Thermal Solar Desalination

CHAPTER 1

1.1 Introduction

1.2 What is Desalination? – Where does it Apply? 1.2.1 The desalination processes

1.2.1.1 Distillation processes

1.2.1.2 Reverse Osmosis (RO)

1.2.1.3 Electrodialysis – Electrodialysis Reversal (ED – EDR)

1.2.1.4 Mechanical vapor compression

1.2.1.5 Crystallization processes

1.2.1.6 Ion-Exchange processes (IE) 1.3 Operation Steps of a Desalination Plant 1.4 Water and Energy

1.4.1 The energy necessary for desalination 1.5 Thermal Solar Desalination

1.6 New Trends in Desalination 1.6.1 Hybridization

1.6.2 Forward osmosis References CHAPTER 2

2.1 Introduction 2.1.1 What is really water?

2.1.1.1 The molecular structure of water

2.1.2 Natural waters

2.1.3 Water resources

2.1.4 The water problem

2.1.5 Water demand

2.1.6 Recycling and re-use of water 2.2 Water and Seawater Properties – Definitions

2.2.1 General definitions 2.3. The Chemical Composition of Seawater

2.3.1 The chemistry of seawater

2.3.2 What is Salinity(S) – Chlorinity (Cl)

2.3.3 Hardness - Alkalinity 2.4 Properties of seawater

2.4.1 General

2.4.1.1 The Gibbs function – Equation of State

2.4.1.2 Seawater as an electrolyte solution

2.4.1.3 pH

2.4.1.4 Density (ρ)

2.4.1.5 Activity (α) and activity coefficients (γ) – Chemical potential (μ)

2.4.1.6 Thermal conductivity (λ, k)

2.4.1.7 Diffusion – Diffusion coefficient, (D)

2.4.1.8 Viscosity (η, ν)

2.4.1.9 Ionic strength (I)

2.4.1.10 Enthalpy (H) - Specific enthalpy (h)

2.4.1.11 Enthalpy of evaporation (hev, or hfg)

2.4.1.12 Vapor pressure p - Boiling point elevation (ΔTel, or Δtel)

2.4.1.13 Heat capacity(C) - Specific heat (cp,cv)

2.4.1.14 Freezing point of water and seawater

2.4.1.15 The p-V-T diagram of water

2.4.1.16 Electrical conductance (Ec) / electrical resistance (Rc)

2.4.1.17 Dissolved gases and the carbonate system

2.4.1.18 Osmosis – osmotic coefficient 2.5 Suspended Particulate Material in Seawater

2.5.1 Suspended matter evaluation 2.6 Quality of Drinking and Utilization Water

2.7. Corrosion and Scale Formation 2.7.1. Corrosion

2.7.2 Scale formation and fouling

2.7.2.1 Alkaline scale formation

2.7.2.2 Sulfate scale, or acid scale

2.7.3 Scale prevention

2.7.3.1 Acid injection

2.7.3.2 Injection of carbon dioxide

2.7.3.3 Polyphosphates as scale inhibitors

2.7.3.4 The seeding technique 2.8 Conclusion

References

CHAPTER 3

3.1 Introduction 3.1.1 Definitions 3.2 Solar stills

3.2.1 Manufacture-Maintenance

3.2.2 Materials of construction

3.2.2.1 Basin materials

3.2.2.2 The absorbing black material

3.2.2.3 The Frames

3.2.2.4 Glazing material

3.2.2.5 Insulation material

3.2.2.6 The sealing material

3.2.2.7 Auxiliary components

3.2.3 Rain catchments canals

3.2.4 Conditions for proper installation/operation of solar stills 3.3 Operation principles of solar distillation - Solar stills

