"In October 2023, the Louisville Muhammad Ali International Airport powered up its new geothermal heating, ventilation, and air conditioning system—the largest of its kind in the US. More than 600 “wells,” dug 500 feet under the ramp area adjacent to the terminal, use the earth’s temperature to enable an efficient heat exchange that cools the building in the summer and heats it in the winter. Engineers estimate the system will reduce the airport’s carbon emissions from heating and cooling by more than 80%, and save around $400,000 per year—a compelling example for other transportation hubs that are considering making the switch."