Saturday, July 7, 2012

Searing Questions on Massive Solar Experiment in Mojave Desert

At what temperature might a songbird vaporize?
An Ivanpah power plant tower is surrounded by mirrors,
which will bounce radiation from the sun to it. Water stored
inside the towers will be heated to 1,000 degrees, creating
steam power.

Will the glare from five square miles of mirrors create a distraction for highway drivers?

Can plumes of superheated air create enough turbulence to flip a small airplane?

What happens if one of the Air Force's heat-seeking missiles confuses a solar power plant with a military training target?

No one knows for sure. But as the state and federal government push hard to build solar energy plants across the Mojave Desert — there are more than 100 solar applications pending — the military, birders, aviation officials and others are eager for answers.

When completed, a massive plant now under construction near the California-Nevada border will be the largest of its kind in the world. More than 170,000 garage-door sized mirrors will spread across this broad valley. Every 10 seconds, computers will align the mirrors — each equipped with its own GPS device — to track the sun across the desert sky, bouncing radiation to the tops of three 45-story towers. Water stored inside the towers will be heated to 1,000 degrees, creating steam power.

The project's whiz-bang technology has confounded government regulators' ability to analyze the facility, in part because nothing of its type and size exists anywhere else in the world. Although it approved Ivanpah's permit in 2010, the California Energy Commission struggled to assess the public health effects that would be created by the vast field of mirrors and the volumes of hot air pushed upward by spinning turbines and condensers.

Much of the analysis came from computer modeling, most of it provided by the project owners, Oakland-based BrightSource Energy.

In extensive hearings before the Energy Commission, the firm argued that concerns about its plant were overblown and that the project posed no danger to the public. The power plant — one of dozens being fast-tracked by the Interior Department — is slated to open early next year.

Others have their doubts.

"It's an experiment on a grand scale," said Jeffrey Lovich, a scientist with theU.S. Geological Survey.

Most questions begin with birds, which almost certainly will die at Ivanpah, just as they do at many large outdoor industrial operations. There is already documentation linking solar power to bird deaths.

About 30 years ago, ornithologist Robert McKernan and a colleague conducted studies at the Solar One plant near Barstow. By collecting and analyzing bird carcasses, they found that some birds flying through the solar field were incinerated outright. Others perished after their feathers were singed or burned off, or when they collided with the mirror structures or the central tower.

That plant, which began producing power in 1982, had 1,800 mirrors. The Ivanpah facility has 100 times that number and occupies a significantly larger portion of creosote habitat critical to migrating birds. But BrightSource officials contend that there is less risk to birds soaring above Ivanpah, in part because the reflected heat at the new plant there will be one-third as intense as at Solar One.

Birds aren't the only flying objects at risk.

The Defense Department has expressed concern about large-scale solar plants' compatibility with aviation and weapons training at the Mojave region's nine military installations.

The test pilot school at Edwards Air Force base said the most common problems are a result of "electromagnetic intrusion/reflection, vertical obstruction, frequency spectrum overlap, infrared footprint and glint/glare."

Maj. John G. Garza, who represents the Pentagon on a California renewable energy planning group, said potential conflicts with solar plants in the desert are not yet fully understood.

One worrisome possibility?

"The solar tower would be a heat source," Garza said. "A heat-seeking missile could confuse the source, and instead of going to a target on the range, it would go to the tower."

A buffer zone between artillery ranges and solar installations could guard against that scenario. But Garza said no one yet knows how much space would be required.

One known aviation hazard results from the plants' use of high-powered exhaust fans for steam turbines, which can create plumes of superheated air that rise skyward.

Small planes are especially vulnerable.

On the approach to the Blythe airport, for example, aircraft often fly through such superheated air from a fossil fuel power plant at the end of the runway — causing them to buck and veer off course.

"If you hit a plume dead center, you have one wing in and one wing out of it. It would flip an airplane in a heartbeat," said Pat Wolfe, who operated the Blythe airport for 20 years.

Wolfe said he took complaints to the Federal Aviation Administration and the state Energy Commission. "They didn't care," he said. "The information the power companies gave the Energy Commission was computer-generated, non peer-reviewed. It was a joke."

One Energy Commission report detailed a 2004 incident in which flight instructor Luis Magana was in a twin-engine Beechcraft, with a student at the controls. As they flew over power plant cooling towers, the plane began to pitch and roll.

The fledgling pilot was able to land, but Magana reported the hazard, warning that smaller planes possibly could become "inverted and sent into a downward spiral."

The commission has estimated that heat plumes at Ivanpah probably would dissipate at a few hundred feet elevation. But Wolfe challenged that assertion.

"We had a King Air — a big plane — encounter plume turbulence at 2,700 feet" over Blythe, he said. "It was enough to trip the autopilot."

The Ivanpah project is being constructed six miles from the site of a proposed airport outside Las Vegas. In response to concerns, the FAA has said it will issue a notice instructing pilots not to fly directly over the plant or below 1,350 feet anywhere near the facility.

The agency also said it was working to come up with a general siting policy regarding solar power installations, written in conjunction with an industry lobbying arm.

Of all the concerns surrounding the Ivanpah development, mirror glare is one that experts say can be minimized if pilots and motorists use a dose of common sense and avoid staring.

Cliff Ho, who has studied the issue for Sandia National Laboratories, said pilots observing the plant could be afflicted by flash blindness, causing an image to linger in the eye. And the completed facility — rising from the desert and visible at a distance of five miles — will emit a glow that may be all but irresistible to some drivers on nearby Interstate 15.

In the words of James Jewell, an expert on human adaptation to light and former president of the Illuminating Engineering Society of North America, "It will be an unattractive, big industrial blob in the desert."

Ugly, but not dangerous, they say.

Still, Ho stopped short of pronouncing the Ivanpah plant and others like it completely safe.

"I was informed by my superiors that it's dangerous ground to say if a system is safe," he said. "We stick with the analysis."


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