Stillwater Hybrid Plant PV solar, geothermal and concentrated solar power

Enel technologies

Enel Green Power, the Renewable Energies division of Enel Group, is dedicated to the development and operation of renewables across the world, with a presence in Europe, the Americas, Asia, Africa and Oceania. Enel Green Power is a global leader in the green energy sector with a managed capacity of 38 GW across a generation mix that includes wind, solar, geothermal, biomass and hydropower, and is at the forefront of integrating innovative technologies like storage systems into renewables power plants. Its subsidiary, Enel Green Power North America, Inc. (EGP-NA) is a leading owner and operator of renewable energy plants in North America with projects operating and under development in 23 U.S. states and two Canadian provinces. EGP-NA operates more than 100 power plants with a total operating capacity of over 3,200 megawatts (MW) powered by renewable hydropower, wind, geothermal and solar energy.

Solution description

In 2014, Enel Green Power started the construction of a 17 MW Concentrating Solar Power (CSP) plant to operate alongside the existing 33 Mega Watt (MW) Stillwater geothermal power station in Nevada. The geothermal facility was already co-located with a 26 MW photovoltaic plant. Within this hybridization project, the Stillwater geothermal plant, consisting of two binary-cycle units, has been integrated with a CSP solar field, based on 44 parabolic collectors arranged in 11 loops, in order to convey the thermal energy collected from the sun to the geothermal turbines. The hybrid plant, in operation since August 2014, thus combines the continuous generating capacity of binary cycle, medium-enthalpy geothermal power with daytime peak generation from the solar thermal component.


Enel Green Power’s Stillwater plant in the USA brings together PV solar, geothermal and solar thermal power, setting an example of how to combine renewable energy technologies in a way that improves efficiency and sustainability and protects the environment. The National Renewable Energy Laboratory (NREL) and the Idaho National Laboratory (INL), under the oversight of the U.S. Department of Energy Geothermal Technologies Office (GTO), have signed a Cooperative Research and Development Agreement (CRADA) to study the integration of geothermal and CSP to generate power over the coming years. The fruits of this work will be used to explore and quantify the potential benefits of different operating strategies and integration schemes, with the goal of opening doors for the development of future hybrid renewable energy facilities.