Abstract: A geothermal energy system in which a bore hole is drilled into the earth to a depth where a predetermined temperature gradient exists between the earth's surface and the bottom of said bore hole. A liquid refrigerant line passes down the bore hole and connects to an evaporator where the geothermal energy is used to vaporize the refrigerant and from there it passes back up through a high pressure gaseous refrigerant return line to a gas operated turbine located at the earth's surface. The spent refrigerant exiting from the turbine is cooled in a condensing unit and recirculated to the subterranean evaporator unit. The turbine may be used to drive a suitable electrical generator for power production purposes.