Geothermal cooling works the same as geothermal heating, except in reverse. Heat is taken out of the structure in the home, put into the circulating liquid inside the ground loop, and absorbed into the cool earth. This “reversed” cycle is simple to switch a heat pump into with its reversing switch. When a ground source heat pump is in cooling mode it is functioning the same as a refrigerator, pulling heat out of the house, putting it through a refrigerant loop, and then expelling it out. A refrigerator does that using the coils on the back. A GSHP does it using the large earth loop and cool mass of earth, making it more efficient to have heat go to cold instead of hot ambient air.