Table of contents Energy Technologies Subvolume C: Renewable Energy  Title page ................................................................................................................................I
List of Autors ........................................................................................................................V
 Preface ............................................................................................................................... VII
1 Survey of renewable energy [K. Heinloth] .....................................................................1
1.1 Introduction: Renewable energy in the past, at present and in the future ..............................1
1.2 Worldwide demand on energy and potential of renewable energy........................................2
1.3 Technologies to convert renewable primary energy ..............................................................5
1.4 Possible utilization of the different kinds of renewable energy.............................................7
1.4.1 Hydropower to produce electricity ........................................................................................7
1.4.2 Wind energy...........................................................................................................................7
1.4.3 Sun light.................................................................................................................................7
1.4.4 Biomass..................................................................................................................................8
1.4.5 Heat from earth interior .........................................................................................................8
1.4.6 Heat from water, soil and air..................................................................................................9
1.4.7 Survey of main obstacles to increase the use of renewable energy by large .........................9
1.5 Synergy effects of extensive use of renewable energy ..........................................................9
1.6 References for 1 ...................................................................................................................10
2 Hydroelectric power ..........................................................................................................11
2.1 Introduction to hydroelectric power [Th. Strobl, F. Zunic] .............................................11
2.1.1 Development of hydro power ..............................................................................................12
2.1.2 Water power equation..........................................................................................................14
2.1.3 Energy output.......................................................................................................................15
2.1.4 Economical aspects of water power.....................................................................................17
2.1.5 References for 2.1 and additional literature .........................................................................18
2.2 River power plants [Th. Strobl, F. Zunic] .......................................................................19
2.2.1 Types of river power plants .................................................................................................19
2.2.1.1 Storage capacity...................................................................................................................19
2.2.1.2 Pressure head .......................................................................................................................20
2.2.1.3 Installed capacity .................................................................................................................20
2.2.1.4 Other definitions ..................................................................................................................20
2.2.2 Positioning river power plants .............................................................................................21
2.2.3 Diversion canal power plants...............................................................................................22
2.2.4 Components of hydroelectric plants ....................................................................................23
2.2.4.1 Power house.........................................................................................................................23
2.2.4.2 Turbine layout......................................................................................................................24
2.2.4.3 Cavitation.............................................................................................................................26
2.2.5 Auxiliary Buildings..............................................................................................................27
2.2.5.1 Weir .....................................................................................................................................27
2.2.5.2 Sluice ...................................................................................................................................28
2.2.6 Ecological aspects of hydro power plants............................................................................29

2.2.6.1 Residual flow .......................................................................................................................29
2.2.6.2 Fish passages .......................................................................................................................31
2.2.6.3 Effects on the groundwater table .........................................................................................32
2.2.7 References for 2.2 ................................................................................................................33
2.3 High pressure power plants [E. Puerer, G. Goekler].......................................................34
2.3.1 Introduction..........................................................................................................................34
2.3.1.1 Purpose and demand ............................................................................................................34
2.3.1.1.1 Energy production ...............................................................................................................34
2.3.1.1.2 Multi purpose schemes ........................................................................................................34
2.3.1.2 Layout and design................................................................................................................35
2.3.1.2.1 Catchment area inflow, water intake altitude.......................................................................35
2.3.1.2.2 Reservoir volume, storage capacity .....................................................................................37
2.3.1.2.3 Determination of capacity of a HPPP ..................................................................................37
2.3.1.2.4 Efficiency of HPPPs ............................................................................................................37
2.3.2 Types of high pressure power plants ...................................................................................38
2.3.2.1 General aspects ....................................................................................................................38
2.3.2.2 HPPP with reservoir ............................................................................................................38
2.3.2.3 HPPP without reservoir .......................................................................................................39
2.3.2.4 HPPP at the toe of a high dam .............................................................................................40
2.3.3 Intake and storage ................................................................................................................40
2.3.3.1 Concrete dams......................................................................................................................40
2.3.3.1.1 Gravity dams........................................................................................................................42
2.3.3.1.1.1 Constructive particularities for mass concrete .....................................................................43
2.3.3.1.1.2 Special methods of construction: RCC and RCD ................................................................43
2.3.3.1.2 Arch dams ............................................................................................................................44
2.3.3.1.3 Other types of concrete dams...............................................................................................45
2.3.3.2 Earth- and rockfill dams ......................................................................................................45
2.3.3.2.1 Types, conception and linings .............................................................................................46
2.3.3.2.2 Foundation, sealing in the subsoil........................................................................................47
2.3.3.3 Safety aspects of dams .........................................................................................................48
2.3.3.4 Intake structures for diversion .............................................................................................49
2.3.3.4.1 Intake structure (weir)..........................................................................................................49
2.3.3.4.2 Power intake ........................................................................................................................50
2.3.3.5 Bottom and medium outlets .................................................................................................50
2.3.3.6 Spillways..............................................................................................................................51
2.3.3.6.1 Types of spillways ...............................................................................................................51
2.3.3.6.2 Transition and energy dissipation ........................................................................................52
2.3.4 Water conduits for a HPPP ..................................................................................................53
2.3.4.1 Free surface canals...............................................................................................................53
2.3.4.2 Free surface tunnels .............................................................................................................53
2.3.4.3 Pressure tunnels ...................................................................................................................54
2.3.4.3.1 Tunnels without lining and sealing ......................................................................................55
2.3.4.3.2 Tunnels with lining and without sealing ..............................................................................55
2.3.4.3.3 Tunnels with lining and sealing ...........................................................................................56
2.3.4.3.3.1 Pre-stressed concrete lining .................................................................................................56
2.3.4.3.3.2 Lining with plastic membranes ............................................................................................56
2.3.4.3.3.3 Steel lining ...........................................................................................................................56
2.3.4.3.3.4 Thin-walled steel lining .......................................................................................................57
2.3.4.3.3.5 Pressure tunnels with conventional or pre-stressed reinforcement ......................................57
2.3.4.4 Surge tanks...........................................................................................................................57
2.3.4.5 Pressure shaft .......................................................................................................................59
2.3.4.6 Penstocks .............................................................................................................................59
2.3.4.6.1 Penstock manifold................................................................................................................60
