Hot dry rock geothermal energy Hot dry rock geothermal energy Hot dry rock (HDR) is an abundant source of geothermal energy available for use. A vast store of thermal energy is contained within hot - but essentially dry - impervious crystalline basement rocks found almost everywhere deep beneath the earth’s surface. A concept for the extraction of useful amounts of geothermal energy from HDR originated at the Los Alamos National Laboratory in 1970, and Laboratory researchers were awarded a U.S. patent covering it. Although often confused with the relatively limited hydrothermal resource already commercialized to a large extent, HDR geothermal energy is very different. Whereas
Hot dry rock geothermal energy hydrothermal energy production can only exploit hot fluids already in place in the earth’s crust, an HDR system (consisting of the pressurized HDR reservoir, the boreholes drilled from the surface, and the surface injection pumps and associated plumbing) recovers the earth’s heat from hot but dry regions via the closed-loop circulation of pressurized fluid. This fluid, injected from the surface under high pressure, opens pre-existing joints in the basement rock, creating a man-made reservoir which can be as much as a cubic kilometer in size. The fluid injected into the reservoir absorbs thermal energy from the high-temperature rock surfaces and