1sockchuck writes: "With data centers using enormous amounts of electricity, some companies are using the earth to reduce their power bills. Prairie Bunkers plans to use geothermal cooling in a Nebraska project that will convert former World War II ammo bunkers into data centers. This follows news that an Iowa data center used geothermal cooling to achieve the highest rating possible for energy-efficient buildings. Geothermal cooling uses vertical wells housing closed-loop piping systems filled with water or coolant. The cool earth allows the underground piping system to serve as a heat exchanger."