2.3.5 Powerhouse of a HPPP ........................................................................................................61
2.3.5.1 General arrangement of the powerhouse .............................................................................61
2.3.5.2 Open air powerhouse ...........................................................................................................63
2.3.5.3 Underground power stations................................................................................................63
2.3.5.4 Powerhouse at the toe of high dams ....................................................................................64
2.3.5.5 Tailrace ................................................................................................................................65
2.3.6 Economical aspects..............................................................................................................66
2.3.6.1 Investment costs...................................................................................................................66
2.3.6.2 Costs for operation and maintenance ...................................................................................67
2.3.6.3 Service life ...........................................................................................................................67
2.3.6.4 Energy costs, price...............................................................................................................67
2.3.7 Further aspects of HPPPs.....................................................................................................67
2.3.7.1 Sedimentation ......................................................................................................................67
2.3.7.2 Effects of a HPPP on the ecology ........................................................................................68
2.3.7.3 Reflections on flood dimensioning ......................................................................................69
2.3.8 Examples of HPPPs and PPs at the toe of a dam .................................................................70
2.3.9 References for 2.3 ................................................................................................................71
2.4 Mechanical and electrical design of the TGP [D. Yuan, Z. Tian, S. Wang] ....................73
2.4.1 Introduction of the Three Gorges Project ............................................................................73
2.4.2 Content and characteristics of the mechanical and electrical design ...................................75
2.4.2.1 The design content of the mechanic and electric engineering .............................................75
2.4.2.2 Characteristics and principles of the mechanical and electrical design ...............................75
2.4.3 Hydro-turbine generator units with a rated power of 700 MW ...........................................77
2.4.3.1 Basic conditions for the selection of units ...........................................................................77
2.4.3.2 Measures for main technical problems ................................................................................78
2.4.3.2.1 Study on stability of Francis turbines ..................................................................................78
2.4.3.2.2 Alternatives of temporary runners .......................................................................................78
2.4.3.2.3 Time limit for the installation of units .................................................................................79
2.4.3.2.4 Study on anti-vibration of the powerhouse..........................................................................80
2.4.3.2.5 Cooling method of the generator .........................................................................................80
2.4.3.2.6 Arrangement of the thrust bearing .......................................................................................80
2.4.3.3 The turbine...........................................................................................................................81
2.4.3.3.1 Basic characteristics of the power station ............................................................................81
2.4.3.3.1.1 Water levels and discharges of the power station ................................................................81
2.4.3.3.1.2 Operating parameters of the power station ..........................................................................81
2.4.3.3.1.3 Probability occurrence of the various heads ........................................................................82
2.4.3.3.1.4 Power station operation modes ............................................................................................82
2.4.3.3.1.5 Tail water levels...................................................................................................................83
2.4.3.3.1.6 Special requirements for the TGP turbine operation ...........................................................84
2.4.3.3.2 Basic characteristics and main parameters of the turbine ....................................................84
2.4.3.3.2.1 Type of the turbine...............................................................................................................84
2.4.3.3.2.2 Specific rating ......................................................................................................................84
2.4.3.3.2.3 Optional speed .....................................................................................................................85
2.4.3.3.2.4 Cavitation coefficient and setting ........................................................................................85
2.4.3.3.2.5 Operational range.................................................................................................................85
2.4.3.3.2.6 Turbine efficiency and energy production ...........................................................................86
2.4.3.3.2.7 Cavitation damage ...............................................................................................................88
2.4.3.3.2.8 Cracking guarantee of the runner.........................................................................................88
2.4.3.3.3 Model tests...........................................................................................................................88
2.4.3.3.3.1 Efficiency and output...........................................................................................................89
2.4.3.3.3.2 Cavitation.............................................................................................................................90
2.4.3.3.3.3 Operating stability................................................................................................................90
2.4.3.3.3.4 Hydraulic thrust ...................................................................................................................92
2.4.3.3.4 Structure of main parts.........................................................................................................93
2.4.3.3.4.1 General arrangement............................................................................................................93
2.4.3.3.4.2 Stay ring...............................................................................................................................93
2.4.3.3.4.3 Spiral case ............................................................................................................................93
2.4.3.3.4.4 Gate operating mechanism...................................................................................................95
2.4.3.3.4.5 Runner and connection between runner and main shaft ......................................................96
2.4.3.3.4.6 Bottom ring and head cover.................................................................................................96
2.4.3.3.4.7 Turbine shaft and shaft seal .................................................................................................97
2.4.3.3.4.8 Air admission system...........................................................................................................97
2.4.3.4 Generator .............................................................................................................................97
2.4.3.4.1 Main parameters and performance of the generator ............................................................97
2.4.3.4.2 Structures, dimensions and weights of the generator main components..............................99
2.4.3.4.2.1 Stator..................................................................................................................................100
2.4.3.4.2.2 Rotor ..................................................................................................................................101
2.4.3.4.2.3 Bearings of the generator...................................................................................................102
2.4.3.4.2.4 Generator shafts .................................................................................................................103
2.4.3.4.2.5 Upper and lower brackets ..................................................................................................104
2.4.3.4.3 Stability of the generator....................................................................................................104
2.4.3.4.4 Rigidity and strength..........................................................................................................105
2.4.3.4.5 Generator cooling method and cooling system..................................................................105
2.4.3.4.6 The generator neutral point grounding system ..................................................................107
2.4.4 Electrical design.................................................................................................................109
2.4.4.1 Integration of the power station into the power system .....................................................109
2.4.4.2 Electric main single line diagram.......................................................................................110
2.4.4.2.1 Combination between generator and transformer ..............................................................111
2.4.4.2.2 Diagram of the 500 kV switchgear ....................................................................................112
2.4.4.3 Selection of the main electric equipment ...........................................................................112
2.4.4.4 Explanation of the main technical issues ...........................................................................114
2.4.4.4.1 Partial discharge level ........................................................................................................114
2.4.4.4.2 Insulation level...................................................................................................................114
2.4.4.4.3 Very fast transient over voltage (VFTO) ...........................................................................114
2.4.4.4.4 100% breaking DC component of circuit breaker .............................................................116
2.4.4.5 Arrangement of the electric equipment..............................................................................116
2.4.5 Automation of the Three Gorges-Gezhouba cascade project ............................................118
2.4.5.1 Functions of the system .....................................................................................................118
2.4.5.1.1 Functions of the cascade dispatch level .............................................................................118
2.4.5.1.2 Functions of the station subsystem level............................................................................118
2.4.5.1.3 Functions of the local level ................................................................................................120
2.4.5.2 System structure.................................................................................................................120
2.4.5.3 Main technical characteristics of the system......................................................................120
2.4.5.4 Communication of the computer supervisory control system............................................121
2.4.6 Communication of the Three Gorges-Gezhouba cascade project......................................122
