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The Two Towers

By Chris Clarke If all goes according to plan, at some point in the next four or five years a pair of gargantuan towers will rise from the floor of the eastern Chuckwalla Valley a couple of miles from Interstate 10, part of the proposed Palen Solar Electric Generating System. The towers will be conspicuous. They will rise 750 feet above the desert floor, and be visible for many miles.

Have trouble imagining what a 750 feet tall tower looks like? The tallest building along Interstate 10 between Los Angeles and Phoenix is the Morongo Casino, which looms over San Gorgonio Pass at 330 feet in height. Stack one Morongo Casino atop another, and each of Palen’s towers would still be 90 feet taller than the resulting skyscraper.

Proposed by BrightSource Energy and Abengoa for 3,794 acres of public land in Riverside County, the Palen Solar Electric Generating System (Palen SEGS for short) is now being considered by the California Energy Commission (CEC). BrightSource and bought the project from the bankrupt firm Solar trust of America in 2012. The CEC had already granted Solar Trust of America approval to build the 500-megawatt project. But Solar Trust’s plan was to use parabolic trough solar technology, in which pipes carry thermal fluid through trough-shaped mirrors, which focus solar energy on the pipes. The pipes warm the fluid,, the fluid heats water to produce steam, and the steam drives turbines.

But BrightSource scrapped that design and plans to build Palen with its own proprietary tech, so the CEC is now considering whether to amend its original approval to allow Palen to go forward.

BrightSource brought Abengoa on board in 2013 after a round of defeats and tactical retreats at other BrightSource projects. BrightSource’s Ivanpah SEGS is now nearing completion near the Mojave National Preserve, but a raft of other proposed projects—Hidden Hills near Pahrump, Nevada, Rio Mesa and Sonoran West near Blythe, Siberia east of Ludlow—have been either suspended, quietly back-burnered, or in the case of Rio Mesa, dropped altogether. Criticisms of the projects have included abrogation of Native cultural rights, damage to visual resource, and displacement of wildlife living on the project sites, with Ivanpah’s desert tortoises likely being the best-known example of the last issue. But the criticisms of the other plants that have attracted the most attention from regulators have centered on two main issues. One was the cost BrightSource would have to charge for its power, which prompted the California Public Utilities Commission to vote down a contract between the Rio Mesa plant and Southern California Edison. The other: the threat to birds who venture into the zone of concentrated solar energy around each power tower.

Visual resources may become a more important issue for Palen than for its dead and dying cousins at Rio Mesa and Hidden Hills. Why? It is planned for the edge of a major transcontinental highway.

Each of Palen’s towers would be surrounded by about 85,000 mirrors the size of billboards. Called “heliostats,” these mirrors will be aimed by computer to focus the sun’s light and heat at thermal collectors, called “solar receiver steam generators” (SRSGs), atop each of the towers. When in operation those SRSGs will become bright enough to be unpleasant to look at, even painful if you’re close enough to the solar power facility.

These towers with their brightly glaring tops will be less than two miles from Interstate 10 near the south end of the Palen Mountains. They will be visible along at least a 17-mile stretch of that high-speed highway. Perhaps “visible” isn’t the right word. Eastbound motorists passing Desert Center on their way to Blythe, as they round the north end of the Chuckwalla Mountains, will begin to see two very bright objects almost directly in front of them. Each will seem a quarter the width of the sun at that distance, hovering just above the horizon. East of Desert Center the freeway curves southeast and aims right at the spot where the towers will be, and for the next 10 miles or so drivers will be unable to avoid looking right at the twin SRSGs without taking their eyes off the road. Westbound drivers out of Blythe will have a similar experience for about 23 miles of their journey.

And pilots passing the facility can add reflective glare from those 170,000 billboard-sized mirrors to the mix.

Within about 8.5 miles of the facility, according to a CEC description of the very similar Hidden Hills project, the brightness from those glowing SRSGs will become seriously unpleasant. That’s the distance at which, in the CEC staff’s slightly bureaucratic language, Palen’s SRSGs “would produce a distinct visual distraction effect and be significant in perceived brightness and discomfort/disruption glare effects.”

At that distance, the SRSGs would appear to be a third the sun’s width and about twice the diameter of the sun above the ground. At just under three miles, the SRSGs would appear the width of the sun.

