Batteries and Charge Controller
In most PV applications, the output energy from PV panel was stored in batteries. Selecting suitable batteries for a system depends on many factors, the most important is the energy storage capability. The electrical power capacity refers to the amount of energy that can be stored by a battery and supplied on demand. Voltage and current stabilization was another factor that influences the battery selection[36]. Supplying electrical power to the system loads at stable voltages and currents was done by suppressing or smoothing out transients that can occur in PV panel systems, which is necessary for operating the system with stable voltages and currents [36], This can be achieved by using several batteries. Five batteries were used in this experiment: four of them at 6 volts, and one atl2 volts. Various connections were made on the batteries to get different voltages for operating the system as shown in Figure 3.3.
A charge controller was also used in this project. Charge controllers regulate the DC voltage that are supplied to the batteries from the PV panels. Charge controllers receive the direct voltage as the input voltage from PV panels and converts it into a suitable direct voltage that was required for charging the batteries. The charging processes in solar systems are necessary to enhance the battery life and performance[36]. The charge controller was employed when the voltage of PV panel was higher than the output voltage required for the


24
load. Because PV solar panels provided about 24- 56 volts in the proposed system, the charge controller became necessary to prevent overcharging and causing damage to the batteries.
Figure 3.3 Mixed connection of the batteries to generate 12 V and 24 V
3.2.3 Coil Heater and Copper Pipe
The specifications of the coil heater used in the experiment are a low-voltage DC power supply, 12-48V, a maximum current of 20 A, a maximum power of 1000 W, a 24 V input with no load current of 3 A, a 48 V input with no load current of 6A, and with dimensions 3.4 x 3.1 x 1.5 in.The specifications of the copper pipe are Handi-coil soft copper tube, a pipe diameter of 0.25 in and 0.5 in, a maximum psi of 1557, a minimum working temperature of -100 F and a maximum working temperature of 778 F.
3.2.4 Description of the Heat Transfer Equation Between the Coil Heater and the Copper Tube
When the coil heater was placed around the tube, the lines of force were concentrated in the air gap between the coil heater and the tube. The force field that was surrounding the


25
coil heater induced an equal and opposing electric current in the copper tube. The heat rate of the tube was dependent on the frequency of the induced current, the intensity of the induced current, the Cp of the material of the tube, the magnetic permeability of the material of the tube, and the resistance of the copper tube to the flow of current. Through the turns of coil heater winding and tube, it was assumed that the flux was perfectly linear in the axially direction. Therefore, flux leakages, flux variations, and end effect could be neglected. Consequently, the current distribution in the tube and coil heater was represented by an equivalent depth, 8 [35] as,
Where / is frequency of 10, p is resistivity, and /j is permeability. The current that passes through the tube was lt = IcfSTc The tube resistance was the resistance of the equivalent current path of the cross-section of the tube and its length, and it was estimated as Rt = pt7rdt xicr6/5tlt. The power that induced in the tube was estimated as [35],
(3.11)
p Iq Nq Ptrc dt x 10
(3.12)
8,1
t At
Moreover, the power lost from coil heater was calculated with,
P
C
(3.13)
The coil heater resistance increases by decreasing the cross- section of the tube and
increasing path length. The effective resistance was found using
(3.14)
Where Nc is the coil turns, Rc is coil resistance, dt is tube outer diameter, dc is coil inner


26
diameter.
The distribution of the magnetic field at any point inside tube was estimated as [35],
d2H 1 dH
+------K jH = 0
dr r dr
(3.15)
Where H is the distribution of the magnetic field, k2 = 8 tt2 /////?, and r is radius of the tube.
3.2.5 Measuring Devices
The following measuring devices were used in this research project:
The Ambient Weather WS-1400-IP OBSERVER Solar Powered Wireless was used for measuring the solar radiation, temperature, and the wind speed.
A Digital multimeter (200mV-200V) was used for measuring the voltage.
A Clamp Meter (0-1000A DC) was used for measuring the current.
A Measuring pitcher gallon was used to measure the quantity of pure water.
3.3 Description Modeling of Single Slope Solar Still Using Matlab Simulink The Matlab Simulink has become a commonly used software package in academia
and industry for modeling and simulating dynamic systems. Matlab Simulink supports linear and nonlinear systems as well as systems used in continuous time. Modeling in Matlab Simulink provided an interactive graphical environment and a customizable set of block libraries that provided the ability to design, test, and implement a variety of configurations for the system. [26], Additionally, it can be used to easily modify an existing model.
The Matlab Simulink was used to model the single slope solar still, and the model
was composed of four groups as shown in Figure 3.4. Fourteen equations were used in the simulation to model the desalination process of the solar still, and they represent the first and second groups in the modeling system. The third group includes the input data, which


27
represents the solar radiation intensity, water temperature, glass temperature data, and depth of the salt-water inside the solar still. The last group denotes the output water products.
Figure 3.4 Schematic of modeling the single slope solar sill 3.3.1 Description of Part 1 and Part 2 in the Modeling
The Part 1, modeling of a single slope solar still, includes eight equations as shown in Figure 3.5. [31]
Cp = 999.2 + 0.1434 x Tv+1.101x10 4 xTv2 353,44
P (Tv x 273.15 )
fi = 107180x10 6 x46.20x10 9 xTv
25.317
e
5144 ^ Tg+273
-67.581x10 9
xT
v
7
(3.16)
(3.17)
(3.18)
(3.19)
K = 0.0244x0.7673x10^ xTv
(3.20)


28
!3 =
Figure 3.5 Schematic of part 1 for the modeling 1
(Tv x 273.15)
25 317- 514+^ T +273
P... =
(3.21)
(3.22)
G =
Dp" AT P g F2
(3.23)
Six equations are contained in part 2 of the model of a solar still system. Figure 3.6 illustrates part 2: [1]
Pr =
K
L = 3.1615xl0bx(l-(7.616xl0^xTv)) [31]
(3.24)
(3.25)
h, = 16.273xlO"3 xh. (Pw Pg) =16.273xlO-3 xf-]c(Gr.Pr)-(Pw Pa)
(TwTa)
Va,
(Tw_Tg)
(3.26)


29
hcw =0.884
T _T (Pw-Pg)(Tw+273.15) w 8 (268.9 xl03-Pw)
(3.27)
qew=hew(Tw-Tg)
hew(Tw-Tg)
m =-----------
L
(3.28)
(3.29)
Figure 3.6 Schematic of part 2 for the modeling 3.3.2 Input and Output Data for Modeling
The experimentally measured values of solar radiation, wind velocity and ambient temperature of the corresponding day and hour were used. The water temperatures and glass cover temperatures were calculated numerically by using the EES program. Figure 3.7 illustrates the EES program used to calculate water temperatures (Tw) and glass temperatures (Tg). As a first iteration, the water temperature and glass temperature were taken as ambient temperature, and the brackish water temperature (dT_w) and the glass cover temperature (d_Tg) were computed for every time interval. Appendix B shows the brackish water temperature iterations.


30
"A_b= area of basinarea of glass;A_w=area of water; ;algha_w=the obsorptivity of water;algha_g=the obsorptivity of glass; m_g=mass of glass;
CP_w=specific heat of water;m_w=mass of water;cp_g= specific heat of water;E_w= emissivity of water; E_g= emissivity of water
T_w=intial water temperature;l=solar radiation;;T_g=intial glass temperature;V= wind speed;T_a=ambeint temperature"
"the energy alance equations"
((l,A_w,algha_w))+Qc_bw=(Qc_wg)+{Qr_wg)+(Qe_wg)+(m_w*Cp_w,(dT_w))
(rA_g*algha_g)+(Qc_wg)+(Qr_wg)+(Qe_wg)=(Qrg_sky)+(Qcg_sky)+{m_g*Cp_g*(dT_g))
"convection heat transfer for plat to water"
Qc_bw=hc_bw*A_b*(T_b-T_w)
"convection heat transfer for water to glass"
Qc_wg=hc_wg*A_w*(T_w-T_g)
"heat transfer coefficient"
hc_wg=0.884,((T_w-T_g)+(((Pw-Pg)*(T_w-T_g))/(268900-Pw)))A(0.333)
"radiation heat transfer for water to glass
Qr_wg=hr_wgA_wf(T_w-T_g);
"heat transfer coefficient"
hr_wg=E_eq*sigma{(T_w+273)A2+(T_g+273)A2)*(T_w+T_g+546)
Ejq=(1/I(E_w)+(1/E j)-1 )-1)
"evaporative heat transfer for water to glass"
Qe_wg=he_wg*A_w*(T_w-T_g)
"heat transfer coefficient" he_wg=(O.I6273*hc_wg*(Pw-Pg))/(T_w-T_g)
"radiation heat transfer for glass to sky"
Qrg_sky=hrg_sky*A_g*(T_g-T_sky)
"heat transfer coefficient"
hrg_sky=E*sigma*((T_g+273)A4-(T_sky+273)A4)/(T_g-T_sky)
"sky temperature"
T_sky=(T_a)-6
"convection heat transfer for glass to sky"
Qcg_sky=hcg_skyA_g*(T_g-T_sky)
"heat transfer coefficient" hcg_sky=2.8+3*V "water pressure"
Pw=eA(25.317-(5144/(T_w+273)))
"water pressure"
Pg=eA(25.317-(5144/(T_g+273)))
T_nw=T_w+dT_w
T_ng=T_g+dT_g
Figure 3.7 EES program to calculate the water and glass temperature


31
3.4 Algorithm Flow Chart to Calculate the Water Production
Start


32
CHAPTER IV THERM AT, ANALYSIS
This chapter will be divided into two parts. The mathematical equations that describe the performance of each component of PV solar desalination system are presented in the first part. The second part illustrates the mathematical equations of the single slope solar still and describes the heat balance, mass balance and heat loss for solar still system.
4.1 Theoretical Analysis of PV Solar Desalination System The operation of PV solar desalination was governed by various heat transfer modes as shown in Figure 4.1. The most prominent were the convection and radiation modes. Convection is accompanied by evaporation and condensation, and radiation is the mode of heat transfer between the coil heater and the copper tube. The coefficient of heat transfer depends on the Nusselt number.
4.1.5 Heat transfer (copper tube and air) 4.1.1 Heat transfer (coil heater and outer pipe wall)
4.1.3 Heat transfer (the water surface and inner pipe wall) 4.1.2 Heat transfer (outer tube wall and inner tube wall)
Figure 4.1 Schematics of the heat transfer in the whole system 4.1.1 Radiation Heat Transfer Between the Coil Heater and Outer Pipe Wall


33
The heat transfer mode between the copper tube and coil heater was radiation as shown in Figure 4.2. The operation temperature of the heater can be calculated as [12],
Qheater=So(T4-T04) (4.1)
(4.2)
T =
t0 +
Qh
so
T
273'+ 1000
8x5.67x10'
(4.3)
Copper tube
Figure 4.2 Heat transfer between the coil heater and copper tube The heat flux of the coil heater can be estimated as [12],
Qheater ~ ^ Ah Th
(4.4)
Qheater =SX 5.67 X 10^ A, X T,
(4.5)
The radiation from the heater was emitted in all directions, and the shape factor determined the amount of radiation that struck the copper tube. Therefore, the radiative heat
transfer coefficient was [12],


34
h = Fh^P
(Th4-TD4)
(Th Tp )
The heat transfer equation can be written as, QhP=hAp(Th-Tp)
Qhp=e Fh aAp(T4-T4)
(4.6)
(4.7)
(4.8)
The net amount of radiation absorbed by the tube is:
QobSe*ed = Fats o AhTh4 (4.9)
To simplify, assuming all the radiation energy that emitted by the heater falls on copper tube,
So Fh_.p=l.
4.1.2 Conduction Heat Transfer Between Outer Tube Wall and Inner Tube Wall
Tl Ts.l Ts,2 T2
Outer surface Inner surface
(Tl, hi)


r2 r
Tl
T2
Heat
Figure 4.3 Heat transfer between the outer wall and inner wall of the copper tube Assuming the heat transfer was steady quasi-one-dimensional heat flow [20],
IA(r.^) = 0
r dr dr
(4.10)
The temperature distribution for constant (K)


35
T =
i(r)
T -T
xs,l xs,2
^ r ^
In
V
vr2y
+ T
vfy
The heat flux and heat rate can be written as [20], dT k (T j-T 2)
qr" = -k.
dr ro
rln
Vr2 J
, ~ 2u k(T jT 2)
qr = 2.r.7i. q =
In

Vr2 J
2Lu k(T j T 2) qr = 2.L.r.7i. q =---------
In
r \
vr2 j
The conduction resistance can be estimated using [20],
In
R
A ^
Vri y
r.cond
2.71 .k
In
R
A ^
vri y
t,cond
2.71 k.L
(4.11)
(4.12)
(4.13)
(4.14)
(4.15)
(4.16)
4.1.3 Convection Heat Transfer Between the Water Surface and Inner Pipe Wall.
The heat transfer between tube and fluid flowing inside the tube can be calculated as
[30],
q,=h,(Ti-Tw).dA (4 17)
The inner wall temperature of the copper tube was calculated according to the outer wall temperature of copper tube and considering that the cylindrical wall has thermal resistance.


36
Ti =Tc+q.
f (d V
In ^
Id J
2.7t k.W
V J
(4.18)
The average temperature of water that flows inside the tube can be calculated as follows [30]:
f r ^ . A
T =
J pU Cp.T.dA
j p.U.C.dA
(4.19)
Due to the constant properties of water, the average water temperature can be written as (after simplifying the equation above mathematically) [11]:
T =T. +
w in
rq.n .(D0-Dj)^ Cp m
.L
(4.20)
The heat flux can also be estimated as the ratio of heater power to the heating area. [11]: Y.I
q =
71. D; .L
(4.21)
The local heat transfer coefficient can be written as,
q

(Ti-Tb)
(4.22)
The local Nusselt number is calculated by [11],(4.23)
The Nusselt number can be estimated based on the type of water flow. Water flow inside the
copper tube can be either laminar flow or turbulent flow, and the thermal entrance length is a
function of the Reynolds number, Re. For laminar flow, the Nusselt number can be
calculated according to the following equation [11],
h.D _ 0.065.Re.Pr.(D/L)
Nu =------= 3.66h----------------------
K l + 0.04(Re.Pr.(D/L)(2/3)
(4.24)


37
It is recommended that this result for the Nusselt number be corrected for the variation of viscosity with temperature across the cross-section of the tube by a factor (p (b)/p (w)) [11], Moreover, the thermal entrance length can be calculated if the velocity profile in laminar flow was fully developed as,
e, thermal
D
0.033 Re. Pr
(4.25)
For turbulent flow, the Nusselt number can be estimated according to the Gnienskis equation
h.D (f/2)(Re-100).Pr
K ~ +l + 12.7(Re)(2/3)-l)(f/8)(0-5)
[11]
(4.26)
4.1.4 Heat Transfer Between the Cold Water and the Steam Inside the Pipe
Figure 4.4 Heat transfer between cold water and vapor Region 1 vapor-solid convection [21]
dqx=V(Th-Tlw).dA (4.27)
qx=hhot(Th-T1w)A
(4.28)


38
T -T. =
^iw
KA
Region 2 Conduction across copper wall [21]
, , dT
dqx =~k-r-
dr
qx =
k ,27i2
copper
In
qxdn

T -T =
o,wall i,wall

k .271L
copper
Region 3 Solid cold liquid convection [21]
dq1=h,(T0,-TjdA
q, =|i.(t,,.,ii-t k.
T -T =
o,wall c
h A
The overall heat transfer coefficient [W/m. K] [21]
T -T =
Rj + R2 + R3
(4.29)
(4.30)
(4.31)
(4.32)
(4.33)
(4.34)
(4.35)
(4.36)
In


hhAi kcopper2^L hcAo
Th-Tc=q:
(4.37)


39
U
r .In


vri y
n-l
+
V\ v \c Vi
AAhot,Ai ^copper AAcold
The overall heat transfer
27tk(Th-Tc)
Q = F
hhot-k
+ In

+ -
rh
V Ai J AoAAcold
4.1.5 Heat Transfer Between the Copper Tube and Air
Air Air
Air
(4.38)
(4.39)
Air
Air
Air
v

Figure 4.5 Heat transfer between the vapor inside the copper tube and air qx =U.A(T T^) (4.40)
U =
r .In
hc h
''vapor 1

r \ r

n-l
k r
^copper'1!
+ -
h. +h
(4.41)
4.2 Theoretical Analysis of Solar Still
To simplify the analysis, assume that:
There is no temperature gradient along the glass cover thickness and the water depth.