2.4.6.1 Functions of the communication system............................................................................122
2.4.6.2 Scheme of the communication system...............................................................................122
2.4.6.3 Supervision and management system of communication network ....................................123
2.4.7 Electric drive and control of the double-line continuous 5-level ship lock .......................124
2.4.7.1 Electric drive and control of miter gates and the culvert valves ........................................124
2.4.7.2 Central auto supervisory control of integral operation for the permanent ship lock..........127
2.4.8 Economical aspects of the Three Gorges Project...............................................................128
2.5 Tidal power plants (TPP) [Won-Oh Song, W. van Walsum] ........................................129
2.5.1 Introduction........................................................................................................................129
2.5.2 The tides.............................................................................................................................130
2.5.2.1 Cause and effect.................................................................................................................130
2.5.2.2 Characteristics....................................................................................................................131
2.5.2.3 Resonance ..........................................................................................................................131
2.5.2.4 Energy potential.................................................................................................................132
2.5.2.5 Coastal zones with substantial tides...................................................................................133
2.5.3 Schemes and operating modes of TPPs .............................................................................134
2.5.4 Preliminary assessment of the annual energy potential of single-basins TPPs..................138
2.5.4.1 Application of the modeling technique to a single, high-basin TPP..................................140
2.5.4.1.1 Geography and hydrography of the chosen site.................................................................140
2.5.4.1.2 Sluicing ..............................................................................................................................140
2.5.4.1.3 Power generation ...............................................................................................................141
2.5.4.1.4 Change in water level Lh of high basin ..............................................................................141
2.5.4.1.5 Building and operating the model......................................................................................141
2.5.4.2 Application of the modeling technique to a single, low-basin TPP...................................142
2.5.5 The economic value of tidal energy...................................................................................142
2.5.5.1 Economic fringe benefits ...................................................................................................143
2.5.6 Tidal power engineering since the 1960s .........................................................................143
2.5.6.1 The La Rance TPP .............................................................................................................144
2.5.6.1.1 Purpose ..............................................................................................................................144
2.5.6.1.2 The site...............................................................................................................................144
2.5.6.1.3 The plant ............................................................................................................................144
2.5.6.1.4 Construction.......................................................................................................................145
2.5.6.1.5 Operation ...........................................................................................................................146
2.5.6.1.6 Environment ......................................................................................................................149
2.5.6.1.7 Cost of energy....................................................................................................................149
2.5.6.2 The Annapolis pilot TPP....................................................................................................149
2.5.6.3 The Kislaya Guba pilot TPP ..............................................................................................151
2.5.6.4 Tidal power applications in China .....................................................................................152
2.5.6.4.1 The Jiangxia experimental TPP .........................................................................................152
2.5.6.4.2 The Shashan TPP ...............................................................................................................154
2.5.6.4.3 The Haishan TPP ...............................................................................................................154
2.5.6.4.4 The Xingfuyang TPP .........................................................................................................154
2.5.6.5 Environmentally-oriented pilot TPPs ................................................................................154
2.5.7 Layout and civil works design of a TPP ............................................................................155
2.5.7.1 Construction in the dry ......................................................................................................156
2.5.7.2 Construction in the wet ......................................................................................................156
2.5.7.3 Power plant design.............................................................................................................157
2.5.7.4 Sluiceway design ...............................................................................................................158
2.5.7.5 Numerical, hydraulic and hybrid models as tools for design and construction planning ..158
2.5.8 Some rules-of-thumb for assessing tidal power potentials ................................................159
2.5.9 The future of tidal energy ..................................................................................................160
2.5.9.1 Environmental concerns ....................................................................................................161
2.5.9.2 Lack of confidence in cost estimates .................................................................................161
2.5.9.3 Concern about the value of tidal energy ............................................................................161
2.5.10 References for 2.5 ..............................................................................................................162
2.6 Pumped storage power plants [W. Bogenrieder] ............................................................165
2.6.1 Basic aspects ......................................................................................................................165
2.6.2 Upper and lower reservoirs................................................................................................168
2.6.2.1 Natural reservoirs...............................................................................................................169
2.6.2.2 Artificial reservoirs ............................................................................................................169
2.6.3 Intake and outlet structures ................................................................................................172
2.6.3.1 Lateral intakes....................................................................................................................172
2.6.3.2 Intake towers......................................................................................................................173
2.6.4 Power stations ....................................................................................................................173
2.6.4.1 Basics .................................................................................................................................173
2.6.4.2 Preliminary exploration .....................................................................................................174
2.6.4.3 Preliminary design .............................................................................................................174
2.6.4.3.1 Cavern geometry................................................................................................................174
2.6.4.3.2 Location of the cavern .......................................................................................................175
2.6.4.3.3 Layout of the parallel and auxiliary structures...................................................................175
2.6.4.3.4 Stability calculations..........................................................................................................175
2.6.4.3.4.1 Determination of geotechnical design parameters .............................................................175
2.6.4.3.4.2 Calculation methods ..........................................................................................................176
2.6.4.3.5 Safety measures .................................................................................................................176
2.6.4.3.6 Dimensions of steel reinforced concrete............................................................................176
2.6.4.3.7 Supervision of structures ...................................................................................................176
2.6.4.4 Hints on construction performance....................................................................................176
2.6.5 Penstocks and tailrace ........................................................................................................177
2.6.5.1 Headrace pipelines .............................................................................................................177
2.6.5.1.1 Non-lined pressure shafts...................................................................................................178
2.6.5.1.2 Simple concrete lining .......................................................................................................178
2.6.5.1.3 Reinforced concrete lining.................................................................................................178
2.6.5.1.4 Concrete lining with sealing foil........................................................................................178
2.6.5.1.5 Thin-walled steel liner with concrete inner ring ................................................................178
2.6.5.1.6 Thick-walled steel liner .....................................................................................................179
2.6.5.2 Tailrace tunnel ...................................................................................................................179
2.6.6 Surge tanks.........................................................................................................................180
2.6.7 Shut-off devices .................................................................................................................180
2.6.8 Mechanical equipment .......................................................................................................181
2.6.8.1 Conventional construction .................................................................................................181
2.6.8.2 Reversible pump turbines ..................................................................................................183
2.6.8.2.1 Design ................................................................................................................................183
2.6.8.2.2 Efficiency...........................................................................................................................183
2.6.8.2.3 Controllability ....................................................................................................................184
