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
London Underground cooling hot air. Conventional brakes on trains rely on friction to slow the train down, transforming kinetic energy into heat. More modern trains feature regenerative braking systems that can feed the energy from braking back into the power supply, minimising heat generation. This has the additional advantage of reducing the amount of brake dust produced by the trains. London Underground cooling In summer, temperatures on parts of the London Underground can become very uncomfortable due to its deep and poorly ventilated tube tunnels: temperatures as high as 47°C (116 °F) were reported in the 2006 European heat wave. Posters may be