Hot dry rock geothermal energy (HDR) is a type of geothermal power production that uses the very high temperatures that can be found in rocks just a few kilometers below ground. This is done by pumping high pressure water down a borehole into the heat zone. The water travels through fractures in the rock, capturing the heat of the rock until it's forced out of a second borehole as very hot water, which is converted into electricity using either a steam turbine or a binary power plant system. Al… (More on Hot-dry-rock)