Next to the Logistics Command headquarters building is a circular field of 306 boreholes drilled 210 feet into the ground. About 1.5 miles of fiber optic cable is used to monitor the temperature in the system.

The water circulating through the pipes in the winter cools the limestone, which is like Swiss cheese and is filled with ground water. The water from the pipes in effect cools or "charges" the limestone and ground water, which doesn't move. That is what cools the water that circulates through the system during the summer.

Then in the winter, the limestone and groundwater around the pipes remains at about 70 degrees, and that allows heating.

Heat Thermal Storage