associate prof. mariam gabr salem report: solar desalination as an adaptation tool for climate...

Technical report:

Solar Desalination as an Adaptation tool for Climate

Change impacts on the Water Resources of Egypt

Associate prof. Mariam Gabr Salem

April 2013

Solar Desalination as an Adaptation tool for Climate Change impacts on the Water Resources of Egypt

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Comments could be sent to:

Associate Prof. Mariam Gabr Salem (email: [email protected])

The designations employed and presentation of material through the

publication do not imply the expression of any opinion whatsoever on the

part of UNESCO concerning the legal status of any country, territory, city

or its authorities, or concerning the delimitation of its frontiers or

boundaries.


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ACKNOWLEDGEMENTS

First of all, I give all the thanks to God for the completion of this work.

I am sincerely grateful to the Climate Change Risk Management Project in Egypt-

UNESCO Cairo Office (UCO) who provides support for the preparation of this

technical report.

I would like to thank Prof. Dr. Mohamed Nour-Eldin, Ain Shams University, Faculty

of Engineering, for his kind guidance and valuable suggestions that I greatly

appreciate.

Thanks also to (UCO) technical stuff, whose assistance contributed to the success of

the work.

I specially acknowledge my family for their encouragement throughout my work. My

sincerest gratitude goes to my father and mother, who kindly and cheerfully

withstood my study.


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CONTENTS

EXECUTIVE SUMMARY ...................................................................................... 10

CHAPTER (1): INTRODUCTION .......................................................................... 14

1.1 General .............................................................................................................. 14

1.2 Problem Definition ............................................................................................ 14

1.3 Criteria ............................................................................................................... 15

1.4 Aim of the Study ............................................................................................... 15

1.5 Outline of the Report ......................................................................................... 15

CHAPTER (2): LITERATURE REVIEW ............................................................... 16

2.1 Potential Solar Desalination Work Globally ..................................................... 16

2.1.1 Historical Background of Desalination and Renewable Energies ................. 16

2.1.2 Principle of Solar Distillation: a State of the Art ........................................... 18

2.1.3 Classification of Solar Distillation Systems ................................................... 18

2.1.4 Performance of Solar Still .............................................................................. 19

2.1.5 Solar Still Coupled with Thermal Storage and Solar Collectors .................... 20

2.1.6 Solar Still Coupled with Thermal Storage and Other Heat Source ................ 21

2.1.7 Plastic Solar Water Purifier with High Output ............................................... 22

2.1.8 Solar Water Desalination System Utilizing a Passive Vacuum Technique ... 27

2.2 Potential Solar Desalination Application in Egypt and Its Future Perspective . 30

2.2.1 Performance of Solar Still in Egypt ............................................................... 30

2.2.2 Concentrating Solar Technologies (CST) ...................................................... 30

2.2.3 Solar Energy Desalination for Arid Coastal Regions: Greenhouse ............... 32

2.2.4 Effect of Dust Deposition ............................................................................... 33

2.2.5 Conventional Desalination Combined with Solar Energy ............................. 33

CHAPTER (3): SOLAR DECISION SUPPORT SYSTEM (SDSS) MODEL ........ 35

3.1 Introduction ........................................................................................................ 35


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3.2 Design Parameters of (SDSS) Model ................................................................. 35

3.3 Classification of (SDSS) Model ......................................................................... 36

3.4 Analytical Hierarchy Process (AHP) to Buildup (SDSS) Model ....................... 43

3.5 (SDSS) Model Inputs.......................................................................................... 44

3.5.1 Saline Water Resources Salinity and Depth .................................................... 44

3.5.2 Solar Energy .................................................................................................... 47

3.5.3 Vulnerable Areas Due To Climate Change, Sea Level Rise (SLR), and

Seawater Intrusion .................................................................................................... 50

3.5.4 Topographic Obstacles .................................................................................... 51

3.5.5 Power Potentiality (Conventional and Renewable) ......................................... 52

3.5.6 Population ........................................................................................................ 54

3.5.7 Land Use .......................................................................................................... 55

3.5.8 National Strategic Plans for Development ...................................................... 56

3.6 (SDSS) Model Outputs ....................................................................................... 56

3.7 Promising Areas for Desalination by Solar Energy in Egypt ............................. 60

3.8 Inundation and New Safe Areas in Egypt .......................................................... 67

CHAPTER (4): ASSESSMENT OF THE SOLAR DESALINATION ................... 69

4.1 Desalination Assessment Model ......................................................................... 69

4.1.1 Model inputs .................................................................................................... 69

4.1.2 Model boundary conditions ............................................................................. 69

4.1.3 Model Database ............................................................................................... 72

4.1.4 Model Output ................................................................................................... 74

4.2 Technical Assessment......................................................................................... 78

4.3 Environmental Assessment................................................................................. 78

4.4 Economical Assessment ..................................................................................... 80

4.5 Solar Pond as a Solution of Brine ....................................................................... 82

CHAPTER (5): CONCLUSIONS AND RECOMMENDATIONS ......................... 85

ABBREVIATIONS .................................................................................................. 87

REFERENCES ......................................................................................................... 91


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List of Tables

Table 1 Primary assessment of brackish groundwater in Egypt ................................. 34

Table 2 Classification of Solar Decision Support System (SDSS) model, numbers in

parenthesis indicate the weights of each factor ........................................................... 38

Table 3 Global solar radiation on horizontal surface (kwh/m2/day) and its annual

average ........................................................................................................................ 49

Table 4 Actual sunshine duration (hr/month) and its annual average ........................ 49

Table 5 Zonal statistical analysis of potential areas of solar desalination in Egypt ... 63


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List of Figures

Fig. 1 Della Porta solar distillation apparatus ............................................................. 17

Fig. 2 Cross-sectional view of multi-wick solar still-passive mode ........................... 19

Fig. 3 Hybrid solar distillation system-active mode ................................................... 19

Fig. 4 Hybrid solar distillation system ........................................................................ 21

Fig. 5 Solar still with storage tank and external heat source ...................................... 22

Fig. 6 Plan view of solar water purifier showing water flow path .............................. 23

Fig. 7 Single unit solar water purifier ......................................................................... 23

Fig. 8 Orientation of solar water purifier in southern hemisphere .............................. 25

Fig. 9 Align solar water purifier to the sun ................................................................. 25

Fig. 10 Level solar water purifier ............................................................................... 26

Fig. 11 Dynamic mode operation in southern hemisphere ......................................... 26

Fig. 12 Schematic of vacuum system ......................................................................... 28

Fig. 13 Evaporator–condenser of vacuum system ...................................................... 29

Fig. 14 El-Nasr pilot solar steam generation plant layout .......................................... 31

Fig. 15 Solar parabolic trough collector in EL-Nasr Plant ......................................... 32

Fig. 16 Seawater greenhouse ...................................................................................... 33

Fig. 17 Solar desalination plant .................................................................................. 33

Fig. 18 User interface of (SDSS) model tool boxes .................................................... 37

Fig. 19 Salt lakes, Drains, Coastal aquifer, and Moghra aquifer in Egypt ................. 44

Fig. 20 Fissured carbonate aquifer, Nubian sandstone aquifer, and major production

wells in Egypt ............................................................................................................. 45

Fig. 21 Average groundwater depth in Egypt ............................................................. 46

Fig. 22 Average groundwater salinity in Egypt .......................................................... 46

Fig. 23 Solar energy intensity in Egypt ...................................................................... 48

Fig. 24 Egypt climatic stations .................................................................................... 48


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Fig. 25 Delta subsidence in Egypt .............................................................................. 50

Fig. 26 Delta sea level rise .......................................................................................... 51

Fig. 27 Sand dunes and land slope in Egypt ............................................................... 51

Fig. 28 Electric and wind power in Egypt .................................................................. 52

Fig. 29 Natural gas in Egypt ....................................................................................... 52

Fig. 30 Potagas in Egypt ............................................................................................. 53

Fig. 31 Possible biogas production in Egypt .............................................................. 53

Fig. 32 Percentage of rural in Egypt ........................................................................... 54

Fig. 33 Population in Egypt ........................................................................................ 54

Fig. 34 Gross domestic product (GDP) in Egypt ........................................................ 55

Fig. 35 Major land use indicators in Egypt ................................................................ 55

Fig. 36 Potential regions for national projects in Egypt ............................................. 56

Fig. 37 Classification degree of promising areas in Egypt for saline water (resources,

salinity, and depth) ...................................................................................................... 57

Fig. 38 Classification degree of vulnerable areas due to climate change, Sea Level

Rise (SLR), and Seawater intrusion in Egypt ............................................................. 57

Fig. 39 Classification degree of topographic obstacles in Egypt ................................ 58

Fig. 40 Classification degree of electric grid, gas, possible biogas from wastes,

natural gas, and wind power potentiality in Egypt ..................................................... 58

Fig. 41 Classification degree of population in Egypt ................................................. 59

Fig. 42 Classification degree of land use in Egypt ..................................................... 59

Fig. 43 Classification degree of potential regions for national strategic plans for

development in Egypt ................................................................................................. 60

Fig. 44 Promising areas for desalination by solar energy in Egypt, Optimistic

Scenario ....................................................................................................................... 61

Fig. 45 Promising areas for desalination by solar energy in Egypt, Moderate Scenario

..................................................................................................................................... 61

Fig. 46 Promising areas for desalination by solar energy in Egypt, Pessimistic

Scenario ....................................................................................................................... 62


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Fig. 47 Soak away (SLR) to Qattara Depression ........................................................ 68

Fig. 48 Thermal desalination flow process assessment model ................................... 70

Fig. 49 Reverse osmosis desalination flow process assessment model ...................... 71

Fig. 50 Solar still flow process assessment model ...................................................... 71

Fig. 51 Desalination assessment model ...................................................................... 72

Fig. 53 Desalination assessment model output ........................................................... 75

Fig. 54 Water process ................................................................................................. 76

Fig. 55 Chemicals process .......................................................................................... 76

Fig. 56 Land use process ............................................................................................. 76

Fig. 57 Energy use process ......................................................................................... 77

Fig. 58 Emissions process ........................................................................................... 77

Fig. 59 Sludge and noise process ................................................................................ 77

Fig. 60 Economical process ........................................................................................ 78

Fig. 61 Solar pond temperature under Egypt climatic conditions .............................. 84


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EXECUTIVE SUMMARY

This study provides recommendations for promoting the use of solar energy in

desalination as a strategic option for overcoming the water resources scarcity

problems in Egypt; especially under the expected climate change impacts. According

to many studies, Egypt already has reached the water poverty due to increased water

demands and population in addition to the complexity of the hydro-political situation

in the Nile Basin. Egypt possesses a high potential of saline water resources (long sea

shores, salt lakes, brackish groundwater available from different aquifers, and long

drainage network). Egypt has the highest rates of sun shining hours almost all year

round in the world. Egypt extends from the Mediterranean coast to the Cancer tropic

that passes in the southern of Egypt. Because of this location the length of daylight in

the summer increases to 14 hours, this increases the amount of solar radiation

reaching Egypt. It is worth to stress on the interrelation of water and energy. If power

is available, desalination and transmission of water would be done. As Egypt suffers

from energy shortage, solar energy could provide potential resources for water

desalination and renewable energy in Egypt.

