For example, a ground probe system (100) may have the following: a fluid conduit (110), wherein the fluid conduit comprises an outer pipe (112) and an inner pipe (114) disposed within the outer pipe, and wherein the fluid conduit is arranged such that a working fluid (120) within the outer pipe can be tempered by means of at least one heat source (130) and at least one heat sink (140) such that the working fluid can sink in the outer pipe and rise in the inner pipe; and a turbine-generator unit (150) disposed in the inner pipe of the fluid guide and arranged such that at least one turbine (152) of the turbine-generator unit can be driven by the working fluid rising in the inner pipe and that mechanical energy from the at least one turbine can be transferred to at least one generator (154) of the turbine- generator unit for generating electrical energy by means of the at least one generator, wherein the working fluid comprises a supercritical fluid.