IMPLEMENTING GROUND SOURCE HEAT PUMP AND GROUND LOOP HEAT EXCHANGER MODELS IN THE ENERGYPLUS SIMULATION ENVIRONMENT by ARUNACHALAM MURUGAPPAN Bachelor of Engineering Annamalai University Chidambaram, India 1998 Submitted to the Faculty of the Graduate College of the Oklahoma State University in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE Oklahoma State University December, 2002 IMPLEMENTING GROUND SOURCE HEAT PUMP AND GROUND LOOP HEAT EXCHANGER MODELS IN THE ENERGYPLUS SIMULATION ENVIRONMENT Thesis Approved: Thesis Adviser Dean of Graduate College ii ACKNOWLEDGMENTS I would like to express my sincere appreciation to my advisor Dr. Daniel E. Fisher, for his continued and unrelenting support through out this project. Thanks for the faith and confidence you had in me. Thanks for the patience you showed towards me during my dark hours. Again I express my gratitude for all your guidance and leadership. I would like to extend my thankfulness to my advisory committee members Dr. Jeffrey D. Spitler and Dr. Afshin J. Ghajar, who offered their guidance, support and constructive criticism, which helped in improving this work to this level. I wish to thankyou Dr. Simon J. Rees for sharing your expertise in the Energy Simulation, which helped me to improve the quality of the work in many ways. Your mental acumen to solve problems helped in finishing this work sooner than it could have taken! I would also like to thank all my colleagues Chanvit Chantrasrisalai, David Eldridge, Kim Tacheol, Hui Jin, Xiaobing Liu for their suggestion and ideas, which helped a long way towards improving the quality of this work. Last but the not least, I like to thank my father Arunachalam, my mother Meenal, my brother Kannappan and my little niece Umachu for their unfathomable love and support during my stay away form home. Support of the U.S. Department of Energy is gratefully acknowledged. iii TABLE OF CONTENTS Section Page Chapter 1. Introduction ....................................................................................................1 1.1. Objective..................................................................................................................1 1.2. Overview of the Simulation Environment. .............................................................. 2 1.3. Overview of the Parameter Estimation Water-to-Water Heat Pump Model ........... 5 1.3.1. Review of Existing Models................................................................................6 1.4. Ground Loop Heat Exchanger Model...................................................................... 9 1.4.2. Review of Existing Models..............................................................................12 Chapter 2. The EnergyPlus Simulation Environment ................................................ 19 2.1. The Plant and Condenser Loop Simulations.......................................................... 20 2.2. Equipment Operation............................................................................................. 22 2.3. Implementing the Geothermal Systems in EnergyPlus ......................................... 23 2.3.1. Fluid Properties............................................................................................... 23 2.3.2. Multi-year Simulation..................................................................................... 24 2.4. Summary................................................................................................................ 25 Chapter 3. Implementing the Heat Pump Model......................................................... 26 3.1. Description of the model........................................................................................ 28 3.1.1. Compressor Model.......................................................................................... 28 3.1.2. Evaporator and Condenser Models................................................................. 30 3.1.3. Expansion Device ........................................................................................... 31 3.2. Model input parameters ......................................................................................... 32 3.3. Sensitivity Analysis ............................................................................................... 33 3.3.1. Sensitivity to model’s estimated parameters................................................... 34 3.3.2. Sensitivity to changes in model inputs............................................................ 37 iv Section Page 3.4. Model implementation........................................................................................... 40 3.4.1. Input Specification.......................................................................................... 43 3.4.2. Model Implementation.................................................................................... 45 3.5. Summary................................................................................................................ 51 Chapter 4. Variable Short Time Step Model of Vertical Ground Loop Heat Exchangers ...................................................................................................................... 52 4.1. Variable System Time Step in EnergyPlus............................................................ 52 4.1.1. System Simulation in EnergyPlus................................................................... 53 4.2. Ground Temperature Response Factors................................................................. 54 4.2.1. Long Time-Step Response Factors ................................................................. 55 4.2.2. Short Time-Step Response Factors................................................................. 57 4.3. Development of the EnergyPlus Variable Short Time Step Model....................... 58 4.4. Analytical Comparison .......................................................................................... 60 4.4.1. The Line Source Model .................................................................................. 61 4.4.2. Superposition of Pulses................................................................................... 65 4.4.3. Results of Stand-Alone Model Tests with no Load Aggregation................... 68 4.5. Load Aggregation .................................................................................................. 78 4.6. Description of the Load Aggregation Scheme....................................................... 79 4.7. Summary of Variable Short Time Step Response Factor Model........................... 86 4.8. Effect of Load Aggregation ................................................................................... 90 4.9. Implementing Vertical Ground Loop Heat Exchanger Model in EnergyPlus....... 96 Chapter 5. Case Studies.................................................................................................102 5.1. Introduction.......................................................................................................... 102 5.2. Example Building and Plant Description............................................................. 102 5.3. Building load Profiles .......................................................................................... 106 5.4. The Heat pump Selection..................................................................................... 107 5.5. Ground Loop Configuration ................................................................................ 108 5.6. Results.................................................................................................................. 112 v Section Page 5.6.1. Tulsa, Oklahoma............................................................................................112 5.6.2. Anchorage, Alaska.........................................................................................121 5.7. Discrepancy in the Cooling Power Consumption................................................ 124 5.8. Zone and Heat Pump System Interactions........................................................... 129 5.9. Conclusion ........................................................................................................... 134 Chapter 6. Conclusion and Recommendations ...........................................................136 6.1. Conclusion: .......................................................................................................... 137 6.2. Recommendations:............................................................................................... 139 References.......................................................................................................................140 vi LIST OF TABLES Table Page 3-1 Non-Dimensional influence coefficients type-2, for the water-to-water heat pump model developed by parameter estimation model..................................................... 36 3-2 Influence coefficients and error analysis based on load side outlet temperature of the water-to-water heat pump model. ............................................................................. 38 3-3 Influence coefficients and error analysis based on source side outlet temperature of the water-to-water heat pump model. ....................................................................... 38 3-4 Influence coefficients and error analysis based on heat capacity of the water-to-water heat pump model......................................................................................................