In this study the potential solar desalination and its future perspective and possible

application in Egypt globally were reviewed. Geographic Information System (GIS)

as a tool was used to build up Solar Decision Support System (SDSS) model for solar

desalination. The (SDSS) is a decision support model that defines the situation, set

objectives, put criteria, and establishes priorities to reach a final decision of pilot

areas. The (SDSS) incorporates key data and elements of environment and

meteorological conditions of Egypt. The (SDSS) input 8 parameters. 8 tool boxes

were built to run the (SDSS). These tool boxes classify the potential priorities of

promising area depend on:

1. Areas of lower groundwater depth and salinity; Areas near saline water

resource as seas, salt lakes, main drains, and brackish groundwater source to

overcome shortage in water resources;

2. Areas of higher solar energy intensity, that could be connected to an electric

grid so that continuous power generation is achievable by a mix of

renewable/non-renewable energy production in a dual system;


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3. Lower vulnerable areas, areas far from seawater intrusion in Delta, areas of

lower Sea Level Rise (SLR), areas of lower Delta subsidence;

4. Areas of lower topographic obstacles, lower land slope, far from sand dunes

and mountain chains;

5. Areas of higher power potentialities in both conventional and renewable. The

conventional powers are electric grid, thermal power station, natural gas, and

potagas production. The renewable energy were wind energy and potential

ability to produce biogas from solid wastes and aquatic weed;

6. Areas of higher rural population and lower income.

7. Areas of better land use. These areas are selected near Delta and Nile Valley

Marakez, main port, airports, railways, roads, and main piped water networks;

8. Finally potential areas for national strategic plans for development in tourism,

industry, agriculture, mining, and flash floods that recharge groundwater.

The priorities of all parameters were classified in an ascending order from 1 to 10

degrees. This classification covers the extremes of possible desalination process in

Egypt. The best extreme includes class from 1 to 10 of all elements. The worst

extreme includes classes 4 and 5 of all elements. Three scenarios were run by

(SDSS) to test low, high, and moderate conditions of Egypt. The first is the optimistic

scenario that covers all possible solar desalination process in Egypt from class 1 to

10. The second is the moderate scenario from class 3 to 7. The third is the pessimistic

scenario limited to classes 4 and 5. Accordingly, the (SDSS) outputs are digital maps

of pilot areas of solar desalination potentiality in Egypt. The result of the optimistic

scenario shows that about 0.414 (million Km2) of Egypt is most suitable for solar

desalination. Some of these areas could be developed as follow:

1. 800 (km2) for grass land in North Sinai that has groundwater. The salinity

ranges from 1,500 to 12,000 (ppm).

2. 700 (km2) for industrial activities in Suez, area from Aswan to Red sea, deep

back desert of Beni Suief and Fayoum. The salinity ranges from 1,500 to

5,000 (ppm).

3. 60,000 (km2) for mining along Suez Gulf in both sides in Sinai and in Red Sea

shore until Hurghada, back desert of Qena that has high amount of brackish

groundwater, and North Western Coast near El Alamin. The salinity ranges

from 1,500 to 2,500 (ppm).


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4. 20,000 (km2) for Safari tours near the Oasis in Western Desert. The salinity

ranges from 1,500 to 15,000 (ppm).

5. 50,000 (km2) of crops could be irrigated with brackish groundwater south

Qattara Depression, Qena, and Aswan. The salinity ranges from 1,200 to

15,000 (ppm).

6. 50,000 (km2) of wheat, maize, sunflower, alfalfa, barely, and olive could be

irrigated by brackish groundwater in Old Delta. The solar desalination could

provide drinking water in that area. The salinity ranges from 1,500 to 15,000

(ppm).

The results of the other 2 scenarios show that most of Egypt is suitable for solar

desalination. The (SDSS) process is dynamic and could run on several future change

variables. Solar desalination could save cost of piping and pumping Nile water for

new safe areas.

A spreadsheet model is used for performing comparative evaluation and assessment

of the solar desalination technically, environmentally, and economically. The model

consists of three matrixes. Matrix 1 computes thermal desalination, matrix 2

computes reverse osmosis (RO), matrix 3 computes solar still. Every matrix consists

of 3 processes:

Technical process computes quantities of water discharge, chemicals, energy,

and land use at each stage of desalination process. The desalination process

starts from saline water intake, primary and post treatment, solar

concentrating system, storage and distribution, and brine discharge.

Environmental process computes global warming emissions, cooling water,

brine, noise, and sludge.

Economical process computes the cost.

The model inputs are water quantity and quality (sea, brackish wells, or

drainage); Location potentiality (available land, nearby power station, solar energy

system).


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Model boundary conditions are: drainage water is only used in solar still

technology; Thermal distillation is only used if power station is available; Land

available must be larger than land required.

The model outputs runs show that the emissions, chemicals, and energy are

reduced by 99% when use solar energy. The massive production reduces desalination

cost from 2.7 to 0.06 ($/m3), Solar energy reduce cost from 1.65 to 0.04 ($/m

3),

nearby thermal power station reduce cost from 0.9 to 0.02 ($/m3), combined solar and

power station reduce cost to 0.01 ($/m3). Desalination of brackish water by (RO)

reduces cost from 0.6 to 0.36 ($/m3). Thermal desalination is preferable for coastal

regions for large quantities required for cooling water. This process could supply

fresh water for towns, villages, and new development sustainable projects. Reverse

osmosis is preferable for medium productivity for limited community as hotels,

hospitals, and industrial establishments. Solar still is preferable for small and medium

size desalination for remote area where land is available. Solar pond is a key issue in

solving brine problem in Egypt. Clean renewable energy could be extracted from

solar ponds in which brine is storing sun energy. A numerical model is used to predict

the performance of a solar pond under Egypt climatic condition. The mass and energy

balance equations have been used to compute pond temperature. The results show

that average pond temperature in Egypt reach 75 (ºC) that could be used in

thermodynamic cycles to produce energy.

This study suggests area around Qattara Depression to shift people from inundation

areas due to impacts of climate change induced (SLR) on the Nile delta. The (SLR)

water could be soaked away from lowest point in Delta to the depression. Clean

electric generation could be generated from net head of filling Qattara Depression.

Qattara Depression potentiality of generating hydropower could support Egypt future

needs and could be exported to Eastern Nile countries. The hydropower generation

from Qattara Depression does not need filling time, and high cost building dam.

Keywords: Desalination; Solar Energy; GIS; Mathematical Modeling; Wastewater;

Climate Change; Egypt.


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CHAPTER (1): INTRODUCTION

1.1 General

More than two-thirds of the earth’s surface is covered with water. Most of the

available water is either present as seawater or icebergs in the Polar Regions. More

than 97% of the earth’s water is salty; the remaining 2.6% is fresh water. Less than

1% fresh water is within human reach. This small amount is adequate to support life

and vegetation on earth. Nature itself provides most of the required fresh water,

through the hydrological cycle. A very large-scale process of solar distillation

naturally produces fresh water. The essential features of this process are thus

summarized as the production of vapors above the surface of the liquids, the transport

of vapors by winds, the cooling of air–vapor mixture, condensation and precipitation.

This natural process is copied on solar desalination. As the available fresh water is

fixed on earth and its demand is increasing day by day due to increasing population

and rapidly increasing of industry, hence there is an essential need to get fresh water

from the saline brackish water present on or inside the earth. This process of getting

fresh water from saline brackish water can be done easily and economically by

desalination, [36].

1.2 Problem Definition

In many countries that suffer a chronic shortage of water, such as those of the Middle

East and North Africa, over 80% of all fresh water consumed is used by agriculture.

As fresh water resources are finite, there is a pressure to reduce agricultural use of

water to meet the growing demand for domestic and industrial use, [13]. The number

of desalination plants in Egypt is 230 plants in 2000 with an overall capacity of

220000 (m3/day). The average quota of water resources in Egypt is expected to reach

645 (m3/person) in 2025. So there is a need for desalination to meet the requirements

of industry, tourism, petroleum, electricity, health, and reconstruction. The

desalination plants spread on the Red Sea coast, South Sinai, and the northern coast,

[30].


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1.3 Criteria

Overall evaluation of the various desalination technologies, research, developments

and previous studies show that desalination technologies varied from the

conventional to the advanced methods. Conventional desalination technologies are

thermal technology (distillation) and membrane technology. Advanced methods are

ion exchange, membrane distillation, freezing, and solar distillation.

The Greenhouse Gases (GHG) increases the temperature by about 2°C in 2020.

Reducing emissions of (GHG) could be achieved by switching to renewable energy.

Solar energy represents a huge energy resource for the world, particularly in the

southern countries close to the Equator, where the deserts have some of the best solar

resource levels. Egypt possesses a high intensity of solar radiation, all year round,

that justifies the economical use of this type of clean energy, [21].

The methodology of the present work is: Collect previous work data then analyze it

to get information, indicators, and finally index to put suitable solution to the

problem.

1.4 Aim of the Study

The objectives of the present work are preparation and development of digital maps

of pilot areas of solar desalination potentiality as an adaptation tool for climate

change impacts on the water resources in Egypt.

1.5 Outline of the Report

Chapter (1) offers an outline about the technical report contents. Chapter (2) is

concerned with the literature review. Chapter (3) describes design parameters to build

up Solar Decision Support System (SDSS) model under Egypt meteorological data. A

new safe area is suggested in this chapter as a solution for the inundation areas due to

sea level rise in the Nile delta. Chapter (4) is concerned with evaluation and

assessment of the solar desalination technology. Finally, conclusions and

recommendations are presented in chapter (5).


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CHAPTER (2): LITERATURE REVIEW

2.1 Potential Solar Desalination Work Globally

Worldwide there already exists a water supply crisis and the water quality is a major

concern. It is hoped that attention to this fact will make people more aware that water

resources are finite and water itself is not a totally renewable resource. Historically

and presently, water and energy were and still are two of the most critical and

interdependent fundamental elements of vital importance that determine and drive the

economics and consequently the culture and way of life in a society, [15].

2.1.1 Historical Background of Desalination and Renewable Energies

Delyannis, [8] has studied the history of desalination processes. He found that the sun

was especially esteemed by the Egyptians, Greeks, and Incas. Water and energy are

two inseparable items that govern our lives and promote civilization. Looking to the

history of mankind, one finds that water and civilization were also two inseparable

entities. It is not a coincidence that all great civilizations were developed and

flourished near large bodies of water. Rivers, seas, oases, and oceans have attracted

mankind to their coasts because water is the source of life.

The desalination concept from pre-historic times to middle ages

Of all philosophers of antiquity it is the well-known scientist, Aristotle (384–322),

who described in a surprisingly correct way the origin and properties of natural,

brackish and seawater. He writes for the water cycle in nature:

The sun moving, as it does, sets up processes of becoming and decay, and sweetest

water is every day carried out and is dissolved into vapor and rises to the upper

regions, where it is condensed again by the cold and so returns to the earth. Even

today no better explanation is given for the water cycle in nature. Really, the water

cycle is a huge solar energy open distillation plant. Mouchot (1869, 1879) the

well-known French scientist who experimented with solar energy, mentions in one of

his numerous books that during medieval times Arab alchemists carried out

experiments with polished Damascus concave mirrors to focus solar radiation onto

glass vessels containing salt water in order to produce fresh water.


