Geothermal Heating and Cooling : Design of Ground-Source Heat Pump Systems

Description

"Best practices for designing nonresidential geothermal systems (ground-source heat pump, closed-loop ground, groundwater, and surface-water systems) for HVAC design engineers, design-build contractors, GSHP subcontractors, and energy/construction managers; includes supplemental Microsoft Excel macro-enabled spreadsheets for a variety of GSHP calculations"-- Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xi Acknowledgments.................................................. xiii Symbols, Acronyms, and Abbreviations 1 · Introduction to Ground-Source Heat Pumps .................................. xv 1.1 Overview, Nomenclature, and GSHP Types ...................................1 1.2 Ground-Coupled Heat Pumps..............................................3 1.3 Groundwater Heat Pumps.................................................4 1.4 Surface-Water Heat Pumps................................................5 1.5 Exterior and Building Loop Piping Options ...................................7 1.6 Field Study Results ......................................................7 1.7 Preliminary Assessment, Design Steps, and Deliverables . . . . . . . . . . . . . . . . . . . . . . 12 1.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2 · Equipment for Ground-Source Applications 2.1 Heat Pump Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.2 Water-Source Heat Pump Standards ....................................... 25 2.3 Performance of Water-Source Heat Pumps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2.4 GSHP System Performance .............................................. 38 2.5 Suggested GSHP Specifications........................................... 42 2.6 Outdoor Air and GSHPs.................................................. 42 2.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3 · Fundamentals of Vertical Ground Heat Exchanger Design 3.1 Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 3.2 Equations for Required Ground Heat Exchanger Length . . . . . . . . . . . . . . . . . . . . . . . 52 3.3 Borehole Thermal Resistance ............................................. 58 3.4 Ground Thermal Resistance and Basic Heat Exchanger Design . . . . . . . . . . . . . . . . . 67 3.5 GCHP Site Assessment: Ground Thermal Properties . . . . . . . . . . . . . . . . . . . . . . . . . . 73 d Contents dd F2_TOC.fm Page vii Thursday, November 13, 2014 10:57 AM viii Geothermal Heating and Cooling 3.6 GCHP Site Evaluation: Thermal Property Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 3.7 Long-Term Ground Temperature Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 3.8 Comments on the Design of Vertical Ground Heat Exchangers . . . . . . . . . . . . . . . . . . 89 3.9 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 4 · Applied Ground-Coupled Heat Pump System Design 4.1 System Design Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 4.2 Applied Design Procedure for Vertical GCHPs (Steps 1–10). . . . . . . . . . . . . . . . . . . . . 93 4.3 Design Alternatives (Step 11) ............................................ 110 4.4 Performance Verification and Necessary Documents . . . . . . . . . . . . . . . . . . . . . . . . . 121 4.5 References ........................................................... 122 5 · Surface-Water Heat Pumps 5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 5.2 Heat Transfer in Reservoirs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 5.3 Thermal Patterns in Reservoirs and Streams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132 5.4 Fundamentals of Closed-Loop Surface-Water Heat Exchangers . . . . . . . . . . . . . . . . 139 5.5 Closed-Loop Surface-Water Heat Exchangers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 5.6 Circuits and Layout of Surface-Water Heat Exchangers . . . . . . . . . . . . . . . . . . . . . . . 154 5.7 Open-Loop Surface-Water Heat Pump Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 5.8 Direct Cooling and Precooling with Surface-Water Systems . . . . . . . . . . . . . . . . . . . 164 5.9 Heat Transfer in GSHP Headers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 5.10 Environmental Impact of Surface-Water Heat Pumps. . . . . . . . . . . . . . . . . . . . . . . . . 173 5.11 Recommendations for the Design of Surface-Water Heat Pumps . . . . . . . . . . . . . . . 176 5.12 References ........................................................... 177 6 · Piping and Pumps for Closed-Loop Ground-Source Heat Pumps 6.1 Overview of GCHP and SWHP Piping Systems and Pumps . . . . . . . . . . . . . . . . . . . . 179 6.2 Impact of Pump Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182 6.3 Impact of Pump Energy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185 6.4 Piping Fundamentals................................................... 189 6.5 Pipe Materials, Dimensions, and Loss Characteristics . . . . . . . . . . . . . . . . . . . . . . . . 190 6.6 Pump Fundamentals ................................................... 