2.6.8.2.4 Pump turbines with variable speed ....................................................................................184
2.6.8.2.4.1 Turbine operation...............................................................................................................184
2.6.8.2.4.2 Pump operation ..................................................................................................................185
2.6.9 Electrical equipment ..........................................................................................................186
2.6.9.1 Motor-generator .................................................................................................................186
2.6.9.2 Exciters ..............................................................................................................................187
2.6.9.3 Starting device ...................................................................................................................187
2.6.9.4 Switching devices ..............................................................................................................188
2.6.9.5 Unit transformer.................................................................................................................189
2.6.9.6 Network connection...........................................................................................................189
2.6.9.7 Station service system........................................................................................................190
2.6.9.8 I&C and protective system.................................................................................................190
2.6.10 Case study  Goldisthal PSP..............................................................................................191
2.6.11 References for 2.6 ..............................................................................................................196
2.7 Turbines for hydroelectric power [W. Braitsch, H. Haas] .............................................197
2.7.1 Introduction........................................................................................................................197
2.7.1.1 Theory of turbines..............................................................................................................197
2.7.1.2 Types of turbines ...............................................................................................................200
2.7.2 Francis turbines..................................................................................................................202
2.7.2.1 Example and working principle of a Francis turbine.........................................................203
2.7.2.2 Hydraulic design of a Francis runner.................................................................................203
2.7.2.3 Manufacture of a Francis runner........................................................................................204
2.7.2.4 Operating problems with Francis turbines .........................................................................204
2.7.2.5 Pump turbines ....................................................................................................................205
2.7.3 Kaplan turbines ..................................................................................................................206
2.7.3.1 Example and working principle of a Kaplan turbine .........................................................206
2.7.3.2 Hydraulic design of a Kaplan runner .................................................................................209
2.7.3.3 Manufacture of a Kaplan runner ........................................................................................209
2.7.3.4 Operating problems with Kaplan turbines .........................................................................209
2.7.3.5 Comparison between Kaplan turbines and Francis turbines ..............................................210
2.7.3.6 Tubular turbines.................................................................................................................210
2.7.3.6.1 Example and working principle of a tubular turbine .........................................................210
2.7.3.6.2 Types of tubular turbines ...................................................................................................212
2.7.3.7 Comparison between tubular and conventional Kaplan turbines.......................................212
2.7.4 Pelton turbines ...................................................................................................................213
2.7.4.1 Example and working principle of a Pelton turbine ..........................................................213
2.7.4.2 Hydraulic design of a Pelton runner ..................................................................................215
2.7.4.3 Manufacture of a Pelton runner .........................................................................................215
2.7.4.4 Peculiarities and operating problems of Pelton turbines....................................................215
2.7.4.5 Comparison between Pelton and Francis turbines .............................................................216
2.7.5 Michell-Bnki turbines ......................................................................................................216
2.7.5.1 Example and working principle of a Michell-Bnki turbine .............................................216
2.7.6 Performance and control of turbines..................................................................................217
2.7.6.1 Basic considerations ..........................................................................................................217
2.7.6.2 Performance characteristics of turbines .............................................................................219
2.7.7 Costs of turbines ................................................................................................................221
2.7.8 References for 2.7 and additional literature .......................................................................222
3 Wind energy conversion [H.-J. Wagner]......................................................................223
3.1 History ...............................................................................................................................223
3.2 Different converter types: an overview..............................................................................224
3.3 Physical basics ...................................................................................................................225
3.3.1 Origin of wind energy........................................................................................................225
3.3.2 Energy content of the wind ................................................................................................226
3.3.3 Energy conversion on a blade............................................................................................227
3.3.4 Power coefficients..............................................................................................................228
3.3.4.1 Betz law and the power coefficient cp..............................................................................228
3.3.4.2 Tip speed ratio ...................................................................................................................229
3.3.4.3 Power efficiency ................................................................................................................229
3.4 Technical design of converters ..........................................................................................231
3.4.1 The design with gearbox....................................................................................................231
3.4.2 The design without gearbox...............................................................................................231
3.4.3 The Multibrid design .........................................................................................................231
3.4.4 Aspects of design ...............................................................................................................233
3.4.4.1 The tower ...........................................................................................................................233
3.4.4.2 Heat energy ........................................................................................................................233
3.4.4.3 Control and monitoring......................................................................................................233
3.4.4.4 Mechanical stability ...........................................................................................................233
3.4.4.5 Wind direction set-up ........................................................................................................234
3.4.5 Technical figures for two modern wind converters ...........................................................234
3.5 Connection to the electrical grid ........................................................................................235
3.5.1 Requirements of the grid....................................................................................................235
3.5.2 Adaptation of grid frequency and speed of electrical generator ........................................236
3.5.3 Special aspects of the connection of offshore wind parks .................................................236
3.6 Use of wind energy ............................................................................................................237
3.6.1 World-wide status ..............................................................................................................237
3.6.2 Federal Republic of Germany............................................................................................237
3.7 Economical and environmental aspects .............................................................................239
3.7.1 Environmental comparison ................................................................................................239
3.7.2 Energy payback time .........................................................................................................239
3.8 Outlook ..............................................................................................................................241
3.9 References for 3 .................................................................................................................241
4 Solar power.......................................................................................................................242
4.1 Solar thermal power plants [A. Neumann].......................................................................242
4.1.1 Overview............................................................................................................................242
4.1.2 Principles of the technology of solar thermal power plants...............................................243
4.1.2.1 Solar radiation....................................................................................................................243
4.1.2.2 Solar brightness distribution ..............................................................................................247
4.1.2.3 Optical principles...............................................................................................................248
4.1.2.4 Concentration of radiation .................................................................................................248
4.1.2.5 Parabolic geometry ............................................................................................................249
4.1.2.6 Fresnel geometry................................................................................................................251
4.1.2.7 Non-imaging optics............................................................................................................251
4.1.3 Designs for concentrating solar radiation ..........................................................................252
4.1.3.1 Paraboloidal reflector.........................................................................................................252
4.1.3.2 Spherical reflector..............................................................................................................253
4.1.3.3 Hemispherical bowl concentrator ......................................................................................253