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The development of solar desalination during the Renaissance period

Later on during the Renaissance, Giovani Batista Della Porta (1535–1615), one of the

most important scientists of his time wrote many books. In the volume on distillation

he mentions seven methods of desalination, but the most important reference is in the

19th

volume where he describes a solar distillation apparatus that converted brackish

water into fresh water (Della Porta). Fig. 1 shows the Della Porta solar distillation

unit. He also describes, in the second chapter of volume 20, a method to obtain fresh

water from the air (nowadays called the humidification– dehumidification method).

Fig. 1 Della Porta solar distillation apparatus, [8]

In 1870 the first American patent on solar distillation was granted to Wheeler and

Evans the inventors described the greenhouse effect, analyzed in detail the cover

condensation and re-evaporation, discussed the dark surface absorption and the

possibility of corrosion problems. High operating temperatures were claimed as well

as means of rotating the still in order to follow the solar incident radiation. Two years

later, in 1872, an engineer from Sweden, Carlos Wilson, designed and built the first

large solar distillation plant, in Las Salinas, Chile (Harding, 1883).


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2.1.2 Principle of Solar Distillation: a State of the Art

Solar still is an air tight basin, usually constructed out of concrete/cement, galvanized

iron sheet (GI) or fiber re-enforced plastic (FRP) with a top cover of transparent

material like glass, plastic etc. The inner surface of the base known as basin liner is

blackened to efficiently absorb the solar radiation incident on it. There is a provision

to collect distillate output at lower ends of top cover. The brackish or saline water is

fed inside the basin for purification using solar energy, [36].

2.1.3 Classification of Solar Distillation Systems

Solar distillation systems are classified as passive and active solar stills. In the case of

active solar stills, an extra-thermal energy by external mode is fed into the basin of

passive solar still for faster evaporation. The external mode may be collector

concentrator panel. Different types of solar still available in the literature are:

Conventional Solar Stills

Single-slope Solar Still with Passive Condenser

Double Condensing Chamber Solar Still

Vertical Solar Still

Conical Solar Still

Inverted Absorber Solar Still

Multi-Wick Solar Still

Multiple Effect Solar Still, [36]

Fig. 2 and Fig. 3 show the cross-sectional view of multi-wick solar still and Hybrid

solar distillation system.


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Fig. 2 Cross-sectional view of multi-wick solar still-passive mode, [36]

Fig. 3 Hybrid solar distillation system-active mode, [36]

2.1.4 Performance of Solar Still

The meteorological parameters namely wind velocity, solar radiation, sky

temperature, ambient temperature, salt concentration, algae formation on water

and mineral layers on basin liner affect significantly the performance of solar stills.

It is observed that there is about 10–15% effect in overall daily yield due to change of

climatic and operational parameters within the expected range, [36]. For better

performance of a conventional solar still, following modifications were suggested by

various researchers:

Reducing bottom loss coefficient

Reducing water depth in basin/multi-wick solar still using reflector

Using internal and external condensers


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Using back wall with cotton cloth

Use of dye

Use of charcoal

Use of energy storage element

Use of sponge cubes

Multi-wick solar still

Condensing cover cooling

Inclined solar still

Increasing evaporative area, [36].

Millions of people have no access to a secure source of fresh water. Nevertheless,

since many arid regions are coastal areas, seawater desalination is a reasonable

alternative. On the other hand, the energy requirements of desalination processes are

high. Then, the energy supply in low development countries or isolated areas may be

a problem, especially if electricity is required. Since most arid regions have high

renewable energy resources, the use of renewable energies in seawater desalination

exhibits an interesting chance, or even the only way to offers a secure source of fresh

water. The status and perspectives of development of coupling renewable energy

systems with desalination units seem to be the most mature ones, [12].

2.1.5 Solar Still Coupled with Thermal Storage and Solar Collectors

In summer the collector energy is not used at its whole. The hybrid design of this

system, which is able to supply not only desalted water but also hot water, from the

tank, could lead to higher water productivity in the day and night. This new system

consists of three parts:

1. asymmetric type single-effect solar still of greenhouse type

2. integrated storage

3. flat-plate solar collector field, Fig. 4.


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There is a water tank with the same dimensions as the basin just below the still’s

basin. There is no insulation between basin and storage tank, thus direct thermal

contact is established through the bottom of the basin. The tank is, insulated exactly

as the still’s basin in the bottom and sides. Inside the tank there exists a heat

exchanger, through which the heating medium coming from the solar collector field

flows. The water amount produced with the solar field in operation is about the

double than that when the still operated alone, in a 24 (hr) period, having an average

increase of distilled water productivity of around 100%. The night increase is higher

from about 60% up to 180%. This increase in the night operation is expected since

the water in basin remains hot enough so that distillation is continued during the

night.

Fig. 4 Hybrid solar distillation system, [25]

2.1.6 Solar Still Coupled with Thermal Storage and Other Heat Source

The conventional solar still is a solar device, which can use other heat sources.

Examples of these cases are:

shallow geothermal fields

solar ponds

industrial waste heat

heat recovery in condenser of chiller

cooling towers in air-conditioning installations, Fig. 5.

This type could save money that is needed for the rejection of the heat, improving at

the same time efficiency of other energy installations, such as air-conditioning units.


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Coupling solar still with storage tank leads to a significant increase in the production

rates. For example, system productivity under constant saline water temperature of 50

(°C) is almost five times more than productivity of the solar still working alone, for

similar weather conditions. The behavior of a solar still coupled with heat storage

tank has been found to be dint than that of the solar still itself regarding dependence

on solar radiation. Changes in solar radiation do not significantly affect production,

meaning that in the coupled still the hot water storage tank acts as the heat-collecting

unit and the solar still serves mainly as condensation unit.

Hot water usage from the distillation system; An interesting aspect of the solar still

coupled with storage tank and collector field is the ability to use it as a conventional

solar water heating system, that is to draw-off quantities of hot water from the storage

tank parallel to distilled water production.

Fig. 5 Solar still with storage tank and external heat source, [25]

2.1.7 Plastic Solar Water Purifier with High Output

Ward, [37] studied a solar water purifier which consisted of a carefully designed

black plastic sheet covered by a white glass window. The plastic was formed into an

array of interconnected square cells which contained impure water. The selected

material ensures that no plastic taste, color or smell is transferred to the pure water

output. There were no filters, no electronics, no moving parts and cleaning was rarely

needed. It was lightweight, cheap, strong, and durable and can be used in any sunny

location on Earth. Seawater input with 35,000 (ppm) of totally dissolved solids.

(TDS) was converted into potable water with a TDS of 1–2 (ppm). Yields up to 9

(liter/m2day) were obtained at 35 (°C) ambient or approximately 1000 (W/m

2) of

insulation. It is useful for poor communities suffering from polluted water and water-


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borne diseases affecting the health and life of young people in particular. It is a small

family units to have access to their own, self-made, pure drinking water that would

produce high-quality, potable water output from virtually any type of dirty input

water such as sea, bore, effluent, urine, radioactive, arsenic contaminated, brackish

etc. This device known as a ‘‘solar water purifier’’

Description of the solar water purifier: A black plastic sheet was vacuum formed

onto an aluminum pattern which had been machined to the desired shape. The

resultant plastic sheet consisted of a rectangular shaped array of shallow, square

section trays which were interconnected by a series of weirs. Each individual tray was

about 100 by 100 (mm) in cross-section and about 10 (mm) deep. The liquid holding

capacity of each tray was thus about 100 (ml). In all, the array consisted of 32 trays

and suitable channels for distributing and collecting the impure and pure water

outputs. Fig. 6 and Fig. 7 show the arrangement used.

Fig. 6 Plan view of solar water purifier showing water flow path, [37]

Fig. 7 Single unit solar water purifier, [37]


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The black plastic absorber panel was covered by a toughened, white-glass window

and sealed to it using the surface tension of the condensed water vapor produced

during its escape from the trays of impure aqueous liquid. A condensation collector in

the pure water collection channel redirected the sheeting flow of water from the

underside of the cover glass into the channel itself. The underside of the absorber

panel was thermally insulated. The solar water purifier was then mounted in an

aluminum frame for strength and shadow minimization. Finally, the frame was fitted

with folding legs so that overall, the system was inclined at 12.5 o

to the horizontal. A

handle for ease of carrying could be fitted if required. Large banks of solar water

purifiers could be used to obtain large volumes of potable water, neither legs nor

carry handles were needed.

Principle of operation: Short wavelength as ultraviolet, infra-red radiation (0.7–2.5

µm) from the sun is transmitted through the white glass, through the water and

absorbed by the black plastic. The plastic re-radiates at long wavelengths (8–10 µm),

hemi-spherically from each side of the plastic. On the non-water-side, an aluminum

reflector transfers this long wavelength radiation back to the plastic where it is

absorbed. On the water-side of the plastic, the long wavelength radiation is directly

absorbed by the water. The water gets hot and vaporizes. The water vapor drives out

the air in the cavity between the glass and water surfaces. The kinetic energy of the

water vapor molecules on the glass cannot return to its source, and to conserve

energy, the individual droplets coalesce forming a sheet of water which then runs

down the underside of the glass window into a collection channel. The ultraviolet

radiation (0.34–0.40 µm) combined with prolonged exposure times proves to be

extremely effective for the high killing rates (measured at >99.99%) of many

commonly occurring bacteria, such as, Salmonella spp., Shigellaspp., Escherica coli,

Campylobacter coli, etc. The good design geometry made the bacteria unable to cross

over the water vapor barrier above each tray of impure water.

Positioning the solar water purifier: In the southern hemisphere the purifier should

be oriented with the input end facing south as shown in Fig. 8, while in the northern

hemisphere the north and south positions must be interchanged. The purifiers is

facing in the north–south direction when the purifier shadow is aligned along the

purifier itself around 12 o’clock noon at your location, as shown in Fig. 9. This is the


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orientation to use if you want to operate the purifier in a fixed, stationary position.

For example, if you rotate the purifier every 30 (min). So throughout the day so that

its shadow is underneath itself then the overall output for that day will increase by

about 30%. Effectively you are tracking the sun. However, if you move the panel in

this way then you must be very careful to keep the panel level and avoid slopping any

impure water into the pure water outlet channel.

Fig. 8 Orientation of solar water purifier in southern hemisphere, [37]

Fig. 9 Align solar water purifier to the sun, [37]

The purifier must be adjusted to the horizontal so that the water level at both ends of

the input channel is the same height, as shown by the symbol H in Fig. 10. To avoid

the possibility of impure input water overflowing into the pure water outlet, the input

water should be fed slowly into the input channel until all the trays are full and water

is just starting to flow out of the impure water outlet. 4.5 (liter) of input water is

sufficient to fill the purifier unit. To maintain the purity of the output, a clean glass


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bottle rather than plastic should be used to collect the pure water output. The purifier

can be operated in two modes: in Static mode’ where the initial fill of 4.5 (liter) is not

replenished throughout the day, or in Dynamic mode’ as shown in Fig. 11 where

impure water from a reservoir drip feeds continuously through the purifier at a rate of

about 10–15 (liter/day).

