How Geothermal Cooling Works   The cooling process involves extracting heat energy from the air in the building and moving it into the earth. Transferring heat from the building into the earth requires a cycle of expansion, compression, condensation and evaporation. A refrigerant is used as the heat transfer medium. The cooling cycle begins as the compressor deliverers refrigerant to the water-to-refrigerant heat exchanger. Heat from the refrigerant is absorbed by (rejected into) the low temperature source (earth loop fluid or well water), thereby cooling the refrigerant. The cold refrigerant then passes through a refrigerant-to-air heat exchanger. As warm, humid air from the return air duct system passes over the cold air coil, the air is cooled and dehumidified, then returned into the building. The heat from the warm air returning to the unit is absorbed into the cold refrigerant, turning the refrigerant into a gas. The gaseous refrigerant is then returned to the compressor, where the process is repeated. Some of the refrigerant from the compressor is diverted into a separate refrigerant circuit, where hot water is generated and delivered to the hot water heater by way of a small pump. Learn more: How Geothermal Heating Works