One of the US’ two large concentrating solar power plants that have attached storage continues to have difficulties remaining online after going commercial almost four years ago.

The 110-MW Crescent Dunes Concentrated Solar Power facility near Tonopah, Nevada, was offline most of the second quarter of this year, reporting just 765 MWh of wholesale power sales made in the first days of April to the Federal Energy Regulatory Commission in its Q2 2019 Electric Quarterly Report, seen by S&P Global Platts this week.

According to data compiled by Platts, the solar thermal facility developed and owned by SolarReserve and brought online in late 2015, operated in Q2 2019 at a 0.3% capacity factor.

By Friday, SolarReserve executives had not responded to several queries on the current status of the plant.

One longtime observer of the project who no longer works for SolarReserve told Platts that there has been speculation that some of the facility’s problems stem from “inferior” construction work, not from problems with the facility’s employed technology.

Concentrated Solar Power technology is distinct from the more ubiquitous solar PV facilities that use large numbers of solar panels linked together in long rows.

The Crescent Dunes facility, located in the desert north of Las Vegas, has a large circular array of over 17,000 heliostat mirrors that reflect the sun’s rays onto a boiler on a 540-foot tower set in the middle which produces electricity by driving a conventional steam turbine. There are also thermal storage tanks on the tower that store hot and cold liquid salt heat transfer fluids.

The CSP tower, when operating, has enough molten salt stored to allow it to generate for eight to 10 hours after the sun goes down.

The facility has experienced outages before. It reported no wholesale sales in November and December 2016 after a leak in a tank filled with molten salt forced a shutdown.

It also has a 25-year power purchase agreement with NV Energy subsidiary Nevada Power for power priced at 13.5 cents/kWh. An NV Energy spokeswoman on Friday declined to comment on the status of the Crescent Dunes facility.

Solar Reserve’s subsidiary Tonopah Solar Energy, which owns the facility, reported no wholesale power sales to FERC in the entire first half of 2017. It had a slow operational rebound, with capacity factors of just 4% and 5% in Q4 2017 and Q1 2018, respectively.

The facility’s highest average quarterly capacity rates have come in the summer of 2016 and 2018. Its record high quarterly capacity average was 36.7% in Q3 2018.

A CSP WITH STORAGE WITH HIGH USAGE

Abengoa’s 250-MW Solana Solar facility in Gila Bend, Arizona is the only other CSP facility with storage. Its parabolic trough system uses curved mirrors to concentrate heat on a synthetic heat transfer fluid that heats water to produce steam which drives a conventional steam turbine generator. The facility stores heated molten salt that can give the facility approximately six-hours of additional generation after the sun goes down.

Certainly compared to Crescent Dunes, Solana has had relatively stable quarterly capacity rates that uniformly vary according to the time of year.

Historical FERC data shows that the Solana facility’s optimal time of usage is in the second quarter of the year. In Q2 2016, it had a 43% capacity factor. In Q2 2017, the capacity factor was 53.5% and it was 51.6% in Q2 2018.

Solana’s average capacity factors in the third quarters of 2016, 2017 and 2018 have ranged from 30.6% to 47.9%.

Its Q4 and Q1 capacity factors have averaged in the 19% and 22% range, respectively, over the past three years.

CSP WITHOUT STORAGE

The two CSP facilities with storage were both recipients of federally guaranteed construction loans under the US Department of Energy’s 1705 loan guarantee program established by the US Congress and launched at the beginning of the Obama Administration. The two loans totaled $2.187 billion for 360 MW of capacity.

As part of the same loan program that also launched a surge in utility-scale solar PV projects, the DOE guaranteed an additional $3.65 billion in construction loans for three other concentrating solar projects, none of which had storage. Those facilities have 892 MW of combined capacity and are all located in California

According to the data, the Q2 2017 and Q2 2018 capacity factors of NextEra Energy Resources 250-MW Genesis facility that uses a parabolic trough system but has no storage, rival those of the Solana facility. In Q2 2017, the Genesis capacity factor averaged 53.6 % and in Q2 2018 it averaged 51.4%.

NRG Energy, BrightSource and Google’s 392-MW Ivanpah CSP facility, which uses tower power technology, had a 24.6% capacity factor in 2017, which improved to 28.9% in Q2 2018.

Numbers for Q2 2019 are not yet available.

— Jeffrey Ryser, jeffrey.ryser@spglobal.com

— Edited by Richard Rubin, newsdesk@spglobal.com

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