Common Sense & Some Science Too….
On June 20th, the Los Angeles Times published an article by Julie Cart titled, “Searing questions on massive solar experiment in Mojave Desert,” which raises several questions about the impact of the Ivanpah solar project on birds, drivers, airplanes and military training activities. Unfortunately, the article cites individuals who have had no involvement with the project as expert sources and omits much of the relevant background information available on this important solar power project.
The conclusions drawn in the article ignore the many years of experience in several countries with the power tower technology, and the nearly four years of thoughtful consideration from the California Energy Commission staff and the Bureau of Land Management, in conjunction with state and federal experts on wildlife, aviation, military activity and transportation. These agencies include US Fish and Wildlife Services, Federal Aviation Administration (FAA), US Department of Defense (DOD), California Department of Fish and Game, California Department of Transportation (CalTrans) and California Highway Patrol (CHP). Subject-matter experts from these agencies used science to determine that the Ivanpah solar power plants will not have any significant impact on birds, drivers, pilots or military activity.
The article suggests that the technology is unprecedented and an “experiment.” In fact, in addition to the Solar One project cited in the article, power towers have also been in operation in Israel and in Spain for several years, with no serious concerns. We’ve gone to great lengths to identify all potential risks, learning from the Solar One project and others, and to eliminate those risks:
- Birds: Our technology has been specifically designed to avoid harming birds. Unlike older technology, when our mirrors are not focused at the top of the tower, the light is focused in a diffuse ring around the top of the tower, at concentration levels too low to have any detrimental effect on birds. We have also reduced the size of the heliostats and placed them lower to the ground to avoid collisions, and we avoid siting projects adjacent to actively farmed and irrigated agricultural land or standing water that might attract insects and birds.
- Driver Distraction: Our solar power towers will not cause glare – the brightness, when fully illuminated, will be the equivalent of looking at a 100-watt light bulb from 25 feet away during daylight. LED billboards or LED headlights on newer automobiles are brighter and would be more distracting. Our heliostats mirrors are precisely focused to concentrate light onto the boiler atop the tower, and beyond the tower; the light quickly diffuses.
- Aviation: The Federal Aviation Administration (FAA) reviewed the Ivanpah solar project and determined that it would not impact aviation safety. The height of the towers was deemed a non-issue. The large, high velocity exhaust plumes from a gas or coal turbine engine simply do not exist at Ivanpah. Instead of traditional cooling towers, which can emit large visible vapor plumes, Ivanpah will use an air-cooled condenser (ACC) to cool its steam, which would emit only warm air at much lower velocity.
- Military Activity: The Department of Defense reviewed the Ivanpah solar project and did not have any objections. Furthermore, the Ivanpah project is not located in an area where the military trains.
Below we have provided a more in-depth response to each of the concerns raised in the article, as well as a summarized history of solar power tower technology, which has been deployed around the world for over three decades.
Impact on Birds
The LA Times says: The Ivanpah project presents a threat to birds.
Facts: Through the evolution of our solar power plant technology, we have dramatically reduced the threat a plant may pose to birds.
Many regulatory agencies were involved in the nearly four-year permitting process of the Ivanpah solar project, including agencies that specialize in the protection of birds and other species. The Ivanpah solar project was reviewed and approved by the California Energy Commission and Bureau of Land Management with significant input and guidance from the United States Fish and Wildlife Service and the California Department of Fish and Game. They determined that the risks to birds and other species were insignificant and mitigable with the proper planning.
It is true that older, early generation power tower plants have experienced issues with birds. The 1986 study of power tower impacts on avian species that the reporter cites in her article was conducted at the Solar One facility, which is very different than the technology being deployed at Ivanpah. That study concluded that Solar One’s impact on avian species was minimal, but identified key risks and causes of avian injury and mortality at the facility. The primary cause (more than 80%) was found to be collision with heliostat mirrors. The secondary cause (less than 20%) was presumed to be birds flying through four “standby” points, where Solar One’s mirrors would be focused when not directed to the top of the tower (although birds were never observed being harmed by flying through the standby points). Both of these risks at Solar One were exacerbated by the presence of nearby fertile agricultural land and more than 100 acres of standing water adjacent the facility, which attracted birds.
