Organic Rankine Cycle is a technology that convert low-temperature heat sources into a mechanical energy, and it can be used to produce electrical energy in a closed system. The heat sources can be received from renewable energy such as geothermal, solar, and biomass.

Geothermal power plants use steam to produce electricity. The steam comes from reservoirs of hot water found a few miles or more below the earth's surface. The steam rotates a turbine that activates a generator, which produces electricity.

Geothermal energy is heat energy from the earth—Geo (earth) + thermal (heat). Deep underground, the presence of hot rocks, fluid, and permeability (the ability for that fluid to move among the rocks) offer conditions from which electricity can be generated.

Small underground pathways, such as fractures, conduct fluids through the hot rocks. In geothermal electricity generation, this fluid can be drawn as energy in the form of heat through wells to the earth's surface. Once it has reached the surface, this fluid is used to drive turbines that produce electricity.