Solar energy could exceed California's current energy demand three to five times using equipment built on and around the state's existing infrastructure, claim researchers at the Carnegie Institution for Science
at in Stanford, Calif. They detailed their findings online March 16 in the journal Nature Climate Change.
With a total area of more than 400,000 square kilometers, California has more land than 189 countries, including Germany. A little more than 8 percent of this land has already been developed by humans. The Stanford scientists explored how much opportunity this developed land presented for power generation via photovoltaic solar power and concentrating solar power. Photovoltaics convert light directly into electricity, whereas concentrating solar power typically uses concentrated sunlight to heat fluid that drives a steam turbine to generate electricity.
In all, the researchers discovered that California has more than 27,286 square kilometers of developed land suitable for photovoltaics and more than 6,274 square kilometers of developed land usable for concentrating solar power. The rooftops and open spaces in these urban and suburban areas could generate up to 15,000 terawatt-hours of energy per year using photovoltaics and 6,000 terawatt-hours of energy per year using concentrating solar power technology, which is three to five times more than California's current energy demands.
The scientists also found an additional 55,733 square kilometers of land potentially compatible for photovoltaics and 27,215 square kilometers potentially compatible for concentrating solar power. These areas are neither ecologically sensitive nor federally protected, and could in principle be developed with minimal environmental impact, generating roughly three times as much energy as the developed sites the research team explored.
California is currently working to meet requirements that 33 percent of retail electricity be provided by renewable sources by 2020 and that greenhouse-gas emissions are 80 percent below 1990 levels by 2050. The researchers suggest their findings might help the state reach these goals, and noted their work could apply to the rest of the country as well, with a 2008 National Renewable Energy Laboratory report suggesting that 20 to 27 percent of all U.S. residential rooftop space and 60 to 65 percent of commercial rooftops could host photovoltaics.
Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum. He has written for Scientific American, The New York Times, Wired, and Science, among others.