Plug-in cars could actually increase air pollution
— -- The expected introduction of plug-in hybrid electric vehicles could cut U.S. gasoline use but could increase deadly air pollution in some areas, two reports say.
That's because a plug-in's lower tailpipe emissions may be offset by smokestack emissions from the utility generating plants supplying electricity to recharge the big batteries that allow plug-ins to run up to 40 miles without kicking on their gasoline engines. Plug-ins, called PHEVs, are partly powered, in effect, by the fuel used to generate the electricity.
About 49% of U.S. electricity is generated using coal, so in some regions a plug-in running on its batteries is nearly the equivalent of a coal-burning vehicle. The trade-off is one that even plug-in backers acknowledge. It could undercut the appeal of vehicles that appear capable of using no gasoline in town and hitting 50 to 100 mpg overall fuel economy.
If large numbers of plug-in hybrids were being recharged with power from the least-sophisticated coal plants, "There is a possibility for significant increases of soot and mercury," says a report by environmental advocacy group Natural Resources Defense Council. Soot particles can make it hard to breathe, especially for asthmatics. Mercury is toxic.
"Plug-in hybrids are perhaps not good for all areas," says Howard Learner, executive director of the Environmental Law & Policy Center, a Chicago-based advocacy group. In "states that are heavily coal, that equation doesn't work out very well for the environment."
After PHEVs drain their stored energy, they operate like conventional hybrids, triggering their gasoline engines to help drive the wheels and recharge the batteries. Conventionals can't be plugged in; their batteries are recharged only while driving.
The longer a plug-in is designed to operate on just the batteries, the less gasoline it uses, but the more electricity it needs to recharge the larger batteries.
Thus, the better the PHEV — that is, the longer it goes just on its batteries — the greater the charge required and the more the pollution that might result from an electric utility's power generation.
Learner calls PHEVs "really important emerging technology — where the cleaner technologies are used to charge them."
Sulfur dioxide also may be an issue
A study by the Minnesota Pollution Control Agency found plug-ins also could result in more sulfur dioxide (SO2) emissions. SO2 is toxic in large amounts and is a component of corrosive acid rain.
The Minnesota study found that use of PHEVs would lower most emissions compared with other vehicles, but that resulting SO2 emissions would be more than double those from gasoline vehicles and about three or four times greater than from driving a regular hybrid. Exactly how much depends on how far the PHEV can run on battery power alone.
The Minnesota study also found that PHEVs would emit more carbon dioxide (CO2) than driving a conventional hybrid. CO2 is a greenhouse gas thought to contribute to global warming.
The Minnesota numbers are striking because they predict the big jump in SO2 even if 40% of the state's electricity were generated by wind power, not coal or other polluting fuels. About 4% of the state's electricity now is from wind, according to state officials.
The state's PHEV study concludes: "Alternative vehicles offer benefits, but no single technology currently stands out as a clear choice."
The NRDC calculus shows that a plug-in charged from a power plant burning the dirtiest type of coal still has an overall pollution level less than a conventional gasoline car. But it would produce 11% more greenhouse gas emissions than a regular, non-plug-in hybrid, according to Luke Tonachel, vehicles analyst at the NRDC and co-author of the group's report on plug-ins. The report was produced jointly with the non-profit Electric Power Research Institute.
He says, however, that charging a plug-in with electricity from renewable resources — wind or water, for instance — cuts overall greenhouse gas emissions to as low as a conventional gasoline car getting 74 mpg. No current gasoline car does that.
The NRDC and Minnesota studies were published last year but have yet to trigger alarms. PHEVs still are experimental; their possible threat is distant.
"It seems a little premature to think of it being a problem — but there are a lot of issues we should have been thinking of sooner," says Charles Griffith, auto project director at the Ecology Center, an environmental non-profit based in Michigan. He cites as an example debate over use of land to grow crops for ethanol fuel vs. for food.
Even so, Griffith says, "The scenario where there are so many plug-in hybrids plugged into the (electric power) grid that you'll see a change in air quality just doesn't sound true to me."
Plug-ins may be on streets soon
Automakers say PHEVs could be on the streets in significant numbers within five years. Prototypes being tested by car companies suggest they should be able to go up to 40 miles on battery power, which could enable them to deliver average mileage in the neighborhood of 100 mpg in general driving.
The first plug-in vehicle in production, however, is likely to be General Motors' Chevrolet Volt, which is not a hybrid. Due in 2010 or 2011,Volt runs entirely on battery power. Like PHEVs, its battery pack can be recharged by plugging into a normal outlet, using electricity from a utility generating plant. A small gasoline engine recharges Volt's batteries when an outlet isn't handy, but unlike in a hybrid, that engine never directly powers the car. GM could sell 60,000 or more a year, forecasts consultant J.D. Power and Associates, if the price is $30,000 or less.
GM said at the Detroit auto show in January that it also will produce a plug-in hybrid version of its Saturn Vue SUV near the same time Volt is to launch.
Toyota Motor and Ford Motor each showed a prototype plug-in hybrid at auto shows this year and will test the designs. "It will come," says Toyota's Jaycie Chitwood, senior planner at the automaker's advanced technologies unit in the USA. "It's more a question of 'when' than 'if.' "
Ford's Greg Frenette, chief engineer of zero-emission vehicles, says it should take no more than five years to decide if plug-ins can be made reliable and inexpensive enough.
The U.S. Energy Department is backing PHEVs.
In January it offered $30 million for projects to "deliver up to 40 miles of electric range without recharging" and to make plug-ins "cost-competitive by 2014 and ready for commercialization by 2016."
"We look at plug-in hybrids as the next generation of hybrids. They run cleaner, they save oil and they can save consumers money at the pump," NRDC's Tonachel says. But, he says, "Until our oldest power plants are replaced or upgraded, there could be increases in local particulate matter and ozone."