According to research performed by University of California – Santa Barbara Bren School of Environmental Science & Management and published in the journal Environmental Science & Technology, photovoltaics outperform biomass in just about every metric – and it isn’t even close.
The research was done to address the question of how to most efficiently power alternative fuel or battery powered electric vehicles. It’s an important question considering electric vehicles are ostensibly better for the environment than traditional gasoline powered vehicles.
When you switch from a gas powered vehicle to an electric vehicle pollution from tailpipe emissions is effectively eliminated. But things aren’t as straight forward as that. The source of the electricity used to charge the electric vehicle’s battery can have a substantial impact on the true environmental cost of your commute.
Most Texas electricity (the vast majority in the U.S in fact) still comes from coal or natural gas. As a result, the environmental savings of electric vehicles, while still positive, are not as great as they could be. To truly maximize the impact of electric powered transportation the electricity needs to be sourced from truly clean and renewable energy sources.
The University of California study compares two such potential sources; photovoltaics and biofuel. Both methods work by extracting energy from the sun. Photovoltaics achieve this by directly converting solar radiation into electricity while biofuel relies on photosynthesis to extract energy from the sun’s light. From there, biomass can be used to create fuel (such as corn ethanol) for internal combustion engines or it can be used to generate electricity.
One of the study’s findings was that acre for acre, solar cells produce around 30 times more electricity than the most efficient biofuel crops. This means the land use efficiency of solar vs. biofuel is better by a factor of 30. For some of the least efficient crops, the land-use efficiency of solar power is about 200 times greater. Compounding the effect, consider that solar cells don’t have to be placed on agriculturally valuable land. They can be installed within cities and on roof tops.
Adding to the case for solar over bio is the fact that this gap in efficiency is likely to continue to widen. The best photovoltaic technology currently converts about 10 percent of the solar radiation it receives into energy. As the technology continues to advance this conversion ratio is only likely to improve, even as prices come down. Biofuels however are hamstrung by the fundamental limitations of photosynthesis which only converts about 1% of the sun’s radiation it receives into energy.