When it comes to transforming the sun’s energy into commuter miles, it looks like photovoltaics beat out our best biofuels. A recent study published in the journal Environmental Science & Technology investigated the relative efficiencies of the two technologies by focusing on traditional methods of turning corn and other plants into ethanol, turning energy crops into electricity, and using photovoltaics to directly convert sunlight into fuel. The team found that PV’s were far more efficient at creating “sun-to-wheels” energy for vehicles.
The study was led by Roland Geyer from UC Santa Barbara and David Stoms and James Kallao of the Norwegian University of Science and Technology. It examined the effects of biofuels and PVs on direct land use, greenhouse has emissions, and lifecycle greenhouse gas. Photovoltaics came out way ahead in all three categories.
“Even the most efficient biomass-based pathway…requires 29 times more land than the PV-based alternative in the same locations,” the authors stated. “PV BEV systems also have the lowest life-cycle GHG emissions throughout the U.S. and the lowest fossil fuel inputs, except in locations that have very high hypothetical switchgrass yields of 16 or more tons per hectare.”
PV conversion also yields lower GHG emissions than cellulosic biofuels throughout the technology’s entire lifespan. The “bottleneck” for crops is that photosynthesis is only 1 percent efficient at converting sunlight into electricity while PVs average about 10 percent. As the cost of solar technology continues to drop, the researchers believe that electric vehicles will show an advantage over biofuel combustion cars, and that subsidies that keep investing in biofuels are in essence “barking up the wrong tree”. While biofuels may improve within the next five years, solar electric vehicle technology is accelerating at a fast pace, making the gap between the two all the more pronounced. With corn ethanol having little effect on reducing CO2 emissions and posing a threat to ecosystems and food supplies, solar may be driving the future of transportation.
Via Science Daily