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Title: A Tower of Molten Salt Will Deliver Solar Power After Sunset
Source:
IEEE Spectrum
URL Source: http://spectrum.ieee.org/green-tech ... liver-solar-power-after-sunset
Published: Oct 21, 2015
Author: Peter Fairley
Post Date: 2015-10-26 08:30:00 by Tooconservative
Keywords: None
Views: 3080
Comments: 9
Solar power projects intended to turn solar heat into steam to generate electricity have struggled to compete amid tumbling prices for solar energy from solid-state photovoltaic (PV) panels. But the first commercial-scale implementation of an innovative solar thermal design could turn the tide. Engineered from the ground up to store some of its solar energy, the 110-megawatt plant is nearing completion in the Crescent Dunes near Tonopah, Nev. It aims to simultaneously produce the cheapest solar thermal power and to dispatch that power for up to 10 hours after the setting sun has idled photovoltaics. “When the grid wants 110 MW, we’ll provide 110 MW. There will be no variability,” says Kevin Smith, CEO for SolarReserve, the plant’s developer, based in Santa Monica, Calif. 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 tower—a layout resembling California’s massive Ivanpah solar power tower. However, while Ivanpah’s receiver heats steam and pipes it directly to turbine generators, SolarReserve’s heats a molten mixture of nitrate salts that can be stored in insulated tanks and withdrawn on demand to run the plant’s steam generators and turbine when electricity is most valuable. Smith expects that NV Energy, the Las Vegas–based utility contracted to buy Crescent Dunes’ output, will want it mostly during the utility’s unusually late demand peak, which the Vegas Strip’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 SolarReserve’s are “the next-generation technology” 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 °C, whereas oil-based plants top out at 400 °C. That temperature boost squeezes 5 to 6 percent more power from the plant’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, SolarReserve won a US $2.4 million grant from the U.S. Department of Energy to develop a ceramic receiver that can withstand 732 °C. Now the company just needs to make Crescent Dunes run. SolarReserve finished its construction early this year and was targeting first power generation at press time in early October. Smith says that one of the biggest complexities to master is the repositioning of the mirrors—more than 1 million square meters of reflective glass—every 60 seconds to keep their beams focused on the receiver. A 20-MW demonstration-scale plant completed in 2011 by Spanish solar thermal developer Sener Grupo de Ingeniería is running well, according to Mehos, but it must coordinate about one-sixth the number of mirrors as the new Nevada plant. Crescent Dunes promises to be the first of many big molten salt towers. Sener and fellow Spanish solar thermal developer Abengoa have large towers under construction in Morocco and Chile, respectively. SolarReserve expects to break ground this year in South Africa on its second plant. With the first plant completed, costs are coming down. Crescent Dunes’ generation earns about $190 per megawatt-hour, including the value of federal subsidies, whereas Smith says the company’s South Africa plant will get $125/MWh with no subsidies. At present, solar thermal makes the most sense in markets where, unlike the United States, natural gas is pricey enough to make gas-fired plants less attractive for managing peak demand. But stronger growth is projected in the United States as well, because climate protections there threaten to restrict the use of natural gas to balance power generated by increasing levels of intermittent renewable power. NREL has predicted that solar thermal plants could be doing as much grid balancing in California as gas-fired and hydro plants combined by 2030, when that state’s utilities are mandated to use 50 percent renewable electricity. That is, unless declining battery costs make storing PV power more economical. James Nelson, a California-based energy modeler with the Union of Concerned Scientists, says this intrasolar race will be good for the environment: “I’m glad we have multiple technologies that can help the transition from gas power plants.”
(1 image)A Tower of Molten Salt Will Deliver Solar Power After Sunset
For the first time, solar thermal can compete with natural gas during nighttime peak demand
Pillar Of Salt: More than a million square meters of mirrors focus on a tower of molten salt to generate power for the Las Vegas Strip.
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Begin Trace Mode for Comment # 8.
#1. To: TooConservative (#0)
The Crescent Dunes solar power plant, putting out a pathetic 110MW, is expected to cost $1 billion. A similar sized natural gas plant would be about $150 million to build. But no one would ever build one that small. "Dominion Virginia Power yesterday announced plans to spend more than $1 billion constructing a combined-cycle, natural gas-fired power station ... the 1,300 megawatt Brunswick County Power Station would be built on a 205-acre site on U.S. Route 58 east of Lawrenceville."
A much much larger use of land than the salt tower in Nevada. Probably 5-10 times as much land. This first plant will be by far the most expensive. It is a technology that will scale up well. And you could build a lot of these in deserts around the world (Sahara, Saudi, Gobi, Mojave, etc.) to supply electricity to cities, particularly to provide for the growth of air conditioning demands around the world. There's nothing wrong with having some alternatives to coal/gas/nuclear plants. None of them are perfect either.
I looked it up. The Solar field aperture is 269 acres. For 110 MW.
What is the solar field aperture? I'm talking about the acres occupied by the plant itself. No way that plant is physically occupying 269 acres.
The solar array occupies a circular field with a diameter of 1.75 miles.
There are no replies to Comment # 8. End Trace Mode for Comment # 8.
Top • Page Up • Full Thread • Page Down • Bottom/Latest"For the first time, solar thermal can compete with natural gas during nighttime peak demand"
#2. To: misterwhite (#1)
a 205-acre site
#3. To: TooConservative (#2)
"A much much larger use of land than the salt tower in Nevada. Probably 5-10 times as much land".
#5. To: misterwhite (#3)
#8. To: TooConservative (#5)
"I'm talking about the acres occupied by the plant itself."
Replies to Comment # 8.
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