While the insights from Solar One are valuable, it is unreasonable to assume that its impacts would apply to newer, state-of-the-art technology that is specifically designed to avoid those risks. Solar One used a now-outdated 1980’s technology that deployed large heliostats that could not be precisely controlled. In comparison, our technology uses smaller, highly precise software-controlled heliostats. Solar thermal tower technology has made much advancement in the past two decades and eliminated the root causes of the avian concerns. For example:
Reduction of mirror size, lower placement to the ground
Solar One had large, 22.6 x 22.6 feet heliostat mirrors, reaching up to 25 feet off the ground. The mirrors used at Ivanpah are much smaller, only 10.5 x 7.5 feet and reaching a maximum of 13 feet off the ground, significantly reducing the potential for collisions.
Reduction in concentrated solar “flux”
Modern solar tower technology no longer uses the highly-concentrated standby points that were presumed to have harmed birds at Solar One. Unlike Solar One, when the Ivanpah mirrors are not focused on the top of the towers, sunbeams will be diffused in a standby zone rather than focused into concentrated standby points.
See picture below for example of the standby points associated with outdated 1980’s technology:
Avoidance of nearby agricultural land or water, which attracts birds
The Solar One plant was surrounded by fertile agricultural land and had large, unnetted evaporation ponds, which cultivated insect populations and attracted birds. The Ivanpah plant is buffered from any farmland (active or inactive) and will have only a few acres of netted evaporation ponds.
Visual Impact to Drivers
The LA Times says: The glare from the project will distract drivers on Interstate-15.
Facts: Looking at the nearest Ivanpah tower from Interstate 15 is the equivalent of looking at a 100 watt light bulb from 25 feet away.
The nearest tower of the Ivanpah project is approximately 1.5 miles from the freeway. While it may draw some attention, as it is an incredibly beautiful, interesting facility and different from the nearby casinos and golf course, we expect that drivers will use common sense and pay no more attention to the project than to other interesting sights that are nearby freeways, and will focus on the road while driving. The LED billboards in Los Angeles or Las Vegas are considerably brighter than our towers, and with text and changing images, would likely be at least as distracting.
The Ivanpah solar project received significant input and guidance from the California Department of Transportation (CalTrans), California Highway Patrol (CHP) and the San Bernardino Associated Governments (the transportation planning agency for San Bernardino County). These local transportation experts determined that there was insignificant risk to drivers.
Scientifically, the brightness of the solar receiver atop the power towers as seen from I-15 would be 38 cd/m2 (candela per square meter), the technical measure of luminance. This level of brightness is equivalent to the brightness of a 100-watt light bulb seen at a distance of approximately 25 feet during daylight. This level of brightness is well below the scientific threshold for glare, which refers to levels of brightness that cause discomfort or interfere with vision.
The heliostat mirrors will be focused on or near the solar tower’s boiler (the top section of the tower), or in a horizontal position when not in use. They will not be pointed in the direction of the highway at any time. Furthermore, the mirrors, once installed on the heliostats, have a convex shape, giving them very precise and specific focal lengths which only concentrate light to the boiler a the top of the tower. Once the light passes the focal point, which is at a maximum of 1000 meters, it becomes diffuse. When outside the boundaries of the solar plant, there would be no significant impact from heliostat reflections for either ground observers (drivers, hikers, etc.) or airborne observers.
The active solar power tower plants in the US and in Spain have not caused significant driver distraction issues.
Impact to Aviation
The LA Times story reports: The Ivanpah project presents a potential threat to aviation.
Facts: The Federal Aviation Administration (FAA) did not raise any concerns about the Ivanpah project and issued a “Determination of No Hazard.”
The article asserts that heat plumes at Ivanpah will create dangerous conditions for small aircrafts. The Federal Aviation Administration (FAA) is mandated by Congress to ensure the safety of aviation in the U.S. As part of this mandate, the FAA conducts extensive aeronautical studies on the potential impact of solar projects on the safety and efficiency of aviation. Subsequent to the FAA review, Ivanpah received its Determination of No Hazard and was found not to impact aviation safety.
The concern about superheated air plumes in the article was raised by Pat Wolfe, an ex-airport operator in Blythe, CA. Mr. Wolfe’s quotes from this story refer not to Ivanpah, but to a natural gas plant located adjacent the Blythe airport near the end of one of the runways. There are many important distinctions between the natural gas power plant Mr. Wolfe describes and the Ivanpah solar power plant:
1) Proximity of the airport to the power plant: Unlike the proximity of the Blythe airport to the adjacent natural gas power plant, the nearest commercial airport to the Ivanpah plant is nearly 40 miles away, and the nearest general aviation airport is over 15 miles away.
