File:Steam release and pressure check from experiment hole.jpg

English: Scientists used hydraulic fracturing to create a heat extraction loop in the hot granitic rock under the Jemez plateau in New Mexico. The two wells were 8500 feet deep and the surrounding rock was 365 degrees f. Water is pumped into one well, absorbs heat as it circulates through the fracture, and is brought to the surface through the second well under sufficient pressure to prevent boiling. This water is cooled and injected into the well to bring up more heat. Steam to hot water heat exchanger

During a nine month run, researchers extracted heat at rates up to five million watts (17 million btu/h). Water-loss rates were low, water quality remained good and there were no detectable environmental effects from the system operation. When it did not interfere with the experiments, part of the heat from the water was used to boil Freon 114, whose heavy vapor drove a small turbine which rotated an alternator, producing 60 KVA of electrical power that was used at the site.

A Department of Energy Photo