Series Editor's Preface ........................................ xi
Preface ........................................................ xv
Acknowledgments .............................................. xvii
Series Editor ................................................. xix
Author ........................................................ xxi
Chapter 1 Introduction ......................................... 1
The Global Energy Landscape ..................................... 1
The Historical Role of Fuel .................................. 1
The Impact of Population Growth and per Capita Energy Use .... 2
Fuel Emissions and Environmental Considerations .............. 3
Geothermal Energy as a Renewable Energy Source .................. 4
No Fuel, Few Emissions ....................................... 4
Geothermal Energy Is a Flexible Energy Resource .............. 5
Electrical Demand and the Characteristics of Geothermal
Energy .......................................................... 7
Generating Electrical Power for the Grid ..................... 7
Generating Electrical Power for Local Use .................... 8
How This Book Is Organized ...................................... 8
Synopsis ........................................................ 8
References ...................................................... 9
Further Information Sources ..................................... 9
Chapter 2 Sources of Geothermal Heat: Earth as a Heat
Engine .............................................. 11
Origin of Earth's Heat ......................................... 11
Heat from Formation of the Core ............................. 11
Heat from Radioactive Decay of Long-Lived Isotopes .......... 12
Transfer of Heat in the Earth .................................. 14
Radiation ................................................... 14
Conduction .................................................. 15
Convection .................................................. 19
Plate Tectonics and the Distribution of Geothermal Resources ... 20
Availability and Utilization of Geothermal Energy .............. 23
Synopsis ....................................................... 26
Case Studies ................................................... 26
Spreading Centers ........................................... 26
Subduction Zones ............................................ 27
Hot Spots ................................................... 27
References ..................................................... 28
Further Information ............................................ 29
Chapter 3 Thermodynamics and Geothermal Systems ................ 31
The First Law of Thermodynamics: The Equivalence of Heat and
Work and the Conservation of Energy ............................ 31
Conservation of Energy ...................................... 31
Internal Energy .......................................... 31
PV Work .................................................. 33
Enthalpy ................................................. 33
The Second Law of Thermodynamics: The Inevitable Increase of
Entropy ........................................................ 34
Efficiency .................................................. 34
Carnot Cycle ................................................ 34
Heat Capacity ............................................... 35
Entropy ..................................................... 37
Gibbs Function and Gibbs Energy (AG) ........................... 38
The Standard State .......................................... 39
Thermodynamic Efficiency ....................................... 40
Case Study: The Thermodynamic Properties of Water and Rock-
Water Interaction .............................................. 41
Synopsis ....................................................... 47
References ..................................................... 47
Further Information ............................................ 48
Chapter 4 Subsurface Fluid Flow: The Hydrology of
Geothermal Systems ............................................. 51
A General Model for Subsurface Fluid Flow ...................... 51
Matrix Porosity and Permeability ............................... 51
Definition of Matrix Permeability ........................... 54
The Kozeny-Carman Equation .................................. 55
Hydraulic Conductivity ...................................... 55
Fracture Porosity and Permeability ............................. 55
Fracture Permeability ....................................... 56
Fracture Transmissivity ..................................... 57
Effect of Depth on Porosity and Permeability ................... 58
Hydrologic Properties of Real Geothermal Systems ............... 60
Case Study: Long Valley Caldera ................................ 61
Synopsis ....................................................... 65
References ..................................................... 65
Further Information ............................................ 66
Chapter 5 Chemistry of Geothermal Fluids ...................... 69
Why the Geochemistry of Geothermal Fluids Matters .............. 69
Water as a Chemical Agent ...................................... 70
Components and Chemical Systems ................................ 72
Chemical Potentials, μ, and Gibbs Energy .................... 72
Activity, α ................................................. 74
Saturation and The Law of Mass Action .......................... 74
Equilibrium Constants ....................................... 74
Activity Coefficients, γ .................................... 75
Affinity .................................................... 76
Ion Exchange ................................................ 77
Kinetics of Geothermal Reactions ............................... 78