Fig. 10 Level solar water purifier, [37]

Fig. 11 Dynamic mode operation in southern hemisphere, [37]

Maintenance of the solar water purifier: The major maintenance activity required

to ensure that the solar water purifier continues to provide pure water output is

cleaning. When the purifier is operated in the Dynamic mode, the dissolved solids in

the water continuously flow through the purifier into the overflow channel. Virtually

none of the dissolved solids settle out in the trays and therefore the purifier rarely

needs cleaning. If the purifier is operated in the Static mode, then the solids which

were in solution are deposited on the surface of each tray and further exposure to the

sun ultimately produces a colored hardened deposit that is undesirable. This deposit

can readily be removed by cleaning with a dilute acid solution such as citric acid (or

lemon juice) or oxalic acid, which are not harmful. In either operating mode, the

outer surface of the glass must be cleaned regularly to remove dust and any other


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contamination to allow maximum transmission of the sun’s rays through the glass and

into the water. Visually the glass will appear to be quite white, because these small

bubbles reflect the sun’s visible and near infrared radiation and totally prevent the

water from heating up, thus lowering considerably the efficiency of the purifier. This

occurs because of a buildup of a very thin, almost molecular layer on the glass

surface which prevents wetting taking place. This problem can be overcome by

removing the glass, cleaning it thoroughly and replacing it in its original position.

2.1.8 Solar Water Desalination System Utilizing a Passive Vacuum Technique

The efficiency of the solar stills depends on the temperature difference between the

water surface and the glass cover. To increase the temperature difference:

Increase the water surface by coupling the solar still to a flat plate solar

collector.

Reduce the temperature of the glass cover.

Increase the temperature difference between the saline water surface and the

transparent cover could by adding a condenser to the still, thus increasing the

heat sink capacity,

Increase the evaporation rate by using vacuum conditions to evaporate at a

low temperature and pressure.

Al-Kharabsheh, Yogi Goswami, [3] studied utilizing vacuum conditions for

evaporation and condensation, where a vacuum is created using natural forces of

gravity and atmospheric pressure. They proposed a desalination system consisted of a

solar heating system, and an evaporation chamber and a condenser at a height of

about 10 (m) above ground level, connected via pipes to a saline water supply tank

and a fresh water tank, respectively. Fig. 12 shows a schematic of the system. A

vacuum is created by balancing the hydrostatic and the atmospheric pressures in the

supply and discharge pipes.

The distillation of water at a lower temperature level requires less thermal energy.

This heat can be provided from solar collectors, which will operate at a higher

efficiency because of lower collector operating temperatures. Simple flat plate

collectors may be used to heat the saline water in the evaporator.


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As saline water in the evaporator starts evaporating, its salinity increases which tends

to decrease evaporation rate, so it becomes necessary to withdraw the concentrated

brine at a certain flow rate and inject saline water at a rate equivalent to the

withdrawal plus evaporation rates. The withdrawn water will be at a temperature

equal to that of the evaporator, so it becomes necessary to recover the energy from it.

A tube-in-tube heat exchanger is used for this purpose, where injected water flows

inside the inner tube and withdrawn water will flow in the annulus in a counter-

current direction.

Under the influence of vacuum conditions at the saline water surface in the

evaporator, water can be injected by the atmospheric pressure; hence no pumping

power is required. This makes the proposed system a continuous process type, unlike

a flat basin solar still which is usually a batch process. The withdrawn concentrated

brine can be concentrated further and used to construct a solar pond, which may be

used as a solar energy collection and storage system. The system will require periodic

cleaning by flushing and restarting it, so that the non-condensable gases are not

allowed to accumulate destroying the vacuum.

Fig. 12 Schematic of vacuum system, [3]

The evaporation chamber was feed by the cold fluid directly. The chamber was

provided by solar or other low-grade thermal energy through a closed loop heat


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exchanger as well as withdrawing the concentrated brine. The incoming cold fluid

and withdrawn brine pass through a tube-in-tube heat exchanger in order to extract

the maximum possible heat from the hot brine. The evaporation chamber is connected

to a condenser, which dissipates the heat of condensation to the environment. It is

known that the vapor pressure of seawater is about 1.84% less than that of fresh water

in the temperature range of 0–100 (°C). This means that if the top of the two

chambers (saline water evaporator and fresh water condenser) are connected while

maintained at the same temperature, water will distill from the fresh water side to the

saline water side. In order to maintain the distillation of potable water from the saline

water the vapor pressure of the saline water must be kept above that of the fresh

water, which is done by increasing the temperature of the saline water by solar

energy. To start up the unit, it is filled completely with water initially. The water is

then allowed to drop down out of the unit under the influence of gravity. Depending

on the barometric pressure, water falls to a level of about 10 (m) from the ground

level, leaving behind a vacuum above the water level in the unit. Vacuum enables

Fig. 13 shows the evaporator–condenser.

Fig. 13 Evaporator–condenser of vacuum system, [3]

A vacuum equivalent to 3.7 (kPa abs) or less can be created depending on the

ambient temperature at which condensation will take place. The effect of various

operating conditions (withdrawal rate, depth of water body and temperature of the

heat source) were studied experimentally and compared with theoretical results. The


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experimental results agreed well with the theoretical predictions. It was found that the

effects of withdrawal rate and the depth of water in the evaporator were small while

the effect of heat source temperature was significant. Based on theoretical simulations

the present system would perform much better than a simple flat basin solar still. A

multi-effect system based on the same principle, which would utilize the latent heat

of condensation from one stage to evaporate a part of water in the next stage, would

improve the performance even further, [3].

2.2 Potential Solar Desalination Application in Egypt and Its Future Perspective

2.2.1 Performance of Solar Still in Egypt

Abdel-Wahaab, El-Shazly, Swelam, [1] studied the performance of solar still to

maximize the productivity according to Egypt conditions. These modifications are

cover thickness, cover slope, evaporation and condensation surface areas and shapes

and the internal volume. They concluded that, when the cover thickness increased

from 2 to 3 then to 4 (mm), the daily output decreased by 2% and 7% respectively.

The cover slope with tilt angles with 17o, 25

o, 50

o and 75

o on vertical direction has

been tested with tilt angles on horizontal direction the tested tilt angles were 5o, 8

o

and 11o. The greatest amount of fresh water obtained under tilt angle of 50

o and 11

o.

The effect of the internal volume experimentally studied and observed that,

increasing the internal volume by 25%, 50% and 78% decreases the still output by

4.4%, 12.8% and 21% respectively. Increasing the evaporation surface area by 46.2%

increase the productivity by 16.7%, while increasing the condensation surface area by

24% it improved the productivity by 20%.

2.2.2 Concentrating Solar Technologies (CST)

Concentrating Solar Technologies (CST) involve devices, which concentrate solar

energy by focusing solar radiation onto a focal point or line. Mohamed, Mohsen,

Kaddah, [26] studied the performance of El Nasr pilot solar plant project involves the

construction of a 1,900 (m2) parabolic trough field to produce saturated process steam

at 7.5 (bars) and 175 (ºC) to supply El Nasr Pharmaceutical Chemicals factory in

Cairo, Egypt. The solar field comprises 144 solar parabolic trough collectors arranged

in 8 rows with 18 collectors in each row. The solar plant design includes the solar

field and process equipment, Fig. 14. The collectors are arranged to form four

identical hydraulic loops of 36 collectors each, through which the condensate passes

to gain solar heat and transfer it to the flash drum. In this plant, the flash drum,


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instead of the heat exchanger, is used to produce saturated steam. This is a first in

Egypt: The parabolic trough solar collectors are locally built and manufactured of

aluminum with dimensions 6 (m) long by 2.3 (m) aperture, Fig. 15. The heat absorber

tube lies in the focus of the collector where the direct beam solar radiation

concentrates, and is manufactured from carbon steel pipes coated with a black nickel

surface (selective emitter coat) with highly effective absorption and surrounded by a

glass envelope to minimize the heat losses. The solar collectors are monitored and

tracked automatically to follow the sun with a simple mechanism using electric

motors and worm gear actuators and a group of ropes and pulleys.

Processes: The condensate (or hot water) enters the condensate tank at 85 (°C) [as

per design, actually 25 (°C) only] from the existing EL-Nasr factory network. The

condensate pump transfers condensate from the condensate tank to the liquid outlet at

the bottom of the flash drum to replace the generated steam. The condensate pump

operates intermittently through two level switches (high/low) that monitor the level of

the condensate liquid inside the flash drum. The two streams are mixed together

before entering the recycle pump, which boosts the pressure of the mix to about 26

bars and sends it to the solar field at a constant rate of 28 (m3/hr), where solar heat is

added to the condensate as it travels through the solar collectors. The solar-heated

condensate returns to the flash drum at about 23 (bars) through an orifice/atomizer.

As the pressure inside the flash drum is kept (by the predominant El-Nasr steam

network) at some 7.5 (bar), flash steam is generated due to the flashing process. The

pressure of the solar plant is maintained and controlled by a check valve located on

the steam delivery line, [26]

Fig. 14 El-Nasr pilot solar steam generation plant layout, [26]


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Fig. 15 Solar parabolic trough collector in EL-Nasr Plant, [26]

2.2.3 Solar Energy Desalination for Arid Coastal Regions: Greenhouse

The most common desalination methods are based on fossil fueled thermal and

membrane processes, alternative techniques, such as solar desalination, are also being

considered. Solar methods are well suited for the arid and sunny regions of the world

as in North Africa and the Arabian Peninsula. Both efficiency and economics need to

be considered when choosing a solar desalination system. The Seawater Greenhouse

is a new development that produces fresh water from sea water, and cools and

humidifies the growing environment, creating optimum conditions for the cultivation

of temperate crops.

Fig. 16 shows the humidification–dehumidification method in a greenhouse structure

for desalination and for crop growth. The Sea-water Greenhouse produced fresh

water and crops in one unit. The temperature difference between the solid surfaces

heated by the sun and cold water drawn from below the sea surface was the driving

force in the system. The Greenhouse acted as a solar still while providing a controlled

environment suited for the cultivation of crops.

This technology founded to be of real benefit to coastal farms, worldwide, that are

struggling with the problem of saline intrusion. It will provide a real alternative to

increasing shortages of groundwater, [13].


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Fig. 16 Seawater greenhouse, [13]

2.2.4 Effect of Dust Deposition

El-Nashar, [11] studied the performance of a solar desalination plant (whether using

thermal or photovoltaic collectors

The dust deposition on the collector surface causes a drop in the transmittance

of the glass cover that affects both the collector efficiency and subsequently

the amount of heat collected.

Higher amount of dust accumulated means lower production. Production can

drop by about 40% when the transmittance drops from its clean condition

value of 0.98 to a very dusty value of 0.70.

2.2.5 Conventional Desalination Combined with Solar Energy

A field of tube collectors, thermally stratified heat accumulator could be used to

preheat seawater in a multiple effect distillation (MED) unit, Fig. 17.

