A geothermal heating and cooling system for the Macon County Justice Center saves taxpayers in the county thousands of dollars per year. BWSC provided A/E design for the 40,732-SF facility, which included a 128-bed jail facility, four courtrooms, sheriff’s offices, sallyport and county clerk offices.

The building is conditioned by a geothermal heat pump system. Geothermal heat pumps operate in much the same way as residential heat pumps except that the outdoor air-cooled condenser is replaced with a water-cooled condenser. The water for the heat pumps is routed underground to a long network of piping buried in the ground. The water is cooled by the constant temperature of the earth and then circulated back to the building. Like in an air-conditioned heat pump, the cycle is reversed in the heating mode. Since the ground maintains a more constant temperature than the air, the efficiency of geothermal heat pumps is much better than air-cooled heat pumps. For this project, the geothermal piping network is located under the parking lot and circulates water through vertical borings containing small diameter plastic pipes.  Heat pump units inside the building absorb or reject heat to the circulating water to heat and cool the building.  A total of 110 borings were used, each 260 feet deep.

Key points
$5.5 million construction cost
Geothermal heating and cooling
Estimated energy cost savings of $75,000 per year
Project received 2002 Rebuild Tennessee award