A Year After Launch, Major Solar Plant Apparently Running at Half Capacity

All three of Ivanpah's units online in November | Photo: ATOMIC Hot Links/Flickr/Creative Commons License

More than a year after the formal launch of the nation's largest existing solar tower power plant, its operators seem to be having trouble keeping it all the way online. According to records provided by California's grid operator, the Ivanpah Solar Electric Generating System is running at around half its capacity so far in 2015.

The information comes in the form of reports generated by the California Independent System Operator (CaISO), the independent agency that manages most of the state's power grid, as a daily snapshot of which of the state's more than 1,000 power plants are offline, or in CaISO's terminology, "curtailed."

According to those records, each of Ivanpah's three units has been curtailed for between 26 and 29 days so far this year, with the entire plant shut down for ten days. The outages have limited the plant's potential contribution to the state's power grid to half of the plant's rated capacity, and that's assuming that the units worked at maximum capacity when they were up and running.


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The curtailment records reflect the status of each of the state's power plants at 3:15 in the afternoon, and thus may overstate a plant's actually downtime: if a plant shuts down for maintenance at 2:30 and is back online by 3:20, CaISO records it as curtailed.

That said, all but half a dozen of the daily curtailments recorded for Ivanpah were described as "planned." Since those planned curtailments occurred on many successive days, it's unlikely that any of them were short-term.

When in operation, Ivanpah's three units each generate power by using thousands of targetable mirrors to focus sunlight on boilers atop three 459-foot towers. That concentrated sunlight heats water to create steam, which drives turbines that generate power. Ivanpah's Units 2 and 3 can generate up to 133 megawatts of power each, while the slightly smaller Unit 1 has a maximum rated capacity of 123.2 megawatts. Any single one of the units being curtailed is thus equivalent to taking a small gas-fired plant offline, at least in terms of the amount of energy that's thus not flowing onto the state's power grid.

A year ago, as most of the renewable energy press lauded the formal launch of the Ivanpah facility, Rewire reported that the plant spent most of January 2014 similarly offline. In October, amid reports that Ivanpah had produced only about one-quarter the amount of power expected since its January 2014 launch, NRG Energy spokesman Jeff Holland told renewable energy reporter Pete Danko that both technical problems and cloudy desert days had impeded the plant's performance, adding:

NRG Energy operates Ivanpah on behalf of its business partners BrightSource Energy, which designed the plant, and Google.

That consistent improvement in performance may have faltered, if CaISO's curtailment reports are any guide. Since January 6, the last day this year on which all three of Ivanpah's units were online, Unit 1 and Unit 2 have been either partly or completely offline for 28 days, and Unit 3 for 27 days.

Each of the three units was down for an extended length of time during the first eight weeks of the year. Unit 1 was offline from January 7-30; Unit 2 from January 18 through February 10, and Unit 3 from February 9 through Wednesday. Each of the units was also curtailed on sporadic additional days.

December 2014 also saw a lot of curtailments at Ivanpah, with all three units down for five days that month, and Units 1 and 3 down for 13 and 12 days, respectively.

Asked for an explanation for the apparent extended downtime at Ivanpah in January and February, Jeff Holland of NRG Energy told Rewire that "the periodic curtailments on each unit were for planned inspections and routine maintenance." Holland added that downtime on January 11 was due to work being done on the nearby Eldorado Substation, and that NRG had shut down the plant on that day after being asked to by Southern California Edison and Pacific Gas & Electric.

CaISO's curtailment records suggest that Ivanpah has been running at a maximum of 50.07 percent capacity since New Year's. And that doesn't necessarily correspond to Ivanpah's actual power output, which may have been cut even further by more of the Mojave Desert clouds that bedeviled Ivanpah's output in 2014. As the plant relies at least in theory on sales of power to Southern California Edison and Pacific Gas & Electric for its income, further curtailments may not bode well for the plant's owners.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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