Hot dry-rock energy

The Resource. The largest quantity of accessible geothermal energy exists in the form of hot rock which contains insufficient natural fluids to allow the tianspoit of its energy to the surface. Because hot dry rock (HDR) is widely distributed, it also has the greatest potential for widespread... 

In principle the normal geothermal gradient produces a useful temperature difference anywhere on the globe. If a hole is drilled to a depth of 6 kilometers (which is feasible), a temperature difference of about I80°C (324°F) is available, but no technology has been developed to take advantage of this resource. At this depth, water is unlikely, and the problems of extracting the energy are similar to the difficulties encountered with hot, dry rocks near the surface. 

J. W. Tester, D. W. Brown, and R. M. Potter, Hot Dry Rock Geothermal Energy—A New Energy Agendafor the 21st Century, Los Alamos National Laboratory Report LA-11514-MS, Los Alamos, N.M., 1989. 

Hot dry rock (HDR) -geothermal resource [RENEWABLE ENERGY RESOURCES] (Vol 21)... 

Geothermal Electric Power Generation Electricity derived from heat found under the earth s surface. Also see Flash Steam Generation, Binary Cycle Generation and Hot Dry Rock Geothermal Energy Technology (HDR). ... 

Hot Dry Rock Geothermal Energy Technology (HDR) A technique that drills holes into the ground until rock of a suitably high temperature is reached. Pipes are then installed in a closed loop. Water is pumped down one pipe, where it is heated to extraordinarily high temperatures, and then is... 

Hot Dry Rock - A geothermal energy resource that consists of high temperature rocks above 300 F (150 C) that may be fractured and have little or no water. To extract the heat, the rock must first be fractured, then water is injected into the rock and pumped out to extract the heat. In the western United States, as much as 95,000 square miles (246,050 square km) have hot dry rock potential. 

The utilization of hot dry rocks for energy requires fracturing of the hot formation, followed by injection of water and withdrawal of steam. This technology is still in the experimental state but promises approximately 10 times as much energy production as steam and hot water sources. 

Most Hot Dry/Wet Rock (HDR/HWR) development programs, and all geothermal projects presently completed for commercial energy utilization, have focused on water/vapor reservoir(s) of limited size and temperatures below the critical temperature of water. 

Hot brine solution is held in an open pan approximately 4-6 m wide, 45-60 m long, and 60 cm deep at 96°C. Flat, pure sodium chloride crystals form on the surface and fall to the bottom. The crystals are raked to a centrifuge, separated from the brine, and dried. A purity of 99.98% is obtained. Grainer salt dissolves more readily and is preferred in some applications, such as the butter and cheese industries. It is more expensive because of energy use for the hot brine. Its cost can be as much as six times that of rock salt and 20 times that of brine. 

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