Geothermal heat harvesters

Abstract

Thermal energy is extracted from geological formations using a heat harvester. In some embodiments, the heat harvester is a once-through, closed loop, underground heat harvester created by directionally drilling through hot rock. The extracted thermal energy can be converted or transformed to other forms of energy.

1 . (canceled) 
     
     
         2 . A geothermal heat harvesting system, comprising a closed fluid flow path having a first segment, a second segment and a third segment, wherein the first segment, second segment and third segment are disposed below a surface such that, during use, a working fluid is directed through the closed fluid flow path along a direction that includes, in sequence, the first segment, second segment and third segment, wherein the closed fluid flow path includes a fluid entrance and a fluid exit that are co-located at the surface, and wherein (i) the second segment is free of thermal insulation, (ii) the third segment is thermally insulated, and (iii) the second segment comprises a horizontal portion between two sharp turns.