40
There is no vapor leakage in the still. Therefore, productivity and efficiency will increase.
There is one-dimensional heat flow through the glass cover and basin insulation.
The heat capacity of the glass cover and insulation bottom and insulation sides of basin insulation are neglected.
4.2.1 The Energy Balance for Glass Cover
The heat loss from the cover glass to the ambient air is convection and radiation,
Figure 4.6 Energy balances for the whole solar still
Qig Q* + Qcg
(4.42)
The convection heat loss from cover glass to the ambient air is [4],
(4.43)
The convective heat transfer coefficient is [13],
hcg= 2.8 +0.3 V
(4.44)
The radiation heat loss from glass to ambient air is,


41
Q*=MT8-T.) <445>
The radiative heat transfer coefficient is [4],
, _ Tsky) (4.46)
fe-Tj
The sky temperature can be estimated as [1],
T T _6 (4-47)
sky a
Q_cg Q_rg
Figure 4.7 Energy balance for glass cover
The heat gain by the glass cover is from radiation, convection, and evaporation [13],
= QwB +(,)' Qwg [Qiw + Qcw + Qew]^b The radiation heat flux from the water inside basin to the cover glass can be estimated as
(4.48)
(4.49)
[1],


42
QBr=Feo(T:-Tg4) (4.50)
Where F is the shape factor of radiation. The shape factor is governed by the geometry of the solar still system and the solar radiation. Assuming the geometry of solar still is two parallel planes, and the solar radiation involved is diffuse radiation with long wavelengths. For this case, the shape factor is taken as 0.9. So, the equation becomes,
Qrw = 0.9 s o (T4 -Tg4) (4.51)
Where s is the effective emissivity of the water surface, and it can be calculated by the following equation [4],
Sw Sg
The convection heat flux from the water inside the basin to the cover glass can be estimated [1] as,
Qcw = hcw (Tw-Tg) hcw = 0.884
(Pw -Pg)(Tw + 273)
T -T H----------------
w g 268900-pw
-i 0.333334
The water pressure and glass pressure can be calculated [31] as,
f
25.317-
V
5144
Tg + 273y
Pse
(4.53)
(4.54)
(4.55)
f
25.317-
V
5144 T +273
w /
P e
-Tw
(4.56)
The heat loss from evaporation between the water surface and the glass cover is [1]


43
Qew = hew (Tw-Tg)
(4.57)
The evaporative heat transfer coefficient from water is:
h
ew
(4.58)
The hourly-desalinated water productivity of solar still basin is [3]
Mw = 3600 x ^
(4.59)
Where L is the latent heat of water evaporation (J/kg). The energy balance for glass cover can be written as follows [3]:
The first term on the left represents the solar energy absorbed by the glass cover. The evaporative, radiative and convective heat transfer between the water interface and the inner side of the glass cover are represented in second terms, while the first term on the right represents the radiative and convective heat losses between the glass cover and the ambient air.
4.2.2 The Heat Balance of the Bottom and Sides of the Basin
The heat transfer modes between seawater inside the basin to the ambient air through the insulation are:
Convection heat transfer between seawater and inner surface of insulation.
Conduction heat transfer between inner surface and outer surface of bottom and
Q
(4.60)
+ Qcg ] Ag + CgMg ^ (4.61)
s s s dt
sides.


44
Radiation heat transfer between the outer surface of insulation and ambient air.
Qb
Figure 4.8 Energy balance for the bottom and side basin The heat loss from the bottom and sides of the basin is:
Qib = [Qb + Qs + Qbg] ^
Heat loss from the bottom of the basin is [4]:
Qb=hb(Tw-Ta) (4.63)
The bottom heat loss coefficient can be written as:
1
Ubl I I
+ ^ +-----
hw ki/ Li hcb hrb
(4.64)
Where K is the thermal conductivity of air, and I. is thickness of the basin insulation The heat loss from the sides of the basin are [3]:
Q, = h, (T.-T.)
The heat loss coefficient for the sides can be written as: 1
(4.65)
(4.66)
hw ki/Li hcs hrs


45
The heat gain by the bottom and sides of the basin is:
Qggb = (b) I (t) (Abr6 )I(t)
The energy balance for the bottom and sides can be written as follows: [3]:
Qggb Qlb
(ab)i(t)(Abrb )i(t) =QbgAb+(Qb+Qs)Ab
(4.67)
(4.68)
(4.69)
Where Ab represents the area of the absorber plate, I (t) represents the incident solar flux,
Tb represents the transmissivity of basin water and glass cover respectively, and
represents the absorptivity of the absorber plate (or basin liner). The term on the right-hand side represents the energy absorbed by the absorber plate. The term on the left side is the loss
of heat from the bottom and sides to the atmosphere through the insulation and Qbg is convection heat from the bottom and sides of the basin.
4.2.3 The Equations of Energy Balance on the Water Surface Inside the Basin
Figure 4.9 Heat transfer for seawater interface


46
The heat gain by the bottom and sides of the basin is:
Qgain,w = w ) I (t ) Aw +QbAb+MwCwAw ^
The heat loss from the bottom and sides of the basin is:
Qloss,w | Qrw T Qcw T Qe
A.
The energy balance for the water surface can be written as follows [3]:
w ) I (t) Aw +QbAb + MWCWAW = [ Qto + Qcw + Qew ] A,
(4.70)
(4.71)
(4.72)
Where Mb Represents the mass of absorber plate per unit area, andCb represents the specific heat of the absorber plate.


47
CHAPTER V
RESULTS AND DISCUSSION
This chapter will be separated into two parts. The first part describes the methods used to take measurements of the PV solar desalination system and indicates the results taken from experimental measurements. The second part illustrates theoretical measurements of single slope solar still and describes the effects of feed water on the pure water production.
5.1 Experimental Location
The experiment was conducted on the campus of the University of Denver Colorado in the Boulder Creek building which is located at latitude/longitude 3974' N, 10499' W South of the equator as shown in Figure 5.1.
Figure 5.1 Image of the location of the Boulder Creek Building, University of Colorado Denver campus.
5.2 Method to Obtain Measurements:
The following steps were taken to obtain the measurements:


48
Instantaneous periodic measurements to the voltage and current of the PV panel as well as the amount of output fresh water were taken. Measurements were taken at every quarter hour in the morning and every half hour in the afternoon when the PV panels were at 30 .
The Ambient Weather WS-1400-IP OBSERVER Solar Powered Wireless was used to measure solar radiation, ambient temperature, and wind speed. The Ambient Weather unit included a sensor array, observer IP, router with internet, cloud service, and a display monitor.
A Clamp meter (0-1000A DC) and digital multimeter (200mV-200V) were used to measure current and voltage.
The results were taken on four days: August 9, September 4, October 2, October 28.
5.3 Results Obtained from Measurements
5.3.1 Experimental Measurements for Seawater on August 9
In this experiment, the PV solar desalination system was used, and the solar radiation values were calculated for the inclined surface. The relationship between the solar radiation intensity and time of day is shown in Figure 5.2 when the tilted angle of PV panels was 30. The data illustrates the solar radiation intensity on a sunny day. From the indicated Figure, it is seen that the values of solar radiation increased slowly in the early hours of the morning and sharply increased at noon and decreased in the afternoon. There were three different intervals throughout this day. The first interval was between the hours of 7 am -12pm, and the solar radiation sharply increased from 25 to 935 kW/m2during this interval and it started to decline gradually through the second interval, and reached 706 kW/m2 at 4 pm with a sudden drop at 1 pm. In the last interval, solar radiation decreased between the


49
hours of 4 7 pm, and changed from 706 to 33 kW/ m2.
(August 9)
Time(hr)
Figure 5.2 Hourly solar radiation values on a 30tilted Surface on August 9 Next, the power generated by PV solar panels and consumed by heater values were compared on August 9. Figure 5.3 shows a comparison between power generated by PV solar panels and the power consumed by the heater. Changing the values of generated power corresponds with the changing of solar radiation values, while the power consumption remained stable. As shown in the Figure, the generated power started from zero at 6 am and increased to 16 W at 7 am, and it reached a peak value of 598 W at 12 pm. At 3 pm, generated power gradually declined until it reached 21.5W at 7 pm. However, the power consumption remained stable between the hours of 12 am 11 pm, and was approximately 382 W. Power supplied to the system went through three intervals. The first interval occurred between the hours of 7 10 am, and power relied entirely on batteries. The power generated by PV panels started to supply power to the system as well as charge the batteries during the second period between the hours of 10 am 4 pm. In the last interval, the batteries again


50
started to supply the power to the system after 4 pm.
(AUGUST 9)
600
generated Power by PV Panel
consumption power by coil heater
Time(hr)
Figure 5.3 Comparison of the generated power and power consumed on August 9 During the experiment, the ambient air temperature and the fresh water produced were also measured. Figure 5.4 illustrates the output from the experimental of the PV solar desalination system that was tested on August 9. An accumulated output of 5.4 liters of fresh water was obtained by the system after 3 hours (9 am 12 pm). From the data, it is seen that the water product started after 1.24 minutes due to the time spent heating the water to vapor as well as heating the copper tube. After that, the water production was stable at a rate of 0.03 liters per minute. Furthermore, it was noted that the ambient temperature gradually increased from 80F to 92F between 9 am 12 pm, but this change in temperature did not affect the amount of water produced due to the batteries that make the power supply stable.


51
seawater desalinated
Time(minute)
(D
i_
D
-M
H3
l_
(D
Q.
E
(D
Pure water
temperatur
e(F)
Figure 5.4 Hourly variation of the experimental desalinated water yield and ambient temperature (seawater)
Also, voltage and current consumption were measured experimentally. Figure 5.5 shows the consumption of voltage, current, and power on August 9. As seen from the Figure, the accumulated output of fresh water grew to 5.4 liters over 3 hours, and consumption of current, voltage, and power remained stable.
Consumption Voltage & Water product VS.Tune
9:00 9:01:24 9:15 9:30 9:45 10:00 10:15 10:30 10:45 11:00 11:15 11:30 11:45 12:00
TIME(MIUNTE)
Consumption Current & Water product VS.Time
9:00 9:01:24 9:15 9:30 9:45 10:00 10:15 10:30 10:45 11:00 11:15 11:30 11:45 12:00
TIME(MINUTE)

Consumption Power and Current & Water product VS.Time
11 unit tn r ii
Power (KW)
9:00 9:01:24 9:15
10:00 10:15 10:30 10:45 11:00 11:15 11:30 11:45 12:00
TIME(MINUTE)
Figure 5.5 Voltage, current, and power consumption on August 9 (SeaWater)
The Figure consists of three sections. Voltage consumption was clarified in the first section,


52
while the second section indicates the quantity of current consumption. Moreover, the power consumption ,which is equal to the current multiplied by voltage, is shown in the last section. From the data above, it is clear that voltage and current values were 22.7 V and 16.8 A respectively, which are required to obtain 5.4 liters of fresh water between 9 am -12 pm. The system needed to 382 W to generate the heat required to vaporize the water.
5.3.2 Experimental Measurements for Salt-Water on September 4
In the second part of the experimental study, the experiment was repeated using saltwater instead of seawater on September 4, and the relationship between the solar radiation intensity and time was estimated when the PV panels were tilted at 30. Figure 5.6 shows the experimental measurement of solar radiation intensity on a sunny day. The data shows that solar radiation exceeded zero during the period between 7 am 7 pm, and the highest value of the solar radiation was 860 kW/ m2at 11 am. The behavior of solar radiation during this day can be divided into two intervals. In the first half 7 am 11 pm, solar radiation jumped from 32 to 860 kW/m2 and started to decline after 1 pm until reaching 12 kW/m2 at 7 pm.
(September 4)
time(hr)
Figure 5.6 Hourly solar radiation values on a 30tilted surface on September 4.


53
The power generated by the PV solar panels and power consumed by the heater were measured. Figure 5.7 presents a comparison between the generated power by PV solar panel and power used by the heater on September 4. As shown in Figure 5.7, it is clear that batteries supplied power to the system during the period of 12 6 am because there was no power generated by PV solar panels. However, the PV solar panels started to generate power to the system between the hours of 11 am 3 pm and began to charge the batteries. After 3 pm, the batteries started to supply power to the system. Also, it was noted that the generated power started at zero at 12 am until 6 am, and sharply increased from 20 to 268 W between the hours of 7 9 am, and reached its highest value of 550 W at 11 am. After 3 pm, the generated power decreased until it reached 7W at 7pm.
Figure 5.7 Comparison of generated power and power consumed on September 4 On September 4, experimental measurements were taken for the output of fresh water of the PV solar desalination system. The water used in this experiment was a mixture of 16 liters of pure water and one batch of NaCl. Figure 5.8 illustrates the relationship between the salt-water produced and the ambient temperature over time. From the data shown, it is seen that the


54
desalination process started after 1.26 minutes, and the amount of water produced was 0.005 liter. After 3 hours, the accumulated output of pure water was 5.1 liters, with a constant rate of product equal to approximately 0.028 liters per minute. Moreover, it was observed that ambient temperature increased from 67 F to 79 F between the hours of 9 am 11 am. After that, it decreased to 77F at 12 pm, but this change did not affect the amount of pure water produced because the PV solar desalination system contains batteries that allowed the input power to remain constant.
salt water desalinated
Figure 5.8 Hourly variation of the desalinated water and temperature (salt-water)
The voltage and current consumption were also estimated experimentally on September 9. Figure 5.9 shows the experimental measurements of the voltage, current, and power by the PV solar desalination system in obtaining pure water. The amount of fresh water, voltage and current were measured on September 4. It was noted that the amount of voltage and current was 22.7 V and 16.8 A respectively, the power consumed to operate the system was 382 W. Also, the power, voltage, and the current were stable, and they did not change with the weather.


55
Figure 5.9 Voltage, current, and power consumption on September 4 (salt-water)
5.3.3 Experimental Measurements for Tap Water and Lake Water on October 2 and 28
In the last part of the study, the experiment was repeated using tap water and lake water instead of salt-water on October 2 and 28. The relationship between solar radiation intensity and time was estimated on October 2 when the PV panels were tilted 30 as shown in Figure 5.10. The data presents the experimental measurement of solar radiation intensity on a sunny day. In general, the solar radiation rate in October fell below the rate during August and September. Also, it was noted that the maximum value of solar radiation on October 2 was approximately 758kW/ m2. The amount of solar radiation changed from 0 to 5kW/m2 at 7 am. Afterward, it continued to rise until it reached to the highest value at 2 pm. Then, after 3 pm, the solar radiation intensity decreased until reaching 12 kW/m2 at 6 pm.
On October 28, the experimental measurements of solar radiation intensity were estimated on the cloudy day as shown in Figure 5.11. According to the data on October 28, the values of solar radiation intensity were an instantaneous variable due to the variability in the thickness of cloud layers. Solar radiation intensity increased from 19 to 700 kW/m2 in the morning


56
between the hours of 8 11 am. Due to the clouds in the afternoon, the solar radiation intensity dropped to 623.4 kW/m2 at 12 pm. After that, it increased again at 1 pm. Moreover, due to dense cloud layers, radiation sharply decreased from 260 to 99 kW/m2 at 6 pm.
October 2
Time(hr)
Figure 5.10 Hourly solar radiation values on 30tilted surface on October 2
October 28
Time(hr)
Figure 5.11 Hourly solar radiation values on 30tilted surface on October 28 Additionally, the power generated by PV solar panels and consumed by the heater on


57
October 2 was measured. Figure 5.11 illustrates a comparison between power generated by PV solar panels and consumed by the heater. The power generation rate also fell below the consumption rate during August and September. It was noted that the highest amount of power generated on October 2 was approximately 485 W. From the Figure ,it is clear that the solar desalination system relied entirely on batteries between 12 6 am and 7-11 pm, while generated power started to supply part of power to the system between 7 10 am and 4-6 pm. However, the solar desalination depended only on generated power by the PV solar
panels between 11 am 3 pm.
Figure 5.12 Comparison of generated power and power consumed on October 2 A comparison between power generated by the PV solar panels and power consumed by the heater on October 28 is shown in Figure 5.13. From the Figure, it is seen that the power generated is unstable due to the variability of the cloud layers. The power generated increased sharply in the morning between 8 11 am from 12 to 477 W. Due to the clouds, the generated power decreased to 393W at 12 pm. After that, it increased again at 1 pm.


58
(OCTOBER 28)
500
400
§- 300 a>
| 200 a.
100
0
Power supply from PV
Figure 5.13 Comparison of generated power and power consumed on October 28 Figures 5.14 and Figure 5.15 show experimental measurements of the desalinated tap water and lake water. The amount of pure water and temperature values were measured on October 2 for tap water and on October 28 for the lake water. The quantity of fresh water obtained from the PV solar desalination system was almost the same for both, and the production rate was 0.028 liters per minute for tap water and 0.0282 liters per minute for the lake water. The amount of pure water obtained from tap water was 4.98 liters after 3 hours between 1-4 pm, and 5 liters after the same interval for the lake water. The desalination process for tap water started after 1.23 minutes. The lake water needed the same amount of time to begin the desalination process. Also, Figure 5.14 shows the temperature behavior between the hours of 1 4 pm, and it is clear that the temperature slowly rose from 78 F to
81F.


59
Tap water desalinated
Time(minute)
Figure5.14 Hourly variation of experimental desalinated water yield and temperature (tap water)
Time(minute)
Figure 5.15 Hourly variation of experimental desalinated water yield and temperature (lake water)
To compare the boiling seawater and the tap water, it is clear that the boiling point of fresh water was 212 F and seawater was 214F, but the heat capacity of the seawater was lower than the heat capacity of tap water. The high heat capacity means more resistance to an increasing temperature. However, a lower heat capacity makes raising the temperature level


60
easier. Because the fresh water has a high heat capacity and seawater has less heat capacity, seawater boils faster than fresh water.
To explain this behavior chemically, during the boiling process the positive ions of salt in the seawater attract the negative ions of fresh water and gas is released in the process, producing heat. Every oxygen atom in fresh water is bonded to two hydrogen atoms, and every hydrogen atom is bonded to its oxygen atoms by a shared pair of electrons. When NaCl dissolves in water, the positive parts of atoms in the water attract the negative chloride ions of the salt. Also, the negative molecules attract the positive parts of sodium ions in NaCl. As a result, the presence of salt in the pure water makes the boiling process occur more rapidly. Also, increasing the amount of salt leads to reducing the time that water needs to start boiling.
5.4 Salinity Measurements
Experimental measurements of salinity in seawater, salt-water, lake water, and tap water were taken. A sample of desalinated water from these four types was tested by using an ATC salinity refractometer. The table 5.1 shows the percentage of the saline in seawater, salt- water, lake water, and tap water before and after the desalination process. From these data, it is clear that highest percentage of salt was found in seawater while the tap and lake water have the lowest percentage. Experimental measurements illustrated that the percentage of salt in seawater was approximately 40000 ppm (40 ppt). After many desalination processes, the percentage of salt decreased to less than 5000ppm (5 ppt), while the salinity level for tap and lake water became less than 250 ppm (0.25 ppt) after the desalination
process.


