Bioenergy, Solar, Utility Scale

Preventing Bird Deaths at Solar Power Plants, Part 1

In the aviation industry alone, there have been over 117,000 bird strikes in the 20 years from 1990 and 2010, according to the FAA. These pose a flight risk to pilots and passengers on planes. In the 1980s, attempting to prevent bird strikes at JFK Airport, the USDA killed 28,000 gulls.

Bird strike damage to aircraft exceeds $50 million a year. So it is in the airline industry’s own interest to cut the risks of bird strikes, as the risk they pose is to the convenience and pocketbooks of flying humans.

Today, Canadian and U.S. firms have devised more advanced prevention methods to cut losses to the aviation industry. In recent years, the numbers of bird strikes have decreased due to the wide use of increasingly advanced bird deterrent technologies developed for the aviation industry, and also used by landfill operators, resorts and by some regulated oil and gas toxic waste ponds.

Bird strike damage to aircraft exceeds $50 million a year. Birds also strike buildings, power lines and transmission towers by the millions every year.

Birds also strike buildings, power lines and transmission towers by the millions every year so it shouldn’t come as a big surprise that some birds have also died at large-scale solar plants, either from collision with solar panels, or in the case of power tower Concentrated Solar Power (CSP), collision with heliostats or exposure to elevated concentrations of solar flux (reflected sunlight) close to the tower.

Power Tower CSP generates electricity the same way a conventional power plant does by making steam but without burning fossil fuels. A heat transfer fluid (water or a another liquid) is heated by the sun using an array of heliostats (mirrors) that reflect the sunlight up to a tower receiver. The heated fluid descends gravitationally to the bottom of the tower where it is fed to a conventional power block to generate power.

Are Bird Strikes At CSP Plants A Big Problem?

At 377 MW net, the Ivanpah project is the first U.S. and largest power tower CSP project in the world. Birds have collided with the heliostats close to the ground, and suffered feather singeing while flying close to the tower, impairing flying ability.

Although the numbers are relatively low compared to other sources of avian mortality, it appears that spring and fall migrations will have the highest numbers. A team of biologists was hired to count and identify bird species killed and injured.

The low count was 16 in February to and a high of 97 in April (see chart below) dead or injured birds, ranging from humming birds and sparrows to mourning doves, swallows and larks. The June count was back down to 41.

The majority of the species found at Ivanpah SEGS comprised of hummingbirds – 18, warblers – 17, doves – 12, swallows and sparrows – 10 each.

Ivanpah was developed by BrightSource Energy in partnership with majority owner NRG Energy and Google. NRG operated the plant.

BrightSource Energy also partnered with Abengoa as Palen Solar Holdings (PSH) to develop the 500 MW Palen project in California.  With the financing in hand, and PPAs to buy the power, PSH was making its way through California’s rigorous multi-year permitting process until concerns over bird deaths at Ivanpah surfaced (some of which have been greatly exaggerated in press articles). The concerns prompted closer scrutiny of bird impacts and sparked interest in deterrent options.

When complete, the Palen project will be larger than Ivanpah, at approximately 3,800 acres with flux fields generated around — and sometimes above — two 750 foot tall power towers. The California Energy Commission (CEC) recently reopened the evidentiary at Palen to consider this new information.

Bird Deterrence is Not Hard

The fast is that safely deterring birds is not that difficult, according to experts and several good options are already in use in other industries. In May, the US Fish and Wildlife Service sent a letter sent to a number of solar companies to outline common sense steps they could take to reduce avian mortality.

Based on where the birds have been found to date at Ivanpah, mortality is expected to gradually increase as birds approach each tower. Ivanpah has three towers, and Palen will have two towers but they will be taller, measuring 750 ft high.

To effectively reduce risk, a deterrent, or combination of deterrents, would need to exclude birds from the entire area around the towers. Solar flux begins several hundred feet off the ground around the power tower. Because the flux field is sometimes “aimed” above the tower during standby, this potential flux field is sometimes taller than the tower itself.

“The first step in learning anything about what to do is to identify the species of birds that are being affected,” said Carla Dove, who heads up the Smithsonian Institution’s forensic lab where a team of ornithologists routinely examine feathers from bird strikes from multiple causes such as aviation to identify the species affected. (See photo, note that these birds were not collected at solar plants.)

Dove’s lab receives up to 20,000 birds a day from a wide range of industries, but she was not familiar with CSP.

“If you know the species, then you know what they eat, when they are there and why they are there. Once you have that bit of knowledge then it may be possible to mitigate the problem to make it less hazardous to birds.”

Distress Calls

BirdBusters Founder Jack Wagner describes his firm as the grandaddy of the firms supplying distress-call-based bird deterrents to a wide range of industries.

Fear of predation is the most effective deterrent. The sounds of predators or the distress calls of each species are the basis for many deterrent technologies. For bio-acoustic deterrence, biologists record the distress calls of each of the species that need to be deterred by catching a bird and digitally recording its call.

“You just catch one bird in a throw net, you hold it upside down for 10 seconds and you’ll get the distress call,” said Wagner. “Typically you can just lure them in with food, or the mating cry; there’s a lot of different ways to attract birds.”

This technique uses an extensive library of distress calls, digitally recorded and played over loudspeakers aimed up into the air space where birds are to be deterred.

But relying on any one technique, in any one position can allow birds to habituate, so a combination of technologies is even more effective.

In Part 2 of this article, we’ll list more bird deterrant techniques and summarize the action plan that Brightsource has decided to take.

Lead image: Trekandshoot via Shutterstock