4.1.3.4 Two-stage heliostat concentrator design............................................................................254
4.1.3.5 Concentrating heliostats and tower ....................................................................................255
4.1.3.6 Beam down tower design...................................................................................................255
4.1.3.7 Parabolic trough reflector ..................................................................................................255
4.1.4 Solar to thermal energy conversion ...................................................................................256
4.1.4.1 General consideration ........................................................................................................256
4.1.4.2 Energy flow in a solar thermal power plant.......................................................................258
4.1.4.3 Schematic solar thermal power plant .................................................................................259
4.1.5 Receiver designs ................................................................................................................260
4.1.5.1 External receiver ................................................................................................................260
4.1.5.2 Evacuated tube receiver .....................................................................................................261
4.1.5.3 Internal cavity receiver ......................................................................................................261
4.1.5.4 Volumetric receiver ...........................................................................................................262
4.1.5.5 Direct absorption receiver..................................................................................................262
4.1.5.6 Comparison of receivers ....................................................................................................263
4.1.6 Storing thermal energy.......................................................................................................263
4.1.7 Solar thermal power plants ................................................................................................266
4.1.7.1 Solar pond power plant ......................................................................................................266
4.1.7.2 Solar chimney power plant ................................................................................................267
4.1.7.3 Parabolic trough power plant .............................................................................................268
4.1.7.4 Dish power plant................................................................................................................271

Table of contents 

4.1.7.5 Central receiver power plant..............................................................................................273
4.1.8 Comparison of solar thermal power plants ........................................................................275
4.1.8.1 Performance .......................................................................................................................275
4.1.8.2 Costs ..................................................................................................................................276
4.1.9 Outlook ..............................................................................................................................277
4.1.10 References for 4.1 ..............................................................................................................278
4.2 Photovoltaic power generation [A. Goetzberger] ..........................................................280
4.2.1 Introduction, PV markets ...................................................................................................280
4.2.2 Principles of photovoltaic cells..........................................................................................280
4.2.3 Potential and relevance of photovoltaic solar energy ........................................................283
4.2.4 Physics of solar cells..........................................................................................................285
4.2.4.1 I/V characteristic................................................................................................................285
4.2.4.2 Loss mechanisms ...............................................................................................................287
4.2.5 Solar cell technology .........................................................................................................287
4.2.5.1 Silicon ................................................................................................................................287
4.2.5.1.1 Silicon material ..................................................................................................................287
4.2.5.1.2 Cell and module technology ..............................................................................................289
4.2.5.1.2.1 Production of pn- and pp-junctions ...................................................................................289
4.2.5.1.2.2 Oxidation process ..............................................................................................................289
4.2.5.1.2.3 Electrical contacts ..............................................................................................................289
4.2.5.1.2.4 Antireflection technologies................................................................................................289
4.2.5.1.2.5 Module technology ............................................................................................................290
4.2.5.2 Thin film materials.............................................................................................................290
4.2.5.2.1 Amorphous silicon.............................................................................................................290
4.2.5.2.2 Copper indium diselenide and related compounds ............................................................291
4.2.5.2.3 Cadmium telluride .............................................................................................................291
4.2.5.3 Tandem cells, concentrating systems.................................................................................292
4.2.6 Future developments and new materials ............................................................................293
4.2.6.1 Crystalline silicon ..............................................................................................................293
4.2.6.1.1 Materials technologies .......................................................................................................293
4.2.6.1.2 The silicon supply problem................................................................................................293
4.2.6.2 Other materials and concepts .............................................................................................294
4.2.7 Applications .......................................................................................................................295
4.2.7.1 Survey of applications .......................................................................................................295
4.2.7.2 Stand alone systems ...........................................................................................................297
4.2.7.3 Grid-connected systems .....................................................................................................298
4.2.8 Cost and energy balance ....................................................................................................300
4.2.8.1 Cost ....................................................................................................................................300
4.2.8.2 Environmental effects and energy balance ........................................................................301
4.2.9 Conclusions........................................................................................................................302
4.2.10 References for 4.2 ..............................................................................................................303
4.3 Nonfocusing solar heat collection [N.M. Fisch, V. Huckemann] ...................................304
4.3.1 Summary............................................................................................................................304
4.3.2 Active use of solar thermal energy  range of application ................................................304
4.3.3 Basics .................................................................................................................................305
4.3.3.1 Collectors ...........................................................................................................................305
4.3.3.2 Storage ...............................................................................................................................307
4.3.4 Technical realization of low temperature applications ......................................................310
4.3.4.1 Plants with absorber...........................................................................................................311
4.3.4.2 Small solar plants and system configuration......................................................................312
4.3.4.2.1 Solar plants for domestic hot water preparation ................................................................312
4.3.4.2.2 Two special designs ...........................................................................................................313
4.3.4.2.3 Solar combisystems for DHW-preparation and space heating ..........................................313
4.3.4.3 Large scale solar plants with short- and long-term storage ...............................................316
4.3.4.3.1 Large scale plants with short-term storage ........................................................................318
4.3.4.3.2 Large scale solar heating with long-term storage ..............................................................321
4.3.4.4 Project examples ................................................................................................................323
4.3.4.4.1 Pilot project Friedrichshafen-Wiggenhausen .................................................................323
4.3.4.4.2 Solar district heating in Hanover-Kronsberg .....................................................................325
4.3.4.4.3 Neckarsulm-Amorbach  an extensible long term storage ................................................325
4.3.4.4.4 Hannoversch Mnden ........................................................................................................328
4.3.4.4.5 Comparison of the above mentioned projects....................................................................328
4.3.5 Market development and potential of solar thermal plants ................................................330
4.3.5.1 Cost development of small scale solar thermal plants .......................................................330
4.3.5.2 European solar thermal market ..........................................................................................331
4.3.6 References for 4.3 and additional literature .......................................................................333
5 Biomass .............................................................................................................................334
5.1 Biomass energy  An overview [F. Rosillo-Calle] .......................................................334
5.1.1 General overview...............................................................................................................334
5.1.2 Introduction........................................................................................................................336
5.1.3 Biomass potential...............................................................................................................337
5.1.3.1 Utilization of residues ........................................................................................................337
5.1.3.1.1 Agricultural residues..........................................................................................................337