2) Combustion exhaust heat plumes: Mr. Wolfe’s concerns are likely in relation to the heat plumes generated by a natural gas plant’s combustion emission points from massive gas turbines, referred to as an “exhaust stack,” which shoot concentrated exhaust upwards at temperatures near 300 degrees Fahrenheit. Ivanpah does not have similar stacks because solar thermal does not have a combustion cycle.
3) Cooling towers heat plumes: The article infers that there is a hazard from a power plant cooling towers, which typically emit steam clouds of a much lower heat than natural gas plant’s exhaust stacks. The hot air rising from a cooling tower is closer to 100 degrees Fahrenheit, depending on the ambient temperature of the location. Regardless, BrightSource uses an air-cooled condenser (ACC) to cool its steam – not a cooling tower. Heat rising from the ACCs at Ivanpah will be very close to ambient air temperature. During the permitting process, the California Energy Commission estimated that any heat plumes from the ACCs at Ivanpah would dissipate within a few hundred feet elevation.
The exhaust stack concerns at fossil power plants warrant precaution for small private aircraft. Pilots flying in the Ivanpah area would follow the same safety requirements as they fly over any of the other 460 thermal power plants currently operating in California, which have not been associated with any major concerns for small planes.
Impact to Department of Defense Training Activities
The LA Times story reports: The potential conflicts with Department of Defense (DOD) training activities and solar plants in the desert are not yet fully understood.
Facts: The Ivanpah project is not sited in an area where the military trains, and DOD is working with BrightSource and other solar companies regarding other sites.
The Department of Defense (DOD) does have concerns about the potential impact of utility-scale solar projects on training programs in the desert. BrightSource has met with the DOD and the services extensively about the potential impacts solar projects, including Ivanpah, could have on operations, and we – and other solar developers – are working closely with DOD to address any concerns.
The DOD was consulted on the Ivanpah project, and had no objections. The Ivanpah project is not sited in an area where the military trains. At no point during our extensive four-year permitting process were we asked to mitigate or change the project by the DOD.
We continue to be in regular dialogue with the DOD on all of our forthcoming projects to identify and address any potential risk.
The History of Solar Thermal Power Tower Technology around the World
The LA Times says: There is nothing of [Ivanpah’s] type and size exists anywhere else in the world.
Facts: There are numerous examples of this technology deployed around the world.
It is true that once complete, Ivanpah will be the largest solar thermal power tower plant in the world. However, contrary to the article, there are many examples of solar power tower technology deployed in the US and in Spain. Below is a short history of solar thermal power tower technology:
In the 1970’s Sandia National Laboratories in Albuquerque, New Mexico studied the power tower concept and proposed a test facility to investigate the concept and qualify components and systems for larger‑scale evaluation at a pilot plant. As a result, the National Solar Thermal Test Facility (NSTTF) was built at Sandia in 1976. At NSTTF, 222 large heliostats directed the sun into four test bays on a 205-foot (63-meter) tower to produce a total thermal capacity of 5 megawatts.
The tower technology was first developed and made operational for electricity production in 1982 by the U.S. Department of Energy (DOE), working with an industry consortium. This consortium built a 10 megawatt project, known as Solar One, in Barstow, California. Solar One produced over 38 million kilowatt-hours of electricity during its operation from 1982 to 1988.
Between 1992 and 1999, the U.S. DOE enlarged and retrofitted Solar One to use molten salt for heat transfer and thermal storage, and renamed it Solar Two. During its operational period, from April 1996 to April 1999, Solar Two successfully demonstrated efficient collection of solar energy and dispatch of electricity, including the ability to routinely produce electricity during cloudy weather and at night. In one demonstration, it delivered power to the grid for 153 straight hours (nearly a full week) before extended cloudy weather interrupted its round-the-clock operation.
More recently, the first commercial power tower – an 11 megawatt plant known as PS-10, was commissioned near Seville, Spain in March 2007. A 20 megawatt plant known as PS-20 was completed adjacent to PS-10 in April 2009. Also in Spain, the 17 megawatt Gemasolar plant became operational in 2011. In the US, a 110 megawatt plant is now under construction in Nevada.
BrightSource has built two demonstration facilities with its own proprietary tower technology. The first 6 MW thermal pilot plant – the Solar Energy Development Center – began operation in June 2008. This pilot plant has proven BrightSource’s technology by consistently producing highly efficient, utility-grade steam of 525 degrees Celsius. In October 2011, BrightSource completed a 29 MW thermal solar power tower facility for Chevron in central California, which is actively producing high temperature, high pressure steam for industrial purposes.