July 2013 Issue
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Last Word

I drive a plug-in vehicle.

I charge it at Carnegie Mellon’s Electric Garage, a former gas station on Forbes Avenue, which CMU’s ChargeCar group is now using to convert gasoline vehicles into electric vehicles. The Electric Garage has a half-dozen charging stations that have become increasingly crowded with Chevy Volts, Nissan Leafs, Plug-in Prii, converted Honda Civics, and a Ford C-Max Energi and Tesla Model S charging away.

Plug-in vehicles are exciting. I once filled up my Plug-in Prius in August and didn’t have to refuel until December (don’t try this at home; it’s bad for the injectors). Plug-in vehicles have the potential to mitigate our dependency on oil while simultaneously reducing greenhouse gas emissions and air pollution from tailpipes.

But if you think electric vehicles are a panacea, think again.

Burning gasoline releases emissions, but so does producing batteries and electricity. And it matters where we emit, because pollution does more damage when released upwind of population centers.

If you account for full life-cycle emissions and the damages they cause, it turns out that vehicles with large battery packs, such as those needed to give pure-electric vehicles a comfortable range, can actually cause more damage than comparable gasoline vehicles on average. Modest batteries in gasoline-powered hybrids and low-range plug-in hybrids provide the greatest social benefits. That’s an encouraging finding because smaller batteries are much cheaper. And, because these vehicles use gasoline for long trips, we don’t need a massive network of chargers—charging at home is good enough. That’s also encouraging, because public charging infrastructure is among the most expensive ways to save gasoline.

Unfortunately, federal and state policies favor larger batteries and public charging infrastructure. But bigger isn’t necessarily better.

In fact, even under the most optimistic electrification scenarios—where gasoline prices reach European levels and innovation drives battery costs way down—electric vehicles aren’t for everybody. About 80% of U.S. households have off-street parking, yet close to half of U.S. vehicles lack reliable access to a dedicated off-street parking spot at an owned residence where a charger could be installed.

Consumers will buy what they like, but when it comes to spending taxpayer dollars and setting mandates, we should be targeting the largest benefits to society. Spending limited funds to put a few pure-electric vehicles on the road does less good than encouraging transitional hybrid technologies that offer more benefit in the near term and have a better shot at mainstream adoption. And this path will help us learn how to make cheaper batteries while keeping our options open if a breakthrough in fuel cells, biofuels, or natural gas forces us to rethink the future of personal transportation.

      Rather than mandating specific technologies, the foundation of our energy policy should be asking polluters to pay for the damages they cause. This means putting a price on carbon and other air emissions as well as taxes on petroleum. Revenue from such policies could be used to lower other taxes and reduce the deficit. But the incentive would encourage us to drive less or purchase smaller, more fuel-efficient, or alternative-fuel vehicles while preserving freedom of choice—as long as we pay for the damages we cause.
Jeremy J. Michalek

Jeremy Michalek is an associate professor of mechanical engineering and of engineering and public policy. He directs the Carnegie Mellon Vehicle Electrification Group. The studies whose results are described here have appeared in the peer-reviewed journals Energy Policy and Proceedings of the National Academy of Sciences. He is affiliated with the university’s Wilton E. Scott Institute for Energy Innovation, which is an interdisciplinary endeavor that includes university research centers and faculty with longstanding expertise in technology, policy, integrated systems, and behavioral science.

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