5.1.3.1.2 Forestry residues ................................................................................................................337
5.1.3.1.3 Livestock residues..............................................................................................................338
5.1.3.1.4 Energy forestry/crops.........................................................................................................338
5.1.4 Current and future uses of biomass energy........................................................................342
5.1.4.1 Traditional applications of bioenergy ................................................................................342
5.1.4.2 Modern applications of bioenergy .....................................................................................343
5.1.5 Technology trends .............................................................................................................344
5.1.5.1 Combustion........................................................................................................................345
5.1.5.2 Cogeneration/CHP .............................................................................................................345
5.1.5.3 Cogeneration of electricity from sugarcane bagasse..........................................................347
5.1.5.4 Co-firing ............................................................................................................................347
5.1.5.5 Gasification........................................................................................................................349
5.1.5.6 Pyrolysis ............................................................................................................................350
5.1.6 Liquid and gaseous fuels....................................................................................................350
5.1.6.1 Ethanol fuel........................................................................................................................351
5.1.6.1.1 Brazil..................................................................................................................................352
5.1.6.1.2 USA ...................................................................................................................................352
5.1.6.1.3 EU ......................................................................................................................................353
5.1.6.1.4 Technology trends .............................................................................................................353
5.1.6.2 Biodiesel ............................................................................................................................354
5.1.6.2.1 Feedstock ...........................................................................................................................354
5.1.6.2.2 Biodiesel in the EU ............................................................................................................355
5.1.6.2.3 Biodiesel in the USA .........................................................................................................355
5.1.6.3 Biogas production and utilization ......................................................................................355
5.1.6.3.1 China..................................................................................................................................356
5.1.6.3.2 India ...................................................................................................................................356
5.1.6.3.3 Nepal..................................................................................................................................356
5.1.6.3.4 Denmark ............................................................................................................................357
5.1.6.4 Charcoal.............................................................................................................................357
5.1.7 Socio-economics of modern biomass ................................................................................358
5.1.7.1 Biomass energy and rural development .............................................................................358
5.1.7.2 Bioenergy and employment ...............................................................................................359
5.1.7.3 The Food versus fuel argument ......................................................................................361
5.1.7.4 The role of externalities .....................................................................................................362
5.1.8 Environmental considerations............................................................................................363
5.1.8.1 Carbon sequestration versus carbon sink...........................................................................364
5.1.9 Institutional changes in the energy market  Implications for bioenergy ..........................364
5.1.10 Conclusions........................................................................................................................367
5.1.11 Policy recommendations and R&D needs .........................................................................368
5.1.12 List of abbreviations ..........................................................................................................369
5.1.13 Main internet contacts........................................................................................................370
5.1.14 References for 5.1 ..............................................................................................................370
5.2 Conversion of biomass to heat and electricity [D. Hein, J. Karl]....................................374
5.2.1 Introduction........................................................................................................................374
5.2.2 Fuel properties ...................................................................................................................374
5.2.2.1 Heating value and energy density ......................................................................................375
5.2.2.2 Inhomogeneity and diversity..............................................................................................376
5.2.2.3 Heating values of solid biomass ........................................................................................376
5.2.3 Generation of heat and power from biomass .....................................................................377
5.2.3.1 Generation of heat..............................................................................................................377
5.2.3.2 Large scale power plants....................................................................................................378
5.2.3.3 Co-combustion...................................................................................................................378
5.2.3.4 Decentralized generation and combined heat and power production (CHP) .....................379
5.2.3.5 Economical aspects............................................................................................................380
5.2.4 Combustion of biomass .....................................................................................................381
5.2.4.1 Combustion efficiency .......................................................................................................381
5.2.4.2 Emissions ...........................................................................................................................383
5.2.4.3 Ash melting behavior.........................................................................................................384
5.2.4.4 Chlorine corrosion .............................................................................................................384
5.2.4.5 Combustion systems ..........................................................................................................385
5.2.4.5.1 Under stocker furnaces ......................................................................................................386
5.2.4.5.2 Grate furnaces ....................................................................................................................387
5.2.4.5.3 Fluidized bed combustion systems ....................................................................................387
5.2.4.5.4 Special designs...................................................................................................................387
5.2.5 Gasification of biomass .....................................................................................................388
5.2.5.1 Definition ...........................................................................................................................388
5.2.5.2 Digestion............................................................................................................................389
5.2.5.3 Thermal gasification ..........................................................................................................389
5.2.5.4 Autothermal gasification....................................................................................................391
5.2.5.5 Allothermal gasification.....................................................................................................392
5.2.5.6 Gas cleaning and process integration.................................................................................394
5.2.6 Tables.................................................................................................................................396
5.2.6.1 Elementary composition and heating values......................................................................396
5.2.6.1.1 Woody biomass .................................................................................................................396
5.2.6.1.2 Herbaceous biomass ..........................................................................................................400
5.2.6.1.3 Other biomass ....................................................................................................................402
5.2.6.1.4 Wastes................................................................................................................................403
5.2.6.2 Energy density ...................................................................................................................405
5.2.6.3 Gaseous fuels .....................................................................................................................406
5.2.6.4 Ash melting behavior.........................................................................................................406
5.2.6.5 Biomass digestion efficiency .............................................................................................408
5.2.6.6 Economical data.................................................................................................................409
5.2.7 References for 5.2 ..............................................................................................................412
6 Renewable carbon-based transportation fuels [A. Bandi, M. Specht] .....................414
6.1 Introduction........................................................................................................................415
6.2 Renewable fuels.................................................................................................................417
6.2.1 Fuel options .......................................................................................................................417
6.2.2 Liquid renewable fuels.......................................................................................................417
6.2.2.1 Ethanol...............................................................................................................................417
6.2.2.2 Bio-diesel and vegetable oils .............................................................................................418
6.2.2.3 Bio-methanol .....................................................................................................................418
6.2.2.4 Synthetic diesel/gasoline fuels ...........................................................................................419
6.2.2.5 Bio-pyrolysis oils...............................................................................................................419
