ESRL Quarterly Newsletter - Spring 2009

Geoengineering Problems

Solar Panels

Proposals to lessen global warming by shooting light-scattering particles into the stratosphere could significantly reduce solar power production, a new ESRL study shows.

To slow climate change, several climate scientists have described geoengineering schemes, which would attempt to cool the planet by injecting particles into the upper atmosphere. Such “aerosol loading” would be similar to the effect of volcanic eruptions, which create particles that scatter sunlight to outer space and cool Earth’s surface.

ESRL’s Dan Murphy, in the Chemical Sciences Division, calculated that one unintended consequence of a successful geoengineering scheme would be a significant drop in power generation by concentrating solar facilities—a 20 percent loss in one scenario. Solar and other types of alternative energy are expected to be part of a transition away from carbon-intensive fuels.

Aerosols would not only reflect sunlight to outer space, Murphy pointed out in the paper, published in March in Environmental Science and Technology. Particles would also scatter sunlight to Earth as diffuse radiation, reducing the direct sunlight on which concentrating solar facilities depend.

Murphy calculated the reduction in direct sunlight using basic physics, and he verified the numbers with data following the eruption of the Philippine volcano Mt. Pinatubo, in 1991. Every 1 percent reduction in total sunlight reaching the Earth, Murphy concluded, would mean a 4 to 10 percent production loss for concentrated solar power. Passive solar designs would also be less efficient.

Peak-power production could be hit harder than total power generation, because peak demand generally occurs during times of day when the sun takes a longer, slanted path through the atmosphere, Murphy noted.

He charted the output of a concentrating solar plant in California before and after the Mt. Pinatubo eruption, and found a 14 percent drop in annual solar output associated with the volcano, and a 34 percent reduction in summertime on-peak capacity.