| 25 January |
Which Is Better: Solar Powered EV or Biofuel Powered Car ? |
Dear Friends, Readers/Viewers/Visitors,
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Before continuing on the next part of our series on solar vehicles, I just want to quickly share an article/paper, responding to a question asked by a professor at the UCSB Bren School of Environmental Science and Management, Professor Roland Geyer‘s,
“The energy source for biofuels is the sun, through photosynthesis. The energy source for solar power is also the sun. Which is better?”
Environ Sci Technol. 2013 Jan 15;47(2):1170-6. doi: 10.1021/es302959h. Epub 2013 Jan 3.
Spatially-Explicit Life Cycle Assessment of Sun-to-Wheels Transportation Pathways in the U.S.
Source
Bren School of Environmental Science and Management, University of California , Santa Barbara, California 93106-5131, United States.
Abstract
Growth in biofuel production, which is meant to reduce greenhouse gas (GHG) emissions and fossil energy demand, is increasingly seen as a threat to food supply and natural habitats. Using photovoltaics (PV) to directly convert solar radiation into electricity for battery electric vehicles (BEVs) is an alternative to photosynthesis, which suffers from a very low energy conversion efficiency. Assessments need to be spatially explicit, since solar insolation and crop yields vary widely between locations. This paper therefore compares direct land use, life cycle GHG emissions and fossil fuel requirements of five different sun-to-wheels conversion pathways for every county in the contiguous U.S.: Ethanol from corn or switchgrass for internal combustion vehicles (ICVs), electricity from corn or switchgrass for BEVs, and PV electricity for BEVs. Even the most land-use efficient biomass-based pathway (i.e., switchgrass bioelectricity in U.S. counties with hypothetical crop yields of over 24 tonnes/ha) requires 29 times more land than the PV-based alternative in the same locations. PV BEV systems also have the lowest life cycle GHG emissions throughout the U.S. and the lowest fossil fuel inputs, except for locations with hypothetical switchgrass yields of 16 or more tonnes/ha. Including indirect land use effects further strengthens the case for PV.
The paper shows that PV cells are far more efficient than biofuels at powering a vehicle by energy from the sun.
“What it says to me is that by continuing to throw money into biofuels, we’re barking up the wrong tree. That’s because of a fundamental constraint, which is the relative inefficiency of photosynthesis. And we can’t say that right now biofuels aren’t so great but they’ll be better in five years. That fundamental problem for biofuels will not go away, while solar EVs will just continue to get more efficient and cheaper. If they’re already looking better than biofuels, in five years the gap will be even greater. A search for a silver bullet is under way through synthetic photosynthesis, but using genetic engineering to improve the efficiency of photosynthesis is a pipe dream. If there is a silver bullet in energy, I think it’s solar power.”
At this moment, please allow me to reshare the video below, the SolarWorld GT Team of Bochum (Germany) University of Applied Sciences, is the first solar-powered vehicle that has circumnavigated the world, started the trip in 2012 from Australia, after the World Solar Challenge:
Gathered and posted by sunisthefuture-Susan Sun Nunamaker
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