Fig. 17 Solar desalination plant, [11]


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Egypt has the highest sun hours all over the year in the world. It has a great advantage

of being in best sun-belt region. Perfect meteorological conditions and land space are

available in remote areas. Solar desalination could supply fresh water for drinking

and for agriculture green house in these remote areas. The development in remote

areas would increase the exports, imports, tours, and political activities, and also

would save high cost of piping and pumping network from the River Nile to these

remote areas. Egypt has its political and cultural weight in the region that would

create development in manufacturing, operating, maintenance in desalination

technologies. Egypt lies on the northeastern side of Africa. Its area is about one

million (km2). Nile Valley and Delta area is 4%; Eastern desert 22 %; Western desert

68 %; and Sinai 6 %. Seawater desalinated represents 0.08% of water resources in

Egypt [5]. Most aquifer systems in Egypt contain high quantities of brackish

groundwater with salinity ranges from 1,500 to 15,000 (ppm). Groundwater sector in

Ministry of Water Resources and Irrigation in Egypt predicted the total amount of

brackish groundwater as shown in table 1, [14].

Table 1 Primary assessment of brackish groundwater in Egypt, [14]

Site Aquifer Salinity (ppm) Inventory

(billion m3)

Egyptian coasts Fissure carbonate

and Wadis

> 2,000 2

Nile Valley Ridges and

North Western Coast

Nile > 1,500 4

Western Delta Moghra > 3,000 1

Western Desert Fissure carbonate > 3,000 5

Sinai and Eastern

Desert

Nubian

sandstone

1,500 – 3,000 100

Total All aquifers 112

Low cost solar water desalination is a strategic solution for Egypt. The number of

desalination plants has increased in the last 30 years and generated 2333.963

(m3/day) in 2004, [35].

In conclusion solar desalination is feasible as the best technologies in Egypt.


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CHAPTER (3): SOLAR DECISION SUPPORT SYSTEM (SDSS) MODEL

3.1 Introduction

Identifying sites for solar desalination as an adaptive tool to climate change

vulnerability requires a clear conceptual framework as follow:

First step data were collected from reports, papers, scientific books, Central

Agency for Public Mobilization and Statistics (CAPMAS), World Bank data

base, and Information and Decision Support Center (IDSC), [17]. These data

were (maps, demography, climate, hydro-geology, aquifer systems, drainage

system, solid waste, and today’s and the future’s water needs).

Second step includes the classification of the data by using Geographic

Information System (GIS) to generate thematic maps. (GIS) and multi criteria

evaluation (MCE) were used in site classification. The concept of

classification degrees were done according to weighted linear combination

(WLC) method, as a kind of (MCE), and an analytic hierarchy process (AHP).

Third step was building up digital database in spread sheets files and

connected it to the previous thematic maps to generate digital maps for all

major elements of the study.

Fourth step was building up Solar Decision Support System (SDSS) model.

3.2 Design Parameters of (SDSS) Model

The input data for this model are the collected digital maps. The model runs through

8 tool boxes that were built in the main interface of the model Fig. 18. These 8 tools

represent the 8 study parameters for promising areas classification as follow:

1. Saline water (resources, salinity, and depth);

2. Solar Energy intensity;

3. Vulnerable areas due to climate change, Sea Level Rise (SLR), and Seawater

intrusion;

4. Topographic obstacles;

5. Power Potentiality (conventional and renewable);

6. Population;


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7. Land use;

8. National strategic plans for development.

3.3 Classification of (SDSS) Model

Each tool box classifies the potential priorities of promising area as in Table 2. The

model was run for each developed 8 factor toolboxes. The outputs of the 8 tool boxes

are digital maps with a detailed spread sheets file report determining where the

promising areas are. Then overlay all these digital maps with equal weights of each 8

tool boxes to produce the final classification of the most promising areas in Egypt.


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Fig. 18 User interface of (SDSS) model tool boxes


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Table 2 Classification of Solar Decision Support System (SDSS) model, numbers in parenthesis indicate the weights of each factor

Item

No.

Factor Parameter Classification degrees

1 2 3 4 5 6 7 8 9 10

1. [1/8]

Saline water

(resources,

salinity, and

depth)

[1/40]

Average

groundwater

depth

<0.002 0.002-0.01 0.01-0.05 0.05-0.5 0.5-0.6 0.6-0.7 0.7-0.8 0.8-.9 0.9-1 >1.5

2. [1/40]

Average

groundwater

salinity

<1,500 1,500-2,000 2,000-

2500

2,500-

3,500

3,500-

5,000

5,000-

6,000

6,000-

8,000

8,000-

10,000

10,000-

12,000

>15,000

3. [1/40]

Distance from

seas

<100 100-200 200-300 300-400 400-500 500-600 600-700 700-800 800-900 >1000

4. [3/80]

Distance from

salt lakes, and

main drains

network,

<50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 >500

5. [1/80]

Distance from

main production

wells

<50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 >500


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Item

No.


1 2 3 4 5 6 7 8 9 10

6. [1/8]

Solar Energy

intensity

[1/8]

Solar energy

intensity

>7.2 6.8-7.2 6.7-6.8 6.6-6.7 6.4-6.6 6.2-6.4 6-6.2 5.8-6 5.4-5.8 <5.4

7. [1/8]

Vulnerable

areas due to

climate change,

Sea Level Rise

(SLR), and

Seawater

intrusion

[1/16]

Delta sea level

rise

- 3-20

(M.S.L)

Sand

protection

3-4

(M.S.L)

Land

2-3

(M.S.L)

Land

1-2

(M.S.L)

Land

0-1

(M.S.L)

Land

-3-0

(M.S.L)

North

Lakes

-3-0

(M.S.L)

Fishers

aquaculture

-3-0

(M.S.L)

Land

Sensitive

attack sub

zones

8. [1/16]

Delta

subsidence

- - - - 0-0.5

(mm/year)

0.5-1

(mm/year)

1-2

(mm/year)

2-3

(mm/year)

3-4

(mm/year)

Above 4

(mm/year)

9. Seawater

intrusion

Seawater

desalination

North lakes

desalination

- - - - - - - Groundwater

desalination

10. Rock faults Out of classification (these areas are removed)

11. [1/8]

Topographic

obstacles

[1/16]

Land slope

<0-2 2-4 4-7 7-10 10-14 14-18 18-23 23-30 30-45 >45

12. [1/16]

Sand dunes

Class degree 10

13. Mountain

Chains

Class degree 10


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Item

No.


1 2 3 4 5 6 7 8 9 10

14. [1/8]

Power

Potentiality

(conventional

and renewable)

Thermal power

stations near sea

shores

Class degree 1

15. [1/80]

Distance from

main electrical

networks

<50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 >500

16. [1/80]

Natural gas

production

>0.011 0.00884-

0.011

0.00716-

0.00884

0.000773-

0.00716

0.000001-

0.000773

0-

0.000773

0 0 0 0

17. [1/80]

Potagas

production

>0.000529 0.000245-

0.000529

0.000225-

0.000245

0.000177-

0.000225

0-

0.000177

0 0 0 0 0

18. [3/40]

Wind speed

>9 9-8 8-7 7-6 6-5 5-4 3-4 stagnant stagnant stagnant

19. [1/80]

Possible biogas

production from

organic

municipal waste

and aquatic

weeds

>2 1-2 0.9-1 0.7-0.9 0.5-0.7 0.4-0.5 0.3-0.4 0.2-0.3 0.06-0.2 >.06


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Item

No.


1 2 3 4 5 6 7 8 9 10

20. [1/8]

Population

[1/20]

Rural to Urban

population ratio

90-100 80-90 70-80 60-70 50-60 40-50 30-40 20-30 10-20 <10

21. [3/80]

Population

(Capita No)

>0.5 0.4-0.5 0.3-0.4 0.25-0.3 0.15-0.25 0.12-0.15 0.08-0.12 0.045-0.08 0.025-

0.045

<0.025

22. [3/80]

Gross domestic

product (GDP)

<5 5-10 10-20 20-30 30-50 50-70 70-90 90-130 130-170 >170

23. [1/8]

Land use

[1/40]

Distance from

Delta and Nile

Valley Marakez

<50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 >500

24. [1/10]

Distance from

main port,

airports,

railways, roads,

and main piped

water networks

<30 30-60 60-90 90-120 120-150 150-180 180-210 210-240 240-300 >300


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Item

No.


1 2 3 4 5 6 7 8 9 10

25. [1/8]

National

strategic plans

for development

[7/80]

Potential

regions

Tourism Industry Old delta

agriculture

New

reclaimed

land with

saline

water

Mining Grassland Low flash

flood

High flash

floods

- -

26. [3/80]

Distance from

mining regions

(quarries, and

petrol fields)

<50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 >500

Distance (km); Salinity (ppm); Solar energy (kwh/m2/day); Gas production (billion metric ton/year); Wind speed (m/s); Ratio (%); Capita No (million)


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3.4 Analytical Hierarchy Process (AHP) to Buildup (SDSS) Model

Egypt is among the most vulnerable regions in Nile Basin Countries. This (SDSS)

model was carried out by overlaying climate hazard maps and potential capacity

maps on the spatial distribution of various areas of Egypt. The model is developed to

select suitable areas of solar desalination in Egypt. Classification degrees are

designed according to (AHP) to define the governing factors of the study. (AHP)

assists the decision-makers to simplify the problem by creating a hierarchy of criteria

that best suits their goal and their understanding of the problem [33]. The steps of

(AHP) are: define problem; set objectives; put criteria for evaluating the options;

establish priorities among the elements of the hierarchy; synthesize these judgments

to yield a set of overall priorities for the hierarchy; check the consistency of the

judgments; come to a final decision based on the results of this process [33]. The

steps of (SDSS) are:

1. Convert thematic feature to raster maps for all factors.

2. Numeric values of 1 to 10 are given for cell of all raster maps.

3. Each raster is weighted according to its importance.

4. The cell values of each input raster are multiplied by its weights.

5. The resulting cell values are added together to produce the output raster.

6. The total influence for all rasters equal 100 %.

7. Generate suitability map ranked in an ascending order. Most suitable areas

classification degree less than 4. Promising areas classification degree ranges

from 4 to 5. Low suitable areas classification degree ranges from 5 to 6.

Higher degree than 6 are unsuitable areas, [32].

8. Three scenarios were run by (SDSS) model to test the two extreme and the

moderate conditions of Egypt. The first is the optimistic scenario that covers

all possible solar desalination process in Egypt from class 1 to 10. The second

is the moderate scenario from class 3 to 7. The third is the pessimistic

scenario limited to classes 4 and 5.


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3.5 (SDSS) Model Inputs

3.5.1 Saline Water Resources Salinity and Depth

The saline water resources in Egypt used in this study are shown from Figs. 19 to 22.

Fig. 19 Salt lakes, Drains, Coastal aquifer, and Moghra aquifer in Egypt, modified

after [16]


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Fig. 20 Fissured carbonate aquifer, Nubian sandstone aquifer, and major production

wells in Egypt, modified after [16]


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Fig. 21 Average groundwater depth in Egypt, modified after [16]

Fig. 22 Average groundwater salinity in Egypt, modified after [16]


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3.5.2 Solar Energy

Egypt is located between latitudes 22° 0`, 31° 26` North extends from the

Mediterranean coast to the Cancer tropic that passes in the southern of Egypt. This

astronomical of Egypt offers warm tropical dry temperature and helps to evaporation.

