NOVELTY - Geothermal heating and cooling system for a power conversion system (40) within an enclosure comprises: (a) a heat exchanger positioned at the power conversion system and within the enclosure (65); (b) one or more pipes (110) positioned within the ground (120); and (c) a heat transfer medium circulating within the heat exchanger and the pipes to transfer heat between the power conversion system and the ground.    USE - The geothermal heating and cooling system for a power conversion system within an enclosure is useful for the thermal management of outdoor power conversion equipment and related components.    ADVANTAGE - The heating and cooling system may reduce dependence of the heating or cooling capacity on ambient conditions and reduce the installed cost per Watt power converted, reduce operating and maintenance costs, and improve the overall efficiency and performance of the system.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method of thermally controlling a solar power conversion system with a geothermal heating and cooling system comprising: (a) providing a heat exchanger of the geothermal heating and cooling system in communication with the solar power conversion system; (b) providing one or more pipes in the ground and in communication with the heat exchanger; and (c) circulating a heat transfer medium between the heat exchanger and the pipes to transfer heat between the solar power conversion system and the ground; and    (2) a solar power generation system comprising: (a) a solar power conversion system in communication with a photovoltaic array; (b) a heat exchanger positioned at the solar power conversion system; (c) one or more pipes positioned within the ground; and (d) a heat transfer medium circulating within the heat exchanger and the pipes to transfer heat between the solar power conversion system and the ground.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the geothermal heating and cooling system for a power conversion system.    Enclosure (65)    Pipes (110)    Ground (120)