Geothermal Heat Pumps and Performance Contracting

Save Energy for U.S.

Approximately 12,000 people live in the Fort Polk Army Base in 4,003 apartments. Initially, the equipment used to heat and cool these apartments was a mixture of poorly-installed minimum-efficiency units that had been selected on the basis of low-cost bids. Fort Polk management knew that renovation was necessary in order to meet the mandates of the Energy Policy Act of 1992 and to reduce the energy cost demand in their tight budget. The opportunity came with an energy savings performance contract (ESPC) with Co-Energy Group (CEG) to finance and install a series of geothermal heat pumps (GHPs) in the Fort Polk residences. CEG also retrofited the apartments with attic insulation, low-flow showerheads, and compact fluorescent lights. Oak Ridge National Laboratory (ORNL) conducted an independent evaluation of the energy savings of this project. The evaluation indicated the potential of GHPs to deliver significant energy and maintenance cost savings as the centerpiece of a comprehensive energy efficiency retrofit.

When CEG was developing the project, none of the 1.5 to 2 ton GHPs on the market had high enough efficiency and low enough installation costs to make the project feasible. The GHP manufacturer ClimateMaster, Inc. overcame this obstacle by developing new compact "VZ" units, which were easy to install and maintain. ClimateMaster reduced installation costs by building the ground loop and desuperheater loop circulators, controls, and valves into the unit. This practice avoids the expense associated with mounting components on walls and making multiple power and plumbing connections.

Technical Data

The GHP configuration at Fort Polk is a closed-loop, vertical-bore hole ground heat exchanger system. The underground piping is high-density polyethylene. All joints are thermally fused, and purchasing the pipe in "uni-coils" put the only outdoor fusion joints near the surface. Since there is no interface to outdoor air, there are no defrosting controls to maintain. GHPs exchange heat with circulating water rather than circulating outdoor air. The entering water temperature to the heat pump is generally closer to the desired temperature than in air-source heat pumps, which leads to greater efficiency, capacity retention, and indoor humidity control.

Energy Data

There was a savings of 26 million kWh of electricity (33%) and 260,000 therms of natural gas per year. The project reduced peak electrical demand by 43%.

Environmental Data

The retrofit resulted in a 22,400 ton annual decrease in CO₂ emissions.

Economic Data

Fort Polk saves about USD 345,000 per year during their contract with CEG, and will save about USD 2.2 million after the contract expires. The contract called for CEG to arrange private financing of about USD 18 million. The Army repays 77% of the savings plus USD 262 per apartment per year for maintenance.

Contacts:

Fort Polk Army Base Greg Prudhomme AFZX-PW-EP Building 2502 Fort Polk, LA 71459 318-531-6029 318-531-2628 (Fax)	U.S. Department of Defense T. Rutherford 3330 Defense, Room 3E1074 Washington, DC 20301-3330 703-697-6193 703-695-1493 (Fax)
Co-Energy Group T. Mitchell 1050 Flamingo Road, Suite N136 Las Vegas, NV 89119 702-650-0557 702-650-0517 (Fax)	ClimateMaster 7300 SW 44^th St Oklahoma City, OK 73179 405-745-6000 405-745-6058 (Fax) http://www.climatemaster.com

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