SPECTRUM: China Stumbles on Path to Solar Thermal Supremacy

In the final days of 2018 a 100-megawatt solar thermal generating station capable of running around-the-clock, 365-days-a-year connected to the Northwest China regional power grid. It was a race against time to commission the plant in temperatures as low as -20 celsius—and one that plant designer and builder Beijing Shouhang Resources Saving Co could not afford to lose.

“We must finish on time. Otherwise we may face a heavy financial problem,” says Chen Han, Shouhang’s director for international markets.

Shouhang was racing to beat the Chinese government’s December 31, 2018 deadline to secure a guaranteed price for the plant’s power. The deadline was part of an aggressive demonstration program launched in September 2016 to slash the cost of solar thermal power and catapult Chinese firms to the head of the global pack—much as China did with solar photovoltaics.

Alas, a little more than two years later, China has stumbled on the path to solar thermal supremacy. While Shouhang’s and two more of the program’s 20 approved projects met the deadline, four others were cancelled last year and the remaining 13 projects are in limbo.

Solar thermal plants are a potentially crucial power source for global grids as they add more wind and PV solar. Unlike their weather-dependent cousins, solar thermal plants can efficiently store heat and then raise steam for their turbine-generators at will. They can thus dispatch power when it is needed most, reducing grid reliance on conventional gas, diesel and coal-fired generators.

However, the technology is comparatively costly and thus growing slowly relative to PV and wind. The technology took a public relations hit back in 2014 when birds killed by intense solar flux at the largest U.S. plant sullied solar thermal’s eco-friendly image. China’s program has been viewed as an opportunity to put solar thermal technology back on track, but the delays and cancellations mean it will fall far short.

The government anticipated adding 5.3 gigawatts by 2022—more than has been installed to date worldwide since the technology’s debut in the 1980s. Adding six more facilities that have a shot at starting this year would bring China’s total to just 550 MW, according to the Beijing-based Du Fengli, the Alliance’s secretary general. Two years from approval to completion was too short since most projects targeted high-altitude desert regions in China’s Northwest, a region with fantastic solar resources that also experiences long, punishing winters that limit outdoor construction to as few as  months.

Du adds that many players were trying to jump into solar thermal energy without prior experience building an entire plant, let alone one of commercial scale. The three projects that met the deadline are the exceptions that prove that rule.

SUPCON Solar and nuclear power giant China General Nuclear Power eachcompleted 50-MW plants in Qinghai province late last year, and both had operated pilot plants there since as early as 2009. Their plants use different approaches: CGN’s ‘trough’ plant employs mirrors to concentrate sunlight on glass tubes, while SUPCON’s ‘power tower’ uses heliostat mirrors to focus solar energy on a central receiver.

Shouhang, meanwhile, erected its own ¥3-billion power tower plant on the southwestern edge of the Gobi Desert in Dunhuang, in Gansu province, adjacent to a 10-MW plant that it began building in 2014.

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Heliostats at Shouhang’s 100-MW solar thermal power plant in Dunhuang. Credit: Shouhang

In a bulletin announcing the 100-MW plant’s startup Shouhang likens it to, “a silver sunflower blooming on the Gobi.” A field of 11,935 heliostats—each up to 115.5-square-meters across—illuminate a 260-meter-high tower where the energy heats a mix of molten nitrate salts. Tanks hold enough hot salt to operate the plant’s steam turbine for 11 hours, enabling continuous power output with or without sunlight. 

Shouhang’s core business is heat transfer devices, so it was able to develop and manufacture the bulk of the plant’s solar equipment in-house, according to Chen. The firm also learned a lot from operating the pilot plant. “We have very complete experience,” he says.

Chen says the new plant is completing tests mandated by grid operator State Grid Corp. of China before it can enter regular operation. He says that so far no one has observed dead birds around the tower. That’s as expected, he says, since the site is not frequented by many birds and is not along a migratory bird flyway.

Shouhang helped build CGN’s plant and is under contract to build others. It has also taken over another 100-MW power tower project in Gansu whose developer backed out last year. But Chen says those opportunities are on hold because the power price for further plants has not been set. Such uncertainty makes it difficult to secure financing for future projects.

