M. S.

Energy extraction from dry geothermal sources (subterranean hot rock), and subsequent conversion to electrical power was analyzed. Analytical closed form solutions of the governing heat conduction equation were used to predict electrical power levels and total outputs. Four subterranean reservoir geometries were considered. A semi-infinite planar crack was ued as a first approximation to the fissure geometry created by hydraulic fracturing of a well in which no subsequent fracture growth occurs. The initial model was later refined using a finite disk to model the fracture geometry. A finite thickness slab, infinite in extent, was used to approximate the fissure geometry created by thermal stress cracking in a hydraulically fractured well. The fourth geometry modeled a cylindrical well bore. In the analyses, heat transfer in the rock and the thermal efficiency of a heat engine were considered in determining the amount of electrical power which could be generated from geothermal energy. For a fracture 1 Km in diameter operating at an optimum heat flux, with an initial rock temperature of 600 K (620 F), and a surface ambient temperature (condenser temperature) of 310 K (100 F), it was calculated that a total of 1.75 million Mw-hrs of electricity could be generated over a 30 year period at a continuous rate of not less than 5 Mw. / M.S.