In the CEC’s Preliminary Staff Assessment of the Palen project, CEC staff say they don’t have enough information to judge whether thee project will pose a safety hazard to passersby, though they’re confident enough to say that any visual damage won’t be permanent:

In the absence of additional information… staff has not been able to fully determine potential glint and glare impacts to motorists and pilots from the project’s heliostats and SRSGs. [B]ased on prior studies prepared for the Rio Mesa and Hidden Hills solar power tower projects, staff has only concluded that neither the heliostats nor the SRSGs would cause retinal damage to motorists or pilots.

That focused solar energy will pose a potential hazard to more than drivers on Interstate 10. Each tower’s 85,000 heliostats will focus a considerable amount of light and heat in the vicinity of the SRSGs at the top of the towers, and any living thing getting in the way of that heat runs the risk of burn injury. The facts that some birds are drawn to glare and others seek out thermals complicates matters: BrightSource’s tech would create both glare and thermals in spades.

How serious is that risk? After a BrightSource contractor conducted a test in which dead birds were hung near the SRSG at a BrightSource facility in Israel and exposed to solar flux, the company has claimed the risk is minimal—but not so minimal that the company was willing to release photos from those tests to the public. Enviros and agency staff are sharply skeptical of those claims.

Public and agency attention to the issue of solar flux injury to birds started mounting during the run-up to approval of Hidden Hills, which would rise in excellent eagle habitat east of Tecopa, and Rio Mesa, which would have been on a prime piece of avian real estate near the Cibola National Wildlife Refuge along the Colorado River. It’s very likely that the issue contributed to BrightSource’s decisions this year to suspend Hidden Hills and kill Rio Mesa.

Palen would be built on an important bird migration corridor between the Colorado River, the Salton Sink, and points west. Other solar facilities in the neighborhood have come under recent scrutiny as birds turn up dead within the projects’ fences, many of them water birds likely drawn to reflective surfaces like mirrors and photovoltaic panels. Adding solar flux the the mix can’t help.

Wildlife on the ground may suffer from Palen as well. The project sits astride a major sand transport corridor vital to maintaining habitat for the Mojave fringe-toed lizard: blocking the movement of sand across the project site would inevitably degrade habitat down”stream.” The Mojave fringe-toed is in less trouble than its close cousin the Coachella fringe-toed lizard, but still can’t afford to have its habitat needlessly degraded. Mojave fringe-toeds are abundant in the area. Though the project has been reconfigured to avoid some of the vegetated dunes in the area that local fringe-toeds seem to prefer, the answer to whether that helps the lizards downwind of the project seems to depend on who’s paying the scientists you ask.

And of course, being on the south shore of a dry lake that hasn’t always been dry, the site is quite possibly replete with archaeological and paleontological resources. Desert tribes have pointed out that the Genesis solar project, a few miles east near Ford Dry Lake, ended up damaging an irreplaceable cultural site that initial surveys had failed to reveal. Sabertooth cat fossils have already been found near the Desert Sunlight project across the valley, and a “world-class” fossil deposit on site was one of the nails in Rio Mesa’s coffin. CEC staff have noted that BrightSource’s construction methods, in which heliostat supports are vibrated into the ground, would very likely destroy any fossils on site without their ever becoming known to science. The same holds for cultural sites. BrightSource and Abengoa are resisting further exploration, saying that such research would put them behind schedule.

That schedule is crucial to BrightSource, which really needs a win right now. The company retrenched its staff significantly in 2013, and taking on Abengoa as the lead construction partner for Palen signaled to many observers that the company was in lifeboat mode, re-envisioning itself as something more like solar plant designer.

Which means the company very likely needs two things to happen this year. First, Ivanpah needs to work as advertised. Problems with the technology there would be very bad news for a company staking its future on more of the same only bigger. And Palen needs to win approval in time this year for the plant to start delivering power to the Northern California utility Pacific Gas & Electric on schedule in 2016. If that contract falls through, so do loans offered the company based on that future income.

Fortunately for BrightSource, the CEC has a habit of approving projects even if their own staff recommends against them. Palen’s backers have already stated they intend to ask the CEC for a finding of “overriding considerations” if it turns out their project will unmitigably damage the desert.

So if you find yourself squinting into twin setting suns every time you venture out on Interstate 10 a few years from now, desperately hoping they don’t drown out any brake lights a hundred yards ahead of you, you know who to swear at.

Chris Clarke is a natural history and environmental writer, editor, and photographer. Clarke’s writing has appeared in numerous publications nationally, as well as for KCET and in his own blog, Coyote Crossing. We’re pleased to have Chris join us here at The Sun Runner.

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