A lot has been written about the impact solar thermal power tower technology – like that used at the Ivanpah Solar Electric Generating System – has on birds. Like any infrastructure project, there are environmental impacts. These are legitimate concerns that must be addressed. But it needs to be put in context. That is where many have by and large missed the point.
BrightSource’s solar thermal power tower technology produces predictable, reliable and cost-competitive clean energy when needed most. We use thousands of software controlled mirrors to concentrate sunlight onto a boiler filled with water that sits atop a tower. When the sunlight hits the boiler, the water is heated and creates high-pressure, high-temperature steam. The steam is then used either in a conventional turbine to produce electricity or in industrial process applications, such as enhanced oil recovery.
Let’s be clear: No one disputes that certain levels of concentrated solar flux present a risk to birds. The U.S. Fish and Wildlife’s Office of Law Enforcement (OLE) was asked to examine the causes of bird mortality at three solar energy facilities in California, including the Ivanpah project. The OLE biologists found that “significant avian mortality is caused by the intense solar flux that produces feather singeing.” i
In fact, Ivanpah reported 321 avian fatalities between January and June 2014, of which 133 were related to solar flux.
When considering the impact our technology has on birds passing through the concentrated sunlight, or solar flux, it is important to keep in mind the leading man-made causes of bird deaths:ii
- An estimated 1.4-3.7 billion birds are killed each year by cats;
- As many as 980 million birds crash into buildings annually;
- 174 million birds die from power lines every year;
- Up to 340 million birds perish from vehicles/roads;
- Approximately 6.8 million birds die flying into communications towers;
- As many as one million die annually in oil and gas fluid waste pits; and
- Up to 330,000 die each year from wind turbines
Solar (light) flux is not the same as thermal (heat) flux.
There is more than one type of flux, and while related, heat flux is not interchangeable with solar flux. Why? We will discuss this in detail in our next blog post, but in short: the conflation of heat flux with solar flux has resulted in errors and misunderstandings regarding estimates of avian impacts due to flux created with BrightSource’s technology.
Birds are not vaporized or incinerated after traveling through solar flux.
There is no scientific evidence that birds are “vaporized” after traveling through solar flux. In fact, OLE biologists found evidence to the contrary, “Birds appear to be able to survive flux burns in the short term, as evidenced by the collection of several live birds with singed feathers.” iii
The area of concern associated with solar flux occurs near the tower, as evidenced by the data collected.
Take the Ivanpah project as an example. In total, the project spans more than 3,500 acres. However, more than 99% of the bird mortalities that have evidence of flux singing were found within 200 meters of a tower. Understanding where the majority of bird deaths occur helps to more accurately estimate the number of birds potentially impacted by flux and focus avian deterrent efforts for maximum effect.
ISEGS – Cumulative Proportion of Fatalities by Distance – SINGED (Click to view data)
Make no mistake, BrightSource is committed to minimizing avian impacts at the projects utilizing our technology. We support the use of technologically advanced cameras, radars and audio systems to assist in detecting, monitoring and deterring bird movement in and around solar facilities. BrightSource is comprised of individuals motivated by the opportunity to contribute in a positive and substantial way to the fight against climate change. We recognize that society as a whole has tradeoffs to make in every interaction we make with the natural world. BrightSource takes its responsibility to the environment seriously and we have built that value into the way we do business. We are committed to letting the science and best available evidence dictate the mitigation and adaptive management efforts most appropriate in solar power projects.
i National Fish and Wildlife Forensics Laboratory, Rebecca A. Kagan, Tabitha C. Viner, Pepper W. Trail, and Edgard O. Espinoza: Avian Mortality at Solar Energy Facilities in Southern California: A Preliminary Analysis
ii CEC Docket Number 09-AFC-07C, Palen Solar Power Project – Compliance, TN# 202736: Exhibit 1157. Anthropogenic sources of avian mortality and associated estimates of the number of birds killed per year.
iii National Fish and Wildlife Forensics Laboratory, Rebecca A. Kagan, Tabitha C. Viner, Pepper W. Trail, and Edgard O. Espinoza: Avian Mortality at Solar Energy Facilities in Southern California: A Preliminary Analysis