An energy exchanger (2) is connected to an earth energy exchanger (18) via a flow line (10) and a return flow line (14). The flow line (10) and the return flow line (14) are both provided with a regulatable stop valve (12, 16). At least one heat-insulated flow pipe (20) is surrounded by a separation pipe (24) in a bore hole (22), whereby a return flow area (28) for circulatory water is connected thereto in a radially outward manner. The return flow area (28) contains at least one return flow pipe (30) connected to the return flow line (14) and a porous filling (38) in addition to being connected, at least on the base of the bore hole (22), to the lower inlet (46) of the flow pipe (20) or the lower inlets (46, 46a) of the flow pipes (20,20a) via one or several through openings (44) in the separation pipe (24). A connectable pressure medium device (56), and preferably a discharge valve (56) for discharging the circulatory water from the flow pipe (20) and triggering the production and transport of steam from the earthly body, is disposed on the flow line (10) between the stop valve (12) and the energy exchanger (18).