61
Table 5.1 Salinity measurements for seawater, salt-water, tap water, and lake water.
Water type Salinity level before desalination process(ppm) Salinity level before desalination process(ppm)
Tap water 350 >250 Less than 250
Lake water 600 >250 Less than 250
Saltwater 10000 >1000 Less than 1000
Seawater 40,000 Between 5000-1000 (after many processes)
5.5 Theoretical Measurements for the Solar Still System
5.5.1 Input and Output Data of Solar Still Modeling on August 9 When the Water Depth Was 5 cm
The table 5.2 lists the hourly values of solar radiation intensity, wind speed, and ambient temperature on August 9. The water temperature was calculated using a computer program as a function of radiation, wind velocity, and ambient temperature. The variation of these parameters during the day was from 8 am until sunset. From the data, it can be seen that the values of solar radiation increased with time until reaching the highest value around noon, while in the afternoon, solar radiation values decreased. The ambient temperature had almost the same behavior of radiation, but it reached its maximum value around 2 pm and


62
remained stable before slightly dropping at 5 pm. Also, the table indicates the variation of the wind speed during the daylight time. It increases from 11.5 m/h in the early morning to 19.5 m/h by the end of the day. Also, the water temperature increased after 9 am until reaching its maximum values of 54C at 1 pm, then it decreased after 1 pm until reaching 35 C at 5 pm.
Table 5.2 Hourly variation of solar radiation, wind speed, ambient temperature, and water temperature on August 9.
Radiation(kW/mA2) Wind speed(mph) Ambient temperature (C ) Water temperature (C)
274 11.5 23.6 30
475 8.1 29.4 36.81
622.21 3.5 31.1 42.86
828.43 10.4 33.3 50.42
935.5 8.1 33.8 54.88
480 4.6 35 37.74
823.71 3.5 35 50.3
773.228 17.3 35 48.39
706 17.3 35.5 45.96
422.33 19.6 32.7 35.57
Also, the fresh water output was estimated. Figure 5.16 shows the output of fresh water of the still when the water depth was 5 cm. The pure water production rate starts very slowly due to warming of the solar still system and the somewhat low solar radiation intensity during the morning hours. A peak production rate occurred at noon. It sharply dropped at 1 pm, and then dropped steeply between 3 pm and 5 pm until it reached 50 ml.


63
Figure 5.16 Hourly variation of theoretical desalinated water yield on August 9 (5 cm depth)
5.5.2 Input and Output Data of Solar Stills Modeling on October 2 (10 cm water depth)
The solar radiation, wind speed, and ambient temperature were measured experimental on October 2, and the water temperature was calculated numerically. Table 5.3 shows the measurement from 9 am 4 pm.
Table 5.3 Hourly variation of solar radiation, wind speed, ambient temperature, and water temperature on October 2
Radiation(kW/mA2) Wind speed(mph) Ambient temperature (C) Water temperature (C)
320.8 8.1 20 31.7
515 8 21.7 38.79
633 8.1 22.8 42.99
668 13.8 25 44.41
712 9.2 25.5 45.92
758 10.4 26.1 47.59
640.8 3.5 26 43.47
344.7 11.5 27.11 32.61


64
From the data above, it is seen that during a daily desalination operation, the temperature increased until it reached the peak level at 1 pm then decreased in the afternoon. The solar radiation intensity has the highest level around 2 pm ,and the lowest level at 9 am and 5 pm. The behavior of the water temperature was similar to the behavior of the ambient temperature.
The output data of solar still modeling on October 2 when the water depth was 10 cm was also calculated. Figure 5.17 illustrates the theoretical measurement of the solar still system tested on October 2. The amount of pure water was measured, and the output of pure water obtained from the system was unstable between hours of 9 am to 12 pm. It reached its highest level from 1-3 pm. The fresh water production rate gradually grew due to warming of the solar still system and the low solar radiation during the morning hours. After 1 pm, water production remains stable until it reached 310 ml at 3 pm. Between 4- 6 pm the production rate went down until it reached to 80 ml at 6 pm.
* 400 c
0 1 2 3 4 5 6 7
Timefhr)
Figure 5.17 Hourly variation of theoretical desalinated water yield on October 2 (10 cm depth)


65
5-5-3 Input and Output Data of Solar Stills Modeling on October 28 When Water Depth Was 15 cm
Table 5.4 Hourly variation of solar radiation, wind speed, ambient temperature, and water temperature on October 28
Radiation(kw/mA2) Wind speed(mph) Ambient temperature (C) Water temperature (C)
198.5 15 21 27.26
454.8 11.5 25 36.87
699.2 6.9 25.5 45.55
623.4 6.9 27.2 42.75
679.4 3.5 26.7 44.87
550.2 6.9 27.2 40.16
278.4 10.4 27.2 37.49
234 5.8 25 28.57
260 8.1 19.5 29.48
Figure 5.18 Hourly variation of theoretical desalinated water yield on October 28 (15 cm depth)


66
5.6 Comparison Between the Experimental Results and Theoretical Data
5.6.1 Comparison Between the Output Water of PV Solar Desalination System and Solar Still on August 9
The output fresh water from the experimental of the PV solar desalination system and from theoretical of the single slope solar still were tested on August 9 as shown in Figure 5.19. An accumulated output of 5.4 liters of fresh water was obtained by the PV solar desalination system after 3 hours (9am 12 pm). While accumulated output of pure water that produced from solar still was 1.3 liters at the same period. The experimental result shows the water product started after 1.24 minutes. After that, the water production was stable at a rate of 0.03 liters per minute. However, the theoretical data illustrates that fresh water production rate from solar still gradually grew due to warming of the solar still system, and the largest amount of the fresh water has accumulated between hours (1 lam-12pm), and it was approximately 0.35 1 liter.
Output fresh water of PV solar desalination & solar still on August 9
Figure 5.19 Comparison of the output water of PV solar desalination and solar still on August 9


67
5.6.2 Comparison Between the Output Water of PV Solar Desalination System and Solar Still on October 2.
Experimental measurements of PV solar desalination system and theoretical results of solar still of the output of freshwater were compare on October 2. The quantity of fresh water that obtained from the PV solar desalination system was 5 liters after 3 hours between 1-4 pm. During the same period, single slope solar still produced 1.15 liter. Figure 5.20 shows comparison between the output water of PV solar desalination and solar still on October 2.
6 5 34 l_ (D 4' Output fresh water of PV solar desalination & solar still (October 2)

PV solar
(D i_ desalination
Q_ ^ 1 > solar still
0 0:i
00 0:21 0:43 1:04 1:26 1:48 2:09 2:31 2:52 3:14 3:36 3:57 4:19 4:40 5:02 TIME (MINUTE)
Figure 5.20 Comparison of the output water of PV solar desalination and solar still on October 2


68
CHAPTER VI
CONCLUSION AND RECOMMENDATIONS FOR FUTURE WORK
The main aim of this research project is to investigate the feasibility of producing potable water from seawater, saltwater, and brackish water using solar desalination systems. Two type of solar desalination technique was developed experimentally and using computer modelling. Experimental tests were performed on the campus of the University of Denver Colorado. The results showed that:
The accumulated output of freshwater grew to 5.4 liters over 3 hours when sea water was the feed water, and the salinity level decreased from (40000) (>5000) ppm.
When the salt-water was a feed water, an accumulated output of 5.4 liters of fresh water was obtained by the system after 3 hours (9 am 12 pm) on September 4. The amount of salt dropped to less than 250 ppm in the water produced.
When the experiment was repeated using lake water and tap water instead of saltwater on October 2 and 28, the quantity of fresh water that obtained from the PV solar desalination system was almost the same for both, and the production rate was 0.028 liters per minute for lake water and 0.282 liters for the tap water.
The results of run the model for single solar still were:
The output fresh water of the solar still system was unstable. When the depth of the feed water inside the system was 5 cm, a peak production rate was 350 ml.
The highest level of output fresh water of the solar still system was less than 310 ml when the depth of the feed water was 10 cm and 15.
The proposed systems have several advantages:


69
The amount of water produced from PV solar desalination system was stable, and it did not influence with changing weather
The PV solar desalination system can be operated in either a continuous or a batch process mode.
Structuring of PV solar desalination system is not complicated, and it does not require a special supporting structure.
Using solar energy in solar desalination system saves conventional energy sources for other applications
Solar desalination reduces pollution and decreases the emissions that cause environmental deterioration.
However, solar desalination system has some disadvantages, such as PV solar desalination system consumed high electrical power, the water produced by solar still is not constant and a function of solar radiation and ambient temperature.
In general, this research study enhances understanding the performance of solar desalination systems under a range of different conditions and makes a significant contribution to the advancement of knowledge in this area. Also, the performance of PV solar desalination system and the solar still system can be improved significantly if they combine. The water produced will be stable with a low level of power consumption.


70
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[20] J. H. Lienhard IV and J. H. Lienhard V, A Heat Transfer Textbook. Massachusetts: Cambridge, 2001
[21] S. H. Liu, Heat Exchangers Selection, Rating, and Thermal Design. Florida: CRC Press LLC, 2002.
[22] F. Lokiec and A.Ophir, The Mechanical Vapor Compression: 38 Years of Experience, October, 2007
[23] E. Lorenzo, G. Araujo, A. Cuervas, M. Egido, J. Minano, and R. Zilles, "Solar Electricity Engineering of Photovoltaic Systems", Spin: Progensa,1994.
[24] S. Loupasis, 2002. Technical analysis of existing renewable energy sources desalination schemes. Commission of the European Communities Directorate-General for Energy and Transport.
[25] S. A. Maleki, H. Hizam and C. Gomes, Estimation of Hourly, Daily and Monthly Global Solar Radiation on Inclined Surfaces: Models Re-Visited, Energies. January 2017.
[26] The Math Work, Simulink Simulation and Model-Based Design, United States of America: the MathWorks, Inc.
[27] A. May ere, Solar Powered Desalination, University of Nottingham, August 2011
[28] Metcalf & Eddy, Inc. an AECOM Company, Takashi Asano, Franklin Burton and Harold Leverenz: Water Reuse: Issues. Technologies, and Applications. McGraw-Hill Professional, 2007


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[29] T. Pankratz, 2000. Large-scale desalination plants-A drought-proof water supply, International Desalination News. Issue 3-4 (2000) 3-6.
[30] S.M. Peyghambarzade, Forced convection heat transfer in the entrance region of horizontal tube under constant heat flux, World Applied Sciences Journal, vol. 15, pp. 331-338, 2011
[31] J. Raikwar, M. Pandey and A. Gour, Determination of Total Internal Heat Transfer
Coefficient of Single Slope Solar Still with Different Depth of Water, International Journal of Emerging Technology and Advanced Engineering, vol. 3, pp. 2250-2459. December 2013.
[32] M. Schorr, Desalination, Trends and Technologies, Intech, 2011
[33] V. P. Sethi, K. Sumathy, S. Yuvarajan and D. S. Pal, Mathematical model for
computing maximum power output of a PV solar module and experimental validation, Journal of Fundamentals of Renewable Energy and Applications, vol. 2, pp. 5, 2012.
[34] M. Shatat, S. Riffat and M.Worall, Experimental Investigation of a Novel Solar
Powered Psychometric Low Grade Water Desalination System, Institute of Sustainable Energy Technology. vol5, pp. 13-20, 2013.
[35] P. G. Simpson, Induction Heating Coil and System Design, United States of America:
McGraw: Hill Book Company, Inc. 1960
[36] Sumathi, S., Ashok Kumar, and L., Surekha, P., Solar PV and Wind Energy Conversion Systems, Switzerland: Springer International Publishing, 2015.
[37] G. N.Tiwari and H. N. Singh, Solar Distillation, History, Development and Management of Water Resources.
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[42] The World Bank. Web site: http://www.worldbank.org/en/topic/water/overview


73
APPENDIX A
EES PROGRAM (POWER CALCULATIONS)
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EES Ver. 10.097: #3483: For use only by students and faculty, Mechanical Engineering, University of Colorado Denver
lmp=5.86;Voc=64.8;lsc=6.24;n=1 ;q=1.602*10A(-19);K=1.38048*10A(-23);Vmp=56.74
A=1.559*1 046;Pin=1000
K*T/q=38.647
Voc=(q/(n*K*T))/Vocm
W=ln(Vocm+0.72)
FFactual= (Vocm-(W))/(Vocm+1)
FFtheo=(Vmp*lmp)/(Voc*lsc)
Pmaxactual=FFactual*Voc*lsc
MAXeffactual=Pmaxactual/(Pin*A)
Pmaxtheo=FFtheo*Voc*lsc
MAXefftheo=Pmaxtheo/(Pin*A)
POWER=2*eff *A P
Parametric Table: Table 1
eff P POWER
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Run 9 0.196 320.8 205.1
Run 10 0.196 686.3 438.7
Run 11 0.196 892.4 570.5
Run 12 0.196 870.2 556.3
Run 13 0.196 563.4 360.1
Run 14 0.196 663.6 424.2
Run 15 0.196 604.8 386.6
Run 16 0.196 344.7 220.3
Run 17 0.196 97.5 62.33
Run 18 0.196 34.64 22.14
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A=1.559*1.046;Pin=1000
K*T/q=38.647
Voc=(q/{n*K*T))/Vocm
W=ln(Vocm+0.72)
FFactual= (Vocm-{W))/(Vocm+1)
FFtheo=(Vmp*lmp)/(Voc*lsc)
Pmaxactual=FFactual*Voc*lsc
MAXeffactual=Pmaxactual/(Pin*A)
P maxtfi eo=FFtheo*Voc* I sc MAXefftlieo=Pmaxtheo/{Pin*A)
POWER=2*eff *A P
Parametric Table: Table 1
eff p POWER
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Run 2 0.196 0 0
Run 3 0.196 0 0
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Run 5 0.196 0 0
Run 6 0.196 0 0
Run 7 0.196 0 0
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Run 9 0.196 300.3 192
Run 10 0.196 474.2 303.1
Run 11 0.196 731.8 467.8
Run 12 0.196 820.5 524.5
Run 13 0.196 861.9 551
Run 14 0.196 935.7 598.1
Run 15 0.196 811.2 518.6
Run 16 0.196 732 467.9
Run 17 0.196 559.3 357.5
Run 18 0.196 341 218
Run 19 0.196 120.7 77.17
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Run 22 0.196 0 0
Run 23 0.196 0 0
Run 24 0.196 0 0


75
File:C:\Users\prafiles\App Data\Local\Te m ptE ES 2.EES 1/9/2017 3:02:56 PM Page 1
EES Ver. 10.097: #3483: For use only by students and faculty. Mechanical Engineering, University of Colorado Denver
lmp=5.86;Voc=64.8;lsc=6.24;n=1;q=1.602*10A{-19);K=1.38048*10A(-23);Vmp=56.74
A=1.559*1.046;Pin= 1000
K*T/q=38.647
Voc={q/(n*K*T))A/ocin
W=ln(Vocm+0.72)
FFactual= (Vocm-(W))/(Vocm+1)
FFtheo=(Vmp,lmp)/(Voc,lsc)
Pmaxactual=FFactual*Voc*lsc
MAXeffadual=Ptnaxactual/(Pin*A)
Pinaxtheo=FFtfieo*Voc*lsc
MAXefftheo=Pmaxtheo/(PinA)
POWER=2*eff *A P
Parametric Table: Table 1
eff P POWER
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Run 2 0.196 0 0
Run 3 0.196 0 0
Run 4 0.196 0 0
Run 5 0.196 0 0
Run 6 0.196 0 0
Run 7 0.196 0 0
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Run 9 0.196 198.5 126.9
Run 10 0.196 454.8 290.7
Run 11 0.196 699.2 447
Run 12 0.196 623.4 398.5
Run 13 0.196 679.4 434.3
Run 14 0.196 550.2 351.7
Run 15 0.196 278.7 178.2
Run 16 0.196 233.7 149.4
Run 17 0.196 260 166.2
Run 18 0.196 99.82 63.81
Run 19 0.196 0 0
Run 20 0.196 0 0
Run 21 0.196 0 0
Run 22 0.196 0 0
Run 23 0.196 0 0
Run 24 0.196 0 0


76
File:C:\Users\profiles\AppData\Local\Temp\EES 4.EES 1/9/2017 3:04:38 PM Page 1
EES Ver. 10.097: #3483: For use only by students and faculty, Mechanical Engineering, University of Colorado Denver
lmp=5.86;Voc=64.8;ISC=6.24;n= 1 ;q=1.602*10A(-19);K=1.38048*10A(-23);Vmp=56.74
A=1.559*1 046;Pin=1000
K*T/q=38.647
Voc=(q/(n*K*T))/Vocm
W=lrt(Vocm+0.72)
FFactual= (Vocm-{W))/(Vocm+1)
F Ftheo={V mp* I m p )/(Vocl sc)
Pmaxactual=FFactual*Voc*lsc
MAXeffactual=Pmaxactual/(Pin*A)
Pmaxtheo=FFtheo*Voc*lsc
MAXeffttieo=Pmaxtheo/(Pin*A)
POWER=2*eff *A P
Parametric Table: Table 1
eff p POWER
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Run 2 0.1% 0 0
Run 3 0.1% 0 0
Run 4 0.1% 0 0
Run 5 0.1% 0 0
Run 6 0.1% 0 0
Run 7 0.1% 110.8 70.8
Run 8 0.1% 401 256.3
Run 9 0.1% 490 313.2
Run 10 0.1% 554 354.1
Run 11 0.1% 601 384.2
Run 12 0.1% 533 4 341
Run 13 0.1% 663.6 424.2
Run 14 0.1% 604.8 386.6
Run 15 0.1% 244.7 156.4
Run 16 0.1% 77.65 49.64
Run 17 0.1% 2.1 1.342
Run 18 0.1% 99.82 63.81
Run 19 0.1% 0 0
Run 20 0.1% 0 0
Run 21 0.1% 0 0
Run 22 0.1% 0 0
Run 23 0.1% 0 0
Run 24 0.1% 0 0


77
APPENDIX B
ITERATION (WATER TEMPERAUTURE)
October 2
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 320.8 8.1 20 20
2 26.36
3 29.29
4 30.62
5 31.23
6 31.51
7 31.64
8 31.71
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 515 8 21.7 21.7
2 31.04
3 35.3
4 37.23
5 38.11
6 38.51
7 38.7
8 38.79


