Renewable energy / Godfrey Boyle [ed.]

CONTENIDO
CHAPTER I INTRODUCING RENEWABLE ENERGY
1.1 Introduction 2
Force, energy and power 3
Energy conservation:The First Law of Thermodynamics 4
Forms of energy 4
Conversion and efficiency 6
1.2 Present-day energy use 6
World energy supplies 6
Energy use in the UK 8
1.3 Fossil fuels and climate change 10
1.4 Renewable energy sources 11
Solar energy: Direct uses 11
Solar energy: Indirect uses 12
Non-solar renewables 13
1.5 Renewable energy in a sustainable future 14
References and further information 15
CHAPTER 2 SOLAR THERMAL ENERGY
2.1 Introduction 18
2.2 The rooftop solar water heater 19
The pumped solar water heater 19
The thermosyphon solar water heater 20
2.3 The nature and availability of solar radiation 21
The wavelengths of solar radiation 21
Direct and diffuse radiation 22
Availability of solar radiation 22
Tilt and orientation 24
2.4 The magic of glass 26
Transparency 26
Heat loss mechanisms 27
2.5 Low-temperature solar energy applications 30
Domestic water heating 31
Domestic space heating 32
Varieties of solar heating system 34
2.6 Active solar heating 36
History 36
Solar collectors 36
Robustness, mounting and orientation 37
Active solar space heating 38
Interseasonal storage and solar district heating 39
2.7 Passive solar heating 40
History 40
Direct gain buildings as solar collectors 41
Passive solar heating versus superinsulation 41
Window energy balance 41
General passive solar heating techniques 45
Conservatories, greenhouses and atria 47
Trombe walls 48
Avoiding overshading 48
2.8 Daylighting 49
2.9 Solar thermal engines and electricity generation 51
The first solar engine age 52
The new solar age 54
Power towers 54
Parabolic trough concentrator systems 55
Parabolic dish concentrator systems 56
Solar ponds 56
Ocean thermal energy conversion (OTEC) 57
Solar chimneys 57
2.10 Economics, potential and environmental impact 58
Domestic active solar water heating 58
Swimming pool water heating 60
Active solar space heating and district heating 60
Passive solar heating and daylighting 60
Solar thermal engines and electricity generation 61
Conclusions 62
References 63
CHAPTER 3 SOLAR PHOTOVOLTAICS
3.1 Introduction 66
3.2 introducing photovoltaics 66
A brief history of PV 66
3.3 PV in silicon: basic principles 68
Semiconductors and 'doping' 68
The p-n junction 71
The PV effect 71
Monocrystalline silicon cells 75
3.4 Crystalline PV: reducing costs and raising efficiency 76
Polycrystalline silicon 76
Silicon ribbons and sheets 77
Gallium arsenide 77
3.5 Thin film PV 78
Amorphous silicon 78
3.6 Other thin film PV Technologies 79
Other innovative PV technologies 80
Multi-junction PV cells 80
Concentrating PV systems 80
Silicon spheres 81
Photoelectrochemical cells 81
'Third generation' PV Cells 82
3.7 Electrical characteristics of silicon PV cells and modules 83
3.8 PV systems for remote power 84
3.9 Grid-connected PV systems 85
PV systems for homes 85
PV Systems for non-domestic buildings 89
Large, grid-connected PV power plant 90
Satellite solar power 91
3.10 Costs of energy from PV 92
Reducing the costs of power from PV 94
3.11 Environmental impact and safety 95
Environmental impact and safety of PV systems 95
Environmental impact and safety of PV production 95
Energy balance of Pv systems 96
3.12 PV integration, resources and future prospects 96
Integration 96
PV resources 98
The growing world photovoltaics market 98
Future prospects: national and international PV research, development and demonstration programmes 99
Realizing the global potential 100
References 101
Further information 103
CHAPTER 4 BIOENERGY
4.1 Introduction 106
4.2 Bioenergy past and present 108
From wood to coal 108
Present biomass contributions 108
4.3 Biomass as a fuel 109
What are fuels? 109
Biomass as a solar energy store 111
Conversion efficiencies 112
4.4 Bioenergy sources 113
Energy crops 113
Woody crops 114
Agricultural crops 116
4.5 Bioenergy sources 116
Wastes 116
Wood residues 116
Temperate crop wastes 117
Tropical crop wastes 119
Animal wastes 119
Municipal solid waste 120
Landfill gas 120
Commercial and industrial wastes 122
4.6 Combustion of solid biomass 123
Combustion of wood and crop residues 123
Charcoal 124
Combustion of municipal solid wastes 125
4.7 Production of gaseous fuels from biomass 127
Anaerobic digestion 127
Anaerobic digesters for MSW 130
Gasification 131
4.8 Production of liquid fuels from biomass 133
Pyrolysis to produce bio-oil 133
Synthesizing liquid fuels 134
Fermentation te produce ethanol 134
Vegetable oils to biodiesel 136
4.9 Environmental benefits and impacts 137
Atmospheric emissions 137
Land use 139
Energy balance 140
4.10 Economics 141
Energy Prices 141
Costing bioenergy 141
Electricity from wastes 142
Electricity from Energy crops 143
4.11 Future prospects 144
References 145
CHAPTER 5 HYDROELECTRICITY
5.1 Introduction 148
5.2 The Galloway hydros 148
Origins 148
The scheme 149
Power 150
The turbines 150
The salmon 151
Economics 152
5.3 Hydro:The resource 153
The world resource 153
World capacity and output 154
5.4 Stored energy and available power 155
Stored potential energy 155
Power, head and flow rate 156
5.5 A brief history of water-power 157
The prime mover 157
Nineteenth-century hydro technology 160
5.6 Types of hydroelectric plant 16
Low, medium and high heads 162
Estimating the power 164
5.7 The Francis turbine 164
Action of the turbine 164
Maximizing the efficiency 167
