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.
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
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%.
The retrofit resulted in a 22,400 ton annual
decrease in CO2 emissions.
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.
Fort Polk Army Base
AFZX-PW-EP Building 2502
Fort Polk, LA 71459
U.S. Department of Defense
3330 Defense, Room 3E1074
Washington, DC 20301-3330
1050 Flamingo Road, Suite N136
Las Vegas, NV 89119
7300 SW 44th St
Oklahoma City, OK 73179