Gases in Geothermal Fluids ..................................... 80
Gas Partitioning between Liquid and Vapor ................... 81
Fluid Flow and Mixing in Natural Systems ....................... 83
Simulating Reactive Transport .................................. 84
Case Study: The Silica System .................................. 85
Synopsis ....................................................... 86
References ..................................................... 87
Chapter 6 Exploring for Geothermal Systems .................... 91
Field Geology and Surface Manifestations ....................... 91
Volcanoes: Active and Dormant ............................... 91
Faulting and Associated Rock Alteration ..................... 92
Surface Deposits ............................................ 93
Geochemistry as an Exploration Tool ............................ 95
Fluid Composition and Geothermometry ........................ 95
Isotopes ................................................... 100
Geophysics as an Exploration Tool ............................. 104
Aeromagnetic Surveys ....................................... 104
Resistivity and Magnetotelluric Surveys .................... 105
Gravity Surveys ............................................ 107
Seismicity and Reflection Seismology ....................... 108
Temperature Measurements ................................... 110
Remote Sensing as an Exploration Tool: A Promising New
Technique ..................................................... 111
Multispectral Studies ...................................... 111
Case Study: Fallon, Nevada .................................... 113
Synposis ...................................................... 115
References .................................................... 116
Further Information ........................................... 118
Chapter 7 Resource Assessments ............................... 119
Assessing a Geothermal Resource ............................... 119
Resource Base and Reserves .................................... 120
Uncertainty ................................................ 120
Establishing the Reservoir Volume ............................. 122
Establishing the Reservoir Heat Content ....................... 123
The Significance of Heat Capacity ............................. 125
Efficiency of Heat Extraction ................................. 126
Case Study: Establishing the United States Geothermal
Resource ...................................................... 129
Synopsis ...................................................... 132
References .................................................... 133
Further Information ........................................... 134
Chapter 8 Drilling ........................................... 135
Background .................................................... 135
Drilling for Ground Source Heat Pump and Direct Use
Applications .................................................. 135
Drilling Equipment and Technology .......................... 136
Drilling Fluid and Circulation ............................. 137
Properties of Drilling Fluids .............................. 139
Well Completion ............................................ 140
Environmental Issues ....................................... 140
Drilling for Geothermal Fluids for Power Generation ........... 141
Drilling Rigs .............................................. 141
Confining Pressure and Rock Strength ....................... 141
Temperature and Drilling Fluid Stability ................... 143
Casing and Grouting ........................................ 145
Packers .................................................... 146
Lost Circulation ........................................... 147
Directional Drilling ....................................... 147
Case Study: Kakkonda, Japan ................................... 149
Synopsis ...................................................... 151
References .................................................... 151
Further Information ........................................... 152
Chapter 9 Generating Power Using Geothermal Resources ........ 153
The History of Geothermal Power Production .................... 153
General Features of Geothermal Power Generation Facilities .... 154
Dry Steam Resources ........................................... 155
Hydrothermal Systems .......................................... 161
Flashing ................................................... 163
Steam Quality .............................................. 165
Dual-Flash Systems ......................................... 166
The End State: Condensers and Cooling Towers ............... 167
Binary Generation Facilities: The Organic Rankine Cycle ....... 168
Case Study: The Geysers ....................................... 170
Geology .................................................... 170
Power Generation History ................................... 172
Emissions .................................................. 172
Sustainability and Reinjection ............................. 173
Synopsis ...................................................... 176
References .................................................... 177
Further Information ........................................... 178
Chapter 10 Low Temperature Geothermal Resources: Ground
Source Heat Pumps .................................. 183
Basic Heat Pump Principles .................................... 183
Thermodynamics of Heat Pumps .................................. 186
Coefficient of Performance (COP) and Energy Efficiency
Ratio (EER) ................................................ 187
Near-Surface Thermal Reservoir ................................ 187
Solar Insolation ........................................... 188
