How can hot groundwater generate electricity without entering a turbine?

Hot groundwater can generate electricity without ever entering the turbine. A binary geothermal plant uses two separate fluid circuits. A production well brings hot geothermal fluid from rock underground, where usable heat and flow depend on local conditions. Earth's internal heat includes energy left from its formation and energy released by radioactive decay.

At a heat exchanger, the geothermal fluid transfers energy across metal walls to a separate working fluid chosen to vaporize at a suitable lower temperature. Like energy crossing a cooking pot's metal base, the heat passes through while the materials remain apart. The working vapor expands through a turbine, exerting forces on its blades. Its shaft drives a generator that converts mechanical energy into electricity.

After the turbine, a condenser cools the working vapor into liquid. A pump sends that liquid back to the heat exchanger. Meanwhile, the cooler geothermal fluid can return underground through an injection well. Reinjection can help maintain the fluid resource, but it does not instantly restore all the heat removed from the rock.

The cycle needs somewhere cooler to send part of its energy. Cooling equipment transfers rejected heat to air or water; not all incoming heat becomes electricity. Pumps and other equipment also consume power. The useful output therefore depends on the hot resource, the cooler surroundings and the performance of the complete cycle.

Other geothermal plants use natural steam directly or lower the pressure of hot water to produce steam. Geothermal names the heat source; binary names this particular two-fluid design. Its groundwater, turbine fluid and electrical current can follow three different paths. Heat crossing a solid wall connects the underground resource to a turning machine without sending that groundwater through it.