Monday, April 7, 2008

Update on PHEVs

In previous posts I've touched on PHEVs (Plug-in Hybrid Electric Vehicles), and their role in moving our transportation system away from liquid fuels. Keep in mind that PHEVs are vehicles run on electricity supplied from an outlet such as one in your garage. This is completely different than a HEV or hybrid vehicle that stores energy produced from breaking the car. While hybrids are definitely the way to go in conjunction with biofuels to lower gasoline consumption, PHEVs need to be looked at carefully to ensure a productive transition to their use. What many might not understand is that although there will be no pollution at the tailpipe for PHEVs, the electricity must be generated somewhere. As I noted in an earlier post, this electricity can cost as much as gasoline right now and emit almost 7 times as much GHGs as gasoline burning cars if the majority of the electricity is derived from coal power plants.

A study from Carnegie Mellon University emphasizes this point and clearly shows the difference in advantages gained using PHEVs if the electricity comes from coal burning or a diminished GHG emitting source such as nuclear power or wind/solar power. Below is a chart of their findings:

The results from calculating how much GHGs are emitted throughout the generation and utilization of the energy indicate that using current average electricity rates, using PHEVs could reduce GHG emissions by 32%. This number is approximately equal to that of hybrids -- 30-40% reduction in GHGs. The reduction is even better when combining HEVs or PHEVs with biofuels such as E85, shown in the above chart on the right hand side.
Proponents will be quick to point out that the reason to switch to PHEVs is a continuation of the ideology that simply removing imported petroleum from the equation is a good thing for now and we can deal with the greenhouse gas emissions with developing technology. I agree with this but also feel that switching a majority of the US automobile fleet to electric too quickly would negate any kind of gain from solar/wind energy that might be realized and the result would be a large demand for coal power plants. As the above chart shows, combining renewable technologies such as biofuels and electrically powered cars could be the best solution we've got.
For the full article and to review the above chart, check out:

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