Geothermal energy from hot dry rock: A renew able energy technology moving towards practical implementation

The technology to extract useful amounts of energy from the large, ubiquitous, hot dry rock (HDR) resource has been under development for more than twenty years. Initial work during the 1970's and 1980's showed that it is possible to access and extract HDR energy using techniques originally conceived and tested by the Los Alamos National Laboratory. The process entails drilling a well deep enough to reach hot rock, injecting water at high enough pressure to open natural joints in the rock, and returning the water, heated by the rock, to the surface through one or more additional wellbores. After extraction of its thermal energy, the water is recirculated through the hot rock to mine more heat. In this closed-loop process, nothing is released to the environment except heat, and no long-term wastes accumulate.