Geothermal Heat Pump Systems Being Green by using the Ground Presented by: Warren (Trey) Austin, PE, CEM, CGD, LEED-AP Geo-Energy Services, LLC 1
Most Often Asked Questions What is the difference between geothermal, ground-source or GeoExchange? Where does the energy come from? What makes ground-source heat pumps energy efficient? How does it heat/cool? How much does it cost? What are the O&M costs? Are there rebates or grants? What are the applications? 2
Terminology Geothermal 101 GeoExchange- General term that groups all aspects of the technology and industry together Ground Source Heat Pump- A heat pump the uses the earth or ground as a source for heat of absorption or heat of rejection COP- Coefficient of Performance; Rating for Heating Mode- DHW Heating Only for our case EER- Energy Efficiency Ratio; Rating for Cooling Mode 3
Geothermal 101 Terminology Continued Borehole HDPE Grout Ground Thermal Conductivity q& = k ground dt dt 4
Answers to Common Questions Answers to Common Questions What is the difference between Geothermal and Ground-Source? Geothermal is the typically associated with a direct-use application of high temperature ground water- ACTIVE Ground-source is a term that means you are using the near constant temperature of the earth as a heat sink or heat source- PASSIVE Where Does the Energy Come From? Two Sources The natural passive geothermal gradient The energy absorbed by the Sun! 5
Space Atmosphere 45% absorbed by ground Earth The earth is like a solar battery absorbing nearly half of the sun s energy. The ground stays a relatively constant temperature through the seasons. Passive geothermal gradient U.S. Dept. of Energy 6
Answers to Questions What makes ground-source heat pumps energy efficient? Ground-coupled heat pumps take advantage of 2 ½ to 1 gain in energy output to energy input with the characteristics of heat transfer to fluid in the loop with the ground. How does it Cool? Refrigeration circuit with phase changes moves energy from a hot source to a cold source even at high fluid temperatures (>95 F). 7
Ground Loop Temperature Profile 100 90 80 70 Temperature (F) 60 50 40 30 20 10 0 T fluid = 9600 T ideal = 32,960 Tideal 1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 171 181 191 201 211 221 231 Time (months) 8 Tground Tfluid Theat Tcool
Benefits of GSHP System 30%-60% Lower Operating / Energy Cost 40%-70% reduction in Green House Emissions Longer life span Greater Comfort Less Maintenance, Simplified Controls Better Aesthetics (no exposed outdoor equipment) LEED/Green Building solutions 9
Internal Component of GeoExchange Systems CV Air Units Horizontal HP Vertical HP Console HP Rooftop HP Hydronic Units WW HP 10
Cost and Paybacks Installation cost ranges $10.00 to $20.00 / ft 2 Operating costs $0.35 to $0.85 /ft 2 -yr Paybacks can be immediate to 5 years Average: 5-8 years Some systems can be 8-12 years Rebates Depend on local utilities Tax Credits Federal and some State 11
Project Considerations Know the Design Parameters Space Heating/Cooling Air Distribution Radiant Floor Heating Hot Water/Chilled Water Integrated Systems Other Auxiliary Loads DHW Snowmelt- Heat Rejection Refrigeration Thermal Conductivity Test 12
Project Considerations Loop Fields Performance indifferent when properly designed at the same EWTs Efficiency of equipment directly correlated to EWT Pond/Lake Loops or Plates Be cautious about Icing or Overheating Horizontal Loops Sizing loop must account for frost depths, surface snow, seasonal amplitude temperature changes 13
Project Considerations Loop Fields (continued) Vertical Boreholes Least site restrictive due to greater depths for heat transfer Accounts for majority of all installation (>80%) Typical 2 and 3 header lines 2 = 4-7 boreholes per header 3 = 6-12 boreholes per header Generally like to be the lowest utility 14
Project Considerations Loop Fields (continued) Hybrid Configuration Combine any of three traditional loop field designs to help reduce cost Combine with condensing boiler/solar heating technologies in heating load dominant situations Combine with fluid coolers/cooling towers in cooling load dominant situations Due to increasing use, further research is underway 15
Project Considerations Loop Fields (continued) In certain situations, a retrofit may be site prohibitive. Combine energy efficiency improvements Previous energy efficiency improvements may PROHIBIT a feasible retrofit Consider electrical service upgrades 16
Heat Rejection/Absorption Synergies Space Heating Ground Loop Heat Exchanger Space Cooling Refrigeration Rejection Hot Water Heating Load Rainwater Reclaim Shallow Heat Rejection Slab Fluid Cooler Greywater Reclaim 17
Vertical Loop Installation Equipment Drill Rig Fusion Equipment Flushing Trailer Pipe Vertical Ground Loop Grout 18
Vertical Loop Field 19
Vault 20
Horizontal Slinky (Pit) Loop 21
Pond/Lake Loop 22
Pond Loop- Plate Heat Exchanger 23
Internal The Cx Perspective No Different that any other HVAC system Piping ½ Insulation only for condensation HDPE pipe for interior as potential a cost saving measure Ductwork Flex duct collars to isolate vibration Circulating Pumps Primary/Secondary Lead/Lag Zone Pumping/Individual 24
The Cx Perspective Internal (continued) Equipment Location important for sufficient access Filter Replacement Fan Motor/Housing Compressor Maintenance Mfr s Recommended Clearance- Specific Areas P/T Ports at Unit- can be integrated with hose kits Equipment Cx- Flow and Capacity 25
The Cx Perspective Internal (continued) Equipment Air PSC- Fixed Speeds (L/M/H) ECM-Variable Speed (Dip Switch) Controls Conjoined with 2-speed compressors Basic T-stat operation DDC with integrated internal/external controllers 26
The Cx Perspective Internal (continued) Space Temperature Control Standard heating and cooling setpoints (5 diff.) Single setpoint with autochangeover 27
The Cx Perspective External P/T Ports Supply and Return Header lines Pipe Fusion Joints Butt Fusion Socket Fusion Electro Fusion Reverse Return Properly Flush and Purged 28
The Cx Perspective External (continued) Grout Properly mixed Periodic samples- independently tested by mfr (free service) Grouted from bottom to top No native backfill or pea gravel (by preference) Proper balanced headers at manifold Proper tracer wire/metallic tape 29
The Good, The Bad, The Ugly 30
Developing the Solution Optimization of Energy Performance must consider: Utility Rates Evaluation of ALL System interactions Select a GSHP for the right application Energy performance criteria can influence decisions that may be different for each application Become cognizant and aware of real issues so that informed decisions can be made Understand Peak Load Durations based on system configuration 31
Internet and Literature Resources International Ground Source Heat Pump Association www.igshpa.okstate.edu Geothermal Heat Pump Consortium www.geoexchange.org ASHRAE: Commissioning, Preventive Maintenance, and Troubleshooting Guide for Commercial Ground-Source Heat Pump Systems ASHRAE Publication Operating Experiences with Commercial Ground-Source Heat Pump Systems- 1998 ASHRAE Publication Comparative Analysis of Life-Cycle Costs of Geothermal Heat Pumps and Three Conventional HVAC Systems- 2000 ASHRAE Transactions 32
Questions? 33