The fine was the latest embarrassment for the plant, which was was built by Spain's Abengoa Solar company with loan guarantees from the Obama administration's clean-energy program, plus a 30 percent construction subsidy funded by taxpayers. Since the plant became fully operational in July 2014, Abengoa went broke and was subsequently saved from becoming Spain's largest bankruptcy in history by an infusion of capital from investors. A conglomerate of investors and Abengoa called Atlantica Yield (formerly Abengoa Yield) now owns Arizona Solar One LLC, the company that runs the Solana plant.
The largest of its type in the world, the 900,000-mirror facility is a modern marvel that at times produces enough electricity to power tens of thousands of homes — including for several hours after sunset. Arizona Public Service, the state's largest utility, is under contract to buy whatever Solana produces and distribute the electricity to customers.
Solana works by focusing sunlight energy with its curved mirrors onto tubes that contain a heat-transfer fluid, which is pumped across tanks of a molten-salt brew. The molten salt, which with the help of backup diesel engines is always kept at between 500 and 700 degrees Fahrenheit, provides heat for two big steam turbines in the center of the three-square-mile solar array.
But the plant has been plagued with problems, from reports of federal investigations for potential labor violations to equipment malfunctions that have caused the project to generate only about two-thirds of the electricity that Abengoa said it would.
On top of that, the plant is a polluter. Maricopa County inspectors have dealt with multiple air-quality violations over the plant's first few years, resulting in the announcement this month that Arizona Solar One will pay the largest fine the county has ever imposed on a company for air pollution. The money will be used for various community programs to help improve the county's air quality. Arizona Solar One has also committed to millions of dollars' worth of repairs that may help it from exceeding air-quality standards in the future.
Ironically, the "clean-energy" plant is worse than a natural-gas plant for certain emissions, Maricopa County officials said.
Richard Sumner, permitting division manager for the county's air-quality department, broke the problems down into three main categories.
When the plant began operations in 2014 and the salt was first melted, the plant generated too many tons of nitrogen oxides — poisonous gases that mix with volatile organic compounds (VOCs) to form ground-level ozone, which can damage human lungs. Both nitrogen oxides and VOCs are typical pollutants produced by combustion engines like fossil-fuel power plants and automobiles. Once the salt became molten, nitrogen oxide emissions fell to well within acceptable levels.
The heat-transfer fluid system is a complicated array of pipes and pumps that often leak. The fluid sometimes piles up in drainage ditches, where it emits vapors. Solana is located in a relatively remote desert area west of Gila Bend, well south of Phoenix, but it's near a dairy and a few homes. Several neighbors have complained about the smells coming from the plant.
All told, the plant produces about 16 tons of VOCs annually; county rules permit no more than 8 tons. (Asked to put the figure in context, Sumner said Solana puts out roughly twice as many VOCs as a natural-gas plant of the same size.)
The worst problem, however, is the fact that the leaked heat-transfer fluid emits two substances that are on the U.S. Environmental Protection Agency's Toxic Release Inventory, a list of nearly 200 poisons that can turn up in various emission sources. One of them, biphenyl, is likely emitted by Solana at more than twice the annual standard over the course of a year, inspectors calculated (a total of about eight tons).
Sumner said natural-gas plants typically don't emit high levels of biphenyl. EPA information on biphenyl doesn't indicate how bad the chemical might be for people downwind of the plant, but it suggests Solana's workers could be at risk of exposure. In high levels, biphenyl is known to cause eye and skin irritation, with toxic effects on the liver, kidneys, and nervous system.
The operators of Arizona Solar One didn't return messages from New Times.
Bob Huhn, the county air-quality department's spokesman, said the company has been cooperating with inspectors and attempting to fix the problems.
Still, Sumner said he expects emission problems to continue at Solana for the time being.
"Going forward, we don't know what he full solution is at this time," he said.
A March inspection report shows numerous steps the company is taking to repair the heat-transfer-fluid system and shore up leaks. As New Times reported earlier this month, the plant still suffers from the effects of a microburst that knocked it out temporarily on July 29.
Sumner pointed out that even with all of its air-quality problems, Solana remains far cleaner than a natural-gas plant in some respects. Natural-gas plants pump out nearly eight times as many greenhouse gases like carbon dioxide as Solana, as well as high quantities of other pollutants, he said.
Asked if that means Arizona Solar One LLC paid a $1.5 million fine for emitting roughly one-eighth the total emissions of a natural-gas plant of a similar size, Sumner agreed that was another way to look at it.
As for those eight tons of biphenyl — although it's an unacceptable amount, it's a tiny fraction of the 79 million tons of total Toxic Inventory Release chemicals the EPA estimates get dumped into the air, water, and lands of Arizona every year.