In Defense of Solar ThermalOctober 15, 2014
Is the sacrifice of 28,000 birds in order to offset the energy needs of 57,000 Californians for a year really asking all that much?
“Solar thermal” energy is the concentration of light to heat which can be used to generate electricity or for other purposes. This is different, of course, from solar photovoltaics (my field).
I like to be realistic about energy sources, staying clear of the abundant quasi-religious nonsense. Because of this I am not a great enthusiast for massive solar thermal projects. They may have their place, but they are still expensive. For example, the $2.2 billion Brightsource Ivanpah site in California, which covers 16 square kilometers, could offset the energy needs of people occupying about 22,000 California homes. That works out to about $100,000 per home!
One of the criticisms that is being aimed at the Ivanpah site, and by implication any subsequent solar thermal site, is that they kill a lot of birds. This idea is easy to understand. Concentrating sunlight from a large area to a single central target makes the irradiance blisteringly high near the center. Birds flying close enough get toasted pretty quick. They even have a name for those birds that fly through this hot spot: streamers. Get it? Rather descriptive I’d say.
Widely reported estimates range as high as 28,000 birds per year killed at Ivanpah. But this high number is controversial and widely disputed. Here is a good discussion about the derivation of that number. Let’s accept that number for the moment, just for the fun of it.
Is the sacrifice of 28,000 birds in order to offset the energy needs for the occupants of 22,000 California homes really all that much? That is about 1.3 birds per home. There are 2.6 people per household in California, so 22,000 households works out to about 57,000 people. That works out to about half a bird per person per year.
There are about 8 billion chickens per year eaten in the United States. That is about 25 per person. All of the sudden trading half a bird for a year’s energy supply doesn’t sound like very much, does it? Pet cats kill between 1.4 and 3.7 billion birds per year (about 4 to 11 birds per person) in the US each year.
While every streamer is a tragedy (for the bird), it is important to put things into perspective.
The anti-solar thermal partisans jumped on the 28,000 bird estimate because it puts the solar thermal proponents on the spot. Those proponents tend to be the type of people who use accusations of wildlife harm as a weapon against everything they don’t like. This makes them look like hypocrites – always a good rhetorical weapon.