Geothermal heat mining and utilization

A method for utilizing thermal energy contained in subterranean hot rock, comprising:

• a) providing an insulated conduit extending vertically from the surface of the earth into said hot rock;
• b) providing a plurality of heat conducting pipes, each of which is disposed radially from said conduit and extends from a manifold at a surface of the earth through said hot rock and into a bottom of said conduit thereby forming a closed flow path from said manifold into the bottom of said conduit;
• c) heating a relatively cool liquid by passing said liquid through at least one pipe of said plurality of pipes thereby providing heated liquid containing thermal energy from said hot rock;
• d) passing the heated liquid from said at least one pipe into said bottom of said conduit;
• e) maintaining the wellhead pressure in the top of said conduit to cause a portion of the heated liquid in said conduit to vaporize and form a hot two-phase flow of liquid and vapor as it ascends in said conduit;
• f) discharging said two-phase flow from said top of said conduit;
• g) maintaining a desired reduced pressure of the two-phase flow being discharged from said conduit thereby increasing the vapor content in said flow;
• h) utilizing thermal energy contained in said two-phase flow after being discharged and condensing the vapor in said flow to liquid condensate, thereby cooling said flow and providing cooled liquid;
• and
• i) recirculating said cooled liquid from step "h" to provide the relatively cool liquid in step "c".

Apparatus for recovering thermal energy contained in subterranean hot rock, comprising:

• a) an insulated conduit extending from a wellhead at the surface of the earth to a desired depth in said hot rock for passing a fluid in said conduit from said depth to said wellhead;
• b) a plurality of heat conducting pipes, each of which is connected at a top end through a valve to a manifold at the surface of the earth and at the other end to a bottom of said conduit forming a closed flow path from said manifold into said conduit;
• c) means connected to said manifold for supplying liquid at a relatively cool temperature to said manifold;
• d) throttling means connected to a top of said conduit for maintaining a desired wellhead pressure in said conduit and for maintaining a desired discharge pressure of the fluid being discharged from said throttling means;
• e) means connected to said throttling means for receiving said discharged fluid and for extracting thermal energy therefrom and providing said liquid at said relatively cool temperature;
• and
• f) means connected to the means for supplying liquid for recirculating liquid at said relatively cool temperature from the means for receiving said discharge fluid to said manifold.

Apparatus for utilizing thermal energy contained in subterranean hot rock, comprising:

• a) an insulated riser for passing fluid from a desired depth in said hot rock to the surface of the earth;
• b) a plurality of heat conducting pipes, each of which extends from the surface of the earth to said depth and is disposed outward from the top of said riser to a desired distance from said riser and then inward to join a bottom of said riser thereby forming a closed flow path from each of said pipes into the bottom of said riser;
• c) a manifold at said surface to which each of said pipes is connected through a valve;
• d) means connected to said manifold for supplying liquid at a relatively cool temperature to said manifold, said liquid being capable of existing in vapor phase at elevated temperature;
• e) means for passing liquid from said manifold to at least one of said pipes;
• f) throttling means connected to a top of said riser for maintaining a two-phase flow of liquid and vapor discharging from said riser at a desired pressure;
• g) means connected to said throttling means for receiving said two-phase flow and for extracting thermal energy therefrom and for providing said liquid at said relatively cool temperature;
• and
• h) means connected to said manifold for recirculating liquid at said relatively cool temperature from the means for receiving said discharge fluid to said manifold.