6.2.3 Gaseous renewable fuels....................................................................................................420
6.2.3.1 Hydrogen ...........................................................................................................................420
6.2.3.2 Substitute natural gas (SNG) .............................................................................................420
6.2.3.3 Dimethyl ether (DME).......................................................................................................420
6.2.4 Costs and CO2 emissions of renewable fuels.....................................................................421
6.2.5 Renewable fuels today .......................................................................................................423
6.2.5.1 Ethanol...............................................................................................................................423
6.2.5.2 Bio-diesel ...........................................................................................................................424
6.2.5.3 Bio-gas...............................................................................................................................425
6.3 Technical pathways for renewable fuel generation............................................................426
6.3.1 Fuels via synthesis gas .......................................................................................................427
6.3.1.1 Synthesis gas production from biomass.............................................................................428
6.3.1.2 Directly heated gasifiers ....................................................................................................429
6.3.1.2.1 RENUGAS process ...........................................................................................................429
6.3.1.2.2 Carbo-V process ................................................................................................................430
6.3.1.2.3 HTW process .....................................................................................................................431
6.3.1.2.4 Texaco process...................................................................................................................431
6.3.1.2.5 Schwarze Pumpe waste-to-methanol process ....................................................................432
6.3.1.3 Indirectly heated gasifiers ..................................................................................................432
6.3.1.3.1 MTCI gasification..............................................................................................................432
6.3.1.3.2 DMT indirectly heated steam gasifier................................................................................434
6.3.1.3.3 DM2 staged reforming process..........................................................................................434
6.3.1.3.4 Indirectly heated, twin fluidized bed, steam gasifier (Battelle/FERCO) ...........................434
6.3.1.3.5 FICFB gasification.............................................................................................................436
6.3.1.3.6 Wright-Malta process ........................................................................................................437
6.3.1.3.7 Hynol process ....................................................................................................................437
6.3.1.3.8 AER process ......................................................................................................................438
6.3.1.4 Comparison of gasifiers .....................................................................................................439
6.3.1.5 Gas cleaning.......................................................................................................................441
6.3.1.5.1 Particulates.........................................................................................................................441
6.3.1.5.2 Tars ....................................................................................................................................442
6.3.1.5.3 Sulphur compounds ...........................................................................................................442
6.3.1.5.4 Nitrogen-containing components.......................................................................................442
6.3.1.5.5 Alkali compounds ..............................................................................................................442
6.3.2 Fuel generation from synthesis gas....................................................................................443
6.3.2.1 Methanol synthesis ............................................................................................................443
6.3.2.1.1 Gas-phase methanol synthesis ...........................................................................................443
6.3.2.1.2 Liquid-phase methanol synthesis .......................................................................................445
6.3.2.1.3 Direct oxidation of methane to methanol...........................................................................447
6.3.2.1.4 Methanol synthesis from H2 and CO2................................................................................447
6.3.2.2 Fischer-Tropsch synthesis of gasoline and diesel fuels .....................................................449
6.3.2.2.1 Fischer-Tropsch synthesis from CO2 and H2 .....................................................................450
6.3.3 Bio-fuels via fermentation .................................................................................................451
6.3.3.1 Ethanol production technologies .......................................................................................451
6.3.3.2 Bio-gas production via anaerobic digestion.......................................................................452
6.3.4 Bio-fuels from oil plants ....................................................................................................454
6.3.5 Bio-pyrolysis oil ................................................................................................................455
6.3.6 Further fuel production paths.............................................................................................457
6.3.6.1 Hydrogen ...........................................................................................................................457
6.3.6.2 Methanol-to-gasoline (MTG) process................................................................................457
6.3.6.3 Synthetic (substitute) natural gas .......................................................................................458
6.3.6.4 Dimethyl ether (DME).......................................................................................................459
6.3.6.5 Methanol-to-synfuels (MtSynfuels) process......................................................................459
6.3.6.6 MTBE/ETBE  methyl (ethyl) tertiary butyl ether ............................................................460
6.3.6.7 Higher alcohol synthesis ....................................................................................................461
6.3.6.8 Hydrothermal conversion of biomass ................................................................................461
6.3.6.8.1 The HTU process .............................................................................................................461
6.3.6.8.2 Conversion of biomass in supercritical water ....................................................................462
6.4 Efficiency of fuel generation .............................................................................................463
6.4.1 Fuel yield per hectare of agricultural crop land .................................................................463
6.4.2 Energy efficiency of synfuel generation from biomass .....................................................464
6.5 Resources for the production of renewable fuels...............................................................468
6.5.1 Biomass resources..............................................................................................................468
6.5.2 Renewable electricity for fuel generation ..........................................................................472
6.6 Conclusions / Outlook .......................................................................................................473
6.7 Additional tables ................................................................................................................474
6.7.1 Promising renewable neat fuels and blends for automotive applications ..........................474
6.7.2 Fuel Properties of selected liquid and gaseous fuels..........................................................475
6.8 Glossary and abbreviations ................................................................................................476
6.9 References for 6 and internet references............................................................................478
7 Hydrogen production [S. Richter, U. Wagner].........................................................483
7.1 Introduction........................................................................................................................483
7.2 Hydrogen generation by electrolysis .................................................................................484
7.3 Hydrogen from fossil energy carriers ................................................................................486
7.3.1 Steam reforming ................................................................................................................486
7.3.2 Partial oxidation.................................................................................................................487
7.3.3 Gasification of coal............................................................................................................487
7.3.4 Plasma arc process (Kvaerner process)..............................................................................488
7.4 Hydrogen from renewable energy sources ........................................................................488
7.4.1 Hydrogen generation through photoelectrolysis ................................................................488
7.4.2 Hydrogen from biomass.....................................................................................................489
7.4.3 Photobiological hydrogen generation ................................................................................490
7.4.4 Photochemical and photocatalytical hydrogen production ................................................490
7.4.5 Thermochemical hydrogen production ..............................................................................491
7.5 Conclusion .........................................................................................................................491
7.6 References for 7 .................................................................................................................492
8 Geothermal energy [C. Clauser] ..................................................................................493
8.1 The Earths thermal regime ...............................................................................................493
8.1.1 The structure of the Earth ..................................................................................................493
8.1.2 Energy budget of the Earth ................................................................................................496
8.1.2.1 Heat income .......................................................................................................................497
8.1.2.1.1 External heat sources .........................................................................................................497
8.1.2.1.1.1 Solar radiation....................................................................................................................497
8.1.2.1.1.2 Gravitational energy ..........................................................................................................498
8.1.2.1.2 Internal heat sources ..........................................................................................................498
