Enel Green Power, through its subsidiary Enel Green Power North America, Inc., has started works on the construction of a solar thermodynamic power plant to operate alongside the existing Stillwater geothermal power station, which is already paired with a 26 MW photovoltaic facility.
This is the first hybrid plant in the world able to combine the continuous generating capacity of binary-cycle, medium-enthalpy geothermal power with daytime peak generation from solar thermodynamic.
The Stillwater geothermal plant, consisting of two binary-cycle units with a total net installed capacity of 33 MW, will be integrated with a 17 MWt solar thermodynamic plant. The linear parabolic mirrors of the new thermodynamic plant boast reflecting surfaces totaling 26,000m2, capable of concentrating solar radiation, raising its potential some 75 times, inside receiver tubes filled with demineralised water under pressure.
Thanks to the innovative technology that will enable the use of the sun’s heat to raise the temperature of the geothermal fluid extracted from the wells, it will be possible to improve the cycle’s yield and increase its electricity output.
The use of demineralised water as the heat-vector fluid for collecting and transporting solar energy, in place of the synthetic oils commonly used in solar thermodynamic power plants results in zero environmental impact and eliminates the risk of fire and of contaminating the surrounding land in the event of accidental leaks
The solar thermodynamic plant is expected to start commercial operation by the end of 2014. It will be capable of generating approximately 3 million kWh/year, to be added to the power currently being generated by the existing hybrid plant.
The energy produced will be sold to NV Energy, through the existing 20-year Power Purchase Agreement (PPA).
Combining three generation technologies to produce electricity from renewable sources at the same location allows to produce approximately 200 million kWh of emission free power each year, avoiding the release of 140,000 tonnes/year of CO2 into the atmosphere. Moreover, combining the three generation technologies makes it possible to rely on the existing infrastructure, such as electrical interconnection lines, thereby further reducing environmental impact.
Completion of this project requires a total investment of about $15 million.