78
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 633 8.1 22.8 22.8
2 33.9
3 38.96
4 41.25
5 42.29
6 42.77
7 42.99
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 668 13.8 25 25
2 35.61
3 40.45
4 42.64
5 43.64
6 44.1
7 44.31
8 44.41


79
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 111 9.2 25.5 25.5
2 36.72
3 41.82
4 44.15
5 45.21
6 45.69
7 45.92
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 758 10.4 26.1 26.1
2 37.91
3 43.29
4 45.73
5 46.84
6 47.35
7 47.59


80
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 640.8 3.5 26 26
2 35.53
3 39.88
4 41.86
5 42.76
6 43.18
7 43.38
8 43.47
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 344.7 11.5 27.11 27.11
2 30.15
3 31.54
4 32.18
5 32.47
6 32.61


81
August 9
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 274 11.5 23.6 23.6
2 27.14
3 28.77
4 29.52
5 29.87
6 30.03
7 30.11
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 457 8.1 29.4 29.4
2 33.45
3 35.29
4 36.13
5 36.52
6 36.69
7 36.77
8 36.81


82
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 622.21 3.5 31.1 31.1
2 37.52
3 40.45
4 41.78
5 42.38
6 42.66
7 42.78
8 42.84
9 42.86
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 828.43 10.4 33.3 33.3
2 42.65
3 46.9
4 48.83
5 49.7
6 50.1
7 50.28
8 50.36
9 50.40
10 50.42


83

Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 935.5 8.1 33.8 33.8
2 45.01
3 50.11
4 52.42
5 53.46
6 53.94
7 54.82
8 54.88
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 480 4.6 35 36.49
2 35
3 37.18
4 37.49
5 37.64
6 37.71
7 37.74


84
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 823.71 3.5 35 35
2 43.34
3 47.14
4 48.86
5 49.64
6 50
7 50.16
8 50.24
9 50.28
10 50.3
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 773.228 17.3 35 35
2 42.33
3 45.67
4 47.19
5 47.87
6 48.18
7 48.32
8 48.39


85
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 706 17.3 35.5 35.5
2 41.22
3 43.84
4 45.02
5 45.56
6 45.8
7 45.91
8 45.96
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 422.33 19.6 32.7 32.7
2 34.28
3 35.01
4 35.34
5 35.5
6 35.57


86
October 28
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 198.5 15 21 21
2 24.42
3 25.98
4 26.69
5 27.01
6 27.16
7 27.23
8 21.26
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 454.8 11 25 25
2 31.35
3 34.25
4 35.57
5 36.17
6 36.45
7 36.58
8 36.64
9 36.67


87
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 699.2 6.9 25.5 25.5
2 36.47
3 41.46
4 43.73
5 44.76
6 45.24
7 45.45
8 45.55
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 623.4 6.9 27.2 27.2
2 35.75
3 39.64
4 41.4
5 42.21
6 42.58
7 42.75


88
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 679.4 3.5 26.7 26.7
2 36.63
3 41.15
4 43.21
5 44.15
6 44.58
7 44.78
8 44.87
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 550.2 6.9 27.2 27.2
2 34.28
3 37.52
4 38.99
5 39.66
6 39.96
7 40.1
8 40.16


89
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 478.7 10.4 27.2 27.2
2 32.85
3 35.34
4 36.56
5 37.12
6 37.38
7 37.49
Iteration no. Radiation Wind speed Ambient temperature Water temperature
1 234 5.8 25 25
2 26.97
3 27.88
4 28.29
5 28.48
6 28.57


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DISS_title EXPERIMENTAL AND THEORTICAL STUDY OF A SOLAR DESALINATION SYSTEM
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DISS_para An innovative new concept of a solar water desalination system that uses PV panels and batteries was developed. The concept utilizes solar cells to collect solar radiation and uses them as an electrical source to supply power to the system thereby raising its efficiency. Batteries are also used in the proposed system to provide a stable power supply to the system as well as to store the energy supplied by solar cells. The battery gives continuity to the process in times when the system lacks solar energy. The system was constructed in three parts: electrical, thermal, and condensation. The uniqueness of this concept is that the PV solar panels and batteries create a stable desalination system for the production of fresh water and provides a higher rate of pure water production compared to thermal systems.
Additionally, in this research, Matlab Simulink was used to model a single slope solar still, and the model was composed of four groups. Fifteen equations were utilized in the simulation process, and they represent the second and third groups in the modeling, while part one and four are the input and output data. The input data includes the solar radiation intensity, water temperature, glass temperature data, and the depth of the salt-water inside the solar still. The output was the production of pure water.
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PAGE 1

EXPERIMENTAL AND THEORTICAL STUDY OF A SOLAR DESALINATION SYSTEM by HUSSEIN ABDULHASAN ABBOOD B.S., University of Basrah, 2007 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the re quirements for the degree of Master of Science Mechanical Engineering Program 2017

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ii 2017 HUSSEIN ABDULHASAN ABBOOD ALL RIGHTS RESERVED

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iii This thesis for the Master of Science degree by Hussein Abdulhasan Abbood has been approved fo r the Mechanical Engineering Program B y Peter Jenkins, Chair Kannan Premnath Maryam Darbeheshti Date: May 13, 2017

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iv Abbood, Hussein Abdulhasan (M.S., Mechanical Engineering Progr am ) Experimental and Theoretical Study of a Solar Desalination System Thesis directed by Professor Peter Jenkins ABSTRACT An innovative new concept of a solar water desalination system that uses PV panels and batteries was developed. The concept utilizes solar cells to collect solar radiation and uses them as an electrical source to supply power to the system thereby raising its efficiency. Batteries are also used in the proposed system to provide a stable power supply to the system as well as to store the energy supplied by solar cells. The battery gives continuity to the process in times when the system lacks solar energy. The system was constructed in three parts: electrical, thermal, and condensation. The uniqueness of this concept is that the PV solar panels and batteries create a stable desalination system for the production of fresh water and provides a higher rate of pure water production compared to thermal systems Additionally, in this research, M atlab Simulink was used to model a single slope sol ar still, and the model was composed of four groups. Fifteen equations were utilized in the simulation process, and they represent the second and third groups in the modeling, while part one and four are the input and output data. The input data includes t he solar radiation intensity, water temperature, glass temperature data, and the depth of the salt water inside the solar still. The output was the production of pure water. The form and content of this abstract are approved. I recomme nd its publication. Approved: Peter Jenkins

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v T ABLE OF CONTENTS C HAPTER I NTRODUCTION ................................ ................................ ................................ ............... 1 B ACKGROUND, O BJECTIVES OF THE S TUDY AND S COPE OF W ORK ................ 4 2.1 Water ................................ ................................ ................................ ............................ 4 2.2 Water Salinity ................................ ................................ ................................ ............... 5 2.3 Desalination ................................ ................................ ................................ .................. 6 2.4 Desalination Technologies ................................ ................................ ........................... 8 2.4.1 Thermal P rocesses and M embrane P rocesses ................................ ....................... 9 2.4.1.1 Multi St age Flash D esalination (MSF) ................................ .......................... 9 2.4.1.2 Multi Effect Boiling (MEB) P rocess ................................ ............................ 10 2.4.1.3 Vapor C ompression (VC) ................................ ................................ ............ 11 2.4.1.4 Re verse O smosis (RO) ................................ ................................ ................. 1 1 2.4.1.5 Electrodialysis (ED) ................................ ................................ ..................... 1 2 2.4 .1.6 Electrodialysis R eversal (EDR) ................................ ................................ 1 3 2.5 Solar Radiation ................................ ................................ ................................ ............ 13 2.5.1 Solar Radiation Intensity on the H orizonta l and Inclined S urfaces ...................... 13 2.5.2 Photovoltaic Solar Panels and the Method to Generate Power Using Solar C ells ................................ ................................ ................................ ...................... 1 5 2.6 Solar Desalination P rocesses ................................ ................................ ........................ 1 6 2.7 Objectives of T his Research ................................ ................................ ........................ 1 7 2.8 Scope of Work ................................ ................................ ................................ .............. 1 8

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vi S OLAR D ESALINATION S YSTEM D ESIGN ................................ ................................ 19 3.1 Description and Operating Principle of the Proposed System ................................ ....... 19 3.2 System Design ................................ ................................ ................................ ............... 2 0 3.2.1 PV P anels ................................ ................................ ................................ ............... 2 0 3.2.2 Batteries and Charge C ontroller ................................ ................................ ............. 2 3 3.2.3 Coil Heater and Copper P ipe ................................ ................................ ................. 2 4 3.2.4 Description of the Heat Transfer Equation Between the Coil H e ater and the C opper T ube ................................ ................................ ................................ ......... 2 4 3.2.5 Measuring D evices ................................ ................................ ................................ 2 6 3.3 Description Modeling of Single Slope Solar Still Using Matlab 6 3.3.1 Description of Part 1 and Part 2 in the M odeling ................................ .................. 2 7 3.3.2 Input and O utp ut Data for M odeling ................................ ................................ ..... 29 3.4 Algorithm Flow Chart to Calculate the Water Pr oduction ................................ ............ 3 1 T HERMAL ANALYSIS ................................ ................................ ................................ .... 3 2 4.1 Theoretical Analysis of PV Solar Desalination System ................................ ................ 3 2 4.1.1 Radiation Heat T ransfer B etween the C oil H eater and O uter P ipe W all ............... 3 2 4.1.2 Conduction H eat T ransfer B etween O uter T ube W all and I nner T ube W all ......... 3 4 4.1 .3 Convection H eat T ransfer B etween the W ater S urface and I nner P ipe W all ......... 3 5 4.1.4 Heat T ransfer B etween the C old W ater and the S team I nside the P ipe ................. 37 4.1.5 Heat T ransfer B etween the C opper T ube and A ir ................................ .................. 39 4.2 Theoretical Analysis of Solar S till ................................ ................................ ................. 39 4.3.1 The E nergy B alance for G lass C over ................................ ................................ ..... 4 0 4.3.2 The H eat B alance of the B ottom and S ides of the B asin ................................ ....... 4 3

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vii 4.3.3 The E quations of E n ergy B alance on the W ater S urface I nside the B asin ............ 4 5 R ESULTS AND DISCUSSION ................................ ................................ ....................... 47 5.1 Experimental Location ................................ ................................ ................................ .. 47 5.2 Method to Obtain Measurements ................................ ................................ .................. 47 5.3 Results Obtained from Measurements ................................ ................................ .......... 48 5.3.1 Experimental M easurements for S eawater on August 9 ................................ ........ 48 5.3.2 Experimental M easurements for S alt w ater on Sep tember 4 ................................ 5 2 5.3.3 Experimental M easurements for T ap water and L ake water on October 2 and 28 ................................ ................................ ................................ ............................ 5 5 5.4 Salinity Measurements ................................ ................................ ................................ ... 6 0 5.5 Theoretical Measurements for the Solar Still System ................................ .................... 6 1 5.5.1 Input and O utput D ata of S olar S tills M odeling on Aug ust 9 W hen the W ater D epth W as 5 cm ................................ ................................ ................................ ...... 6 1 5.5.2 Input and O utput D ata of S olar S tills M odeling on October 2 W hen the W ater D epth W as 10 cm ................................ ................................ ................................ .... 6 3 5.5.3 Input and O utput D ata of S olar S tills M odeling on October 28 W hen the W ater D epth Was 15 cm ................................ ................................ ................................ .... 6 5 5.6 Comp arison Between the Experimental Results and Theoretical Data ........................ 6 6 5.6.1 Comparison B etween the Output Water of PV Solar Desalination System and Solar Still on August 9 ................................ ................................ ........................... 6 6 5.6.2 Comparison B etween the Output Water of PV Solar Desalination Sy stem and Solar Still on October 2 ................................ ................................ ........................... 6 7 C ONCLUSION AND R ECOMMENDATION OF F UTURE WORK .............................. 6 8

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viii B IBLIOGRAPHY 70 A PPENDI X A EES PROGRAM (POWER CALCULATION) .............. 3 B ITERATIONS ( WATER TEMPERATURE) ... 7 7

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ix L IST OF TABLES T ABLE 2.1 Percentage of wate r resources across the globe ................................ ................................ .. 4 2.2 Composition of seawater with salinity of 36000ppm ................................ .......................... 6 2.3 Water desalination categories ................................ ................................ .............................. 9 2.4 I ndirect solar desalination system ................................ ................................ ...................... 1 7 5.1 Salinity measurement s for seawater, salt w ater, tap water and lake w ater ....................... 6 1 5.2 Hourl y variation of solar radiation, wind speed, ambient temperature, and water temperature on A ugust 9 ................................ ................................ ................................ .......... 6 2 5.3 Hourly variation of solar radiation, wind speed, ambient temperature, and water temperature on October 2 ................................ ................................ ................................ ......... 6 3 5.4 Hourly variation of solar radiation, w ind speed, ambient temperature, and water temperature on October 28 ................................ ................................ ................................ ....... 6 5

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x L IST OF FIGURES F IGURE 2.1 Global installed capacities of desalination ................................ ................................ ........... 8 2.2 Multi stage flash desalination (MSF) process ................................ ................................ ... 10 2.3 Diagram of a multi effect boiling (MEB) proc ess ................................ ............................. 11 2.4 Schematic diagram of a reverse osmosis process ................................ .............................. 12 2.5 Direct radiation incident on the horizontal and inclined surfaces ................................ ...... 1 5 3.1 Schematic of the proposed system ................................ ................................ ..................... 2 0 3.2 A PV solar panel ................................ ................................ ................................ ................ 2 1 3.3 Mix ed connection of batteries to generate 12 V and 24 V ................................ ................ 2 4 3.4 Schematic of modeling the single slope solar sill ................................ .............................. 2 7 3.5 Schematic of part 1 for the m odeling ................................ ................................ ................. 2 8 3.6 Schematic of part 2 for the modeling ................................ ................................ ................. 29 3.7 EES program to calculate the water and glass t emperature ................................ ............... 3 0 4.1 Schematic of the heat transfer in the whole system ................................ ........................... 3 2 4.2 Heat transfer between the coil heater and copper tube ................................ ...................... 3 3 4.3 Heat transfer between the outer wall and inner wall of the copper tube ............................ 3 4 4. 4 Heat transfer between cold water and vapor ................................ ................................ ...... 37 4. 5 Heat t ransfer between the vapor inside the copp er tube and air ................................ ........ 39 4. 6 Energy balances for the whole solar still ................................ ................................ ........... 4 0 4. 7 Energy balance for glass cover ................................ ................................ .......................... 4 1 4. 8 Energy balance for the bottom and side basin ................................ ................................ ... 4 4 4. 9 Energy balance for s eawater i nterface ................................ ................................ ............... 4 5

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xi 5.1 Image of the location of the Boulder Creek Buildi ng University of Colorado Denver campus ................................ ................................ ................................ ................................ ..... 47 5.2 Hourly solar radiation values on a 30 o tilted surface on August 9 ................................ .... 49 5.3 Comparison of the generated power and power consumed on August 9 ........................... 5 0 5.4 Hourly variation of the experimental desalinated water yield a nd ambient temperature (seawater) ................................ ................................ ................................ ........................... 5 1 5.5 Voltage, current, and p ower consumption on August 9 (s eawater) ................................ .. 5 1 5.6 Hourly solar radiation values on a 30 o tilted surface on September 4 .............................. 5 2 5.7 Comparison of generated power and power consumed on September 4 ........................... 5 3 5.8 Hourly variation of the desalinated water and temperature (salt water ) ........................... 5 4 5.9 Voltage, current, and power c onsumption on September 4 ( s alt w ater) .......................... 5 5 5.10 Hourly solar radiation values on 3 tilted surface on October 2 ................................ ..... 5 6 5. 11 Hourly solar rad iation values on 3 tilted surface on October 28 ................................ ... 56 5.12 Comparison of generated power and power consumed on October 2 ............................. 57 5.13 Comparison of generated power and power consumed on October 28 ........................... 58 5.14 Hourly variation of experimental desalinated water yield and temperature ( t ap water) 59 5.15 Hourly variation of experimental desalinated water yield and temperature ( lake water) ................................ ................................ ................................ ............................. 59 5.16 Hourly variation of theoretical desalinated water yield on August 9 (5 cm depth) ........ 6 3 5.17 Hourly variation of theoretical d esalinated water yield on October 2 (10 cm depth) ..... 6 4 5.18 Hourly variation of theoretical desalinated water yield on October 28 (15 cm depth) ... 65 5.19 Comparison of the o utput w ater of PV s olar d esalination and s olar still on August 9 ... 6 6 5. 20 Comparison of the o utput w ater of PV s olar d esalination and s olar still on October 2 .. 6 7

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1 CHAPTER I NTRODUCTION Currently, fresh water shortage is predicted to be the biggest problem of the world due to unsustainable water consumption rates and population growth. The Uni ted Nations Environment Programm e nations with insufficient fresh water to support the population and, by 2025, two thirds of the world population The scarcit y of pure water has become a major issue in several countries around the world. According to the World Bank, there are about eighty countries today that have water shortages that threaten the health and economies population live in arid, remote areas and islands, and have no access to fresh water [42] In developing nations and in the Middle East there are approximately 3 billion people who have no access to potable water sources, and approximately 1.76 billion p eople live in regions already facing a severe shortage of fresh water [34]. Water covers 70% of the earth surface and t he total amount of the global water reserves are approximately 1.4 billion cubic meters of water Ocean wate r is estimated to be more than 97% from the total water reserves w hile 2.5% is fresh water on the surface of the earth Rivers and lakes are the main sources of the fresh water, and it also exists in the atmosphere, as polar ice, and as groundwater [37] The pollution of rivers la kes and underg round water by industrial waste has increased the problem I n many countries around the world, the purity of river s and lakes is threatened by overuse and pollution. R ivers and lake water are often no longer able to provide the pure water th at people need while the impact of pests and diseases is increasing

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2 Moreover, powerful underground pumping (fracking) and long distance piping are depleting groundwater aquifers well beyond sustainable recovery levels I n many cases this convert s clean water to brackish water with high concentrations of dangerous minerals which result in health problems. Besides the prob lems of water shortage and pollution, providing energy to desalinate water constitutes another challenge The water desalination proce ss requires the consumption of a large amount of energy. It was calculated that the production of 1 million m3/day of fresh water needs 10 million tons of oil per year [ 15 ]. T herefore many developing countries suffer from lack of fresh water due to fuel c osts and poor infrastructure [34 ]. Furthermore most of the current desalination systems depend on conventional technologies which produce large amounts of waste and greenhouse ga sses. They also cause environmental degradation and increase pollution in th e atmosphere. Renewable energy sources, such as solar energy and wind energy, h ave gained more attraction for use in desalination plants due to their ability to save conventional energy for other applications, reduce environmental pollution, and provide lo w maintenance Solar energy systems can be classified into two main types : thermal systems and photovoltaic system s. The s olar thermal system uses solar radiation to provide heat and uses solar collectors to harness the solar ene rgy. The solar collector a bsorbs solar radiation through a heat transfer medium and converts it into useful energy. The Photovoltai c (PV) desalination system converts solar radiation directly into electricity and it has a higher effic iency when compared to thermal systems The pro posed system in this research deals with the thermal solar water desalination system, a nd presents a desalination system that uses non tradit ional and innovative technology.