198 6.7 Closed-Loop Water Distribution System Design Procedure . . . . . . . . . . . . . . . . . . . . 201 6.8 Pump Control and Heat Pump Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208 6.9 Ground-Loop Piping Circuits ............................................ 214 6.10 Summary of Piping and Pump Design Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223 6.11 References ........................................................... 224 7 · Hydrology, Water Wells, and Site Evaluation 7.1 Groundwater Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 7.2 Water Well Terminology ................................................ 230 7.3 Common Water Well Completion Variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233 F2_TOC.fm Page viii Thursday, November 13, 2014 10:57 AM Contents ix 7.4 Selected Topics in Water Well Construction and Design . . . . . . . . . . . . . . . . . . . . . . 236 7.5 Site Evaluation for GWHP Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243 7.6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261 8 · Groundwater Heat Pump System Design 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 8.2 General Design Approach ............................................... 268 8.3 Production/Injection Well Separation ...................................... 274 8.4 Building Loop Pumping for GWHP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276 8.5 Well Pumps .......................................................... 276 8.6 Heat Exchangers ...................................................... 291 8.7 System Design Example ................................................ 296 8.8 GWHP Economics ..................................................... 311 8.9 References ...........................................................318 9 · GSHP Performance and Installation Cost 9.1 Field Study Performance Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321 9.2 Prediction of the Performance of GSHP Design Options . . . . . . . . . . . . . . . . . . . . . . 333 9.3 Field Study Installation Cost Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338 9.4 Estimation of the Cost of GSHP Design Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347 9.5 Characteristics of Quality GSHPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356 9.6 References ...........................................................358 Appendix A—Conversion Factors Appendix B—Standards and Recommendations for GSHP Components and Procedures Appendix C—Pressure Ratings and Collapse Depths for Thermoplastic Pipe C.1 High-Density Polyethylene Pipe Pressure Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 C.2 Fiberglass-Core Polypropylene Pipe Pressure Ratings. . . . . . . . . . . . . . . . . . . . . . . . 363 C.3 HDPE Pipe Collapse Depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363 C.4 References ........................................................... 367 Appendix D—Vertical-Loop Installation Equipment and Procedures D.1 Vertical-Loop Drilling Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 D.2 Vertical-Loop Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 D.3 Vertical-Loop Backfill and Grouting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370 D.4 References ........................................................... 373 Appendix E—Example of Field Study Results E.1 County Water Agency Operations and Maintenance Office . . . . . . . . . . . . . . . . . . . . 375 F2_TOC.fm Page ix Thursday, November 13, 2014 10:57 AM Appendix F—Properties of Antifreeze Solutions Appendix G—Volumes of Liquids in Pipe Appendix H—High-Density Polyethylene and Polypropylene Pipe Fusion Methods Appendix I—Determination and Impact of Ground Coil Flow Imbalance x Geothermal Heating and Cooling I.1 Flow Imbalance in Closed-Loop GSHPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387 I.1 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388 Appendix J—Grain Size Classification Appendix K—Well Drilling Methods K.1 Cable Tool Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 K.2 Conventional Rotary Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 392 K.3 Air Rotary Drilling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 K.4 Air Hammer Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 K.5 Drilling Method Effectiveness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 K.6 Reference ............................................................ 398 Appendix L—Well Flow Test and Water Chemistry Analysis Specification Appendix M—Example Well Chemical and Biological Analysis Results M.1 Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403 M.2 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405 Appendix N—Well Problems and Strategies to Avoid Them N.1 Understanding Well Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407 N.2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410 Appendix O—Heat Exchanger Temperature Prediction Spreadsheet O.1 Spreadsheet Tool. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 411 O.2 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415