8.1.2.1.2.1 Radiogenic heat..................................................................................................................498
8.1.2.1.2.2 Original heat ......................................................................................................................499
8.1.2.1.2.3 Potential energy .................................................................................................................499
8.1.2.1.2.4 Frictional heat ....................................................................................................................499
8.1.2.2 Heat expenditure ................................................................................................................500
8.1.2.2.1 Long-wavelength heat radiation ........................................................................................500
8.1.2.2.2 Volcanism ..........................................................................................................................501
8.1.2.2.3 Global heat flow ................................................................................................................501
8.1.2.3 Heat budget ........................................................................................................................501
8.1.3 The thermal regime of the Earths crust.............................................................................501
8.1.4 Heat storage .......................................................................................................................503
8.1.4.1 Measuring techniques ........................................................................................................504
8.1.4.2 Calculated heat capacity ....................................................................................................505
8.1.5 Heat transport.....................................................................................................................515
8.1.5.1 Heat conduction .................................................................................................................515
8.1.5.1.1 Measuring techniques ........................................................................................................516
8.1.5.1.2 Indirect methods ................................................................................................................516
8.1.5.1.2.1 Estimation from mineralogical composition and saturating fluids ....................................516
8.1.5.1.2.2 Correlations with other physical properties .......................................................................518
8.1.5.1.3 Thermal conductivity of minerals ......................................................................................520
8.1.5.2 Thermal conductivity of rocks ...........................................................................................531
8.1.5.2.1 Thermal conductivity of sedimentary, volcanic, plutonic and metamorphic rocks ...........532
8.1.5.2.1.1 Influence of porosity and the dominant mineral phase ......................................................532
8.1.5.2.1.2 Influence of ambient temperature ......................................................................................534
8.1.5.2.2 Influence of various factors on thermal conductivity ........................................................538
8.1.5.2.2.1 Pressure..............................................................................................................................538
8.1.5.2.2.2 Porosity and saturating fluid ..............................................................................................539
8.1.5.2.2.3 Partial saturation ................................................................................................................539
8.1.5.2.2.4 Anisotropy .........................................................................................................................540
8.1.5.3 Heat advection ...................................................................................................................543
8.1.5.4 Heat radiation and thermal conductivity in the Earths mantle..........................................546
8.1.6 References for 8.1 ..............................................................................................................548
8.2 Geothermal energy resources.............................................................................................549
8.2.1 References for 8.2 ..............................................................................................................550
8.3 Types of geothermal energy use ........................................................................................551
8.3.1 Direct use ...........................................................................................................................551
8.3.1.1 Space heating .....................................................................................................................555
8.3.1.1.1 Earth coupled heat extraction systems ...............................................................................555
8.3.1.1.1.1 Horizontal Earth coupled heat exchangers ........................................................................555
8.3.1.1.1.2 Shallow borehole heat exchangers.....................................................................................556
8.3.1.1.1.3 Heat exchanger piles ..........................................................................................................557
8.3.1.1.1.4 Deep borehole heat exchangers .........................................................................................558
8.3.1.1.2 Hydrothermal heating systems...........................................................................................559
8.3.1.2 Commercial and industrial applications.............................................................................560
8.3.2 Power generation ...............................................................................................................562
8.3.3 References for 8.3 ..............................................................................................................565
8.4 Technological and economical aspects of geothermal energy ...........................................566
8.4.1 Direct use ...........................................................................................................................566
8.4.1.1 Earth coupled heat extraction systems ...............................................................................567
8.4.1.1.1 Ground-source heat pump systems ....................................................................................567
8.4.1.1.2 Deep borehole heat exchangers .........................................................................................571
8.4.1.2 Hydrothermal heating systems...........................................................................................573
8.4.2 Power generation ...............................................................................................................575
8.4.2.1 Natural steam power plants................................................................................................575
8.4.2.1.1 Dry steam power plants .....................................................................................................575
8.4.2.1.2 Flash steam power plants ...................................................................................................577
8.4.2.2 Binary power plants ...........................................................................................................579
8.4.2.3 Power plants for hot dry rock or enhanced geothermal systems........................................581
8.4.2.4 Technical, economic and ecological aspects of geothermal power production .................584
8.4.2.4.1 Efficiency...........................................................................................................................584
8.4.2.4.2 Cost and life time ...............................................................................................................585
8.4.2.4.2.1 Natural steam systems........................................................................................................585
8.4.2.4.2.2 HDR and enhanced systems...............................................................................................587
8.4.2.4.3 Pollution.............................................................................................................................588
8.4.2.4.3.1 Air pollution.......................................................................................................................588
8.4.2.4.3.2 Water pollution ..................................................................................................................591
8.4.2.4.3.3 	Land subsidence.................................................................................................................592
8.4.2.4.3.4 	Induced seismicity .............................................................................................................592
8.4.2.4.3.5 	Noise ..................................................................................................................................593
Summary and Acknowledgements.....................................................................................593
8.4.3 	References for 8.4 ..............................................................................................................595
9 	Heat pumps [H.J. Laue] .................................................................................................605
9.1 	Introduction........................................................................................................................605
9.2 	Historical development ......................................................................................................605
9.3 	Basic principles..................................................................................................................606
9.4 	Heat pump technology .......................................................................................................608
9.5 	Heat sources.......................................................................................................................609
9.6 	Heat pump working fluids .................................................................................................611
9.6.1 	HFC-mixtures ....................................................................................................................612
9.6.2 	Natural working fluids .......................................................................................................612
9.7 	Heat pumps in residential and commercial buildings ........................................................614
9.7.1 	Heating-only heat pumps ...................................................................................................614
9.7.2 	Heating and cooling heat pumps........................................................................................615
9.7.3 	Heat pump water heater .....................................................................................................615
9.8 	Heat pumps in industry ......................................................................................................615
9.8.1 	Closed cycle compression heat pumps...............................................................................617

Table of contents 9.8.2 Mechanical vapor recompression systems .........................................................................617
9.8.3 Thermal vapor recompression (TVR) systems ..................................................................618
9.8.4 Absorption heat pumps ......................................................................................................618
9.8.5 Heat transformers...............................................................................................................618
9.9 Energy-efficiency and environmental aspects ...................................................................618
9.10 Economical aspects............................................................................................................624
9.11 Conclusion .........................................................................................................................625
9.12 References for 9 .................................................................................................................626

