Patent ID: 8430166

Claim:
A geothermal energy extraction method comprising, in a geologic formation: introducing coolant fluid into a first fracture system at a first height; collecting the coolant fluid from a second fracture system at a second height and in fluid communication with the first fracture system to provide collected coolant fluid, the second height being lower than the first heigh, wherein the coolant fluid introduced into the first fracture system percolates through a geologic formation from the first fracture system to the second fracture system, collecting heat from the geologic formation; and periodically evaporating or liberating fluid and condensing or dissolving fluid within the first or second fracture systems by lowering the fluid pressure of the first or second fracture systems below the saturated pressure of the coolant fluid in one cycle, followed by increasing the fluid pressure of the first or second fractures systems above the saturated or dissolution pressure in another cycle, wherein the evaporation increases the surface area of the first or second fracture systems and condensation replenishes coolant fluid in the first or second fracture systems, thus increasing the surface area for heat exchange in the first or second fracture systems.