Functioning solar collection station after sundown? Pppffffttt!
Or, maybe not.
Crescent Dunes, due to come on line by the end of this year, uses over 17,000 mirrors to focus sunlight on a heat receiver atop a 165-meter-high towerâ€”a layout resembling Californiaâ€™s massive Ivanpah solar power tower. However, while Ivanpahâ€™s receiver heats steam and pipes it directly to turbine generators, SolarReserveâ€™s heats a molten mixture of nitrate salts that can be stored in insulated tanks and withdrawn on demand to run the plantâ€™s steam generators and turbine when electricity is most valuable. Smith expects that NV Energy, the Las Vegasâ€“based utility contracted to buy Crescent Dunesâ€™ output, will want it mostly during the utilityâ€™s unusually late demand peak, which the Vegas Stripâ€™s nightlife routinely stretches toward midnight.
Mark Mehos, thermal systems group manager at the National Renewable Energy Laboratory (NREL), says molten salt towers akin to SolarReserveâ€™s are â€œthe next-generation technologyâ€ for solar thermal power. Plants without storage may never be able to compete with PV, says Mehos. And while molten salt storage is often added to trough-style plants, which use hectares of parabolic mirrors to heat synthetic oil flowing through pipes suspended above them, salt towers are cheaper and more efficient, he says.
Eliminating the heat exchange between oil and salts trims energy storage losses from about 7 percent to just 2 percent. The tower also heats its molten salt to 566 Â°C, whereas oil-based plants top out at 400 Â°C. That temperature boost squeezes 5 to 6Â percent more power from the plantâ€™s steam turbines and enables a tank of salt to hold two to three times as much energy. The temperature advantage could grow: In September, ÂSolarReserve won a USÂ $2.4Â million grant from the U.S. Department of Energy to develop a ceramic receiver that can withstand 732 Â°C.
OK, engineers. Have at it.
Will this work?