The Crescent Dunes Solar Energy Project is a 110 megawatt net solar thermal power project with 1.1 gigawatt-hours of energy storage, located near Tonopah, about northwest of Las Vegas. Crescent Dunes was the first concentrated solar power plant with a central receiver tower and advanced molten salt energy storage technology. Developed by SolarReserve and owned by Tonopah Solar Energy, the Crescent Dunes project was anticipated to cost less than $1 billion and was backed by a $737 million in U.S. government loan guarantees. The plant suffered several technical problems, and substantially missed its intended 50% capacity factor, only achieving about a 20% capacity factor in 2018, resulting in lawsuits and changes of control. The site has not produced power since April 2019 and its sole customer, NV Energy, subsequently terminated their contract. Bloomberg reports that NV Energy wasn’t allowed to sever its agreement with the plant until after the DoE took over the shuttered plant in August 2019. Since the initial failure of the Crescent Dunes project, SolarReserve took down their website and were believed to have permanently ceased operations. Currently proceeding through its subsequent bankruptcy proceedings, Tonopah Solar Energy has stated it has hopes for a restart of the Crescent Dunes plant by the end of 2020. According to court documents, Tonopah is owned by SolarReserve, , a division of Spanish construction company ACS Group and Banco Santander, S.A..
History
In late September 2011 Tonopah Solar Energy received a $737 million loan guarantee from the United States Department of Energy and the right to build on public land. The capital stack included $170,000,000 in EB-5 investment through SolarReserve/ACS Cobra partner CMB Regional Centers. Under a power purchase agreement between SolarReserve and NV Energy, all power generated by the Crescent Dunes project in the next 25 years would have been sold to NV Energy for $0.135 per kilowatt-hour. For comparison, the average U.S. cost per kilowatt-hour in 2011 was $0.12, and in 2019 the cost has risen to $0.133, so NV Energy's deal was essentially market-rate and competitively neither high nor low. Ground was broken on the project in September 2011. Construction terminated at the end of 2013, followed by several months of testing the plant systems. The project entered commissioning phase in February 2014 following completion of construction. It began operation in September 2015, but went off-line in October 2016 due to a leak in a molten salt tank. The owners warned the EPC about flaws in the salt tank foundations with formal comments lodged on the record in March 2012 progress meeting with DOE and its engineer present. It returned to operation in July 2017. NV Energy—the project's sole customer—terminated its contract in October 2019 on the basis of the project having "failed to produce." Alleging a takeover of Tonopah Solar Energy by the DOE, SolarReserve then raised the possibility of the project filing for bankruptcy, which subsequently happened. SolarReserve also filed a lawsuit, claiming that the Department of Energy was looking to appoint two new members to Tonopah Solar Energy’s board of managers, giving the appearance of the Energy Department in complete control of Tonopah directors which comprise the entirety of the Tonopah Board of Managers. An interim outcome in this regard was that SolarReserve took down their website and was believed to have ceased operations permanently. Tonapah Solar Energy filed for bankruptcy on July 30, 2020. Pending the approval of the bankruptcy court, a $200 million settlement with the remaining debtors — Tonopah Solar Energy LLC and ACS Cobra — for the return of taxpayer dollars was also announced at the end of July 2020. The amount is less than half of what taxpayers are owed on the outstanding $425 million of public debt. Under the settlement agreement and as a function of subsequent repairs, restoration of the plant to power production and acquisition of new long-term customers, ACS Cobra is liable for an additional $100 million in otherwise suspended debt.
Technology
The project's EPC Contractor was ACS Cobra, which carried out the engineering design, procured the equipment and materials necessary, and then constructed and delivered the facility to Tonopah Solar Energy. The project includes 10,347 heliostats that collect and focus the sun's thermal energy to heat molten salt flowing through an approximately tall solar power tower. Each heliostat is made up of 35 6× mirror facets, yielding a heliostat overall usable area of. Total solar field aperture adds up to. The molten salt circulates from the tower to a storage tank, where it is then used to produce steam and generate electricity. Excess thermal energy is stored in the molten salt and could be used to generate power for up to ten hours, including during the evening hours and when direct sunlight is not available. The storage technology thus eliminated the need for any backup fossil fuels, such as natural gas. Melting about of salt took two months. Once melted, the salt stays melted for the life of the plant and is cycled through the receiver for reheating. Maximum actual energy output that accounts for maintenance was re-estimated at 500 GWh annually, though the highest producing year thus far, 2018, only attained 40% of that.
Production
Crescent Dunes began operation in September 2015, but went off-line in October 2016 due to a leak in a molten salt tank. It returned to operation in July 2017. While its average monthly production was expected to exceed 40,000 MWh, as of May 2019 it never reached that value and only exceeded half of it during 9 months. The commissioning of a new thermal power plant requires a four to six months from the first grid connection to full production. At Crescent Dunes, it was to be expected a similar progression, but the failure of the storage tanks in 2016 due to a documented design flaw, froze the commissioning. Following that, first full production year was delayed to 2018, starting with a 40% output.
Shutdown
The first three months of 2019 showed good progression, topping all previous monthly data, but in April the plant was shut down because the project's sole buyer, NV Energy, terminated the Power Purchase Agreement for failure to produce the contracted power production. The power generated also cost NV Energy about $135 per megawatt-hour, compared with less than $30 per MWh available from a new Nevada photovoltaic solar farm. But the Tonopah solar project power is dispatchable whilst photovoltaic power is intermittent. It is inappropriate to compare intermittent generating technologies, like wind and solar, with dispatchable generating technologies like nuclear, gas combined cycle, and coal. Crescent Dunes project is more on the conventional type of generation. The difference between the noon low hourly prices and the evening high hourly prices, can be up to four orders of magnitude, if capacity payments for generating capacity available to supply power during peak hours is included.