Limits to the Francis turbine 167
5.8 'Propellers' 168
5.9 Impulse turbines 169
Pelton wheels 169
Turgo and cross-flow turbines 171
5.10 Ranges of application 172
Specific speed 172
5.11 Small-scale hydroelectricity 173
World-wide developments 173
SSH in the UK 175
5.12 Environmental considerations 177
Hydrological effects 177
Dams and reservoirs 179
Social effects 181
Small-scale systems 182
Comparisons 182
5.13 Integration 183
Power stations as elements in a system 183
Pumped storage 184
5.14 Economics 186
Capital costs 186
Investing in hydroelectricity 188
5.15 Future prospects 190
Small-scale hydro (SSH) 191
References 192
CHAPTER 6 TIDAL POWER
6.1 Introduction 196
The nature of the resource 197
Basic physics 198
Power generation 203
6.2 Technical factors 204
6.3 Environmental factors 210
6.4 Integration 215
6.5 Economic factors 218
6.6 Tidal energy potential 223
United Kingdom 223
World 225
6.7 Tidal barrages: conclusions 228
6.8 Tidal streams 230
Practical projects in the UK 231
Tidal current projects and concepts around the world 234
6.9 Tidal current turbines: the next stage 237
6.10 Tidal current assessment 239
References 241
CHAPTER 7 WIND ENERGY
7.1 Introduction 244
7.2 The wind 245
Energy and power in the wind 248
7.3 Wind turbines 249
A brief history of wind energy 249
Wind turbine types 252
Horizontal axis wind turbines 253
Vertical axis wind turbines 255
7.4 Aerodynamics of wind turbines 256
Aerodynamic forces 256
Aerofoils 258
Relative wind velocity 259
Harnessing aerodynamic forces 261
Horizontal axis wind turbines 261
Vertical axis wind turbines 264
7.5 Power and energy from wind turbines 265
How much power does a wind turbine produce? 265
How much energy will wind turbines produce? 266
Estimating wind speed characteristics of a site 268
7.6 Environmental impact 270
Environmental benefits of electricity generation by wind energy 270
Environmental impacts of wind turbines 270
Electromagnetic interference 273
Wind turbines and military aviation 274
Visual impact 274
Public attitudes to wind power 275
Wind turbines and birds 276
Additional environmental factors 277
Planning and wind energy 277
7.7 Economics 278
Calculating the costs of wind energy 278
7.8 Commercial development and wind energy potential 280
Wind energy developments world-wide 280
Small-scale wind turbines 283
Local community and co-operatively-owned wind turbines 283
Wind energy and buildings 284
Wind energy potential 285
7.9 Offshore wind energy 286
Offshore wind energy in the UK 288
References 292
Further Reading 295
Internet Sources 296
CHAPTER 8 WAVE ENERGY
8.1 Introduction 298
Recent history 298
8.2 Introductory case studies 299
8.3 Physical principles of wave energy 303
Typical sea state 303
Variations in the wave power at any location 307
Wave direction 308
What happens beneath the surface? 308
Moving into shallow water 309
Refraction 310
8.4 Wave energy resources 310
8.5 Wave energy technology 312
Fixed devices 314
Floating devices 317
Tethered devices 322
Wave energy research and development activity around the world 324
8.6 Economics 332
8.7 Environmental impact 334
8.8 Integration 334
Wave energy for isolated communities 334
Wave energy for large electricity grids 336
8.9 Future prospects 337
References 337
CHAPTER 9 GEOTHERMAL ENERGY
9.1 Geothermal energy an overview 342
The mining of geothermal heat 342
The source of heat 344
Historical perspective 346
9.2 The physics of geothermal resources 350
Primary ingredients 350
Volcano-related heat sources and fluids 353
The heat source in sedimentary basins 355
Geothermal waters 357
Why are there hot dry rocks? 358
9.3 Technologies for geothermal resource exploitation 359
Resources in high-enthalpy steam fields 359
Dry steam power plant 360
Single flash steam power plant 361
Binary cycle power plant 362
Double flash power plant 362
Future developments 363
Resources for direct use geothermal energy 363
Ground source heat pumps 364
Hot dry rock technology 368
9.4 Environmental implications 373
9.5 Economics and world potential 375
9.6 Geothermal potential in the United Kingdom 378
Sedimentary basin aquifers 378
Hot dry rocks 379
References 381
Further reading 381
The world wide web 381
Conference proceedings 382
Background material 382
CHAPTER 10 INTEGRATION
10.1 Introduction 384
10.2 The existing UK energy system 385
Energy flows 385
Distribution 386
10.3 How much renewable energy is available? 388
10.4 Are renewable-energy supplies available where we want them? 391
The present electricity grid 392
Wave, wind and tidal power 393
10.5 Are renewable-energy supplies available when we want them? 394
Renewables as heat suppliers 395
Integrating renewable electricity 396
10.6 Some system solutions 404
Grid strengthening 404
Demand management 405
PV, micro-CHP and emergency generators 405
Hydrogen - the fuel of the future? 406
10.7 Balancing economic options 410
Renewables and conservation 410
Balancing economic and environmental considerations 411
Renewable energy and planning permission 413
10.8 Promoting renewables 414
Supporting research and development 414
Targets 415
Legislation and building regulations 415
Financial incentives 415
Future EU policies 419
10.9 Energy scenarios: Danish examples 420
10.10 Global scenarios 422
International Energy Agency projections 422
10.11 Conclusions 429
References 430
Further information 432
Appendix 433
A1 Investing in renewable energy 433
A2 Units 437
ACKNOWLEDGEMENTS 439
INDEX 443