3.3.1 The phase movement inside the still

3.3.2 The cover inclination

3.3.3 The optical behavior of the transparent cover

3.3.4 Thermal behavior of solar stills

3.3.4.1 Heat balance - Heat transfer – Heat transfer coefficients

3.3.4.2 Efficiency, output and performance of solar stills

3.3.5.2 Nocturnal operation

3.3.6 The significance of the water depth

3.3.7 Increasing productivity of simple solar stills

3.3.7.1 Increasing vapor condensation rate

3.3.7.2 Increasing solar radiation absorption

3.3.7.3 Increasing feed seawater temperature

3.3.7.4 Connected to flat-plate collectors and to storage

CHAPTER 4

4.1 Introduction4.1.1 A short historical introduction 4.2 Terminology

4.3 Membrane Distillation 4.3.1 The Process

4.3.2 Process Configurations

4.3.3 Advantages – Disadvantages and Applications 4.4 Mass and Heat Transfer

4.4.1 Direct Contact Membrane Distillation (DCMD)

4.4.1.1 Mass Transfer

4.4.1.2 Heat Transfer

4.4.2 Air Gap Membrane Distillation (AGMD)

4.4.2.1 Mass Transfer

4.4.2.2 Heat Transfer

4.4.3 Sweep Gas Membrane Distillation (SGMD)

4.4.4 Vacuum Membrane Distillation (VMD)

4.4.5 Performance Parameters of MD Process 4.5 Characteristics of MD Configurations

4.6 Heat Recovery

4.7 Solar Powered Membrane Distillation (SPMD) 4.7.1 Techno-economic performance of solar powered systems 4.8 Membrane’s Characteristic Properties

4.8.1 Membrane Permeability

4.8.2 Liquid entry pressure (LEP) 4.9 Membrane Modules

4.10 Membrane Types 4.10.1 Commercial Membranes

4.10.2 Membranes Synthesis

4.10.2.1 Polymeric Membranes (polymer blends and additives)

4.10.2.2 Composite Membranes (Multi-layer, Hydrophilic/Hydrophobic)

4.10.2.3 Ceramic Membranes

4.10.2.4 Carbon Nanotubes

4.10.2.5 Electrospun Membranes References

CHAPTER 5

5.1 Introduction

5.2 Definitions

5.3 General operation principles 5.3.1 The setup of single effect conventional H/D system

5.3.2 Basic operation principles

5.3.3 Humidifying step – h-x diagram 5.4 Mathematical models

5.4.1 Conventional single effect H/D process

5.4.2 The dewvaporation process 5.5 Multiple-effect humidification-dehumidification (MEH)

5.5.1 H/D system using two collector fields 5.6 Other concepts of the H/D method

5.6.1 The desiccant absorption/desorption H/D process

5.6.2 Membrane drying humidification

5.6.3 H/D under varied humidification cycle

5.6.4 H/D systems with vapour compression 5.7 Solar H/D systems with storage tanks

5.8 The economics of the H/D method

5.9 Coupling solar stills or H/D systems to greenhouses

References

CHAPTER 6

6.1 Introduction 6.1.1 The available solar energy

6.1.2 Solar collectors

6.1.2.1 Solar Ponds (SP)

6.1.2.2 Flat Plate Collectors (FPC)

6.1.2.3 Evacuated Tube Collectors (ETC)

6.1.2.4 Concentrating Solar Collectors 6.2 Short historical review

6.3 Definitions and Nomenclature

6.4 Factors which influence the selection of the desalination system 6.4.1 Energy demand

6.4.2 Water demand 6.5 Factors influencing the selection of the solar system

6.5.1 Suitability of solar collectors for desalination6.6 Conventional desalination systems-Distillation methods

6.6.1 Multiple Effect Distillation (MED)

6.6.1.1 Τhe temperature distribution

6.6.1.2 Brief mathematical analysis

6.6.2 Multi-Stage Flash (MSF)

6.6.2.1 Thermal analysis of an MSF distillation system

6.6.3 Mass and energy balance

6.6.3.1 Heat and mass balance at the water cooling section

6.6.3.2 Heat transfer coefficients

6.6.3.3 Temperature ranges

6.6.4 Distillation with vapour (re)compression (MVC - TVC)

6.6.4.1 Mechanical vapour compression

6.6.4.1.1 MVC mathematical analysis

6.6.4.2 Thermal vapour compression 6.7 Dual purpose plants

6.8 Solar desalination combinations

References

Appendix I

Appendix II

Appendix III