Crescent Dunes Solar Energy Project

Coordinates: 38°14′00″N 117°22′01″W / 38.2333°N 117.367°W / 38.2333; -117.367
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Crescent Dunes Solar Energy Project
CountryUnited States
LocationTonopah, Nye County, Nevada
Coordinates38°14′00″N 117°22′01″W / 38.2333°N 117.367°W / 38.2333; -117.367
StatusPost-bankruptcy reorganization, restart
Construction began2011; 12 years ago (2011)
Commission date2016; 7 years ago (2016)[1]
Construction cost$975 million
Owner(s)Tonopah Solar Energy, LLC (SolarReserve, LLC)
Operator(s)Vinci SA[2]
Solar farm
CSP technologySolar power tower
Collectors10347 × 115.72 m²
Total collector area296 acres (1,200,000 m2)
Site resource2,685 kW·h/m2/yr[3]
Site area1,670 acres (676 ha)
Power generation
Units operational1
Make and modelAlstom
Nameplate capacity110 MW
Capacity factor51.9% (planned)
20.3% (2018)
Annual net output196 GW·h over 1 year (2018)
Storage capacity1,100 MW·he
External links
WebsiteCrescent Dunes
CommonsRelated media on Commons

The Crescent Dunes Solar Energy Project is a solar thermal power project with an installed capacity of 110 megawatt (MW)[4] and 1.1 gigawatt-hours of energy storage[1] located near Tonopah, about 190 miles (310 km) northwest of Las Vegas.[5][6] Crescent Dunes is the first commercial concentrated solar power (CSP) plant with a central receiver tower and advanced molten salt energy storage technology at full scale (110 MW), following the experimental Solar Two and Gemasolar in Spain at 50 MW. As of 2023, it is operated by its new owner; ACS, and in a new contract with NV Energy, it now supplies solar energy at night only, drawing on thermal energy stored each day: What happened with Crescent Dunes?

Startup energy venture company SolarReserve, created via seed funding US Renewables Group and United Technologies, was the original owner of Tonopah Solar Energy LLC, the owner and operator of the Crescent Dunes plant. The Crescent Dunes project was subsequently backed by a $737 million in U.S. government loan guarantees and by Tonopah partnering with Cobra Thermosolar Plants, Inc. The overall venture had a projected cost of less than $1 billion.[7][8] The plant suffered several design, construction and technical problems and, having not produced power since April 2019, its sole customer, NV Energy, subsequently terminated their contract. Bloomberg reported 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.[9][10]

Since the initial failure of the Crescent Dunes project, SolarReserve took down their website and is believed to have permanently ceased operations.[11][12] Upon the developer's silence as the involved parties sought legal recourse, the plant's exact status was publicly unknown for some time and was left to conjecture.[13][14][15]

While proceeding through its subsequent bankruptcy proceedings, Tonopah Solar Energy stated that it had hopes for a restart of the Crescent Dunes plant by the end of 2020.[16][17] According to court documents, Tonopah is owned by SolarReserve, Cobra Energy Investment LLC, a division of Spanish construction company ACS Group and Banco Santander, S.A.[18] On September 11, 2020, the bankruptcy court approved Tonopah Solar Energy's disclosure statement. On December 3, 2020 the Chapter 11 bankruptcy reorganization plan was confirmed by the court.[19] As one result of this plan's confirmation, Cobra now has operational control of the plant.[17] In July 2021, the project restarted production for NV Energy.[20]


Workers installing heliostats at Crescent Dunes

In late September 2011 Tonopah Solar Energy received a $737 million loan guarantee from the United States Department of Energy (DOE) and [5] the right to build on public land.[21] The capital stack included $170,000,000 in EB-5 investment through SolarReserve/ACS Cobra partner CMB Regional Centers.[22][23][15] Under a power purchase agreement (PPA) 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.[8]

Ground was broken on the project in September 2011.[24] 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.[25] It began operation in September 2015,[26] 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 (and other matters) with formal comments lodged on the record in March 2012 progress meeting with DOE and its engineer present (the lender did not voice any objection). It returned to operation in July 2017.[27]

The plant having last produced power in April 2019, 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,[10] SolarReserve then raised the possibility of the project filing for bankruptcy, which subsequently happened.[28][29] 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.[10] An interim outcome in this regard was that SolarReserve took down their website and was believed to have ceased operations permanently.[12]

Tonopah Solar Energy filed for bankruptcy on July 30, 2020.[18] 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.[30] The amount is less than half of what taxpayers are owed on the outstanding $425 million of public debt.[31] 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.[32]