So this site earns air and land of Egypt high solar radiation. The sun sends rays of a

vertical or near vertical to the land of Egypt in the summer when the sun is

perpendicular to the Cancer Tropic. The sun intensity is medium during the spring

and autumn and low during winter months (December-January-February) when the

sun is perpendicular to the Capricorn Tropic. Because of this location the length of

daylight in the summer increases to 14 (hr), this increases the amount of solar

radiation reaching the Earth in that period, [16]. Climatic Atlas of Egypt, [7]

describes the meteorological condition for data record of 30 years. It indicates that the

maximum global radiation is in June and minimum at December, which agree with

the movement of the sun. Moreover, the sky radiation reaches its maximum value in

spring season (April, May) this season is characterized by rising sand and sand

storms, while the minimum occurs during December and January. The range of

annual radiation is about 6 (MJ/m2/day).The direct solar radiation is maximum in

June and minimum in January over Cairo and Aswan with secondary maximum in

February. Two minimum take place in both May and October at Aswan, which are

due to the cloud covers during spring and autumn in the southern region in Egypt.

The lowest solar radiation occurs in the north of Egypt, where cloud increases. Solar

radiation increases further southwards as clear skies predominate. Solar radiation

decreases to small extent over mountainous areas, especially in the Sinai and Red

Sea, due to the formation of orthographic clouds. The annual solar radiation is 5

(kwh/m2/day) in northern Egypt, while it ranges from 7.1 to 20 (kwh/m

2/day) in

southern Egypt, Fig. 23, [29]. Table 3 shows global solar radiation on horizontal

surface (kwh/m2/day) and its annual average, [29]. Fig. 24 shows Egypt climatic

stations. Table 4 shows actual sunshine duration (hr/month) and its annual average,

[29].


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Fig. 23 Solar energy intensity in Egypt, [29]

Fig. 24 Egypt climatic stations


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Table 3 Global solar radiation on horizontal surface (kwh/m2/day) and its annual average, [29]

No Station Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

Average

1 Sidi Barani 3.11 3.77 5.26 6.65 7.07 7.95 7.98 7.21 6.17 4.65 3.38 2.79 5.50

2 Mersa Matruh 3.10 3.97 5.33 6.61 7.37 8.01 7.98 7.37 6.3 4.73 3.51 2.92 5.60

3 El-Arish 3.37 4.01 5.31 6.16 7.56 7.69 7.78 7.14 6.07 4.58 3.56 3.14 5.53

6 Cairo 3.04 3.70 5.04 6.05 6.96 7.45 7.25 6.64 5.71 4.49 3.29 2.85 5.21

7 Assuit 3.88 4.91 5.98 6.91 7.47 7.93 7.82 7.29 6.48 5.37 4.18 3.6 5.99

8 Aswan 4.70 5.65 6.61 7.41 7.68 8.02 7.94 7.45 6.76 5.81 7.96 4.39 6.70

9 Kharga 4.43 5.43 6.38 7.17 7.66 8.02 7.9 7.45 6.7 5.64 4.68 4.13 6.30

10 Hurghada 4.26 5.36 6.53 7.41 7.88 8.27 8.18 7.75 6.96 5.56 4.48 3.91 6.38

11 Abu Rudeis 3.90 4.97 6.28 7.27 8.01 8.15 8.11 7.74 6.77 5.16 4.23 3.58 6.18

Table 4 Actual sunshine duration (hr/month) and its annual average, [29]

No Station Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

Average

1 Sidi Barani 6.76 7.72 7.65 8.99 10.65 12.06 12.34 12.01 10.6 9.54 7.84 6.59 9.40

2 Mersa Matruh 6.84 7.61 8 8.98 10.59 11.85 12.19 11.89 10.52 9.01 7.87 6.2 9.30

3 El-Arish 6.98 7.93 8.06 9 10.75 11.78 11.75 11.4 11.34 9.33 7.64 6.82 9.40

6 Cairo 7.52 8.14 8.63 9.89 10.78 11.59 11.57 11.05 10.19 9.47 8.54 7.27 9.55

7 Assuit 8.53 9.46 9.77 10.2 11.3 12.3 12.43 12.03 10.7 10.1 9.64 8.38 10.40

8 Aswan 9.73 9.80 9.73 10.43 10.93 12.07 12.07 11.57 10.37 9.94 9.9 9.43 10.50

9 Kharga 9.49 10.13 10.35 10.45 11.53 12.33 12.45 12.05 11.24 10.6 10.08 9.77 10.87

10 Hurghada 9.20 9.70 9.66 10.49 11.59 12.81 12.47 12.08 11.17 10.17 9.73 8.85 10.66

11 Abu Rudeis 8.70 9.20 9.56 10.12 10.48 11.19 12.21 11.76 10.92 10.16 9.2 8.14 10.14


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3.5.3 Vulnerable Areas Due To Climate Change, Sea Level Rise (SLR), and

Seawater Intrusion

Climate change scenarios refer to a minimum temperature increase of 2 (ºC) leads to

sea level rise (SLR) of 0.5 and 1 (m) at the end of the 21st century, [18]. Delta is one

of the areas that are most prone to inundation as a result of expected (SLR). (SLR) is

also accompanied by soil subsidence at varying rates. Delta coastal zone is divided

into three sub zones depending on the degree of exposure and vulnerability to the risk

of erosion and sea level rise as follow:

Sub-Zone one: Areas of high risks. It is also vulnerable to subsidence or

erosion at high rates. These areas include Manzala Lake shore, Rosetta,

Gamasa, Damietta port, and Alexandria’s coastal strip that is considered as

one of the most vulnerable areas to the risk of inundation due to land levels

falling to less than 3 (m) below the current sea level, Fig. 25.

Sub-Zone two: Areas are relatively safe, as the presence of sand dunes

creates a natural defense line.

Sub-Zone three: Areas of naturally and artificially protected shores, Fig. 26,

[25].

Delta vulnerable to seawater intrusion, the seawater frontage reached 40 (km) near

Tanta city in the Delta [27].

Fig. 25 Delta subsidence in Egypt


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Fig. 26 Delta sea level rise, [18]

3.5.4 Topographic Obstacles

Relatively flat ground with lower slope far from sand dunes are preferable, Fig. 27.

Fig. 27 Sand dunes and land slope in Egypt, modified after [16] and [39]


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3.5.5 Power Potentiality (Conventional and Renewable)

The wind energy in Egypt reaches 10 (m/s). The potential areas of using wind power

are in the Northern Western Coast, Northern Sinai, the Gulfs of Suez and Aqaba, the

Red Sea coast, and large parts of Western Desert. The early national strategy of Egypt

in 1982 targeted to develop renewable energy to supply 5% of traditional energy

mainly from solar, wind, and biomass. Figs. 28 to 31 show power potentiality in

Egypt.

Fig. 28 Electric and wind power in Egypt, [28]

Fig. 29 Natural gas in Egypt, data from [5]


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Fig. 30 Potagas in Egypt, data from [5]

Fig. 31 Possible biogas production in Egypt, data from [10] and [23]


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3.5.6 Population

Figs. 32 to 34 show population in Egypt.

Fig. 32 Percentage of rural in Egypt, data from [5]

Fig. 33 Population in Egypt, data from [39]


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Fig. 34 Gross domestic product (GDP) in Egypt, data from [39]

3.5.7 Land Use

Fig. 35 shows major land use indicators in Egypt.

Fig. 35 Major land use indicators in Egypt


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3.5.8 National Strategic Plans for Development

Fig. 36 shows national project plans in Egypt.

Fig. 36 Potential regions for national projects in Egypt, Agriculture in Old Delta data

from [2]

3.6 (SDSS) Model Outputs

The first output is the optimistic scenario that covers all possible solar desalination

process in Egypt from class 1 to 10. Figs. 37 to 43 show classification degree of each

tool box of the first optimistic scenario.


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Fig. 37 Classification degree of promising areas in Egypt for saline water (resources,

salinity, and depth)

Fig. 38 Classification degree of vulnerable areas due to climate change, Sea Level

Rise (SLR), and Seawater intrusion in Egypt


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Fig. 39 Classification degree of topographic obstacles in Egypt

Fig. 40 Classification degree of electric grid, gas, possible biogas from wastes,

natural gas, and wind power potentiality in Egypt


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Fig. 41 Classification degree of population in Egypt

Fig. 42 Classification degree of land use in Egypt


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Fig. 43 Classification degree of potential regions for national strategic plans for

development in Egypt

3.7 Promising Areas for Desalination by Solar Energy in Egypt

The final output of the (SDSS) model is a digital map of pilot areas of solar

desalination potentiality in Egypt. The first optimistic scenario is shown in Fig. 44

that covers all possible solar desalination process in Egypt from class 1 to 10. The

second is the moderate scenario from class 3 to 7 is shown in Fig. 45. The third is the

pessimistic scenario limited to classes 4 and 5 is shown in Fig. 46. This (SDSS)

model is dynamic; consequently more result from it could be obtained for future

plans.


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Fig. 44 Promising areas for desalination by solar energy in Egypt, Optimistic

Scenario

Fig. 45 Promising areas for desalination by solar energy in Egypt, Moderate Scenario

+

+


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Fig. 46 Promising areas for desalination by solar energy in Egypt, Pessimistic

Scenario

Table 5 shows the zonal statistical analysis of the 3 scenarios. The potential of solar

desalination is greatest in Eastern Desert, upper Western Desert, Oasis, Old Delta,

and Gulf of Suez.

