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EERE Success Story—Optimizing Geothermal with Geo-Solar Hybrid Systems

May 6, 2015 - 9:10am

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The Stillwater geothermal plant is the first hybrid solar geo facility in the nation. In 2014 Enel Green Power added 2 MW of concentrating solar power to the existing geothermal plant and solar photovoltaic field, for a total installed capacity of ~60 MW. Source: Enel Green Power North America

The Stillwater geothermal plant is the first hybrid solar geo facility in the nation. In 2014 Enel Green Power added 2 MW of concentrating solar power to the existing geothermal plant and solar photovoltaic field, for a total installed capacity of ~60 MW. Source: Enel Green Power North America

DOE is exploring the potential of using hybrid applications to raise power plant outputs at low cost. During 2014, industry partner Enel Green Power—in collaboration with Idaho National Laboratory and National Renewable Energy Laboratory —began work to quantify the economic benefits of combining geothermal and solar thermal systems. Positive results could enhance deployment of these clean, renewable energy technologies in regions where the resources overlap. The research team is evaluating both the technical and economic aspects of hybrid power generation, by combining geothermal energy with concentrating solar power (CSP) technology. The work utilizes data from the operating Stillwater geothermal-photovoltaic hybrid plant in Fallon, Nevada, where CSP was installed this year.

Modeled results achieved a 5% reduction in the levelized cost of energy (LCOE) by using a retrofit geothermal-solar hybrid plant. The magnitude of the results is highly dependent on resource productivity, power purchase agreement (PPA) penalties, solar collector array costs, and solar array installation parameters. The results also indicate that further savings are possible to the LCOE if reduced risk associated with the solar heat source translates to more favorable pre-operation project financing terms. Federal and state renewable energy incentives or tax credits could further decrease LCOE. Hybrid systems are subject to any PPA penalties on the economics of the hybrid plant relative to the base CSP power plant. Additional work is planned to evaluate commercial opportunities and best alternatives for geothermal/solar hybrid systems.

The Office of Energy Efficiency and Renewable Energy (EERE) success stories highlight the positive impact of its work with businesses, industry partners, universities, research labs, and other entities.

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