Geothermal energy is recovered by (1) introducing into a subterranean heat exchange medium which is in heat exchange with a high temperature formation a liquified vapor which will vaporize at the conditions of the medium; (2) vaporizing the liquified vapor; (3) confining the liquified vapor until pressurized; and (4) recovering pressurized vapor having thermal and pressure-volume energy converted from the high temperature formation.

In this solar steam driven water pump steam is periodically generated and then condensed within a cavity to produce first a period of pressure over a column of water and then a period of vacuum to thereby first expell water from the cavity through one check valve and to subsequently fill the cavity with water through another check valve at the time of the vacuum, the generation of said steam pressure within said cavity being effected by a separate small pump within the cavity when this pump move...