+


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Table 5 Zonal statistical analysis of potential areas of solar desalination in Egypt

Scenario Location

Classification Area (m2)

Groundwater Salinity (ppm)

Min Max Majority Minority Median

Optimistic

Scenario

1. Eastern Desert

2. South Sinai

3. Upper North Sinai

4. Strip line parallel to North Western

Coast

5. Western Oasis

6. Old Delta in area from Assuit to Qattara

Depression

7. El Wadi Elgadid

8. South Delta

9. Nile Valley fringes

Most suitable

areas

4.14 E+11 1200 15000 2500 9940 2500

Activities

Grass land 8 E+09 1500 12000 3500 12000 3500

Industry 7 E+09 1500 5000 2500 5000 2500

Mining 6 E+10 1500 15000 2500 9940 2500

Tourist 2 E+10 1500 2500 1500 2500 1500

Agriculture by saline water 5 E+10 1200 15000 2500 9940 2500

Agriculture in old delta 5 E+10 1500 15000 5000 9940 5000

1. Marsa Matruh governorate

2. Middle Sinai

3. Toshka

Promising

areas

3.31 E+11 1200 15000 1500 4800 1500

Activities

Grass land 5 E+09 2000 15000 2000 8000 3500

Industry 2 E+08 1500 3500 2500 1500 2500

Mining 2 E+10 1500 15000 2500 5000 2500


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Scenario Location




Tourist 8 E+09 1500 9940 1500 9940 1500


Agriculture in old delta

9 E+09 1500 15000 15000 5000 15000

1. Great sand sea in border between Egypt

and Libya

Low suitable

areas

8.79 E+10 1500 15000 1500 2400 1500

Activities

Grass land 2 E+07 2000 2000 2000 2000 2000

Industry - - - - - -

Mining 8 E+08 1500 1500 1500 1500 1500

Tourist - - - - - -



1. Rock faults

2. North Delta

3. Red Sea mountain chains

Unsuitable

areas

3.7 E+07 3600 3600 3600 3600 3600

Total area of optimistic scenario

8.33 E+11

Moderate

Scenario

1. Areas near sea shores thermal power

station

2. Old Delta from Assuit to south Qattara

Depression

3. Upper Eastern Desert from Suez Gulf to

Nile Valley

4. Extended Fringes around Qena in

Eastern and Western Desert

5. Lower Western Delta

Most suitable

areas

1.14 E+11 1200 15000 2500 15000 2500


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Scenario Location




Activities

Grass land - - - - - -

Industry 2 E+08 2500 5000 5000 2500 3500

Mining 3 E+10 2000 9940 2500 9940 2500

Tourist 4 E+07 1500 2500 1500 1500 1500



1. Sinai

2. Delta

3. Western Desert

Promising

areas

5.56 E+11 1200 15000 1500 9940 1500

Activities

Grass land 1 E+10 1500 15000 3500 15000 3500

Industry 9 E+08 1500 3500 2500 1500 2500

Mining 5 E+10 1500 15000 2500 2400 2500

Tourist 6 E+08 1500 2500 1500 2500 1500



1. Long Strip pass Great sand sea in border

between Egypt and Libya

Low suitable

areas

4.65 E+10

1500 9940 1500 3600 1500

Activities



Mining 2 E+07 1500 1500 1500 1500 1500

Tourist 6 E+07 2500 2500 2500 2500 2500

Agriculture by saline water - - - - - -

Agriculture in old delta - - - - - -


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Scenario Location




Total area of moderate scenario

2.15 E+11

Pessimistic

Scenario

1. Areas near sea shores thermal power

station

2. Fayoum

3. Wadi Natrun

Most suitable

areas

6.47 E+08 1200 3500 2000 1500 2000

Activities



Mining - - - - - -

Tourist - - - - - -


Agriculture in old delta - - - - - -

1. Most of Western Desert

2. Delta

3. Upper and lower Eastern Desert

4. Longitudinal strip pass Sinai

Promising

areas

6.28 E+11 1200 15000 1500 9940 1500

Activities

Grass land 1 E+08 2000 6000 3500 2500 3500

Industry 5 E+08 1500 5000 2500 5000 2500

Mining 8 E+10 1500 15000 2500 9940 2500

Tourist 8 E+08 1500 2500 1500 2500 1500



Total area of pessimistic scenario

1.63 E+11


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3.8 Inundation and New Safe Areas in Egypt

The inundation areas were described in Fig. 25 and Fig. 26. This study suggests a

new safe area to shift people from inundation areas due to impacts of climate change

induced sea level rise on the Nile delta. The most appropriate areas are North

Western coast and area around Qattara Depression that lies in the northern of Egypt.

This area is about 2% of Egypt. The lowest level of the depression is 134 (m) below

the sea level. The (SLR) water could be soaked away from lowest point in Delta to

the depression. Clean electric generation could be generated from net head of filling

Qattara Depression. Qattara Depression would defend the Delta from the sinking or

inundation of (SLR) and reduce the cost of protecting coastal shores, Fig. 47. The

total volume of depression at zero (MSL) is 1218 (trillion m3). Large quantities of

water could be desalinated and this will safe piping and pumping cost for transfer

Nile water to new safe areas. Qattara Depression would support, fish farming,

tourism, and agriculture. The depression will take 20 years to be filled to level -50

(MSL) and will generate 7100 (million KWH). If it works 8000 (hr) annually, then

the annual total power will be 56800 (MW) during filling period. The Ministry of

Electricity and Energy suggested establishing hydropower station to work 4 (hr/day)

at a level from -60 to +215 (MSL) to generate 2400 (MW) if work 4 (hr/day) and

generate 4800 (MW) if work 8 (hr/day) after filling period. Qattara Depression

potentiality of generating hydropower could support Egypt future needs and could be

exported to Eastern Nile countries. The hydropower generation from Qattara

Depression does not need filling time and high cost building dam, [24].


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Fig. 47 Soak away (SLR) to Qattara Depression


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CHAPTER (4): ASSESSMENT OF THE SOLAR DESALINATION

Technically, Environmentally, and Economically

4.1 Desalination Assessment Model

A spreadsheet model is used for conducting simple technical, environmental, and

economical assessment of desalination process, [22]. The model consists of three

matrixes. These matrixes transform flow desalination process into flow chart

computing system. Every matrix computes technical process, emissions, and cost.

4.1.1 Model inputs

The model inputs are:

Water quantity and quality (sea, brackish wells, or drainage).

Location (available land, nearby power station, solar energy intensity).

4.1.2 Model boundary conditions

For drainage water solar still technology is only used.

If power station is available thermal desalination is only used.

Land available must be larger than land required.

Matrix one is thermal desalination technology could be coupled with thermal

electrical power station or with solar collectors, or with both. The thermal desalination

flow process is shown in Fig. 48. Matrix two is the reverse osmosis desalination

technology could be coupled with solar energy. The reverse osmosis desalination flow

process is shown in Fig. 49. Matrix three is solar still desalination. The solar still flow

process is shown in Fig. 50. The reason for using these three processes is that these

processes are the most commonly used in the world and advisedly for Egypt. The

desalination model is shown in Fig. 51.


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Fig. 48 Thermal desalination flow process assessment model


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Fig. 49 Reverse osmosis desalination flow process assessment model

Fig. 50 Solar still flow process assessment model


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Fig. 51 Desalination assessment model

4.1.3 Model Database

A database worksheet is built for computing all parameters for desalination

technologies alternatives: Conventional thermal desalination; thermal desalination and

concentrating solar power (CSP); thermal desalination and combined heat and power

(CHP); thermal desalination and (CSP) and (CHP); Conventional reverse osmosis;


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reverse osmosis and (CSP); and solar still. Input values into process are negative and

output values from process are positive. The desalination model database is shown in

Fig. 52.

Water and sludge balance process

MED MSF RO

Intake Intake Intake

1.00 1 1.00

cooling water Feed water cooling water Feed water brine freshwater

0.67 0.33 0.7 0.3 0.67 0.33

brine freshwater brine freshwater Sludge (kg)

0.22 0.11 0.2 0.1 101.33

desalination effluent=cooling + brine desalination effluent=cooling + brine

0.89 0.9

Sludge (kg) Sludge (kg)

135.11 136.80

Fig. 52 Desalination assessment model data base


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4.1.4 Model Output

Model runs on virtual case of brackish water 100 (m3/day), using solar energy, and

available land area =5 (feddan) = 21,000(m2). The desalination model output is shown

in Fig. 53. The comparative results are shown from Figs. 54 to 60.


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Fig. 53 Desalination assessment model output

Solar Desalination as an Adaptation tool for Climate Change impacts

on the Water Resources of Egypt

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Fig. 54 Water process

Fig. 55 Chemicals process

Fig. 56 Land use process



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Fig. 57 Energy use process

Fig. 58 Emissions process

Fig. 59 Sludge and noise process



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Fig. 60 Economical process

4.2 Technical Assessment

The model results show that emissions reduced when use solar energy. Thermal

desalination, Process one is preferable for coastal regions for large quantities required

for cooling water. This process could supply fresh water for towns, villages, new

development sustainable projects. Reverse osmosis, Process two is preferable for

medium productivity for limited community as hotels, hospitals, industrial

establishments. Solar still, Process three is preferable for small and medium size

desalination for remote area where land is available, [22].

4.3 Environmental Assessment

The thermal desalination plants burning fuels cause global warming. Brine discharges

contain chemicals as anti-fouling materials. Brine also discharged at high temperature

and very high concentrated salts. The brine harms sensitive marine habitats as algal,

coral reefs, salt marsh, mangrove flats. Seawater and brine pipes may leak and pollute

groundwater. High pressure pumps produce noise over 90 dB (A).

According to World Health Organization (WHO), the permissible limit of salinity in

water is 500 (ppm) and for special cases up to 1000 (ppm). Excess brackishness

causes the problem of taste, stomach problems and laxative effects. One of the control

measures includes supply of water with total dissolved solids within permissible

limits of 500 (ppm) or less. Traditional desalination plants are uneconomical for low



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capacity fresh water demand, under these situations, solar stills are viewed as means

to attain self-reliance and ensure regular supply of water, [36].

Negative impacts of distilled water

No damages for the household uses, but harmful for drinking for long time,

weakening the immune system.

Effect of distilled water on the liver: Distilled water usually used in desert areas

away from the source of fresh water. So vegetables grown in desert land contain a

high concentration of silica. When eating these vegetables, the silica interacts with

distilled drinking water resulting in different silicate compounds in the body, which in

turn transmitted to the blood. It is known that the whole blood passes through the liver

every 4 minutes where the liver blocks the silica compounds resulting in stone

formation which leads to liver failure in the long time, [30].

Effect of distilled water on the skin and hair: Most skin specialists and cosmetics

experts agree that distilled water is the main reason for hair falling and skin dryness.

The distilled water does not contain minerals to feed the roots of the hair and the skin,

[30].

Effect of distilled water on the immune and digestive systems: The use of distilled

water regularly weakens the immunity, thereby exposing the body to infections

resulting from immunodeficiency. It also affected the digestive system by diarrhea

and intestinal diseases, especially when using regular drinking water in other

countries. The Gulf countries residents when using regular drinking water are

suffering from acute virus infection and other viruses associated with

immunodeficiency, [30].

Medical explanation for the harmful effects of distilled water: The human body

contains many salts and minerals in an electrolytic balance. Any imbalance destroys

the body's immunity so that the human body, which in turn begin a series of serious

diseases, [30].

Distilled water damage to vegetation: Desalinated water affects the growth of

plants. It spoils the Cytoplasm which in turn affects the process of photosynthesis in



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plants and could lead to plants death, [30].

Precautions when drinking distilled water: Must eat fresh vegetables, dairy

products and avoid coffee, alcohol, and cigarettes for the prevention of liver stone

formation

1 Consult a doctor specializing in electrolytic balance when feeling ill to treat

the imbalance of salts in the body.

2 To maintain electrolytic balance in distilled water, add manually for every

package of distilled water from 20 to 25 liters

1 spoon of iodine salt

1/4 to 1/2 tea spoon of potassium

1 / 8 iron tablet

Another method is used during the production of distilled water of large quantities by

adding treated sea water by 1:1 or 2:1, [30].

4.4 Economical Assessment

It is very important to conduct economic analysis and evaluation of an engineering

system to test it. The cost of the water produced depends on:

capital cost of equipment

cost of the energy and the operation

maintenance cost other than energy

In the case of solar stills, the cost of energy is a very small fraction of the total one,

since the energy other than solar is generally required for operating pumps and

controls. Thus, the major share of the water cost in solar still is that of the capital cost.

The production rate is proportional to the area of the solar still. This means that solar

still may be more attractive than other methods for small sizes. Solar still plants

having capacity less than 200 (m2/day) are more economical than other plants.

