GEOTHERMAL GROUND-SOURCE HEAT PUMPS

1. GEOTHERMAL (GROUND-SOURCE) HEAT PUMPSIntroduction Dr. John W. Lund, PE Director, Geo-Heat Center Oregon Institute of Technology Klamath Falls, OR, USA

2. World Utilization of GHP Largest geothermal direct-use growth Almost 7x growth since 2000 Mainly USA, Canada and Europe � 43 countries Capacity: 35,200 MWt � 9,800 GWh/yr Typical unit: 12 kW (3.4 tons) Range: 5.5 kW to 150 kW Approx. 3.0 million units installed worldwide LF = 0.19

4. World Utilization of GHP - 2 US: most sized for cooling load � oversized for heating Europe: most sized for base load heating US: 2,000 full-load heating hours/yr CF = 0.23 Europe: 2,000 to 6,000 full-load hours/yr (2,200 hours � typical) CF = 0.23 to 0.68

5. Leading Countries Using GHP Country MWt GWh/yr Number Canada 1,111 2,360 92,600 China 5,210 8,060 434,000 France 1,000 2,800 83,300 Germany 2,230 2,880 185,800 Netherlands 1,394 2,890 116,200 Norway 3,300 7,000 275,000 Sweden 4,460 12,580 371,700 Switzerland 1,017 1,830 84,800 USA 12,000 13,200 1,000,000

6. GHP Example - 1 Galt House East Hotel, Louisville, KY largest installation in the USA Heat and air conditioning provided for 600 hotel rooms 100 apartments 960,000 ft� of office space Total 1,740,000 ft� Using 2,800 gpm from 4 wells @ 57�F Provides 15.8 MW cooling, 19.6 MW heating Energy approx. 53% of similar non-GHP building Saving approx. $25,000 per month

8. Fundamentals - 1 HP = machine causes heat to flow �uphill� From lower to higher temperature Work done � �pump� used to describe Refrigeration unit � reversible Heat absorbed = �source� Heat delivered = �sink� Difference in temperature = �lift� The greater the lift � greater power input

10. Fundamentals - 2 Geothermal (ground-source) heat pumps Uses geothermal resource between 40 and 90�F Either removes heat from a low temperature resource to a higher temperature reservoir (heating) Or removes heat from a high temperature resource to a lower temperature reservoir (cooling) Geothermal use a constant temperature resource The ground or groundwater (below about 30 ft.)

11. Fundamentals -3 Air-source heat pumps � dependent on outside air temperature, which is: Lowest when heating demand is highest, and Highest when cooling demand is highest Thus, supplemental energy (electric) source needed

14. Advantages of GHP(as compared to air-source) They consume less energy to operate They tap a constant temperature resource They do not require supplemental energy during extreme outside air temperature They use less refrigerant Simpler in design and maintenance Does not require a unit outside exposed to the weather Longer equipment life

15. Disadvantages of GHP(as compared to air-source) Higher initial cost due to excavation for piping or drilling of a well Lack of trained and experienced designers and installers Lack of understanding by government regulators Shallow horizontal heat exchangers are affected by surface (air and sun) temperature variations � thus, requiring 30 to 50% more pipe in the ground

16. Definitions - 1 General terms: Ground-Source Heat Pumps (GSHP) Used by engineers and technical types, and The International Ground Source Heat Pump Association Geothermal Heat Pumps (GHP) Used by individual in marketing and government Often confused with direct-use geothermal Geoexchange Used by Geothermal Heat Pump Consortium Geothermal Systems � in many countries � confusing Below ground = �geothermal�

17. Definitions � 2 Ground-coupled or earth-coupled (closed loop) � tubing network directly buried in the ground - generally a thermally-fused plastic pipe (HDPE) with water or antifreeze (20% propylene glycol) solution circulated through the tubing Horizontal Vertical Spiral coil in vertical hole �Slinky� in a horizontal trench Encased in a foundation pile Direct expansion (no heat exchanger) One or more loops in a single hole or pile

18. Definitions - 3 Groundwater or water-source (open loop) systems use well or lake water. Water quality may be a problem due to calcium carbonate (hardness) and/or iron bacteria causing scaling or fouling of the heat exchangers Well water Lake water Mine water Tunnel water Standing column

20. USA Installations USA experience 1,000,000 total installations (estimated) Mainly in midwestern and eastern states 100,000 to 120,000 installed annually 45% horizontal closed loop (mainly residential) 45% vertical closed loop (mainly commercial/institutional) 10% water-source open loops A �unit� = 2 to 6 tons of cooling (ice) 12,000 Btu/hr/ton cooling capacity = 3.5 kW 3 tons for a typical US home of 2000 ft� = 10.5 kW

22. Equipment Most common single package � water-to-air Refrigerant-to-water heat exchanger Refrigerant piping and control valves Compressor Air coils (heats in winter; cools and dehumidifies in summer Fan Controls Desuperheater?

