updated 5/11/2004 10:19:20 AM ET 2004-05-11T14:19:20

Coming this Fall: a backup generator from General Motors that you can also use as a pickup truck. The technology under the hood could have quite an impact. Indeed, it could allow the U.S. to displace 200 million barrels of foreign oil per year with 40 million tons of U.S. coal.

A coal-powered car? Absurd though that may sound, that's exactly what a hybrid becomes if configured to allow its battery to be recharged from an electrical outlet when the car is parked. Chevy's new Silverado hybrid isn't — it sends electric power the other way, through a 2.4-kilowatt AC power outlet that can run your kitchen appliances out in the middle of nowhere. In your own garage, however, it would make more sense to treat the truck as the appliance and recharge its batteries by plugging it into the wall.

A plug-in hybrid would save most drivers a lot on fuel, because big power plants generate electricity a lot more cheaply than little ones. Running on $2-a-gallon gasoline, the Silverado delivers electric power at a marginal cost of 60 cents per kilowatt-hour. Compare that with electric power from the grid. The average residential price is 8.5 cents per kwh. Off-peak prices, at utilities that offer them, are far lower. You could charge your truck at night. Opportunistic recharging would play a role. Once the plug-in hybrid catches on, recharging terminals will proliferate, acting and even looking a whole lot like parking meters. Mall owners will validate your recharge card when you shop in their stores.

To the electricity cost must be added the wear and tear on the rechargeable battery. All told, says Edward Kjaer, director of electric transportation for Southern California Edison, refueling at the plug should cost no more than a third as much as refueling at the pump, and in many cases a lot less than that. Sticking coal with the same highway-construction taxes you pay at the pump would narrow the gap only a bit.

GM's EV-1 all-electric car, offered in California from 1996 to 2000, was a flop despite the cheap all-electric fuel. Reason: Drivers want to take long trips, too, and batteries can't come close to matching the range provided by gasoline. With a plug-in hybrid, however, the gas tank will get you up the mountains on the weekend, while the rechargeable battery gets you to and from the office and the mall. And the battery is far smaller than the 19-kwh monster used in the all-electric car.

At present the main reason for going hybrid isn't to tap into the grid. It's to improve efficiency by running the gas engine at a much steadier speed, switching it off entirely whenever the car stops and recapturing a bit of energy from the brakes. The hybrid became feasible only with the recent advent of high-power semiconductors that make the mechanical-electrical-battery interfaces compact, reliable and cheap.

But once you go there, it doesn't take much to let the grid recharge the battery. "We now have the sophisticated control systems, power electronics and battery management," says Robert Graham, who studies electric cars at the Electric Power Research Institute. "I don't see any technical hurdles to practical plug-in hybrids coming to market now and displacing very significant amounts of gasoline."

Larry T. Nitz, GM's executive director of hybrid powertrain engineering, disagrees. "It's not a crazy concept," he responds. "But it forces you to have a large battery, and that upsets the cost equation. Right now the batteries are not there." Nitz is certainly right about the cars GM is now offering--the GM Silverado (and a similar product from Dodge) are "light" hybrids with lead acid batteries that spit out only 1 kwh. But the nickel-metal-hydride (NiMH) batteries in other hybrids, either available now or on the way, store 2 to 5 kwh of power, enough for 5 miles of typical travel. Most trips aren't much longer.

The economics of rechargeable hybrids hang on the fact that central station power plants have access to very cheap base-load fuel — 50 percent coal, 20 percent uranium. The heat from one pound — 2 cents' worth — of coal can generate a kilowatt-hour of power. No gasoline-powered hybrid currently burns less than about one pint of gasoline — 25 cents' worth — to do the same. Coal kilowatts are far cheaper because coal is a low-grade fuel and because a power plant's huge boiler, turbine and dynamo are a lot more efficient than a V-8 and its little generator.

The main cost of coal-fired miles is in fact incurred inside the car. An NiMH battery good for 6,000 charge/discharge cycles should cost about $250 in mass production, says Graham — which translates into 4 additional cents per kilowatt-hour of grid power stored and retrieved. "We're now reaping the benefits of years of research and development in next-generation batteries," says Graham. "We see manufacturers stepping up to the plate to make these batteries in the volumes and prices that will make plug-in hybrids practical."

The prospect of plug-in hybrids delights utilities, of course. "Hybrids provide a near-term path to practical electric transportation and a huge benefit for air quality — not to mention a way for utilities to get more value out of their generating assets," says Kjaer. Environmental groups, however, are a lot more equivocal. Most regulators in charge of urban air quality are happy to see the midtown tailpipe give way to a distant smokestack. But the global warming crowd hates coal for its high carbon content and also blames it for acid rain. The manufacturers of hybrids don't really know where they stand. More efficiency wins them green friends; more coal doesn't. And it will take time to persuade consumers that buying batteries by the pack every few years is cheaper than buying gasoline by the gallon once a week.

Be that as it may, some 10 percent of all hybrid cars could end up running almost entirely on the grid, because they travel less than 6 miles per day. Stick an additional 90 pounds — $800 worth — of NiMH batteries in a hybrid, recharge only in garages and parking lots, and we'll shift about 25 percent of a typical driver's most-fuel-hungry miles to the grid. "With a plug-in hybrid," Kjaer believes, "most urban drivers will be able to go five days a week without ever going to a gasoline station."

U.S. cars eat 2.9 billion barrels of crude oil a year. The right kind of hybrid could make a real dent in that figure.

Peter Huber is a senior fellow of the Manhattan Institute and a partner, along with Mark P. Mills, of the Digital Power Group.

© 2012


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