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Abstract

Method and apparatus for recovering and utilizing thermal energy from subterranean hot rock by means of a self-powered closed system which transfers heat from the hot rock to a relatively cool liquid, e.g. water, flowing in a heat-conducting pipe that extends in a loop descending from the earth's surface to and through the hot rock to a depth, e.g., in the range of 5,000 to 50,000 feet, and connects to the bottom of a heat-insulated riser in which the heated liquid flow ascends to the surface. The heated flow is processed at the surface to utilize recovered thermal energy and is cooled, and the cooled liquid is recycled to the hot rock. A plurality of descending pipe loops are disposed radially a horizontal distance away from said riser and each is connected to the riser. A manifold connecting said pipes at the surface permits rotation of the descending liquid among the pipe loops for continuous operation. The natural temperature of the subterranean hot rock increases with depth causing the temperature of the liquid in the pipes to increase as it descends. The heated flow in the riser ascends to the surface by thermo-siphon circulation which results from the hydraulic head difference between the descending higher density relatively cool liquid flow and the ascending lower density flow of heated liquid and flashed vapor. At the surface, the thermal energy of the heated flow in the riser is recovered and utilized, e.g., by heat exchange and/or by use of flashed vapor in a condensing power cycle, and the cooled liquid flow therefrom is recycled to the manifold and pipes for another heat gathering circuit.

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First Claim