You have probably noticed it on a hot summer day: A basement feels cool even when the air outside is baking. The ground does not heat up and cool down as fast as the air does. A few hundred feet down, it stays close to the local yearly average all year, which can be around 50 degrees Fahrenheit (10 Celsius).
In Verona, Wisconsin, the health software company Epic Systems has spent two decades turning that fact into infrastructure. It has drilled roughly 6,100 wells, 300 to 800 feet (90 to 240 meters) deep, that now heat and cool about 40 buildings on its own campus by using the waste heat from a 3.5-megawatt data center.