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3 This thesis is organized as follows. Chapter 2 provides background information abo ut desalination objectives of this research, and the scope of w ork Chapter 3 describes the design of the solar desalination system and the operating p rinciple of the proposed system an d provides the description for m odeling of singl e slope solar still. C hapter 4 shows the thermal analysis for every component in a PV solar and solar still system. Chapter 5 shows the experimental and theoretical data for the production of pure water in four days from the solar desalination system. Finally, chapter 6 provide s conclusions and recommendations for future work in this area

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4 C HAPTER B ACKGROUND O BJECTIVES OF T HIS R ESEARCH AND SCOPE OF WORK 2.1 Water Water has unique chemical properties regarded as a part of the cycle and balance of life. Organisms n eed water for survival 70% water, but only 2.5% is considered fresh water, and 80% of that fresh water is frozen in the ice caps of mountains or in the form of soil moisture [7]. Water resources, volume, and percentage of water reso urces Table 2.1. Table 2.1 Percentage of water reso urces across the globe. Historically, rivers and lakes were the main sources of water that humans used. In recent history, aquifers have become one of those sources However, with the growing human population, the demand for fresh water has increased dram atically According to the US Census Bureau, the population has grown from 3 billion to 6 billion between No. Resource Volume Fresh water percent Total water percentage 1 Atmospherics 12,900 0.001 0.01 2 Glaciers 24,064,000 1.72 68.7 3 Ground Ice 300,000 0.021 0.86 4 Rivers 2,120 0.0002 0.006 5 Lakes 176,400 0.013 0.26 6 Marshes 11,470 0.0008 0.03 7 Soil Moisture 16,500 0.0012 0.05 8 Aquifers 10,530,000 0.75 30.1 9 Lithosphere 23,400,000 1.68 10 Ocean 1,338,000,000 95.81 Total 1,396,513,390

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5 1960 2000, and it will reach 9 billion in 2045[38]. The population has already grown rapidly, and the consumption of fresh water has increas ed while the a mount of fresh water has remained constant Therefore, the world is suffering from a shortage of fresh water, and this shortage is expected to increase in the future. Today, water shortage is estimated at approximately 40% and could grow to 6 0% by 2025[7]. Population growth is not the only reason for water shortage. It can be attributed to changes in lifestyle, an increase in economic processes, and human activities. United States Geological Survey shows that the water consumption rate in the United States in 2010 is 306,000 million gallons per day fresh water and 48,300 million ga llons per day saline water [41]. Today, many countries suffer from water shortages that threaten their health and economies while clean water is unaccessible remote areas and islands[42]. 2.2 Water Salinity Water is classified based on salinity into three groups. The first group has a salinity range of 0.005 1 ppt. This group includes water that is safe to drink, me ets household requirements and is used in some industrial applications [7]. The main sources of this type of water are rivers and lakes, or it can be generated by desalination In fact, in desalination plants, the percentage of water salinity never exceeds 0.005 ppt [7]. There are many uses for this type of water such as dairy, food, cooling, washing, and cleaning. Additionally, the low salinity level is used for ion exchangers that operate using desalinated water. Also, boilers and heat exchangers in indus trial applications need less stringent water quality to operate [7]. Water that contains a salinity range of 1 3ppt falls within the scope of the second group of water, and it is suitable for irrigation and industrial cooling. The third group of

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6 water tha t is above 10 ppt, and it is called high salinity water. Seawater, which has a salinity range of 30 50ppt, is considered the largest source of the third water category. The average salinity of seawater is 34ppt, which varies depending on local ambient an d topographical conditions [7]. Seawater is a mixture of water, dissolved salts and minerals. The composition of seawater is shown in Table 2.2. Seawater also contains other suspended materials, such as sand, clay, microorganisms, viruses, and colloidal ma tter, and their size ranges from Table 2.2 Composition of seawater with salinity of 36000ppm 2. 3 Desalination De salination is the process of separating the dissolved salts and minerals from the fresh water. Desalination processes are used in many applications, such as municipal, industrial, and commercial. Up until 1800, single stage stills that were used for water desalination were operated in the batch mode, and cook stoves or furnaces supplied the energy without recovering the heat of condensation. The real beginning of water desalination Compound Composition Mass Percent Ppm Chloride Cl 55.03 19,810.80 Sodium Na 30.61 11,019.60 Sulfate (SO4) 7.68 2,764.80 Magnesium Mg 3.69 1,328.40 Calcium Ca 1.16 417.6 Potassium K 1.16 417.6 Carbonic Acid (CO3) 0.41 147.6 Bromine Br 0.19 68.4 Boric Acid H3BO3 0.07 25.2 Strontium Sr 0.04 14.4 Total 100 36,000

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7 was at the beginning of the twentieth century [7]. In 1912, a six effect d esalination water plant was built in Egypt with a capacity of 75 m/d. When the oil industry started during the period of 1929 1937, the total production capacity of water desalination increased [7]. During World War II, pure water supplies were limited a nd there was a significant effort to convert salt water into clean Act and it provided federal support to develop water desalination processes The i nitial development of technology for water desal ination processes was between the 1950s and 1960s when the U.S. Department of the Interior, through the Office of Saline Water (OSW), provided funding. In 1961, the first modern desalination plant was built in Texas [17]. With technological advancements, desalination processes have come to play a significant role in meeting the growing population needs. However, water conservation has become one of the requirements of modern life. Many communities around the world entirely rely on desalinated water, and this is one of the main reasons for the survival of these countries. So, there are significant efforts to encourage people to conserve water before turning to desalination. There are different methods of water desalination used in various countries, and t hey depend on desalination sources and the geological region of the country. It has been observed that 48% of the global desalination production takes place in the Middle East. It is mostly concentrated in Gulf countries, while the US occupies second place with 19%. Asia, Europe, and Africa have 14%, 14% and 6% of global desalination production respectively [19]. Furthermore, over the past decade the number of desalination plants has increased almost twice much as their total capacity [19]. In general, wat er desalination capacity grew approximately twenty percent every year from 1972 1999, and over 8,600 desalination plants had been built around the world (40). Figure

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8 2.1 describes the desalination production capacity which exceeded 65 million m per day in 2008. It also shows the capacity of desalination plants continuously grew until reaching approximately 130 million m per day in 2016 [16]. Figure 2.1 Global installed capacities of desalination 2.4 Desalination Technologies Desalination can be classified into two major categories: thermal and membrane. Thermal technology is based on the natural water processes of desalination and often involves heat transfer, while membr ane technology is based on filtration through a membrane and often uses electricity as an energy source. Total dissolved solids of water produced by thermal technology are estimated at approximately 20ppm while, with membrane technology, around 100 500 ppm [18]. Within these two main types, there are sub categories as shown in Table 2.3, and they use various techniques to desalinate water. There are other desalination technologies, but they are either not very common or are currently under research. The ov erall capacity of both thermal and membrane technology is estimated to be 7 billion gallons per day ( bgd ) at the beginning of 2000, with each contributing 50% of the total

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9 capacity [40]. Table 2.3 Water desalination categories 2.4.1 Thermal P rocesses and M embrane P rocesse s The thermal desalination process includes multi stage flash (MSF), multi effect evaporation (MEE) and vapor compression (VC). Currently, almost all multi effect evaporation processes are combined with vapor compression technologies. Membrane processes co ver Reverse Osmosis (RO), Electrodialysis reversal (EDR), and Electrodialysis (ED). 2.4. 1. 1 Multi Stage Flash D esalination (MSF) Today, Multi Stage Flash Desalination has become the most common technique for desalinating water and it uses a brine heater th at heats and pressurizes salt water, and the hot water flows into chambers or stages. The saltwater flashes and converts to vapor due to lower pressure in the stage. Seawater passes from one stage to another and the flashings are repeated without additiona l energy consumption Flashing converts seawater to vapor and heat exchangers in each stage condenses the vapor and converts it to fresh water. The number of stages of a Multistage Flash Desalination process range from 4 40, and it operates at Thermal Technolog y Membrane Technology Multi Stage Flash Distillation (MSF) Electrodialysis (ED) Multi Effect Distillation (MED) Electrodialysis reversal (EDR) Vapor Compression Distillation (VCD) Reverse Osmosis (RO)

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10 temperatur es ranging from100 110 C to produce 6 11kg of desalinated water per kg of steam applied [29]. The life span of a MSF is expected to be 12 40 years [24]. The maximum temperature level for Multi Stage Flash Desalination is limited by the levels of salini ty in the water to avoid scaling, and this limits the performance of this technology. A key design feature of Multistage Flash Desalination systems is bulk liquid boiling which alleviates problems with scale formation on the heat transfer tubes [32]. Figu re 2.2 illustrates a Multi Stage Flash Desalination process. vacuum Solar collector sea water D esalinate demisters Flow down Figure 2.2 Multi stage flash desalination (MSF) process 2.4. 1. 2 Multi Effect Bo iling (MEB) P rocess The principles of the multi effect boiling process are based on evaporation and condensation at different stages. In this technology, steam is condensed in one of the stages, and the heat loss is used to heat salt water in t he next stage and is then converted to vapor Seawater passes through multiple stages of boiling without requiring additional energy. The preheated steam from the boiler is fed into a series of tubes, and the vapor heats the tube and acts as a heat exchan ger to evaporate incoming seawater from another channel. After that, the vapor is condensed into pure water. The system includes heat exchangers instead of a solar collector or heater, and it is used to preheat the feed water. Figure 2.3 described the Mult i

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11 effect boiling process. vacuum Solar collector Flow down Sea water Desalinate Figure 2.3 Diagram of a multi effect boiling (MEB) process 2.4. 1. 3 Vapor C ompression (VC) One of the main advantages of the VC technology is that it does not require an e xternal heat source Vapor Compression technology has a similar operating principle to Multi effect boiling except that this method generates heat. In VC technology, compression provides heat to vaporize the water while in MEB technology, a boiler heats th e salt water and converts it to vapor. Vapor Compression units are often built as relatively small units, and their capacity ranges from a few liters up to 3000m per day [22]. 2.4. 1. 4 Reverse O smosis (RO) Membrane technology (Reverse Osmosis t echnology) is the fastest growing technology of all water desalination processes. Reverse osmosis technology uses pressure to force seawater through a membrane, and that results in obtaining pure water by separating the salt. In Reverse Osmosis, heating or phase changes are not required and there is no energy consumption for heating. However, energy is needed to pressurize the feed water to pressure needed to convert sea water to fresh

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12 water ranges from 50 80 bars, while brackish water requires 10 25 bars. Most of Reverse Osmosis systems use turbines that recover most of the consumed energy. The energy required to desalinate sea water is 5 kWh/m, while brackish water needs 3kWh/m [27]. The cost of building Reverse Osmosis plants is low. Figure 2.4 shows a RO. P ump Membrane Assembly Pre treatment P ost treatment Salt water F resh w ater T urbine Brine Figure 2.4 Schematic diagram of a reverse osmosis process [27] However, maintenance costs are high due to the cost of membrane replacement and the parts used for energy generation. Also, the system requires intensive pre/post treatment. The capacity of Reverse Osmosis systems ranges from 0.5m per day for a small system to 330,000m per day for the largest plant [27] 2.4. 1. 5 Electrodialysis (ED) In the early 1950s, the first Electrodi alysis system was introduced commercially, and this was ten years before the design of Reverse Osmosis [27]. The operation of Electrodialysis technology systems is based on an electrical potential to move salts selectively through a membrane and obtain pur e water from seawater The higher salinity in the feed water consumes a greater amount of electrical energy and has a higher cost The average energy consumption to produce fresh water with 500 ppm is about 1.5 4 kWh/m when the salinity level of the fee d water ranges from 1500 3500 ppm [24]. Figure 2.4 shows the ED system. The ED design has a high cost if it used for seawater desalination, and it does not have a barrier effect against microbiological contamination. Therefore, it is more

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13 appropriate for brackish water. The capacity of Electrodialysis ranges from 1m per day for the small system to 220.000 m for the largest ED plant. 2.4. 1. 6 Electrodialysis R eversal (EDR) In the early 1970s, the EDR desalination system was introduced Electro dialysis reversal system is based on the same principle that ED technology uses, except that both the product and concentrate channels are identical in construction. Also, the same membranes are used to provide a continuous self cleaning ED process that u ses periodic reversal of the DC polarity to allow systems to run at high recovery rates. [28] 2.5 Solar Radiation 2.5.1 Solar Radiation Intensity on the Horizontal and Inclined S urfaces The intensity of solar radiation that falls on the earth 's surface depends on the surface orientation and its inclination Although surfaces that are perpendicular to the sun's rays receive the largest amount of sun radiation, the processes to track the sun are often expensive and impractical. As a result, the most appropriate solution is using inclined solar panels. Thus, it was essential to calculate the incident of solar radiation on the inclined surfaces [28]. Figure 2.5 shows the direct radiation that falls on horizontal and inclined panels surfaces. The i n tensity of the incident of solar radiation on the earth's surface on a clear day can be expressed in the following relationship [6], (2.1) Where is the solar constant (1367 W/m2), is the latitude, the angular location either north or south of the equator is the declination and represents the angular position of the sun at solar noon. is the hour angle which is the angular displacement of the sun east

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14 or west of the local meridian due to rotation of the earth on its axis at 15 per hour, with morning negative and afternoon positive. The daily theoretical solar radiation on a horizontal surface is obtained by [25], (2.2) In locations that often have a clear and dry atmosphere (high places or arid regions), the results from the previous relationship m ust be multiplied by the C factor. Similarly, in places that frequently have cloudy and wet weather, the C factor should be calculated when the amount of solar radiation incident is estimated Incident solar radiation on the inclined surface con sists of three components: beam, diffuse, and ground reflected radiation [25] (2.3) is the daily beam radiation on an inclined surface, is the daily diffuse radiation on an inclined surface, and is the daily reflected radiation on an inclined surface. The daily beam radiation can be estimated as, (2.4) The diffuse component includes three subcomponents: Isotropic, which is received uniformly from all of the sky dome, C ircumsolar diffuse which results from forward scattering of solar radiation and is concentrated on the part of the sky around the sun, and the third part is concentrated near the horizon and is large in clear skies Thus, the daily solar radiation inciden t on inclined surfaces is given in the following relationship [6]: (2.5)

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15 The Hourly solar radiation incident on inclined surfaces is given in the following relationship [6]: (2.6) H dir, k H dir, h H dir, s k z Figure 2.5 Direct radiation incident on the horizontal and inclined surfaces The Monthly solar radiation incident on inclined surfaces is given in the following relationship (2.7) Where is the month ly average daily geometric factor, and it is calculated by [6], (2.8) 2.5.1 Photovoltaic Solar P anels and the Method to Generate Power U sing Solar C ells PV cells are one of the best methods to convert solar energy into electrical energy. This method has several advantages compared with the thermodynamic method, such as high

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16 reliability, different sizes and a variety of uses, and they can be composed of independent parts with productivity equal to the whole PV solar panel. Additionally, the design that uses this method is simpler th an other methods because it includes portable panels which make it possible to reduce panels and sometimes dispense maintenance entirely. Solar radiation passes through the surface of the cells when the sunlight falls on a PV panel. Part of i t is absorbed by the first cell layer, which contains phosphorus, while the majority of the incident solar radiation is absorbed by the layer that includes silicone mixture with Boron This process generates a free movement of electrons, and the free elec trons flow through the electrical connector in cells. DC power will be generated and an electrical load can be connected to the cell. Moreover, the movement of electrons increases with the increasing intensity of the incident solar radiation on the cell. Therefore, PV solar panels are directed at a suitably tilted angle to face the sun so that solar radiation falls vertically on it [23]. 2.6 Solar Desalination P rocesses One of the applications of solar energy is providing the required energy for a water desalination process either in the form of thermal or electric energy. Using solar energy in water desalination processes reduces the cost required to convert salt water to drinkable water. Solar desalination processes can be categorized into two main parts indirect solar desalination systems and direct solar desalination systems. Indirect systems require two separate subsystems. A collector used to collect solar energy and a system that uses the collected solar energy to produce pure water [10 ]. The indirect desalination system has been subjected to several analytical and experimental studies. The table 2.4 illustrates some of the studies that have analyzed this type of system. The indirect solar collector systems are

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17 affected by several facto rs. Table 2.4 Indirect solar desalination system 2.7 Objec tives of T his Research The objectives of this research are the following: Conduct an experimental study for the PV solar desalination system, and compare t he results with theoretical data obtain from modelling of a single slope solar still system. Develop a theoretical mod el by using Matlab Simulink to s imulate the performance of the single solar still. C ollector types Desalination type Authors Title Source photovoltaic Reverse osmosis Bendfeld, J., Broker, Ch., Menne, K., Ortjohann, E., Temme, L. powered reverse osmosis pl ant for desalination of brackish water[5] Parabolic trough collector ME Rodriguez and Camacho benefits of the use of solar energy in multi stage flash Evacuated tube ME El Nashar, A.M ign of a solar Hybrid system Reverse osmosis Joyce, A., Loureiro, D., Rodrigues, C., and Castro, S., using PV systems for water purification in rural Solar pond Multi stage flash AlHawaj, O., and Darwish, M.A.,

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18 Conduct a thermal analysis of a PV solar desalination system and a single slope solar still desalination system Perform numerical calculations using the EES program Compare the numerical and experimental results 2.8 Scope of Work The experimental study was conducted on a solar water desalination sy stem by using new concepts to develop the performance of this system. Also, the simulation system was designed for solar stills. Through this research, the following tasks were performed : The mathematical and thermal analysis was conducted for each compone nt of both systems by using a coupled set of equations. The Experimental work includes the following steps: o The design, operation and testing the experimental system. o Testing the system on different days. o Collect and evaluate the results. The theoretical work includes the following: o Design a theoretical model of the system to simulate the performance of the system. o Run the simulation model and collect the data.