Sunlight heating molten sand in the central tower

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 656-foot (200 m) tall[12] solar power tower. Each heliostat is made up of 35 6×6 feet (1.8 m) mirror facets, yielding a heliostat overall usable area of 1,245 square feet (115.7 m2). Total solar field aperture adds up to 12,882,015 square feet (1,196,778 m2). 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.[5] The storage technology thus eliminated the need for any backup fossil fuels, such as natural gas. Melting about 70,000,000 pounds (32,000,000 kg) 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.[33]

The thermal storage high-temperature salt tank buckling failure[edit]

Crescent Dunes was the first large (110 MW) tower CSP with thermal storage. While storage tanks of trough CSP operate at 400 °C (752 °F), Crescent Dunes operated the storage tank at almost 600 °C (1,112 °F), while keeping 280 °C (536 °F) as base (cold) temperature. Higher temperatures differences result in a greater expansion of the tank floor, generating greater compressive forces around the floor plate. At very large diameters, as the big tank of Crescent Dunes, that resulted in a high probability of failure under cycling loading.[34]


Crescent Dunes began operation in September 2015,[26] but went off-line in October 2016 due to a leak in a molten salt tank. It returned to operation in July 2017.[27] 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.[35]

Generation (MW·h) of Crescent Dunes Solar Energy[36]
Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
2015 1,703 1,831 0 3,534
2016 1,508 9,121 7,099 2,158 11,485 6,216 25,560 28,267 30,514 5,410 0 0 127,338
2017 0 0 0 0 0 0 9,420 9,192 13,666 9,263 488 0 42,029
2018 795 5,145 5,907 13,801 10,653 33,387 23,749 33,169 31,632 21,253 8,130 8,189 195,810
2019 12,889 14,431 20,041 2,807 Production suspended 50,168
2020 Production suspended 0
2021 Production Suspended 3,974 15,445 20,796 11,929 17,489 5088 74,721
2022 14,635 12,238 0 0 0 0 0 8,852 22,166 24,710 10,590 7,475 100,666

The commissioning of a new thermal plant requires up to four years to achieve 100% operating level, from the first grid connection to full production. As an example the Edwardsport production data, whose progression, skipping first partial year, is a 40% output the first full year, 57% the second full year, the next year the progression was stopped by a problem in October, but resumes with a 73% the fourth and next year.[37] At Crescent Dunes, it was to be expected a similar progression, but the failure of the storage tanks in 2016, froze the commissioning.[38] Following that, first full production year was delayed to 2018, starting with a 40% (200 over 500) output.


The first three months of 2019 (January, February and March) 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.[39][15] But to compare fairly, it must be taken into account that the Tonopah solar project power is dispatchable whilst photovoltaic power is intermittent. Truly levelized cost comparisons must include the capacity payments for generating capacity available to supply power during peak hours. By doing so, low-to-high hourly wholesale electricity prices have been shown to vary by up to four orders of magnitude.[40][41]

In July 2021, the project restarted production.[20]


See also[edit]


