Solar Energy Pocket Reference David Thorpe

Pages 204
Views 267
Size 2.5 MiB
Downloads 52
Solar Energy Pocket Reference David Thorpe
Tags:

Contents

List of figures and tables xiii
1 Sunlight 1
1.1 The nature of sunlight 1
1.2 Calculating photon flux 4
1.3 Spectral irradiance 5
2 Modelling available solar radiation 6
2.1 Total radiant power density 7
2.2 Black-bodies 8
2.3 Standard solar spectra 10
2.4 Solar time 11
2.4.1 The equation of time 12
2.4.2 The hour angle 13
2.4.3 The declination angle 14
2.4.4 The elevation angle 15
2.4.5 The azimuth angle 16
2.5 Sun path diagrams 17
2.5.1 Shading factor 17
2.6 Solar radiation at the earth’s surface 20
2.6.1 Net radiation 20
2.6.2 Air mass 20
viii Contents
2.6.3 Global horizontal irradiance (GHI) 22
2.6.4 The clearness index 23
2.6.5 The clear-sky index 24
2.7 Tilted surfaces 25
2.7.1 Solar incidence angles 25
2.7.2 Irradiance components 25
3 Emissivity and absorption of materials 30
3.1 Selective surfaces 31
3.1.1 Band gaps 33
3.2 Emittance 36
3.3 Absorptance 38
3.4 Absorption and emissivity of selective surfaces 40
3.5 Absorbed solar radiation by material 41
3.6 Spectral absorption of solar radiation in water 45
3.7 Light refraction in transparent materials 46
4 Photovoltaics 48
4.1 Photovoltaic cells 48
4.2 Types of cell 49
4.2.1 Wafer-based crystalline silicon
technology 49
4.2.2 Thin film 53
4.2.3 Concentrating solar power 55
4.2.4 Organic PV 56
4.2.5 Advanced inorganic thin films 57
4.2.6 Perovskite 57
4.3 Power calculations 58
4.4 Balance of system elements 62
4.5 General PV system design advice 65
4.6 Costs 66
4.7 Capacity factor 67
4.8 Small-scale stand-alone system design 67
Contents ix
4.9 Utility-scale PV 69
4.9.1 Fixed or tracking arrays? 70
4.9.2 Suggested time line for a project (with average
time estimate) 70
4.9.3 Operation and maintenance 72
4.10 Worked example 72
4.11 Safety issues 76
4.12 PV power for water pumping 79
4.13 Social and environmental aspects of PV 81
4.13.1 Energy payback 81
4.13.2 Carbon payback 81
4.13.3 Environmental effects of photovoltaics 82
5 Solar thermal systems 87
5.1 Collector types: small/medium scale 87
5.2 Small-scale solar thermal system types 90
5.2.1 Open loop system 92
5.2.2 Closed loop system 92
5.3 Medium-scale solar thermal system design 94
5.3.1 System efficiency 96
5.3.2 Tank sizing 96
5.3.3 Pump sizing 97
5.3.4 Safety issues 99
5.4 Collector types: large scale 100
5.4.1 Parabolic trough 100
5.4.2 Fresnel reflector 101
5.4.3 Solar tower 103
5.4.4 Solar dishes 103
5.4.5 Solar updraft tower 105
5.5 Large-scale solar system types 106
5.6 Evaluating collectors 109
5.6.1 Unglazed collectors 109
5.6.2 Flat collectors 110
x Contents
5.6.3 Concentrating collectors 111
5.6.4 Evacuated tubes 112
5.7 Solar thermal system calculations 113
5.7.1 Calculating thermal energy
requirements 113
5.7.2 Calculating flow rates in
heating systems 115
5.7.3 The f-chart method 115
5.7.4 Piping and tank losses 118
5.7.5 The utilisability method 119
5.8 Thermal storage systems 121
5.8.1 Sensible heat storage 122
5.8.2 Phase change materials (PCMs) 122
5.8.3 Thermo-chemical storage 126
5.8.4 Storage options for larger systems 126
6 Desalination and drying 129
6.1 The need for desalination 129
6.2 Technologies for desalination 130
6.3 Solar options for desalination 132
6.3.1 Concentrated solar power (CSP) 132
6.3.2 PV 138
6.3.3 Photovoltaic thermal technology (PV/T) 140
6.3.4 Concentrated evaporation 140
6.3.5 Plasmon-mediated solar desalination 141
6.4 Solar desalination greenhouse 142
6.5 Small scale: solar stills 143
6.5.1 Passive design 143
6.5.2 Active PV design 144
6.6 Solar drying 145
6.6.1 Three designs 145
6.6.2 Solar kiln 147
6.7 Solar pasteurisation 147
Contents xi
7 Solar cooling 151
7.1 Space cooling 151
7.1.1 Absorption NH3/H2O 152
7.1.2 Absorption H2O/LiBr 153
7.1.3 Adsorption 154
7.1.4 Open cycle liquid desiccant cooling 155
7.1.5 Solid desiccant air handling unit 156
7.1.6 Desiccant-enhanced evaporative (DEVAP)
air-conditioner 157
7.2 Solar design considerations 158
7.2.1 Evaluation 160
8 Making the business case 161
8.1 Financial case 161
8.1.1 Estimate the resulting cash flow 161
8.1.2 Apply the discount rate 162
8.1.3 Calculate the net present
value (NPV) 165
8.1.4 Compare the internal rate of
return (IRR) 165
8.2 Carbon offsetting 166
9 Units 169
9.1 SI radiometric units 169
9.2 Prefixes 171
9.3 Other energy units 172
9.4 Conversion factors 172
9.4.1 Conversion factors for mass 173
9.4.2 Conversion factors for volume 173
9.5 Power and energy 174
10 Standards 175
10.1 Standard setting bodies 175
10.2 Standards for solar measurement 176
xii Contents
10.3 Standards for solar thermal 176
10.4 Standards for solar PV 177
11 Resources for calculation and modelling 178
11.1 Datasets 178
11.2 Software 180
11.3 Case studies and technical information 181
Index 183