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19 C HAPTER S OLAR DESALINATION SYSTEM DESIGN 3.1 Description and Operating Principle of the Proposed System This research involved the development and study of a solar desalination system that used PV solar panels and batteries. The concept utilized solar cells to c ollect the largest possible amount of solar radiation and used it as an electrical source to supply power to the system. Batteries are also used in the proposed system to provide power as well as store the energy supplied by the solar cells. The uniqueness of this concept is that the PV solar panels and batteries in a desalination system create a stable production of fresh water and a higher rate of pure water production compared to the conventional thermal systems The system, as shown in Figure 3.1, was c onstructed with PV solar panels, and it consists of three parts: electrical, thermal, and condensation. The electrical part contains PV panels, a charge controller, batteries, and electrical connections. The thermal part includes a coil heater and a copper tube, while the condensation part includes a water container and cold water tap. The solar cells received the solar radiation and converted it to electrical power. PV panels were connected to the batteries that stored electrical energy from the PV panels as well as supplied power to the coil heater, a heat source for the system, which converted the water into steam. The coil heater received power from the batteries and generated heat to the water inside the copper tube. Furthermore, the system includes a w ater tank containing provisions to feed the cold salt water directly from the external water source. The water tank was connected to a copper tube that absorbed the heat from the coil heater. The copper tube passed through another water tank that contained cold water, which worked as a condenser The copper tube extended to the top, approximately 30 cm above the lower base of the

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20 system, to allow the water vapor to rise and leave the salts Then it lowered to about 10 cm and passed through the cold water. Water tank Control valve Pure water Coil Heater Batteries PV solar panel Figure 3.1 Schematic of the proposed system To start the operation the water tank was filled completel y with salt water. The water was allowed to rise in the copper tube under the influence of pressure and created a water level in which the heat of the coil could reach. Depending on the water pressure, the water level raised to about 20 cm above the lower base of the system, and the coil heater was installed at the same level When the batteries started to apply power to the coil heater, they provided the required heat to evaporate the salt water to vapor. The water vapor would then rise inside the copper t ube and pass through the cold water tank. Heat exchange took place between the vapor and the cold water. Consequently, the vapor was condensed, and fresh water was produced in a separate container. 3.2 System Design 3.2.1 PV P anels :

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21 Two PV so lar panels were utilized in this solar desalination system. Both of the PV panels had output power ratings of 320 watts and they were connected in parallel as shown in Figure 3.2 Figure 3.2 PV solar panel The maximum out put pow er from the PV solar panels c ould be estimated dependi ng on short circuit current, open circuit voltage, and fill factor as well as the o perati n g temperature. In fac t, the operating temperature has an influence on the efficiency of a PV solar cell, and th at can be traced to its effects on the current and the voltage B oth Voc and FF decrease substantially with an increase in temperature due to the thermally excited electrons dominating the electrical propertie s of the semiconductor. The Ics increases with temperature but only slightly for C Si solar cells [33]. T he maximum out put power from PV solar panel is given as, (3.1) The fill fa ctor can be calculated by two methods (actual and theoretical)[33]: (3.2)

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22 (3.3) The t heor e tical fi ll factor can be calculated as, (3.4) The maximum current and maximum voltage of PV panel can be estimated as, (3.5 ) The Newton to calculate in the equation (3.5) in an iterative form, and the subscript i indicates the i th iteration [33]: (3.6) (3.7) (3.8) Fu r thermore t he relation ship between the current and voltage for PV solar cells was illustrated by Wagner [33 ] as: (3.9) (3.10) Where indicates the electric current generated by illumination, denotes the diode

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23 current and is the resistance an approximately indicates the thermal voltage and can be estimated depending on the temperature (T) of the cells by using the following equation, = ( /q). n indicates the diode factor, q is the cha rge (1.602 ), and k represents the Boltzmann constant (1.38 J ).The diode current ( ) was calculated by measuring open circuit voltage with = / 3.2.2 Batteries and C harge C ontroller In most PV applications, the output energy from PV panel was stored in batteries Selecting suitable batteries for a system depends on many factors, the most importan t is the energy storage capability. The electrical power capacity refers to the amount of energy that can be stored by a battery and supplied on demand. Voltage and current stabilization was another factor that influences the battery selection[36] Supplyi ng electrical power to the transients that can occur in PV panel systems, which is necessary for operating the system with stable voltages and currents [36]. This can b e achieved by using several batteries. Five batteries were used in this experiment: four of them at 6 volts and one at12 volts Various connections were made on the batteries to get different voltages for operating the system as shown in Figure 3.3. A ch arge controller was also used in this project. C harge controller s regulate the DC voltage that are supplied to the batteries from the PV panels. Charge controllers receive the direct voltage as the input voltage from PV panels and converts it into a suitab le direct voltage that was required for charging the batteries. The charging processes in solar systems are necessary to enhance the battery life and performance[36]. The c harge controller was employed when the voltage of PV panel was hig her than the outpu t voltage required for the

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24 load Because PV solar panel s provided about 24 56 volts in the proposed system, the charge controller became necessary to prevent overcharging and causing damage to the batteries. 12v 12 v 6v 6v 6v 6v 6v 6v 12v 24 v 6v 6v Figure 3.3 Mixed connection of the batteries to generate 12 V and 24 V 3.2.3 Coil Heater and Copper P ipe The specifications of the coil heater used in the experiment are a low voltage DC power supply, 12 48V, a maximum current of 20 A, a maximum power of 1000 W, a 24 V input with no load current of 3 A, a 48 V input with no load current of 6A, and with dimensions 3.4 x 3.1 x 1.5 in.T he specifications of the copper pipe are Handi coil soft copper tube, a pipe diam eter of 0.25 in and 0.5 in, a maximum psi of 1557, a minimum working temperature of 100 F and a maximum working temperature of 778 F. 3.2.4 Description of the Heat T ran sfer Equation B etween the Coil H eater and the Copper T ube When the coil heater was placed around the tube the lines of force were concentrate d in the air gap between the coil heater and the tube. The force field that was surrounding the

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25 coil heater induce d an equal and opposing electric current in the copper tube. The heat rate of the tube was dependent on the frequency of the induced current, the intensity of the ind uced current, the Cp of the material of the tube the magnetic permeability of the material of the tube, and the resistance of the copper tube to the flow of current. T hrough the turns of coil heater winding and tube, it was assumed that the flux was perfectly linear in the axially direction Therefore, flux leakages, flux variations and end effect could be neglected Consequently the current distribution in the tube a nd coil heater was represented by an equivalent depth [35] as, (3.11) Where is frequency of is resistivity, and is permeability. The current that passes through the tube was The tube r esistance was the resistance of the equivalent current path of the cross section of the tube and its length, and it was estimated as The power that induced in the tube was estimated as [35], (3.12) Moreover, the power lost from coil heater was calculated with, (3.13) The coil heater resistance increases by decreasing the cross section of the tube and increasing path length The effective resistance was found using (3.14) Where is the coil turns, is coil resistance, is tube outer diameter, is coil inner

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26 diameter. The distribution o f the magnetic field at any point inside tube was estimated as [35], (3.15) Where is the distribution of the magnetic field and r is radius of the tube. 3.2.5 Measuring D evices The following measuring devices were used in this research project: The Ambient Weather WS 1400 IP OBSERVER Solar Powered Wireless was used for measuring the solar radiation, temperature, and the wind speed. A Digital multimeter (200mV 200V) was used for measuring the voltage. A Clamp Meter (0 1000A DC) was used for measuring the current. A Measurin g pitcher gallon was used to measure the quantity of pure water. 3.3 Description Model ing of Single Slope Solar Still Using Matlab Simulink The Matlab Simulink has become a commonly used software package in academia and industry for modeling and simulating dynamic systems. Matlab Simulink supports linear and no nlinear systems as well as systems used in continuous time. Modeling in Matlab Simulink provided an interactive graphical environment and a customizable set of block libraries that provi ded the ability to design, test, and implement a variety of configurations for the system [26]. Additionally, it can be used to easily modify an existing model. The M atlab S imulink was used to model the s ingle s lope s olar s till and the model was compos ed of four groups as shown in Figure 3.4. Fourteen equation s were us ed in the simulation to model the desalination process of the sol ar still, and they represent the first and second groups in the modeling system The third group includes the input data, w hich

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27 represents the solar radiation intensity, water temperature glass temp erature data, and depth of the salt water inside the solar still. The l ast group denotes the output water prod ucts Fi gure 3.4 Schematic of modeling the single slope solar sill 3.3.1 Description of Part 1 and Part 2 in the M odeling The Part 1 modeling of a single slope solar still, includes eight equations as shown i n Figure 3.5. [31] (3.16) (3.17) (3.18) (3.19) (3.20)

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28 Figure 3.5 Schematic of part 1 for the m odeling (3.21) (3.22) (3.23) Six equations are contained in part 2 of the model of a solar still system Figure 3.6 illustrates part 2 : [1] (3.24) [31] (3.25) (3.26)

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29 (3 .27) (3.28) (3.29) Figure 3. 6 Schematic of p art 2 for the m odeling 3.3.2 Input and Output Data for M odeling T he experimentally measured values of solar radiation, wind velocity and ambient temperature of the corresponding day and hour were used The w ater temperature s and glass cover temperature s were calculated numerically by using the EES program. Figure 3.7 illustrates the EES program used to calculate water temperatures (Tw) and glass temperatures (Tg). As a first iteration, the wa ter te mperature and glass temperature were taken as ambient temperature and the brackish water temperature ( dT w ) and the glass cover temperature (d Tg) w ere computed for every time interval. Appendix B shows the brackish water temperature iterations.

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30 Figure 3.7 EES program to calculate the water and glass temperature

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31 3.4 Algorithm Flow Chart to C alculate the W ater P roduction End Calculate hourly productivity (M) Calculate q ew and q ev Calculate h ew and latent heat (L) Compute w ater pressure and g lass cover pressure Input solar radiation, wind velocity, ambient temperature, initial water temperature, initial glass temperature Start

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32 CHAPTER THERMAL ANALYSIS This chapter will be divided into two parts. The mathematical equations that describe the performance of each component of PV solar desalination system are presented in the first part The second part illustrates the mathematical equations of the single slope solar still and describe s the heat balance, mass balance and heat loss for solar still system. 4.1 Theoretical Analysis of PV Solar Desalination System The operation of PV solar desalination was governed by various heat transfer modes as shown in Figure 4.1 The most prominent were the c onvection and radiation modes Convection is accompanie d by evaporation and condensation, and r adiation is the mode of heat transfer between the coil heater and the copper tube. The coefficient of heat transfer depend s on the Nusselt number 4.1.5 Heat transfer ( copper tube and air ) 4.1.1 Heat transfer (coil heater and outer pipe wall) 4.1.4 Condensati on Salt water 4.1.3 Heat transfer (the water surface and inner pipe wall) 4.1.2 Heat transfer (outer tu be wall and inner tube wall) Figure 4.1 Schematics of the h eat transfer in the whole system 4.1.1 Radiation Heat Transfer B etween the Coil Heater and Outer Pipe Wall

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33 The heat transfer mode between the copper tube and coil heater was radiation as shown in F igure 4.2. The operation temperature of the heater can be calculated as [ 12 ] (4.1) (4.2) (4.3) Radiation Radiation Coil Heater Coil heater Copper tube Figure 4.2 Heat transfer between the coil heater and copper tube The h eat flux of the coil heater can be estimated as [12], (4.4) (4.5) The radiation from the heater was emitted in all d irections, and the shape factor determined the amount of radiation that struck the copper tube. Therefore, the radiative heat transfer coefficient was [12],

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34 (4.6) The heat transfer equation can be written as (4.7) (4.8) The net amount of radiation absorbed by the tube is: (4.9 ) To simplify, assuming all the radiation energy that emitted by the heater falls on copper tube S o =1. 4.1. 2 Conduction Heat T ra nsfer Between Outer Tube W all and I nner Tube W all T 1 T s 1 T s 2 T 2 Outer surface I nner surface T 1 (T 1 h 1 ) (T 2 h 2 ) T 2 Heat r 2 r 2 F igure 4 3 Heat transfer between the outer wa ll and inner wall of the copper tube Assuming the heat transfer was s teady q uasi o ne d imensional h eat f low [20], ( 4 .10) The temperature d istribution for c onstant (K)

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35 (4.11) The heat flux and heat rate can be written as [2 0], (4.12) (4.13) (4.14) The conduction resistance can be estimated using [ 20 ], (4.15) (4.16) 4.1.3 Convection Heat Transfer B etween the W ater S urface and I nner Pipe W all. The heat transfer between tube and fluid flowing inside the tube can be calculated as [30], ( 4 .1 7 ) The i nner wall temperature of the copper tube was calculated according to the outer wall temperature of copper tube and considering that the cylindri cal wall has thermal resistance.

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36 (4.18) The average temperature of water that flows inside the tube can be calculated as follows [30]: (4.19) Due to the constant properties of water, the average water temperature can be written as ( after simplifying the equation above ma thematically) [11]: (4.20) The heat flux can also be estimated as the ratio of heater power to the heating area. [11] : (4.21) The local heat transfer coefficient can be written as, (4.22) The local Nusselt number is calculated by [11], (4.23) The Nusselt number can be estimated based on the type of water flow. Water flow insid e the copper tube can be either laminar flow or turbulent flow, and the thermal entrance length is a function of the Reynolds number, Re. For laminar flow, the Nusselt number can be calculated according to the following equation [11]. (4 .24)

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37 It is recommended that this result for the Nusselt number be corrected for the variation of viscosity with tem perature across the cross section of the tube by a factor Moreover, the thermal entrance length can be calculated if the velocity profile in laminar flow was fully developed as, ( 4 .25) For turbulent flow, the Nusselt number can be estimated according to the Gnienskis equation [11] ( 4 .26) 4.1.4 H eat Transfer Between the Cold Water and the Steam I nside the P ipe Region 2 Th T iw Tow Tc Regio n 1 Region 3 Figure 4. 4 Heat transf er between cold water and vapor Region 1 vapor solid convection [21] (4.27) (4.28)

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38 (4.29) Region 2 Conduction across copper wall [21] ( 4 .30) ( 4 .31) ( 4 .32) Region 3 Solid cold liquid convection [21] ( 4 .33) ( 4 .34) ( 4 .35) The overall heat transfer coefficient [W/m. K] [21] ( 4.36) ( 4 .37)

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39 (4.38) The overall heat transfer (4.39) 4.1. 5 Heat T ransfer Between the Copper Tube and A ir Air Air Air Air Air Air Air Air Vapor Air Figure 4. 5 Heat transfer b etween the vapor inside the copper tube and air (4.40) (4.41) 4. 2 Theoretical Analysis of S olar S till To simplify the analysis, assume that: There is no temperature gradient along the glass cover thickness and the water depth.

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40 There is no vapor leakage in the still. Therefore, productivity and efficiency will increase. There is one dimensional heat flow through the glass cover and basin insulation. The heat capacity of the glass cover and insula tion bottom and insulation sides of basin insulation are neglected. Irradiation, I (1 Q_rw Q_ew (1 Q_b Q_b Figure 4. 6 E nergy balances for the whole solar still 4.2 .1 The E nergy B alance for G lass C over The heat loss from the cover glass to the ambient air is convection and radiation (4.42) The c onvection heat loss from cover glass to the ambient air is [4], (4.43) The c onvective heat transfer coefficient is [13], (4.44) The r adiation heat loss from glass to ambient air is

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41 (4.45) The r adiative heat transfer coefficient is [4], (4.46) The sky temperature can be estimated as [1], (4.47) Figure 4. 7 Energy balance for glass cover The heat gain by the glass cover is from radiation, convection, and e vaporation [13], (4.48) (4.49 The radiation heat flux from the water inside basin to the cover glass can be es timated as [1],

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42 (4.50) Where F is the shape factor of radiation. The shape factor is governed by the geometry of the solar still syst em and the solar radiation. A ssum ing the geometry of solar still is two parallel planes, and the solar radiation involved is diffuse ra diation with long wavelengths. For this c ase t he shape factor is taken as 0.9. So, the equation becomes, (4.51) rface, and it can be calculated by the following equation [4] ( 4 .5 2 ) The c onvection heat flux from the wat er inside the basin to the cover glass can be estimated [1] as, ( 4 .5 3 ) ( 4 .5 4 ) The water pressure and glass pressure can be calculated [31] as, ( 4 .5 5 ) (4.5 6 ) The heat loss from evaporation between the water surface and the glass cover is [1]

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43 (4.5 7 ) The evaporative heat transfer coefficient from water is: ( 4 58 ) The hourly desalinated water productivity of solar still basin is [3] (4.59) Where L is the latent heat of water evaporation (J/kg). The energy balance for glass cover can be written as follows [3]: (4.60) (4.61) The first term on the left represents the solar ene rgy absorbed by the glass cover. The evaporative, radiative and convective heat transfer between the water interface and the inner side of the glass cover are represented in second terms w hile the first term on the right represents the radiative and convective heat losses between the glass cover and the ambient air. 4.2.2 The H eat B alance of the B ottom and S ides of the B asin The h eat transfer modes between seawater inside the basin to the ambient air t hrough the insulation are : Convec tion heat transfer between sea water and inner surface of insulation Conducti on heat transfer between inner surfac e and outer surface of bottom and sides

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44 Radiation heat transfer between the outer surface of insulation a nd ambient air. I Figure 4. 8 Energy balance for the bottom and side basin The heat loss from the bottom and sides of the basin is: ( 4 62 ) Heat loss from the botto m of the basin is [4] : (4.63) The bottom heat loss coefficient can be written as: (4.64) Where is the thermal conductivity of air, and is thickness of the basin insulation The heat loss from the sides of the basin are [3]: (4.65) The heat loss coefficient for the sides can be written as: (4.66)

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45 The heat gain by the bottom and si des of the basin is: (4.67) The energy balance for the bottom and sides can be w ritten as follows: [3]: (4.68) (4.69) Where represents the area of the absorber plate, represents the incident solar flux, represents the transmissivity of basin water and glass cover respectively, and represents the absorptivity of the absorber plate (or basin liner). The term on the right hand side represents the energy absorbed b y the absorber plate. The term on the left side is the loss of hea t from the bottom and sides to the atmosphere through the insulation and is convection heat from the bottom and sides of the basin. 4.2.3 The E quation s of E nergy B alance on the W ater S urface Inside the B asin I Q_ew Q_rw Q_cw Q_b Figure 4. 9 Heat transfer for seawater interface

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46 The heat gain by the bottom and sides of the basin is: (4.70) The heat loss from the bottom and sides of the basin is : = (4.71) The energy balance for the water surface can be written as follows [3] : (4.72) Where Represents the mass of absorber plate per unit area, and represents the specific heat of the absorber plate.

