The Department of Energy plans to invest up to $6 million in an engineered geothermal demonstration project in Geysers Geothermal Field in Lake County, Calif. The project has been controversial because of concerns that the rock-drilling involved would trigger earthquakes.
The project’s developer, AltaRock Energy Inc., would create a fractured reservoir by drilling an injection well into 500 F felsite rock at depths of up to 12,500 ft and then circulating water through it to harvest steam to run a turbine. The cooled water would then be returned to the hot rock. Electricity generated by the steam will be sold to Northern California Power Agency.