Science & Technology - Posted by Chriss Swaney-Carnegie Mellon on Thursday, October 13, 2011 16:52 - 2 Comments 
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"Given the major spending cuts under debate in Washington, it is important that we get the most benefits out of spending designed to improve the environment and energy security," Jeremy Michalek says. "In the near term, HEVs and plug-in vehicles with small battery packs offer more cost-effective benefits. (Credit: Stefan Ataman / Shutterstock.com)
CARNEGIE MELLON U. (US) — Thinking about buying a new plug-in vehicle? You may want to check the size of its battery first.
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The text of this article by Futurity is licensed under a Creative Commons Attribution-No Derivatives License.
Jeremy J. Michalek of Carnegie Mellon University and co-authors report that plug-in vehicles with small battery packs and hybrid electric vehicles (HEVs) that don’t plug in can reduce life cycle impacts from air emissions and enhance oil security at low or no additional cost over a lifetime.
But plug-in vehicles with large battery packs are more costly and may have higher or lower emissions than HEVs depending on where and when they are plugged in.
In a study appearing this week in the Proceedings of the National Academy of Sciences, Michalek argues that electrified vehicles with smaller battery packs are more efficient in reducing societal costs for health care, environmental damages, and oil consumption.
“Current government policy provides larger subsidies for vehicles with larger battery packs, assuming that larger is better,” says Michalek, an associate professor of engineering and public policy and mechanical engineering.
“While larger battery packs allow plug-in vehicles to drive longer distances on electric power instead of gasoline, they are also expensive and heavy, they are underutilized when the battery capacity is larger than needed for a typical trip, they require more charging infrastructure and they produce more emissions during manufacturing.”
U.S. policy has been pushing the auto industry to investigate alternatives to fossil fuels. The American Recovery and Reinvestment Act of 2009 provides up to $7,500 in tax credits for up to 200,000 plug-in vehicles.
“Because vehicles with larger battery packs are more expensive, fewer of them can be subsidized, and that can result in lower total benefits,” says Michalek, who recently received a grant from the National Science Foundation to analyze how public policy could help determine the types of vehicles built in coming years and how consumers might respond to these vehicles.
“It’s possible that in the future plug-in vehicles with large battery packs might offer the largest benefits at competitive costs if the right factors fall into place, including sufficiently low cost batteries, high gasoline prices, low emission electricity and long battery life,” says study co-author Mikhail Chester, assistant professor of sustainable engineering at Arizona State University.
“But such a future is not certain, and in the near term, HEVs and plug-in vehicles with small battery packs provide more emissions benefits and oil displacement benefits per dollar spent.”
“With increasing energy and environmental constraints, transitioning from conventional gasoline vehicles to hybrid and plug-in vehicles offers an opportunity for improving energy independence and air quality while helping to address global warming,” says study co-author Constantine Samaras, an engineer at the RAND Corporation.
Michalek’s research is aimed at understanding tradeoffs in the capabilities of new technologies and to predict what near- and long-term strategies should be.
“Given the major spending cuts under debate in Washington, it is important that we get the most benefits out of spending designed to improve the environment and energy security,” Michalek says. “In the near term, HEVs and plug-in vehicles with small battery packs offer more cost-effective benefits. More research on batteries—especially lowering cost—and a transition to a cleaner electricity grid are needed to pursue a future where large battery packs may also be able to help address climate change, air pollution and oil dependency at competitive costs.”
The work was funded by the National Science Foundation.
More news from Carnegie Mellon University: www.cmu.edu/news
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2 Comments
David
I appreciate you sharing this blog.
I have to agree as far as current effects are concerned. The problem with electric-only is the range. To counter the problem of not being able to replenish the energy store easily away from home, either the battery capacities are made larger or the owners buy additional non-electric vehicles for trips or both. Obviously this offsets some of the advantage. Furthermore, although the electric-only vehicles are more efficient, power plants cause undesired effects, too. Nuclear waste (& possible containment), environmental and aesthetic effects of hydroelectric dams, fracking to extract gas, obvious oil and coal issues, aesthetic issues with windmills, land usage for large solar projects, etc.
However, and this is the big “but,” electric-only production is currently tiny. The lessons learned while producing electric-only vehicles are going to apply to hybrids and even ICE-only vehicles. What’s more, electric-only designs will be easier to modify to accept onboard electric generation methods that don’t use internal combustion, such as fuel cells. They will also be easy to adapt to other electric storage methods, such as “batteries” of thousands of small “flywheels” or ultracapacitors, should those technologies become economically viable. Finally, silent cars will help us toward a quieter environment, as long as the “your silent car needs to make a noise” crowd isn’t allowed to get away with their nonsense. Sure, a radar or sonar system onboard can trigger a sound to alert pedestrians, but if I buy a car that would be silent but for some artificial engine noise or beeping all the time, that’s going to be the first device I defeat.
One example of electric-only production benefits: Tesla has designed and produces electric motors for their cars that far exceed the suitability for autos of “normal” motors available. These things are very expensive to produce, being partly handmade, but with a higher rate of production, efficiencies of scale come into play. Who knows? Maybe Tesla could end up selling electric motors to hybrid manufacturers. Nothing says parallel hybrids will always be around, maybe we’ll end up with series hybrids, similar to Diesel-electric train locomotives with batteries.