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47 CHAPTER R ESULTS AND DISCUSSION This chapter will be separated into two parts. The first part describes the methods used to take measurements of the PV solar desalination system and indicates the results taken from experimental measurements. The se cond part illustrates theoretical measurements of single slope solar still and describes the effects of feed water on the pure water production. 5.1 Experiment al Location The experiment was conducted on the campus of the University of Denver Colorado in t he Boulder Creek building which is located at latitude/longitude 39 74' N, 104 99' W South of the equator as shown in Figure 5.1. Figure 5.1 Image of the location of the Boulder Creek Building University of Colorado Denver campus. 5.2 Method to Obtain Measurements: The following steps were taken to obtain the measurements:

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48 Instantaneous periodic measurements to the voltage and current of the PV panel as well as the amount of output fresh water were taken. Measurements were taken at every quarter hour in the morning and every half hour in the afternoon whe n the PV panels were at 30 The Ambient Weather WS 1400 IP OBSERVER Solar Powered Wireless was used to measure solar radiation, ambient temperature, and wind speed. The Ambient Weather unit included a sensor array, observer IP, router with internet clou d service, and a display monitor. A Clamp meter (0 1000A DC) and digital multimeter (200mV 200V) were used to measure current and voltage. The results were taken on four days : August 9, September 4, October 2, October 28 5.3 Results Obtained from Measurem ents 5.3.1 Experimental Measurements for S eawater on August 9 In this experiment, the PV solar desalination system was used and the solar radiation values were calculated for the inclined surface. The relationship between the solar radiation intensity and time of day is shown in Figure 5.2 when the tilted angle of PV panels was 30 The data illustrates the solar radiation intensity on a sunny day. From the indica ted Figure, it is seen that the values of solar radiation increased slowly in t he early hours of the morning and sharply increase d at noon and decreased in the afternoon. There were three different intervals throughout this day. The first interval was between the hours of 7 am 12pm, and the solar radiation sharply increased from 25 to 935 kW/ during this interval and it started to decline gradually through the second interval, and reached 706 kW/ at 4 pm with a sudden drop at 1 pm. In the last interval, solar radiation decreased between the

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49 hours of 4 7 pm, and changed from 706 to 33 kW / Figure 5.2 Hourly solar radiation values on a 30 tilted Surface on August 9 Next, the power generated by PV solar panels and consumed by h eater values were compared on August 9 Figure 5.3 shows a comparison between power generated by PV solar panels and the power consumed by the heater. Changing the values of generated power corresponds with the changing of solar radiation values, while the power consumption remained stable. As shown in the Figure, the generated power started from zero at 6 am and increased to 16 W at 7 am, and it reached a peak value of 598 W at 12 pm. At 3 pm, generated power gradually declined until it reached 21.5W at 7 pm. However, the power consumption remained stable between the hours of 12 am 11 pm, and was approximately 382 W. Power supplied to the system went through three intervals. The first interval occurred between the hours of 7 10 am, and power relied enti rely on batteries. The power generated by PV panels started to supply power to the system as well as charge the batteries during the second period between the hours of 10 am 4 pm. In the last interval, the batteries again 0 100 200 300 400 500 600 700 800 900 1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Radiation(kW/m^2) Time(hr) (August 9)

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50 started to supply the power to the system after 4 pm Figure 5.3 Comparison of the generated power and power consumed on August 9 During the experiment, the ambient air temperature and the fresh water produced were also measured Figure 5.4 illustrates the outp ut from the exp erimental of the PV solar desalination system that was tested on A ugust 9 An a ccumulated output of 5.4 lite r s of fresh water was obtained by the system after 3 hours ( 9 am 12 pm). From the data it is seen that the water product started a fter 1.24 minutes due to the time spent heat ing the water to vapor as well as heating the copper tube After that, the water product ion was stab le at a rate of 0.03 liters per minute Furthermore, it was noted that the ambient temperature gradually increas ed from 80 F to 92 F between 9 am 12 pm, but this change in temperature did not affect the amount of water produced due to the batteries that make the power supply stable. 0 200 400 600 1 3 5 7 9 11 13 15 17 19 21 23 Power (W) Time(hr) (AUGUST 9) generated Power by PV Panel consumption power by coil heater

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51 Figure 5.4 Hourly variation of the experimental desalinated water y ield and ambient t emperature (seawater) Also, voltage and current consumption were measured experimentally Figure 5.5 show s the consumption of voltage, current, and power on August 9 As seen from the F igure the a ccumulated output of fr e s h water grew to 5.4 liter s over 3 hours, and consumption of current, voltage, and power remained stable Figure 5.5 Voltage, current, and p ower consumption on August 9 (SeaWater) T he F igure consists of three sections V oltage c onsu mption was clarified in the first section, 0 0.01 0.45 0.9 1.35 1.8 2.25 2.7 3.15 3.6 4.05 4.5 4.95 5.4 78 80 82 84 86 88 90 92 94 0 1 2 3 4 5 6 8:52 9:12 9:32 9:52 10:12 10:32 10:52 11:11 11:31 11:51 12:11 temperature(F) pure water (L) Time(minute) seawater desalinated Pure water temperatur e(F)

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52 while the second section ind ica tes the quantity of current consumption Moreover the powe r consumption ,which is equal to the current multipl ied by voltage, is shown in the last section From the data above, it is clear that volt age and current values were 22.7 V and 16.8 A respectively, which are require d to obtain 5.4 liters of fresh water between 9 am 12 pm. The system needed to 382 W to generate the heat required to vaporize the water 5.3.2 Experimental Me asurements for Salt W ater on September 4 In the second part of the experimental study, the experiment was repeated using salt water instead of seawater on September 4 and t he relationship between the solar radiation intensity and t ime was estim ated when the PV panels were tilted at 30 Figure 5.6 shows the experimental measurement of solar radiation intensity on a sunny day. The data shows that solar radiation exceeded zero during the period between 7 am 7 pm, and the highest value of the solar radiation was 860 kW / at 11 am. The behavior of solar radiation during this day can be divided into two intervals. In the first half 7 am 11 pm solar radiation jumped from 32 to 860 kW / and started to decline after 1 pm until reaching 12 kW/ at 7 pm Figure 5.6 Hourly solar ra diation values on a 30 tilted surface on September 4 0 100 200 300 400 500 600 700 800 900 1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Radiation(Kw/m^2) time(hr) (September 4)

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53 The power generated by the PV solar panels and power consumed by the heater were measured. Figure 5.7 presents a comparison between the generated power by PV solar panel and power used by the heater on Septembe r 4. As shown in Figure 5.7, it is clear that batteries supplied power to the system during the period of 12 6 am because there was no power generated by PV solar panels. However, the PV solar panels started to generate power to the system between the ho urs of 11 am 3 pm and began to charge the batteries. After 3 pm, the batteries started to supply power to the system Also, it was noted that the generated power started at zero at 12 am until 6 am, and sharply increased from 20 to 268 W between the hour s of 7 9 am, and reached its highest value of 550 W at 11 am. After 3 pm, the generated power decreased until it reached 7W at 7pm. Figure 5.7 Comparison of generated power and power consumed on September 4 On September 4, experimental m easurements were taken for the output of fresh water of the PV solar desalination system. The water used in this experiment was a mixture of 16 liters of pure water and one batch of NaCl. Figure 5.8 illustrates the relationship between the salt water produ ced and the ambient temperature over time. From the data shown it is seen that the 0 200 400 600 1 3 5 7 9 11 13 15 17 19 21 23 Power(W) Time(hr) ( SEPTEMBER 4 ) generated power by PV panel consumption power by coil heater

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54 desalination process started after 1.26 minutes, and the amount of water produced was 0. 005 liter. After 3 hours, the accumulated output of pure water was 5 .1 liters, with a constant rate of product equal to approximately 0.028 liters per minute. Moreover, it was observed that ambient temperature increased from 67 F to 79 F b etween the hours of 9 am 11 a m. After that, it decreased to 77 F at 12 pm, but this change did not affect the amount of pure water produced because the PV solar desalination system contains batteries that allowed the input power to remain constant. Figure 5.8 Hourly variation of the desalinated water and t emperature (salt water) The v oltage and current consumption were also estimated experimentally on S eptember 9. Figure 5.9 show s the experimenta l measurement s of the voltage, current, and power by the PV solar desalination system in obtain ing pure water. The amount of fresh water, voltage and current were measured on September 4 It was noted that the amount of voltage and current was 22.7 V and 16 .8 A respectively the power consumed to operate the system was 382 W Also, the power, voltage, and the current were stable and they did not change with the weather. 0 0.005 0.43 0.86 1.29 1.72 2.15 2.58 3.01 3.44 3.86 4.29 4.72 5.1 66 68 70 72 74 76 78 80 0 1 2 3 4 5 6 8:52 9:12 9:33 9:53 10:13 10:33 10:53 11:13 11:34 11:54 12:14 Temperature (F) pure water(L) Time(minute) salt water desalinated Pure water temperature (F)

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55 Figure 5.9 Voltage, current, and power c ons umption on September 4 (salt w ater) 5.3.3 Experimental M easurements for T ap W ater and L ake W ater on October 2 and 28 In the last part of the study, the experiment was repeated using tap water and lake water instead of salt water on October 2 and 28 The relationship between solar radiation intensity and time was estimated on October 2 when the PV panels were tilted 30 as shown in Figure 5.10. The data presents the experimental measurement of solar radiation intensity on a sunny day. In general, t he solar radiation rate in October fell below the rate during August and September. Also, it was noted that the maximum value of solar radiation on October 2 was approximately 75 8 k W / The a mount of solar radiation changed from 0 to 5k W/ at 7 am. Afterward, it continued to rise until it reached to the highest value at 2 pm. Then, after 3 pm, the solar radiation intensity decreased until reaching 12 kW / at 6 pm. O n October 28, the experimenta l measurements of solar radiation intensity were estimated on the cloudy day as shown in Figure 5.11 According to the data on October 28 the values of solar radiation intensity were an instantaneous variable due to the variability in the thickness of clo ud layers. Solar radiation intensity increased from 19 to 700 kW / in the morning

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56 between the hours of 8 11 am Due to the cloud s in the afternoon, the solar radiation intensity dropped to 62 3.4 k W / at 12 pm. Af ter that, it increased again at 1 pm. Moreover, due to dense cloud layers, radiation sharply decreased from 260 to 99 kW/ at 6 pm. Figure 5.10 Hourly s olar radiation values on 30 tilted surface on October 2 Figure 5.11 Hourly s olar radiation values on 30 tilted surface on October 28 Addition a lly the power ge nerated by PV solar panels and consumed by the heater on 0 100 200 300 400 500 600 700 800 900 1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Radiation(kW/M^2) Time(hr) October 2 0 100 200 300 400 500 600 700 800 900 1000 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Radiation(kW/m^2) Time(hr) October 28

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57 October 2 was measured F igure 5.11 illustrates a comparison betw een power ge nerated by PV solar panels and consumed by the heater The power generation rate also fell below the consumption rate during August and September I t was noted that the highest amount of power generated o n October 2 was approximately 485 W Fro m the F igure ,it is clear that the solar desalination system relied entirely on batteries between 12 6 am and 7 11 pm, while generated power started to supply part of power to the system between 7 10 am and 4 6 pm However, the solar desalination d epended only on generated power by the PV solar panels between 11 am 3 pm. Figure 5.1 2 Comparison of generated power and power consumed on October 2 A comparison between power generated by the PV solar panels and power consumed by the heater on October 28 is shown in F igure 5.13 From the F igure it is seen that the power generated is unstable due to the variability of the cloud layers. The power generated increased sharply in the morning between 8 11 am from 12 to 477 W. Due to the cloud s the generated power decreased to 393W at 12 pm. After that, it increase d again at 1 pm. 0 100 200 300 400 500 1 3 5 7 9 11 13 15 17 19 21 23 Power (W) Time(hr) OCTOBER 2 Generated Power by PV consumption power by coil heater

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58 Figure 5.13 Comparison of generated power and power consumed on October 28 Figures 5.14 and Figure 5.15 show experimen tal measurements of the desalinated tap water and lake water. The amount of pure water and temperature values w ere measured o n October 2 for tap water and on October 28 for the lake water. T he quantity of fresh water obtained from the PV solar desalination system was almost the same for both, and the product ion rate was 0. 0 28 liter s per minute for tap water and 0. 0 28 2 liter s per minute for the lake water. The a mount of p ure water obtained from tap water was 4.98 lite r s after 3 hours between 1 4 pm, and 5 liter s after the same interval for the lake water. The desalination process for tap water started after 1.23 minute s The lake water needed the same amount of time to begin the desalination process Also Figure 5.14 shows the temperature behavior between the hours of 1 4 pm, and it is clear that the temperature slowly rose from 78 F to 8 F. 0 100 200 300 400 500 1 3 5 7 9 11 13 15 17 19 21 23 Power(W) Time(hr) (OCTOBER 28) Power supply from PV

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59 Figure 5.1 4 Hourly variation of experimental desalinated water yield and temperature (tap water) Figure 5.1 5 Hourly variation of experimen tal desalinated water y ield and t emperature (lake water) To compare the boiling seawater and the tap water it is clear that the boiling point of fresh water was 212 F and seawater was 214 F, but the heat capacity of the seawater was lower than the heat capacity of tap water. The high heat capacity means more resistance to an increasing temperature However, a lower heat capacity makes raising the temperature level 0 0.0026 0.39 0.81 1.23 1.66 2.07 2.49 2.9 3.3 3.73 4.15 4.56 4.98 77.5 78 78.5 79 79.5 80 80.5 81 81.5 0 1 2 3 4 5 6 0:00 0:21 0:43 1:04 1:26 1:48 2:09 2:31 2:52 3:14 3:36 3:57 4:19 4:40 temperature (F) pure water(L) Time(minute) Tap water desalinated Pure water TEMPEATURE (F) 0 0.0025 0.4 0.82 1.24 1.66 2.05 2.5 2.91 3.34 3.78 4.2 4.6 5 82 80 81 81 79.5 80 80.5 81 81.5 82 82.5 0 1 2 3 4 5 6 0:00 0:21 0:43 1:04 1:26 1:48 2:09 2:31 2:52 3:14 3:36 3:57 4:19 4:40 temperature(F) pure water(L) Time(minute) Lake water desalinated Pure water

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60 easier. Because the fresh water has a high heat capacity and seawater has le ss heat capacity, seawater boils faster than fresh water. To explain this behavior chemically, during the boiling process the positive ions of salt in the seawater attract the negative ions of fresh water and gas is released in the process, producing heat. Every oxygen atom in fresh water is bonded to two hydrogen atoms, and every hydrogen atom is bonded to its oxygen atoms by a shared pair of electrons. When NaCl dissolves in water, the positive parts of atoms in the water attract the negative chloride ion s of the s alt. Also, the negative molecules attract the positive parts of sodium ions in NaCl. As a result, the presence of salt in the pure water makes the boiling process occur more rapidly. Also, increasing the amount of salt leads to reducing the time that water needs to start boiling. 5.4 Salinity Measurements Experimental measurements of salinity in seawater, salt water, lake water, and tap water were taken. A sample of desalinated water from these four types was tested by using an ATC sa linity refractometer. The table 5.1 shows the percentage of the saline in seawater, salt water, lake water, and tap water before and after the desalination process. From these data, it is clear that highest percentage of salt was found in seawater while t he tap and lake water have the lowest percentage Experimental measurements illustrated that the percentage of salt in sea water was approximately 40000 ppm (40 ppt). After many desalination processes, the percentage of salt decreased to less than 5000ppm ( 5 ppt), while the salinity level for tap and lake water became less than 250 ppm (0.25 ppt) after the desalination process.