  1. ^ a b "Crescent Dunes 24-Hour Solar Tower Is Online". CleanTechnica. February 22, 2016. Retrieved June 15, 2016.
  2. ^ "VINCI completes the acquisition of ACS's energy business (Cobra IS)" (Press release). globalnewswire. December 31, 2021. Retrieved July 17, 2022.
  3. ^ Crescent Dunes Solar Energy Project, National Renewable Energy Laboratory
  4. ^ "Crescent Dunes Solar Thermal Power Plant". Grupo COBRA. 2016. Archived from the original on June 4, 2016. Retrieved May 26, 2019.
  5. ^ a b c "Energy Department Finalizes $737 Million Loan Guarantee to Tonopah Solar Energy for Nevada Project" (Press release). Loan Programs Office (LPO), Dept. of Energy (DOE). September 28, 2011. Retrieved July 2, 2014.
  6. ^ "Crescent Dunes: Project Under Construction". Loan Programs Office (LPO), Dept. of Energy (DOE). September 1, 2015. Retrieved January 17, 2016.
  7. ^ "US Taxpayer Backed Tonopah Solar Energy Files for Bankruptcy Protection - SWFI".
  8. ^ a b Wesoff, Eric (September 29, 2011). "DOE Races Against the Clock: Two Solar Loans Closed, Seven More to Go". Greentech Media. Retrieved September 29, 2011.
  9. ^ Delbert, Caroline (January 10, 2020). "The $1 Billion Solar Plant Is an Obsolete, Expensive Flop". Hearst Digital Media. Archived from the original on January 21, 2021. Retrieved January 27, 2022. Bloomberg reports that even though the plant shut down in April 2019, NV Energy wasn't allowed to sever its agreement with the plant until late in 2019, after the DoE was forced to take over the shuttered plant in August. SolarReserve took the DoE to court.
  10. ^ a b c Schulz, Bailey (October 7, 2019). Cook, Glenn (ed.). "Tonopah solar plant could end up in bankruptcy, developer says". Las Vegas: J. Keith Moyer. Archived from the original on October 8, 2019. Retrieved February 26, 2020. ... major decisions — such as bankruptcy proceedings — require a unanimous vote from the managers, the lawsuit alleges that the Energy Department can determine the fate of Tonopah Solar Energy without any representation of SolarReserve on the board
  11. ^ "America's Concentrated Solar Power Companies Have All but Disappeared". Retrieved September 17, 2023.
  12. ^ a b c "The closure of SolarReserve, an isolated case of the concentrated solar power industry | REVE News of the wind sector in Spain and in the world". February 7, 2020.
  13. ^ "A $1 Billion Solar Plant Was Obsolete Before It Ever Went Online". January 6, 2020.
  14. ^ "EDITORIAL: Future of Crescent Dunes solar plant near Tonopah appears bleak". October 9, 2019.
  15. ^ a b c "NV Energy sends termination notice to massive Tonopah solar project, developer accuses Energy Department of taking over". The Nevada Independent. October 6, 2019.
  16. ^ "Bankrupt Solar Project Owner Hopes for Year-End Restart - Law360".
  17. ^ a b "Post bankruptcy, Crescent Dunes CSP plant owner wants project back online by year's end". August 3, 2020.
  18. ^ a b "Tonopah Solar Energy files for bankruptcy". July 30, 2020.
  19. ^ "Del. Court Confirms $1B Nev. Solar Plant's Ch. 11 Plan - Law360".
  20. ^ a b "Solar plant near Tonopah producing power for NV Energy after stop during bankruptcy". KLAS. October 14, 2021. Retrieved November 7, 2021.
  21. ^ Chris Martin; Nic Querolo (January 6, 2020). "A $1 Billion Solar Plant Was Obsolete Before It Ever Went Online". Bloomberg. Retrieved February 5, 2020. Harry Reid, then the Senate majority leader and senior senator from Nevada, cleared the way for the company to build on public land
  22. ^ "Group IX – Crescent Dunes". Archived from the original on March 28, 2017. Retrieved March 27, 2017.
  23. ^ "Nhóm XI – ACS Cobra". Archived from the original on March 28, 2017. Retrieved March 27, 2017.
  24. ^ Tetreault, Steve (September 28, 2011). "Nevada solar project to get $737 million federal loan guarantee". Las Vegas Review-Journal. Retrieved September 29, 2011.
  25. ^ "Crescent Dunes Solar Energy Project, Nevada, United States of America". Power Technology. Retrieved December 29, 2016.
  26. ^ a b National Renewable Energy Laboratory (November 10, 2015). "Crescent Dunes Solar Energy Project".
  27. ^ a b Las Vegas Review-Journal (July 21, 2017). "Nevada solar plant back online after eight-month outage".
  28. ^ "Will DOE take the Crescent Dunes solar project into bankruptcy?". pv magazine USA. October 7, 2019.
  30. ^ "Tonopah solar project part of $200M settlement | Las Vegas Review-Journal". July 30, 2020.
  31. ^ "Energy Department Poised to Lose Up to $225 Million on Solar Project Bankruptcy - WSJ". Wall Street Journal. July 30, 2020.
  32. ^ "POLITICO Pro".
  33. ^ Hashem, Heba (April 4, 2014). "No drama as SolarReserve commissions world's largest CSP tower with storage". CSP Today Business Intelligence. FC Business Intelligence Limited. Retrieved May 6, 2014.
  34. ^ "In Tower CSP, thermal storage had issues at first". April 4, 2023. Retrieved August 10, 2023.
  35. ^ Leitch, David (February 8, 2018). "SolarReserve still falling short at flagship solar tower project". RenewEconomy.
  36. ^ "Crescent Dunes Solar Energy, Monthly". Electricity Data Browser. Energy Information Administration. Retrieved December 17, 2021.
  37. ^ "EuroTrough Helped Cut Ramp-Up Time of China's 100 MW Urat CSP". SolarPACES. Archived from the original on December 19, 2021. Retrieved February 8, 2022. ... thermal plants require up to four years to ramp-up to 100% operating level...
  38. ^ Santamarta, Jose. "Salt leak shuts down Crescent Dunes Concentrated Solar Power plant".
  39. ^ "A $1 Billion Solar Plant Was Obsolete Before It Ever Went Online". Bloomberg. January 6, 2020.
  40. ^ "(PDF) Comparing the Costs of Intermittent and Dispatchable Electricity Generating Technologies". Retrieved September 17, 2023.
  41. ^ MIT Economics[dead link]

External links[edit]