Soil Characteristics ....................................... 188
Thermal Conductivity and Heat Capacity of Soils ............ 190
Design Considerations for Closed-Loop Systems ................. 191
Heating and Cooling Loads .................................. 191
Calculating Loop Length .................................... 191
Case Study: Weaverville ....................................... 193
Synopsis ...................................................... 198
References .................................................... 199
Further Information ........................................... 199
Chapter 11 Direct Use of Geothermal Resources ................. 201
Assessing the Magnitude of the Direct Use Reservoir ........... 201
The Nature of Thermal Energy Transfer ......................... 203
Heat Transfer by Conduction ................................ 204
Heat Transfer by Convection ................................ 207
Heat Transfer by Radiation ................................. 208
Heat Transfer by Evaporation ............................... 209
Establishing the Feasibility of a Direct Use Application ...... 210
District Heating .............................................. 210
Evaluation and Operation ................................... 210
Managing Return Temperature ................................ 212
Piping and Heat Loss ....................................... 213
Materials Compatibility and Fluid Chemistry ................ 213
Aquaculture ................................................... 214
Drying ........................................................ 216
Case Study. Canby Cascaded System ............................. 217
Synopsis ...................................................... 222
References .................................................... 223
Further Information ........................................... 223
Chapter 12 Use of Geothermal Resources: Environmental
Considerations ..................................... 225
Emissions ..................................................... 225
Carbon Dioxide ............................................. 225
Hydrogen Sulfide ........................................... 228
Mercury .................................................... 229
Solute Load and Resource Recovery ............................. 229
Seismicity ................................................. 231
Mechanics of Seismic Events ................................ 231
Shear Stress, Normal Stress, and Frictional Strength .... 231
Pore Water .............................................. 232
Seismic Activity Associated with Geothermal Projects ....... 233
Seismicity Associated with Injection of Cool Water ...... 233
Rupture Area and Magnitude .............................. 235
Seismicity Associated with Fluid Extraction ................ 236
Seismicity Associated with High-Pressure Injection of
Fluid to Enhance Reservoir Permeability .................... 237
Ground Subsidence ............................................. 238
Water Use ..................................................... 241
Land Use ...................................................... 242
Synopsis ...................................................... 244
References .................................................... 245
Additional Information ........................................ 247
Chapter 13 Use of Geothermal Resources: Economic
Considerations ..................................... 251
Economics of Geothermal Power ................................. 251
Capacity Factors ........................................... 251
Levelized Costs ............................................ 253
Economics of R&D Investment in Geothermal Energy .............. 255
Technology Evolution and S-Curves .......................... 255
Projected Energy Costs ..................................... 255
Developing a Geothermal Project ............................... 257
Rights to Develop a Resource and Permitting ................ 257
Initial Resource Assessments ............................... 258
Refining the Resource Assessment through Exploration
Drilling ................................................... 259
Production Wells and Feasibility Study ..................... 259
Synopsis ...................................................... 260
References .................................................... 261
Chapter 14 The Geothermal Energy Future: Possibilities and
Issues ............................................. 263
Geopressured Resources ........................................ 263
Magnitude of the Resource .................................. 263
Why Geopressured Reservoirs Form ........................... 263
Challenges to Development .................................. 264
Fluid Chemistry ......................................... 264
Reinjection ............................................. 266
Enhanced Geothermal Systems (EGS) ............................. 266
Magnitude of the Resource .................................. 266
Technological Requirements ................................. 269
EGS Efforts to Date ........................................ 270
Drilling and Downhole Equipment ............................ 271
Drilling Fluids ......................................... 271
High-Temperature Downhole Equipment ..................... 271
Reservoir Engineering ................................... 271
Reservoir Management for Sustainability ................. 272
Synopsis ...................................................... 274
References .................................................... 275
Further Information ........................................... 276
Index ......................................................... 277
Index of Locations ............................................ 289
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