Geothermal Energy

Preface xv

About the Authors xix

Acknowledgments xxi

Nomenclature xxiii

1 Introduction to Geothermal Energy 1

1.1 Features of Geothermal Energy 2

1.2 Geothermal Energy Systems 3

1.3 Outline of the Book 4

References 7

2 Fundamentals 8

2.1 Introduction 8

2.2 Thermodynamics 8

2.3 Heat Transfer 18

2.4 Fluid Mechanics 23

2.5 The Nature of the Ground 30

References 32

3 Background and Technologies 34

3.1 Introduction 34

3.2 Heat Pumps 34

3.3 Heat Exchangers 36

3.4 Heating, Ventilating, and Air Conditioning 36

3.5 Energy Storage 37

4 Underground Thermal Energy Storage 39

4.1 Introduction 39

4.2 Thermal Energy Storage Methods 40

4.3 UndergroundThermal Storage Methods and Systems 57

4.4 Integration of Thermal Energy Storage with Heat Pumps 62

4.5 Closing Remarks 68

References 68

5 Geothermal Heating and Cooling 76

5.1 Ground-Source Heat Pumps 77

5.2 Geothermal Heat Exchangers 78

References 85

6 Design Considerations and Installation 86

6.1 Sensitivity to GroundThermal Conductivity 86

6.2 Thermal Response Test 89

6.3 Building Energy Calculations 95

6.4 Economics 105

6.5 Standards 108

References 109

7 Modeling Ground Heat Exchangers 111

7.1 General Aspects of Modeling 111

7.2 AnalyticalModels 116

7.3 Numerical Modeling 133

7.4 Closing Remarks 138

References 139

8 Ground Heat ExchangerModeling Examples 143

8.1 Semi-AnalyticalModeling of Two Boreholes 143

8.2 Numerical Modeling of Two Boreholes 150

8.3 Numerical Modeling of a Borefield 167

8.4 Numerical Modeling of a Horizontal Ground Heat Exchanger 172

8.5 Model Comparison 180

References 182

9 Thermodynamic Analysis 184

9.1 Introduction 184

9.2 Analysis of an UndergroundThermal Energy Storage System 184

9.3 Analysis of a Ground-Source Heat Pump System 192

9.4 Analysis of a System Integrating Ground-Source Heat Pumps and UndergroundThermal Storage 197

References 204

10 Environmental Factors 206

10.1 Introduction 206

10.2 Environmental Benefits 206

10.3 Environmental Impacts 208

References 217

11 Renewability and Sustainability 218

11.1 Introduction 218

11.2 Renewability of Ground-Source Heat Pumps 218

11.3 Sustainability of Ground-Source Heat Pumps 220

References 226

12 Case Studies 228

12.1 Introduction 228

12.2 Thermal Energy Storage in Ground for Heating and Cooling 229

12.3 Underground andWater TankThermal Energy Storage for Heating 231

12.4 Space Conditioning with Heat Pump and SeasonalThermal Storage 239

12.5 Integrated System with Ground-Source Heat Pump,Thermal Storage, and District Energy 242

12.6 Closed-Loop Geothermal District Energy System 249

12.7 Closing Remarks 250

References 251

A Numerical Discretization 252

Reference 254

B Sensitivity Analyses 255

B.1 Parameters AffectingThermal Interactions betweenMultiple Boreholes 255

B.2 Validation of the Two-Dimensional Numerical Solution with a Three-Dimensional Solution 261

B.3 Heat Flux Variation along Borehole Length 267

References 272

Index 273