Plug-In Hybrids: How Green Are They?

September 17, 2006 – Vol.11 No.26

PLUG-IN HYBRIDS: HOW GREEN ARE THEY?

This week the state of California sued the six largest automakers in the United States (and thus selling the most vehicles in California) over the impacts - now and future - of global warming in the state. Only Honda has responded saying the US government should increase fuel economy standards as a way to cut down on greenhouse gas emissions nationwide. The states shouldn’t be allowed to do this on their own.

(Not surprisingly, Honda (as well as Toyota and perhaps Nissan) would find it easy to meet any increase in fuel economy increases the federal government might throw at them. Honda (and the others) already have plenty of cars that could meet higher standards today as well as new technologies under development and near commercialization that could meet very stringent fuel economy standards, perhaps well above 40 miles per gallon, if it came to that.)

Yet while the majors continue to find ways to beat back lawsuits and government mandates, more and more technological opportunities are coming forward that can offer significantly better fuel economy and much lower greenhouse gas emissions.

(Eventually the state of California might come to the obvious conclusion: If the major automakers won’t build the low-emission cars that we want we’ll just have to build them ourselves.

Already there are a handful of fledgling, low-volume green car companies in the state that could be expanded with the state’s help. The heck with Detroit they could say.)

One of the technologies for greener vehicles is plug-in hybrid electric vehicles (PHEVs) which coincidentally seem to have their roots in California.

But are plug-in hybrids the final answer for greener vehicles?

The American Council for an Energy Efficient Economy (ACEEE) has taken a look at and released an in-depth study of the technology: Plug-In Hybrids: An Environmental and Economic Outlook.

First, some notes on the study.

--- ACEEE considers PHEVs as an evolution of current hybrids, thus compares PHEVs with current hybrids and not with conventional cars.

--- There are no PHEVs commercially available, only some retrofitted cars and trucks, so ACEEE can’t compare real PHEVs against real conventional hybrids.

--- ACEEE also concludes that hybrids and PHEVs will continue to be mostly variations of conventional cars and trucks, not purpose-built designs. (Toyota’s second generation Prius owes its success to its purpose-built design. It was built from scratch to be a hybrid, nothing else. Other automakers may choose this route in the future. A successful plug-in hybrid may also have to be purpose-built.)

--- ACEEE considers power plant emissions attributed to charging of the vehicle’s battery from the grid. The advocacy group also looks at the current and potential costs of large battery packs needed for all-electric range of PHEVs.

With the limited information ACEEE has to work with the group has some hopes with some reservations.

--- ACEEE thinks that fuel economy estimates for PHEVs is somewhat overblown and wishes they weren’t. Since policy makers may be dealing with legislation dealing with PHEVs they need more accurate information. Consumers, too, deserve realistic information so as not raise false hopes.

--- Fuel economy for a plug-in with a 20-mile electric-only range would be 30 percent higher than a conventional hybrid, but 50 percent higher if a plug-in traveled 40 miles in all-electric mode.

--- Lithium-ion batteries, because of their low weight and small size, would be best suited for plug-in hybrids, but ACEEE is concerned about their high cost and untested longevity.

--- ACEEE is also concerned about the overall costs of PHEVs. The pay back period for the additional costs of the technology won’t drop to 3 years (seen as desirable) unless the price of batteries drops or the price of gas rises.

--- A PHEV plugged into a California’s fairly clean power grid will see overall greenhouse gas emissions reduced by 32 percent. But, on average nationwide where most electricity is from coal, the figure drops to 15 percent.

--- And, if battery technology continues to improve (as it has been) and the power grid gets cleaner, then pure battery electric vehicles could become a “broadly applicable technology.”

In the end ACEEE calls for more PHEV demonstration programs and incentives for advanced battery production that would lead to a drop in cost for PHEVs.

The full report is available at http://aceee.org/pubs/t061.pdf ( A print version is available for a fee.)