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61 Table 5.1 Salinity measurement s for seawat er, salt water, tap water, and l ake water. 5.5 T heoretical Measurements for the Solar Still System 5.5.1 Input and Output Data of Solar Still Modeling on August 9 When the Water Depth W as 5 cm The table 5.2 lists the hourly values of solar radiation intensity, wind speed, and ambient temperature on August 9. The water temperature was calculated using a com puter program as a function of radiation, wind velocity, and ambient temperature. The variation of these parameters during the day was from 8 am until sunset. From the dat a, it can be seen that the values of solar radiation increased with time until reaching the highest value around noon, while in the afternoon, solar radiation values decreased The ambient temperature had almost the same behavior of radiation, but it reach ed its maximum value around 2 pm and Water type Salinity level before desalination process(ppm) Salinity level before desalination process(ppm) Tap water 350 >250 Less than 2 50 Lake water 600 >250 Less than 2 50 Saltwater 10000 >1000 Less than 1000 Seawater 40,000 Between 5000 1000 (after many processes )

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62 remained stable before slightly dropping at 5 pm Also, the table indicates the variation of the wind speed during the daylight time. It increases from 11.5 m/h in the early morning to 19.5 m/h by the end of the day. Al so, the water temperature increased after 9 am until reaching its maximum values of 54 C at 1 pm, then it decreased after 1 pm until reaching 35 C at 5 pm. Table 5.2 Hourly variation of solar radiation, wind speed, ambient t empe rature, a nd water temperature on August 9. Also, the fresh water output was estimated Figure 5.16 shows the output of fresh water of the still when the wa ter depth was 5 cm. The pure water production rate starts very slowly due to warming of the solar still system and the somewhat low solar radiation intensity during the morning hours. A peak production rate occurred at noon. It sharply dropped at 1 pm and then dropped steeply between 3 pm and 5 pm until it reached 50 ml. Radiation( k W /m^2) Wind speed(mph) Ambient temperature (C ) Water temperature (C ) 274 11.5 23.6 30 475 8.1 29.4 36.81 622.21 3.5 31.1 42.86 828.43 10.4 33.3 50.42 935.5 8.1 33.8 54.88 480 4.6 35 3 7.74 823.71 3.5 35 50.3 773.228 17.3 35 48.39 706 17.3 35.5 45.96 422.33 19.6 32.7 35.57

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63 Figure 5.16 Hourly variation of theoretical desalinated water yield on August 9 (5 cm depth) 5.5.2 Input and Output Data of S ola r S tills M odeling on October 2 ( 10 cm wa ter depth) The solar radiation, wind speed, and ambient temperature were measured experimental on october 2, and the water temperature was calculated numerically. Table 5.3 shows the measurement from 9 am 4 pm. Table 5.3 Hourly variat ion of s o lar radiation, wind speed, ambient t empe rature, and water temperature on October 2 Radiation( kW /m^2) Wind speed(mph) Ambient temperature (C ) Water temperature (C ) 320.8 8.1 20 31.7 515 8 21.7 38.79 633 8.1 22.8 42.99 668 13 .8 25 44.41 712 9.2 25.5 45.92 758 10.4 26.1 47.59 640.8 3.5 26 43.47 344.7 11.5 27.11 32.61

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64 From the data above, it is seen that during a daily desalination operation, the temperature increased until it reached the peak level at 1 pm then decr eased in the afternoon. The solar radiation intensity has the highest level around 2 pm ,and the lowest level at 9 am and 5 pm. The behavior of the water temperature was similar to the behavior of the ambient temperature. The output data of solar still modeling on October 2 when the water depth was 10 cm was also calculated. Figure 5.17 illustrates the theoretical measurement of the solar still system tested on October 2. The amount of pure water was measured, and the output of pure water obt ained from the system was unstable between hours of 9 am to 12 pm. It reached its highest level from 1 3 pm The fresh water production rate gradually grew due to warming of the solar still system and the low solar radiation during the morning hours. Aft er 1 pm, water production remains stable until it reached 310 ml at 3 pm. Between 4 6 pm the production rate went down until it reached to 80 ml at 6 pm. Figure 5.17 Hourly variation of theoretical desalinated water yield on October 2 (10 cm depth)

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65 5 5 3 Input and Output Data of Solar Stills Modeling on October 28 When Water Depth W as 15 cm Table 5.4 Hourly v ariation of solar radiation, wind speed, ambient temperature, and water temperature on October 28 Figure 5.18 Hourly variation of theoretical d esalinated water y ield on October 28 (15 cm depth) Radiation ( kw /m^2) Wind speed(mph) Ambient temperature (C ) Water temperature (C ) 198.5 15 21 27.26 454.8 11.5 25 36.87 699.2 6.9 25.5 45.55 623.4 6.9 27.2 42.75 679.4 3.5 26.7 44.87 550.2 6.9 27.2 40.16 278.4 10.4 27.2 37.49 234 5.8 2 5 28.57 260 8.1 19.5 29.48

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66 5.6 Comparison Between the Experimental Results and Theoretical D ata 5.6.1 Comparison Between the O u tput Water of PV S olar D esalination System and S olar S till on August 9 T he output fresh water from the experimental of the PV solar desalination system and from theoretical of the single slope solar still were tested on August 9 as shown in F igur e 5.19. An accumulated output of 5.4 liters of fresh water was obtained by the PV solar desalination syst em after 3 hours ( 9am 12 pm) W hile accumulated output of pure water th at produced from solar still was 1. 3 liters at the same period. The experiment al result shows the water product started after 1.24 minutes After that, the water product ion was stab le at a rate of 0.03 liters per minute However, the theoretical data illustrates that fresh water production rate from solar still gradually grew due to warming of the solar still system and the largest amount of the fresh water has accumulated between hours ( 11am 12 pm ) and it was approximately 0.35 1liter. Figure 5. 1 9 Comparison of the o utput w ater of PV s olar d esalination and s olar still on August 9 0 1 2 3 4 5 6 8:24 8:41 8:58 9:15 9:33 9:50 10:07 10:24 10:42 10:59 11:16 11:34 11:51 12:08 pure water (L) TIME (minute) Output fresh water of PV solar desalination & solar still on August 9 PV solar desalination solar still

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67 5.6.2 Comparison Between the O utput Water of PV S olar D esalination System and S olar S till on October 2. Experimental measurements of PV solar desalination system and theoretical results of solar still of the output of freshwater were compar e on October 2 T he quantity of fresh water that obtained from the PV solar desalination system was 5 lite r s after 3 hours between 1 4 pm. During the same period single slope solar still produced 1.15 liter Figure 5.20 shows comparison between the o utp ut w ater of PV s olar d esalination and s olar still on October 2 Figure 5. 20 Comparison of the o utput w ater of PV s olar d esalination and s olar still on October 2 0 1 2 3 4 5 6 0:00 0:21 0:43 1:04 1:26 1:48 2:09 2:31 2:52 3:14 3:36 3:57 4:19 4:40 5:02 Pure Water (L) TIME (MINUTE) Output fresh water of PV solar desalination & solar still (October 2) PV solar desalination solar still

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68 C HAPTER C ONCLUSION AND RECOMMENDATIONS FOR FUTURE WORK The main aim of this research project is to investigate the feasibility of producing potable water from seawater, saltwater and brackish water using solar desalination systems. Two type of solar desalina tion technique was developed experimentally and using computer modelling. Experimental tests were performed on the campus of the University o f Denver Colorado. The results showed that: The accumulated output of freshwater grew to 5.4 liters over 3 hours wh en sea water was the feed water, and the salinity level decreased from (40000) (>5000) ppm. When the salt water was a feed water, an accumulated output of 5.4 liters of fresh water was obtained by the system after 3 hours ( 9 am 12 pm) on September 4. T he amount of salt dropped to less than 250 ppm in the water produced. When the experiment was repeated using lake water and tap water instead of salt water on October 2 and 28 the quantity of fresh water that obtained from the PV solar desalination system was almost the same for both, and the production rate was 0.028 liters per minute for lake water and 0.282 liters for the tap water. The results of run the model for single solar still were: The output fresh water of the solar still system was unstable. When the depth of the feed water inside the system was 5 cm, a peak production rate was 350 ml. The highest level of output fresh water of the solar still system was less than 310 ml when the depth of the feed water was 10 cm and 15. The proposed systems have several advantages :

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69 The amount of water produced from PV solar desalination system was stable, and it did not influence with changing weather The PV solar desalination system can be operated in either a continuous or a batch process mode. Structuring of PV solar desalination system is not complicated and it does not require a special supporting structure. Using solar energy in solar desalination system saves conventional energy sources for other applications Solar desalination reduces poll ution and decreases the emissions that cause environmental deterioration However, solar desalination system has some disadvantages, such as PV solar desalination system consumed high electrical power, the water produced by solar still is not constant and a function of solar radiation and ambient temperature In general, this research study enhances understanding the performance of solar desalination systems under a range of different conditions and makes a significant contribution to the advan cement of knowledge in this area. Also, the performance of PV solar desalination system and the solar still system can be improved significantly if they combine. The water produced will be stable with a low level of power consumption.

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70 B IBLIOGRAPHY [1] A. Alaudeen, K. Johnson, P. Ganasundar, A. S Abuthahir stepped type basin in a solar still Journal of King Saud University Engineering Sciences pp. 176 183 May 2013. multi Desalination pp. 119 135. 1994. s olar s till u sing g ranular a ctivated c arbon in Matlab Bonfring International Journal of Power Systems and Integrated Circuit s pp. 2250 1088, December 2011. passive solar distillation Desalination and Water Treatment pp. 1944 3994, April 2014. [5] F. Banat, H. Qiblawey and Q. Al Nasser, Design and o peration of s mall s cale p hotovoltaic d riven r everse o smosis (PV RO) d esalination p lant for w ater s upply in r ural Areas Water, Energy, and Environmental Engineering pp. 31 36 2012 [6] M. Basunia, H Yoshio and T s olar r adiation i ncident on h orizontal and i nclined s urfaces TJER vol. 9, pp. 27 35, 2012. [7] H. T. El Dessouky and H. M. Ettouney, Fundamentals of Salt Water Desalination Amsterdam : Elsevier Science B.V., 2002. [8] A.M. El Desalination pp. 579 614. 1993 [9] L. Garcia Rodriguez and C Gomez Camacho, Conditions for economical benefits of the use of solar energy in multi stage flash distillation, Desalination vol. 125, pp. 133 138, 1999. [10] O.A. Amsterdam : Elsevier Science Publishers pp. 563 579, 1993. [11] F.P. Incropera, Fundamentals of Heat and Mass Transfer U.S.A. : John Wiley & Sons, 2007 [12] Isidoro Martinez, Heat Tr ansfer and Thermal Radiation Modelling Web site: http://webserver.dmt.upm.es/~isidoro/tc3/Heat%20transfer%20and%20thermal%20radia tion%20modelling.pdf b rackish w ater using s olar s tills a r eview Proceedings of the International Conference on Environment and Energy pp. 17 15, December 2014.

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71 [14] A. Joyce, D. Loureiro, C. Rodrigues Desalination pp. 3 9 44, 2001. Renewable Energy vol 4 pp. 351 367, 1997. d esalination: w hen and w here w ill it m ake s ense? Fraunhofer Institute for Solar Energy Systems ISE Freiburg Germany, 2011 CiteSeer 2007 [18] A. Lalzad, Development of Novel Small Scale Desalination, London South Bank University, 2005. [19] S. Lattemann, Development of an Environmental Impact Assessment and Decision Support System for Seawater Desalination Plants. Delft University of Technology, 2010. [20] J. H. Lienhard IV and J. H. Lienhard V, A Heat Transfer Textbook Massachusetts : Cambridge, 2001 [21] S. H. Liu, Heat Exchangers Selection, Rating, and Thermal Design Florida : CRC Press LLC, 2002. [22] F. Lokiec The Mechanical Vapor Compr October, 2007 [23] E. Lorenzo, G. Araujo, A. Cuervas, M. Egido, J. Minano, and R. Zilles, "Solar Electricity Engin eering of Photovoltaic Systems" Spin : Progensa, 1994. [24] S. Loupasis, 2002. Technical analysis of existing renewable energy sources desalination schemes. Commission of the European Communities Directorate G eneral for Energy and Transport. Global Solar Radiation on Inclined Surfaces: Models Re Visited Energies January 2017. [26] The Math Work, Simulink Simulation and Model Based Design United States of America : the MathWorks, Inc. [27] University of Nottingham, August 2011 [28] Metcalf & Eddy, Inc. an AECOM Company, Takashi Asano, Franklin Burton and Harold Leverenz: Water Reuse: Is sues, Technologies, and Applications McGraw Hill Professional, 2007

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72 [29] T. Pankratz, 2000. Large scale desalination plants A drought proof water supply International Desalination News Issue 3 4 (2000) 3 6. c onvecti on h eat t ransfer in the e ntrance r egion of h orizontal t ube under c onstant h eat f lux World Applied Sciences Journal vol. 15, pp. 331 338, 2011 Determination of Total Internal Heat Transfer Coefficient of Single S lope Solar Still International Journal of Emerging Technology and Advanced Engineering vol. 3, pp. 2250 2459. December 2013. [32] M. Schorr, Desalination, Trends and Technologies, Intech, 2011 [33] V. P. Sethi, K. Sumat Mathematical m odel for c omputing m aximum p ower o utput of a PV s olar m odule and e xperimental v alidation Journal of Fundamentals of Renewable Energy and Applications vol. 2, pp. 5, 2012. [34] M. Shatat S. Riffat and M.W Powered Psychometric Low Grade Water Desalination System Institute of Sustainable Energy Technology vol5, pp. 13 20, 2013. [35] P. G. Simpson, Induction Heating Coil and System Design United States o f America : McGraw : Hill Book Company, Inc. 1960 [36] Sumathi S., Ashok Kumar and L., Surekha P., Solar PV and Wind Energy Conversion Systems, Switzerland: Spri nger International Publishing, 2015. History, Development and Management of Water Resources [38] United States Census Bureau. Web site: https://www.census.gov/population/international/data/idb/worldpopgraph [39] United Nations Environment Programme, Web site: http://www.unep.org/themes/fre shwater.html April 2008. [40] U.S. Department of the Interior, Bureau of Reclamation, Desalting Handbook for Planners 3rdEdition, 2003. [41] Web site: https://pubs.u sgs.gov/circ/1405/pdf/circ1405.pdf [42] The World Bank Web site : http://www.worldbank.org/en/topic/water/overview

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73 A PPENDIX A EES PROGRAM (POWER CALCULATIONS)

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77 A PPENDIX B ITERATION (WATER TEMPERAUTURE ) October 2 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 320.8 8.1 20 20 2 26.36 3 29.29 4 30.62 5 31.23 6 31.51 7 31.64 8 31.71 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 515 8 21. 7 21.7 2 31.04 3 35.3 4 37.23 5 38.11 6 38.51 7 38.7 8 38.79

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78 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 633 8.1 22.8 22.8 2 33.9 3 38.96 4 41.25 5 42.29 6 42.77 7 42.99 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 668 13.8 25 25 2 35.61 3 40.45 4 42.64 5 43.64 6 44.1 7 44.31 8 44.41

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79 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 712 9.2 25.5 25.5 2 36.72 3 41.82 4 44.15 5 45.21 6 45.69 7 45.92 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 758 10.4 26.1 26.1 2 37.91 3 43.29 4 45.73 5 46.84 6 47.35 7 47.59

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80 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 640.8 3.5 26 26 2 35.53 3 39.88 4 41.86 5 42.76 6 43.18 7 43.38 8 43.47 I teration no. Radiation Wind speed Ambient temperature Water temperature 1 344.7 11.5 27.11 27.11 2 30.15 3 31.54 4 32.18 5 32.47 6 32.61

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81 August 9 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 274 11.5 23.6 23.6 2 27.14 3 28.77 4 29.52 5 29.87 6 30.03 7 30.11 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 457 8.1 29.4 29.4 2 33.45 3 35.29 4 36.13 5 36.52 6 36.69 7 36.77 8 36.81

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82 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 622.21 3.5 31.1 31.1 2 37.52 3 40.45 4 41.78 5 42.38 6 42.66 7 42.78 8 42.84 9 42.86 Iterat ion no. Radiation Wind speed Ambient temperature Water temperature 1 828.43 10.4 33.3 33.3 2 42.65 3 46.9 4 48.83 5 49.7 6 50.1 7 50.28 8 50.36 9 50.40 10 50.42

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83 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 935.5 8.1 33.8 33.8 2 45.01 3 50.11 4 52.42 5 53.46 6 53.94 7 54.82 8 54.88 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 480 4.6 35 36.49 2 35 3 37.18 4 37.49 5 37.64 6 37.71 7 37.74

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84 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 823.71 3.5 35 35 2 43.34 3 47.14 4 48.86 5 49.64 6 50 7 50.16 8 50.24 9 50.28 10 50.3 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 773.228 17.3 35 35 2 42.33 3 45.67 4 47.19 5 47.87 6 48.18 7 48.32 8 48.39

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85 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 706 17.3 35.5 35.5 2 41.22 3 43.84 4 45.02 5 45.56 6 45.8 7 45.91 8 45.96 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 422.33 19.6 32.7 32.7 2 34.28 3 35.01 4 35.34 5 35.5 6 35.57

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86 October 28 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 198.5 15 21 21 2 24.42 3 25.98 4 26.69 5 27.01 6 27.16 7 27. 23 8 27..26 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 454.8 11 25 25 2 31.35 3 34.25 4 35.57 5 36.17 6 36.45 7 36.58 8 36.64 9 36.67

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87 Iteration no. Radiation Wind spee d Ambient temperature Water temperature 1 699.2 6.9 25.5 25.5 2 36.47 3 41.46 4 43.73 5 44.76 6 45.24 7 45.45 8 45.55 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 623.4 6.9 27.2 27.2 2 35.75 3 39.64 4 41.4 5 42.21 6 42.58 7 42.75

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88 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 679.4 3.5 26.7 26.7 2 36.63 3 41.15 4 43.21 5 44.15 6 44.58 7 44.78 8 44.87 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 550.2 6.9 27.2 27.2 2 34.28 3 37.52 4 38.99 5 39.66 6 39.96 7 40.1 8 40.16

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89 Iteration no. Radiation Wind speed Amb ient temperature Water temperature 1 478.7 10.4 27.2 27.2 2 32.85 3 35.34 4 36.56 5 37.12 6 37.38 7 37.49 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 234 5.8 25 25 2 26.97 3 27.88 4 28.29 5 28.48 6 28.57

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90 Iteration no. Radiation Wind speed Ambient temperature Water temperature 1 260 8.1 19.5 19.5 2 24.95 3 27.43 4 28.58 5 29.09 6 29.32 7 29.43 8 29.48