Whether scorched birds are a major issue at the Ivanpah Solar Electric Generating System in California is a matter of dispute. But the “power tower” solar plant and its owners -- NRG Energy, Google and BrightSource Energy -- might have an even more fundamental problem on their hands: generating adequate electricity.

The Mojave Desert plant, built with the aid of a $1.6 billion federal loan guarantee, kicked off commercial operation at the tail end of December 2013, and for the eight-month period from January through August, its three units generated 254,263 megawatt-hours of electricity, according to U.S. Energy Information Administration data. That’s roughly one-quarter of the annual 1 million-plus megawatt-hours that had been anticipated.

Output did pick up in the typically sunny months of May, June, July and August, as one might expect, with 189,156 MWh generated in that four-month period. But even that higher production rate would translate to annual electricity output of less than 600,000 MWh, at least 40 percent below target.

Another sign of the plant’s early operating woes: In March, the owners sought permission (PDF) to use 60 percent more natural gas in auxiliary boilers than was allowed under the plant’s certification, a request that was approved in August.

Some might point to Ivanpah’s struggles as another potential black eye for the U.S. Department of Energy loan guarantee program, but losses in the DOE portfolio have been small, well under what was budgeted for the program by Congress. Still, the plant’s slow start can’t be good news for its owners, particularly BrightSource, the company whose technology is on display at Ivanpah and which has struggled to advance other planned power tower projects in California.

Plant operator NRG declined to answer emailed questions about Ivanpah’s performance; BrightSource was more responsive.

The company said that “weather at Ivanpah since February has generally been worse than expected, resulting in reduced output.” July, when generation dipped to 35,967 MWh from 64,275 MWh in June -- the plant’s best month so far -- was particularly lacking in sunshine, BrightSource said, at least relative to the expectations the company developed over several years of meteorological study of the area.

BrightSource also pointed to Ivanpah’s unprecedented scale in explaining its slow start.

Ivanpah wasn’t a pilot project; the DOE loan program that aided it was intended for technologies that were well past that stage, but still needed to demonstrate their full-scale commercial value. The 392-megawatt Ivanpah plant fit the bill with its trio of 450-foot-tall boiler-topped towers, where sunlight redirected by some 173,500 twin mirrors sets (heliostats, they’re called) heats water that is then used to generate electricity. Before Ivanpah, the largest power tower plant in the world, in Spain, could generate 20 MW.

“As with any new plant, there have been some equipment challenges which impacted plant availability, although we have seen a consistent improvement in performance since the plant went on-line earlier this year,” the company said. “Since the early planning stages of this one-of-a-kind project, we knew there might be some growing pains along the way, but through continued learnings and our ongoing improvement process, the units are performing better than some of our initial assumptions.”

Increased natural gas consumption

Those growing pains included realization that the plant would need to boost its natural gas consumption. The fuel is used with auxiliary boilers that prime the system in the early morning, allowing the plant to begin generating electricity as soon as possible after sunrise; to maintain performance during intermittent cloud cover; and to eke out more energy as the sun fades at the end of the day.

In its March petition to California regulators (PDF), Ivanpah’s owners said it was only through running the plant that they realized “more boiler steam would be needed than previously expected in order to operate the system efficiently and in a manner that protects plant equipment, and to maximize solar electricity generation.” They added that “auxiliary boilers typically need to operate an average of approximately 4.5 hours a day during startup (an increase from 1 hour daily average originally expected).”

Under the original certification, “total annual natural gas fuel heat input” was not to exceed “5 percent of the total annual heat input from the sun” at each of the three Ivanpah units. That provision has been struck, and now BrightSource can burn a total of 1,575 million standard cubic feet of natural gas every year. To get a sense of that volume, an average U.S. natural gas-fired power plant might be expected to produce about 200,000 MWh from 1,575 mmcf of gas, according to the EIA.

BrightSource dismissed the notion that natural gas itself was being relied on as a meaningful source of energy production at Ivanpah, saying that “the facilities’ total generation for solar will be 40 to 50 times the generation associated with natural gas.” It was unclear if that calculation was based on current generation levels or what had been anticipated back when the project celebrated its opening in February.

U.S. Energy Secretary Ernest Moniz was in attendance at that big to-do. “This project speaks for itself,” he said in prepared remarks. “Just look at the 170,000 shining heliostat mirrors and the three towers that would dwarf the Statue of Liberty. Ivanpah is the largest solar thermal energy facility in the world with 392 MW of capacity -- meaning it can produce enough renewable electricity to power nearly 100,000 homes.”

The secretary’s assertion was based on the DOE’s expectation of annual production of 1,065,000 MWh at Ivanpah.

While talk of possible bird issues swirled in the months after the plant began operating, little was said about Ivanpah’s performance. That changed in late September, although not exactly publicly.

Implications for CSP's future

On September 29, the Platts trade newsletter Megawatt Daily explored Ivanpah’s status, but its article was and remains hidden behind a very pricey paywall. The article noted that the trio of Ivanpah owners had sought extensions on repaying their loans as they waited to receive a cash grant from the U.S. Treasury worth 30 percent of the plant’s cost (news first reported in the Wall Street Journal). Such grants were made available as an alternative to the federal renewable energy Investment Tax Credit through an Obama stimulus provision known as the 1603 program.

The Platts article broke new ground when it highlighted Federal Energy Regulatory Commission reports on second-quarter electricity sales from Ivanpah’s three units (from Units 1 and 3 to PG&E, and from Unit 2 to Southern California Edison; they can be seen here, here and here). The sales totaled 133,807 MWh, and at an average price of $167.85/MWh, that generated $22.46 million in revenue.

That relatively small output, combined with the project’s $2 billion price tag, could no doubt hurt all three Ivanpah owners. But BrightSource, despite having the smallest stake -- 20 percent, according to Platts, compared to NRG’s 50 percent and Google’s 30 percent -- might suffer the most as it tries to sell its technology in a market where cheap and bankable solar PV appears to be winning the day.

Power tower projects in the U.S. have been falling by the wayside; most recently, BrightSource shelved plans to build a single-tower, 500-megawatt plant in Palen, California with Abengoa, despite having waged a lengthy campaign to get the project approved. For now at least, there seems little appetite for such giant projects among the California utilities that were being counted on to buy their power.

So Oakland-based BrightSource and another California-based power-tower developer, SolarReserve, are increasingly looking overseas for business, even as they insist that power towers can be competitive in the U.S., particularly if built with on-site energy storage.

Ivanpah has no energy storage, and none was planned for the Palen project. But SolarReserve will soon get a chance to show how well a system with energy storage can work -- a spokesperson for the company said the single-tower, 110-megawatt Crescent Dunes plant in Nevada, currently in a long commissioning phase, will begin commercial operations in early 2015.

At that plant, the sun will be used to heat molten salts that can retain the heat and extend production several hours into the night. The energy storage capability also means that Crescent Dunes requires no natural gas to get it going in the morning, or keep it running when clouds roll in. SolarReserve, which received a $737 million DOE loan guarantee for the plant, anticipates energy generation of “more than 500,000 megawatt-hours per year.”

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Pete Danko is a writer and editor based in Portland, Oregon. This piece was originally published at Breaking Energy and was reprinted with permission.