Wind power has been declared the most environmentally friendly source of renewable energy in a US comparison. The study, published in the journal Energy & Environmental Science by Mark Jacobson, a professor of civil and environmental engineering at Stanford University, compared nine electric power sources and two liquid fuel sources.

They were solar photovoltaic energy, concentrated solar power, wind, geothermal, hydroelectric, wave, tidal, nuclear, and coal with carbon capture and storage (CCS) technology, and corn-based ethanol and cellulosic ethanol. All these were compared on the basis of their ability to power cars. Battery-electric vehicles, hydrogen fuel-cell vehicles and flex-fuel vehicles run on the ethanol-gasoline blend, E85, were used.

The technologies and fuel sources were ranked against 11 different criteria but big weightings were given to just two - greenhouse emissions over the full life cycle of their production and use, and the health impacts from localised air pollution. Other criteria included energy security, water usage, land use, wildlife and resource availability.

The winning combinations were wind energy used to power both electric battery and hydrogen fuel-cell cars. Then came concentrated solar power powering a battery vehicle, followed by geothermal energy in a battery vehicle and solar photovoltaics in a battery vehicle.

Carbon emissions early on the production life cycle - mining and land cultivation - saw  nuclear energy, carbon capture and storage and ethanol fuel ranked lowest out among the twelve energy and engine technologies tested.

"I felt a need to pull together all the information we had plus that from other sources to quantify and rank the best and worst proposals,” Jacobson told technology journal Arstechnica. “My hope is that policy makers will use this information and begin to focus on the best solutions to climate change, air pollution, and energy security.”

Jacobsen says that, for the same effort that allowed the United States to build 300,000 warplanes in a few years during World War II, between 73,000 and 144,000 five megawatt wind turbines could be built. This could prevent 15,000 pollution-related deaths a year and trim US carbon emissions by 30 per cent.

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Review of solutions to global warming, air pollution, and energy security
Mark Z. Jacobson
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