Green Driving

Prius power On Wednesday, the deputy assistant to the president for energy and climate change, Heather Zichal, gave her support for Sens. Jeff Merkley (D-Ore.) and Lamar Alexander (R-Tenn)’s  Electric Vehicles Bill (S. 948), saying that it could be a means for moving and generating bipartisan energy legislation. Although it may seem like going electric is a win for the environment, the push for more electric cars may reduce our dependence on fuel but it will not necessarily decrease our carbon footprint.

As we are look to develop and deploy plug-in hybrid electric vehicles (PHEV), there are emissions associated to the additional electricity that will be needed for the vehicles. Therefore, what is also needed is a new policy for the power sector to be able to supply low-carbon emission electricity. I was happy to see, also at the start of this week, a white paper released by the Brookings Institution that outlines a proposal for the National Clean Energy Standard that encourages power distributors to adopt, buy or generate their own power through a variety of low-emissions technology in order to meet the outlined standard. This type of technology-neutral approach is interesting and perhaps much more palatable than cap and trade because the system would, for example, allow for a coal plant to be rewarded if it was able to outfit itself with carbon capture technology or any other means to increase its efficiency.

Another means in which electric cars have an impact on our environment through means we may not realize are the battery materials in electric cars. There have been several studies published in Environmental Science and Technology journal assessing the life-cycle of the batteries in plug-in hybrid vehicles and battery electric vehicles. Most recently, Ander Hammer StrØmman from Norwegian University of Science and Technology (NTNU) published such a paper looking generally at Lithium-Ion and Nickel Metal Hydride Batteries (NiMH) (currently the type of battery in the Toyota Prius in the US). This study is unique in that the authors focus their comparitive unit on the amount of energy charged and then discharged by the battery – eliminating factors such as powertrain and driving cycle that is normally assumed when the unit is driving distance or range – thereby solely looking at the environmental impact of the battery.The authors found that with the exception of ozone depletion potential, Nickel Metal Hydride battery had the highest environmental impact. They rationalize that the greater efficiency of the Li-ion attributes to its lower environmental impact, with 2-3 times more storage over its lifetime. In addition, Li-ion batteries uses earth abundant materials. However, where the greatest technological improvement is needed is in the manufacturing energy requirements; for all three batteries that accounted for 97% of the ozone depletion/global warming potential.

It is a great start to want to widely deploy electric vehicles as they do have the potential to decrease emissions. However, policy may want to focus not just on the emissions of the vehicle when consumers are driving and charging but also include the environmental impact during the vehicles entire life cycle. I have only focused specifically on the battery component as that is where I see the most chemistry. But there are a number of aspects that can be improved in order for these green vehicles to be as green as they can be.

Field Emission SEM of Ni-Co-Mn Hydroxide
Image taken by Argonne scientist improving Li-ion battery technology. Images like this help to better understand what is going on at the nanoscale in order to develop new materials.
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