24. Performance Ratings Coefficient of performance in the heating mode: COP = Qh/Qe = heating capacity (kW)/electric power input (compressor) (kW) Energy efficiency ratio in the cooling mode: EER = Qc/Qe = cooling capacity (Btu)/electrical power input (compressor) (kW) That is: for a COP of 4, for every unit of electrical input, the system puts out 4 units of heat energy

25. Estimate of Annual Energy Consumption 1 Denver (Stapleton): 924�F-days cooling (>65�F), 6,282�F-days heating <65�C) System Cooling Heating DHW Total (kWh) (kWh) (kWh) (kWh) Electric 3,910 17,640 4,120 25,670 ASHP 1,960 8,820 4,120 14,900 GHP 1,220 4,650 2,510 8,380 For a 2000 ft� home, newly constructed with desuper-heater: est. annual savings @ 8�/kWh = $1,385 (electric vs GHP), and $522 (ASHP vs GHP)

26. Estimate of Annual Energy Consumption Steamboat Springs, CO: 300�F-days cooling (>65�F), 7,300�F-days heating <65�C), the annual loads are: System Cooling Heating DHW Total (kWh) (kWh) (kWh) (kWh) Nat. Gas 520 25,400 5,150 31,070 Electric 500 20,300 4,120 24,920 ASHP 400 10,150 4,120 14,670 GHP 340 5,400 3,150 8,890 For a 2000 ft� home, newly constructed with desuper-heater: est. annual savings @ 8�/kWh = $1,280 (electric vs GHP), and $462 (ASHP vs GHP). For natural gas at $12/million Btu, the annual savings would be $910 compared to GHP.

27. Estimate of Annual Energy Consumption Steamboat Springs, CO: 750 FLH cooling (>65�F), 750 FLH heating heating <65�F) � annual loads System Cooling Heating DHW Total (kWh) (kWh) (kWh) (kWh) Nat. Gas 47,100 137,500 10,000 194,600 Electric 45,000 110,000 8,000 163,000 ASHP 30,000 55,000 8,000 93,000 GHP 23,550 27,500 4,000 55,050 For a 10,000 ft� commecial building with desuper-heater: est. annual savings @ 8�/kWh = $8,640 (electric vs GHP), and $3,040 (ASHP vs GHP). For natural gas at $12/million Btu the annual savings would be = $5,700 compared to GHP = 8 year payback for new construction for 35 tons and 16 years for retrofit.

28. Cost of Installation (USA) Costs more than conventional system; however, savings are greater Costs depend upon: The availability and experience of contractors Cost of drilling or trenching (or well) Total installed cost (10.5 kW � 3 tons) for a 2000 ft� home with duct work and controls ASHP and Gas with AC ~ US$ 4 to 5,000 ($1300� 1,700/ton) GW GHP ~ US$ 7,000 (+ well cost) ($2,450/ton) Ground-coupled GHP ~ US$ 8 to 9,000 ($2,700 � 3,000/ton) Substantial variation possible by 2x to 3x

29. Cost of Installation - Details Installed cost � ground loops Ground coupled � horizontal: $750/ton Ground coupled � slinky: $900/ton Ground coupled � vertical: $1,025/ton Ground water (3 ton): $570/ton (w/o well) Water-to-air heat pump units 8.8 kW (2.5 tons): $2,750 ($1,100/ton) 10.5 kW (3.0 tons): $3,000 ($1,000/ton) 14.1 kW (4.0 tons): $3,600 ($900/ton) Substantial variations possible. Ref: Kavanaugh & Gilbreath (1995), and Rafferty (2008)

30. Savings in Energy Costs in USA Compared to GHP($ per Btu or kWh) 4x for electric resistance 3x for propane 2x for ASHP 2x for fuel oil 2x for natural gas

31. Large Scale Savings Example Assuming a rebate by local government of $200/kW ($2,000 per home) 5 kW reduction in peak heating demand 2.5 kW reduction in peak cooling demand 200,000 new homes produce 1000 MW savings Power plants installed cost = $3,000/kW Thus, cheaper to provide rebates than build newer power plant ($200 vs $3,000/kW) Rebates offered in USA and Switzerland ($500 to $2,000 per home) to installed heat pumps

32. Commercial Installations(large-scale) Cooling demand usually the largest Using central or multiple control units Groundwater systems the oldest and most widely used approach � with two wells, often reversing source from winter to summer Multiple ground-coupled system becoming popular � vertical bore holes 100 to 400 ft. deep in large fields under parking lots Ref: Kavanaugh & Rafferty, ASHRAE, 1997

34. Conclusions Geothermal (ground-source) heat pumps are not a new technology � Lord Kelvin developed the concept of heat pump in 1852. GHP � popularity started in the 1960s and 70s Growing at least 15%,yr; now 20%/yr Are economically competitive in areas of high alternate fuel cost Best suited for large building loads, such as schools, commercial buildings, etc. Best suited for new construction, as retrofits are expensive

35. Contacts (USA) Geo-Heat Center, Oregon Institute of Technology, Klamath Falls, OR, USA http://geoheat.oit.edu American Society of Heating, Refrigeration and Air-Conditioning Engineers, Atlanta, GA, USA: www.ashrae.org International Ground Source Heat Pump Association, Oklahoma State University, Stillwater, OK, USA: www.igshpa.okstate.edu Geothermal Heat Pumps Consortium, Washington, D.C.: www.geoexchange.org.

36. References An Information Survival Kit for the Prospective Geothermal Heat Pump Owner by Kevin Rafferty, HeatSprings, 2008. Ground-Source Heat Pumps � Design of Geothermal Systems for Commercial and Institutional Buildings by Stephen P. Kavanaugh and Kevin Rafferty, ASHRAE, 1997. Outside the Loop � a Newsletter for Geothermal Heat Pumps Designers and Installers, Univ. of Alabama � also available on the GHC website. International Course on Geothermal Heat Pumps, Proceedings, International Geothermal Days �Germany 2001� IGA and Internat. Summer School