The scarcity of resources and the dependence on fossil fuel are critic points for a sustainable development of the transport sector but they are also driving forces for research. Two main technological research streams for transport greening are biofuels and electric vehicles (EV), and the latter is especially interesting if the electricity comes from photovoltaic panels.

Since both these technologies are based on solar energy being turned into fuel, a specific research based on the principles of Life Cycle Assessment has been made, to find out which system is the most efficient.

The article, published on a recent issue of the journal Environmental Science & Technology (Dec. 26 2012) showed how photovoltaics (PV) is more efficient than biomass at turning sunlight into energy to fuel a car. Focusing the LCA on three key impacts of the two systems – direct land use, life cycle greenhouse gas (GHG) emissions, and fossil fuel requirements – the researchers identified PV electricity used for charging battery electric vehicles as 30 to 200 times (depending on the used crop) more efficient than photosynthesis and subsequent biofuel production as a sun-to-wheels conversion method.

Besides its efficiency in energy conversion, the direct use of photovoltaic energy to fuel cars positively impacts on other environmental aspects, for example reducing CO2 emissions and land use, especially of arable land devoted to food production. However, there are economic and social impacts that have to be considered, first of all on the industry process. It won't be enough to change the engine, but new vehicles need to be built and, thinking in a cascade effect, relevant investments in terms of mobility management are necessary.

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