Distilled water production for potable use might be 3.5 times more economical than



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chemical water acquisition. Condensed water can be mixed with well water to

produce potable water. Impurities like nitrates, chlorides, iron, and dissolved solids in

the water are completely removed by the solar still, [36]. General economic analysis is

not easy to accomplish. The problem is that most of solar still are constructed from

local materials using local personnel. In such a situation, prices differ considerably

from one location to another, [13].

The Key issue in desalination assessment is how to dispose brine?

The answer is discharge the brine to a solar pond

A solar pond is a body of saline water that collects and store solar energy all the year.

Various models are available to predict solar pond performance. Solar pond can be

used to generate heat, generate electricity, and desalinate water. Solar pond heat could

be used for production of chemicals, foods, textiles, greenhouses, livestock buildings,

other low temperature agricultural applications, control of crystallization in certain

mining operations, and separation of crude oil from brine in oil recovery operations.

Solar ponds work in winter even when covered with a sheet of ice and surrounded by

drifts of snow, El Paso Solar Pond in Texas produced temperatures of 68 (°C) hot

enough to generate electricity. The electricity could be used for peaking and base load

power for remote locations. The supply heat from a solar pond can be used to improve

the output of desalting units to purify contaminated or minerally impaired water, and

the pond itself can become the receptacle for the waste brine products. A hyper saline

lake resort could be coupled with hot spa powered by solar pond hot water in tourism.

It is low cost per unit area, continuous storage capacity, and easily constructed over

large areas, it provides heat energy without burning fuel, thus reducing pollution. It is

site built and long life spans, [4]. Solar pond could be constructed in areas where brine

from desalination units or waste thermal energy from power plant cooling systems is

available. The cost of solar pond is 4-7 ($/m2), for surface area of 2000 (m

2) the total

cost is 15000 ($). The cost of power produced by a solar pond is about 120 ($/MWh)

about twice that of wind 20-60 ($/MWh- in a windy area) and three times that of coal

fired power 40 ($/MWh). Photovoltaic (solar cells) combined with batteries to provide

24 (hr) supply cost around 1000 ($/MWh). Solar ponds are much more reliable

delivering power 24 (hr) a day and 365 days a year.



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4.5 Solar Pond as a Solution of Brine

A numerical model is used to predict the performance of a solar pond temperature in

Egypt, [21].

Assumptions:

1. The solar pond is shallow or so large (surface area>>depth) and can be considered

as a one dimensional heat transfer model.

2. Energy and mass balance are calculated per unit area of the pond surface.

3. All side wall of the pond are insulated and do not shade the pond bottom.

4. The ground thermal conductivity is very low and neglected.

5. Inflow and outflow rates are high and can be considered as an un-stratified pond

Governing equations:

Mass balance

∆ṁ(kg/s)=ṁinlet-(ṁout+ṁevaporation+ṁseepageto ground and groundwater)=ρpond(kg/m3)

νpond (m/s) Apond(m2)

ṁevaporation(kg/s)=3600×24×1000

(mm/day)n evaporatioApond(m2) ρfresh water(kg/m3)

Equation (1)

Energy balance

The temperature is calculated from energy balance equations, [4]

qin-qout=dt

dTpondVρpondcp(pond)

balanceenergy for C/s)(º 0,cp V

constant2 +T×constant1

cp V

q+q+q+q+q+q+q

dt

dT

(pond)pond

pond

(pond)pond

fluidgrounwatergroundnevaporatioconvectionthermalsolarpond

Equation

(2)

qsolar = solar radiant heat gain to the pond

qsolar = I (1 – ρ´)Apond

Equation (3)



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qthermal = thermal radiant heat transfer at the pond surface

qthermal = hrApond (Tsky–Tpond)

hr= 3pondsky)

2

T +T (4 ,(Tsky, Tpond) should be (ºK)

Equation (4)

qconvection = convective heat transfer at the pond surface

free qconvection = hcApond (Tair–Tpond)

hc = Lc/s

k Nu fm,fm,, Lc/s= (pond area/pond perimeter)

Num,f = 0.664Repond1/2Prm,f

1/3(laminar flow)

Num,f = 0.037Repond4/5Prm,f

1/3 (turbulent flow)

forced qconvectionhc=hc+hwind,

hwind=Lc/s

k Nu fm,wind, Lc/s=(L+W) for simple assumption

Nuwind = 0.664Rewind1/2Prm,f

1/3(laminar flow)

Nuwind = 0.037Rewind4/5Prm,f

1/3(turbulent flow)

Rewind=fm,

fm, Lc/s WS

Equation (5)

qground = heat transfer to/from the ground in contact with the pond

qground =0 (the pond bottom and side walls are insulated)

Equation (6)

qgroundwater= heat transfer to/from the groundwater

qgroundwater =0 (the pond bottom and side walls are insulated)

Equation (7)

qevaporation= heat transfer due to evaporation

qevaporation = -7.732 ER Apond

Equation (8)



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Thermo-physical properties of saline water

Correlations and data for the thermo-physical properties of seawater were reviewed as

functions of temperature and salinity, [34]. Properties include density, specific heat

capacity, thermal conductivity, dynamic viscosity. The meteorological data are

collected from Weather Underground Inc., [38]. After running the numerical model

with initial pond temperature of 30 (ºC) the variation of temperature and heat

extraction with day time was examined as shown in Fig. 61.

Fig. 61 Solar pond temperature under Egypt climatic conditions, [21]



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CHAPTER (5): CONCLUSIONS AND RECOMMENDATIONS

Solar Decision Support System (SDSS) model was built for identifying

potential areas for solar desalination in Egypt. 3 Scenario were tested and gave

the following result:

Optimistic Scenario: Most suitable areas (0.414 million km2

– major

salinity 2,500 ppm); Promising areas (0.331 million km2

- major salinity

1,500 ppm); Low suitable areas (0.0898 million km2

- major salinity 1,500

ppm); and Unsuitable areas (20 km2

- major salinity 3,600 ppm). These

scenario areas are in Eastern Desert, Sinai, Strip line parallel to North

Western Coast, Western Oasis, Old Delta in area from Assuit to Qattara

Depression, El Wadi Elgadid, South Delta, and Nile Valley fringe.

Moderate Scenario: Most suitable areas (0.114 million km2

- major salinity

2,500 ppm); Promising areas (0.5561 million km2


ppm); and Low suitable areas (0.0456 million km2


ppm). These scenario areas are near sea shores thermal power station,

Upper Eastern Desert from Suez Gulf to Nile Valley, Extended Fringes

around Qena in Eastern and Western Desert, and Lower Western Delta.

Pessimistic Scenario: Most suitable areas (647 km2


ppm); Promising areas (0.628 million km2

- major salinity 1,500 ppm);

while now low suitable areas. These scenario areas are near, Fayoum, and

Wadi Natrun.

This study would help in the decision-making process for the use of water

desalination to be easier, better, faster, and effective.

Spread sheet model was used to perform comparative assessment of thermal,

reverse osmosis, and solar still desalination technologies.

The solar still is the most economical to provide drinking water for domestic

applications at decentralized level. It is simple in design, fabrication, easy to

handle, longer life. Further, low operation and maintenance, it is most suitable

in rural areas that has brackish groundwater.

Solar energy coupled to desalination suitable for remote regions, where



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connection to the public electrical grid is costly, and where the water scarcity

is severe.

The Greenhouse acted as a solar still technology is recommended to coastal

farms, suffering from saline intrusion. The development in these coastal areas

would increase the exports, imports, tours, and political activities, especially

with European Union Nations and also would save high cost of piping and

pumping network from the River Nile.

Starting to establish projects for desalinating large quantities of water to

develop new areas.

The cost of desalination is expected to be cheaper as a result of advances in

solar concentrating systems technology, especially when manufactured locally.

Start building environmental villages in the desert to prevent people transition

from rural to urban areas.

The solar energy could be stored in brine discharged to solar pond with

temperature range from 50 - 75 (ºC).

Through the study results, it can be recommended to enhance the (SDSS)

model with fine resolution maps and satellite groundwater exploration images

in Western Desert for more accurate results.

The (SDSS) and desalination assessment model should be reviewed with

specialist experts to get their feedback and field practices to rerun the model

with different weights and more criteria.



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ABBREVIATIONS

The following abbreviations are used in this study:

A Anti-scalents

AF Anti-foaming

AHP analytic hierarchy process

Apond pond area, (m2)

CHP combined Heat & Power

Cl chlorine

Co coagulants

CO2 global warming

cp(m,f) air specific heat capacity at film temperature, (J/kg·ºC)

cp(pond) pond specific heat capacity, (J/kg·ºC)

CSP concentrating solar power

CST concentrating solar technologies

dpond pond depth, (m)

ER evaporation rate, (mm/day)

Ethen summer Smog

ff fouling factor, (m2·ºC/W)

FRP fiber re-enforced plastic

GDP gross domestic product

GHG greenhouse gases



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GI galvanized iron sheet

GIS geographic information system

I solar radiant flux on horizontal, (W/m2)

k(m,f) air thermal conductivity at film temperature, (W/m·ºC)

kpond pond thermal conductivity, (W/m·ºC)

L pond length, (m)

M metals

MCE multi criteria evaluation

MED Multi-Effect Desalination

MSF multi-Stage Flash

MSL mean sea level

MtCO2e metric tons or tons of carbon dioxide equivalent

Num,f

air Nusselt number at film temperature = 0.664Repond1/2

Prm,f1/3

(laminar flow), 0.037Repond4/5

Prm,f1/3

(turbulent flow)

Nuwind

wind Nusselt number = 0.664Rewind1/2

Prm,f1/3

(laminar flow),

0.037Rewind4/5

Prm,f1/3

(turbulent flow)

PM10 particles

PO4 eutrophication

Ppond pond perimeter, (m)

Prm,f air Prandtl number at film temperature = cp(m,f)μm,f/km,f (-)

Prpond pond Prandtl number at film temperature = cp(m,f)μm,f/km,f (-)

q heat extraction, (W)



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Ram,f air Rayleigh number at film temperature, (-)

Rapond pond Rayleigh number at pond temperature, (-)

Rewind wind Reynolds number = ρm,fWS(L+W)/μm,f, (-)

RO reverse Osmosis

SDSS spatial decision support systems

SLR sea level rise

SO2 acidification

Tair air temperature, (ºC)

TDS totally dissolved solids

Tm,f air film temperature = [(Tair + Tpond)/2]+273.15

Tpond pond temperature, (ºC)

Tsky sky temperature=Tair(0.8+(Tdewpiont/250))0.25

, (ºC)

U fluid overall heat transfer coefficient, (W/m2·ºC)

V pond volume, (m3)

W pond width, (m)

WLC weighted linear combination

WS wind speed, (m/s)



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Greek symbols

∆T temperature difference, (ºC)

μm,f air viscosity at film temperature, (kg/m.s)

μpond pond viscosity, (kg/m.s)

νpond pond velocity, (m/s)

ρ´ reflectance of pond surface (-)

ρm,f air density at film temperature, (kg/m3)

ρpond pond density, (kg/m3)

σ Stephan-Boltzmann constant = 5.67 × 10-8

W/m2·K

4

pond emissivity coefficient (-)



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