Du at the Alliance says the rates will be less than the ¥1.15 ($0.17) per kilowatt-hour secured by the first three projects. She says officials have indicated they will be ¥1.14 for plants completed this year and ¥1.10 for those starting up in 2020 and 2021, but the government has yet to put those prices in writing.

Much hangs in the balance as China’s solar thermal developers struggle to sustain the anticipated build-out. Recent modeling from Beijing-based Tsinghua University suggests that solar thermal power plants can slash the cost of managing variable wind and solar power. For example, they found that replacing 5-20 percent of Gansu’s planned wind and solar PV generation with solar thermal plants would provide flexibility worth 24-30 cents per kilowatt-hour to China’s State Grid—a benefit well above the tariff that Shouhang raced to secure.

At the same time, some top solar researchers are warning that Chinese developers promising big cost cuts could pose a risk to the sector. Exhibit A, they say, is a record low 7.3 cent/kwh bid for power from a big plant in Dubai to be engineered and built by power equipment giant Shanghai Electric. “Something is nonstandard in that bid,” cautions Johan Lilliestam, a professor of renewable energy policy at the Swiss government laboratory ETH Zürich in a recent publication from the Paris-based International Energy Agency.

Robert Pitz-Paal, who chairs an IEA solar thermal research program, stated in the same report that “unseasoned Chinese firms” will hurt the technology’s global standing if they can not deliver: “If they fail, this may become the coffin nail for the technology as the confidence of clients in CSP and its potential for cost reduction may be damaged strongly by Chinese suppliers.”

This post was created for Energywise, IEEE Spectrum’s blog about the future of energy, climate, and the smart grid

Solar Towers Not Avian Annihilators

Solar power towers have had a reputation as alleged avian vaporizers since preliminary reports of birds being burned in mid-air at California’s Ivanpah solar thermal plant. Their reputation was muddied even more during tests early this year at SolarReserve’s Crescent Dunes power tower, whose intense beams of reflected light recently began generating power in Nevada. California public radio station KCET reported that as many as 150 birds were killed during one six-hour test in January. It is obviously upsetting to imagine birds ignited in the name of renewable energy. But avian mortality is a downside common to many modern human creations—including buildings, highways, and powerlines. Full data on bird mortality at Ivanpah, macabre as it might be, shows the death rate to be small and likely of little ecological significance. “The data does support a low level of avian mortalities and hopefully, through adaptive management and deterrence, it will go even lower,” says Magdalena Rodriguez, a senior environmental scientist with the California Department of Fish and Wildlife. Continue reading “Solar Towers Not Avian Annihilators”

The Other Solar Power

Solar thermal power cuts a fascinating contrast with solar photovoltaics and wind turbines — today’s leading renewable energy technologies — besting one on price and the other on quality. Little surprise then that it is being selected for power plants equal in output to large wind farms and ten-times the size of the largest photovoltaic installations.

Whereas photovoltaics employ semiconductors to directly convert sunlight into electricity, solar thermal power stations convert sunlight into heat to generate steam and drive a turbine. This roundabout is, ironically, a huge money-saver. The Abengoa thermal solar power towers in Sevillemirrors, pipes, pumps and steam turbines that form a solar thermal plant cost less than half than an equivalently powerful array of photovoltaics.

Solar thermal cannot similarly challenge wind turbines on cost (at least not at present). But solar thermal plants can store some of the energy they capture and, as a result, produce a much steadier and more reliable supply of electricity than the famously variable wind turbine.

So why then did we hear so much about solar photovoltaics over the past decade and sol little of solar thermal? Because the latter is inherently utility-scale technology, whereas photovoltaic panels provide value one rooftop at a time. Fred Morse, a solar thermal pioneer and currently senior advisor to renewable energy developer Abengoa Solar, likens it to a bakery operating through the depression. “If you had a bakery and you sold cookies or big wedding cakes, during hard times you could sell a lot of cookies,” says Morse. “PV has little niche markets and it could grow and grow and as the price came down it expanded those markets to where it is today.”

These days, thanks to state and (albeit on-again-off-again) federal incentives and record fuel prices, solar power is back to wedding cakes.

For more, check out “Solar without the Panels”

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