The Why Files The Why Files --

Plug 'n play: Could plug-in hybrid cars help the energy crisis?


Plug-in hybrids: The "vehicle-to-grid" solution
Could millions of batteries in plug-in hybrids store solar or wind electricity, and boost the use of alternative energy? Here's a radical thought: Cars that contribute to environmental sanity and foster the growth of carbon-free electricity instead of doing you-know-what....

But plug-in hybrids could help overcome natural limits to the broad use green power faces. The sun only "works" during the day, and the wind can just quit, so you cannot depend on either one to run the electric grid without backup: either backup generators or a cheap, efficient storage system.

Andrew Frank, director of the Hybrid Electric Vehicle Center at the University of California at Davis, says stand-alone batteries are too expensive to back up green electricity, even though they offer the most efficient electric storage.

But the picture changes if millions of people have bought big batteries in their plug-in hybrids, Frank says.

Graph shows that oil use will increase over time, but if hybrids are brought in as specified, it will stabilize
If, starting in 2010, all new cars and light trucks in the United States are conventional hybrids, oil consumption would not fall. Modified graphic from original at National Renewable Energy Laboratory

Using an approach called "vehicle to grid," these batteries would store electricity when it's available, and return it to the utility grid when the grid needs power. Vehicle-to-grid would require smart chargers that respond to the instant-by-instant flow of electricity on the grid, but the approach has major potential, says Frank, whose students compete at electric-car fiestas.

Graph shows that oil use will rise at current rate, but drop dramatically with hybrids, especially if E85 is used as fuel
If all new American cars were hybrid by 2010, and 40 percent were plug-in hybrids that can drive 40 miles on the battery by 2020, oil consumption for transportation will start to ebb. Using ethanol ("E85") fuel would increase the benefits. Government experts consider this a "highly aggressive" rate of technological change. Modified graphic from original at National Renewable Energy Laboratory

An idea whose time has come?
Once a backwater of the energy discussion, vehicle to grid has gotten a huge shove from the headlines. "This global warming business has been getting a lot of press since [Al] Gore won his Nobel Prize," says Frank. "Nobody knows what to do about that, and on top of that is the rising price of gasoline, which is tied to peak oil," the idea that crude oil production may be close to its maximum.

After peak oil, classical economics says that an increase in demand will cause prices to soar. So what will move our cars after peak oil? Fuel cells are trendy, but their hydrogen fuel is generated with gobs of electricity. But if plug-in hybrids gain acceptance around the world, Frank says, all that cheap battery storage could spark a transition "from fossil fuels to renewable transportation." In a vehicle-to-grid scenario, those big car batteries would meet peaks in demand instead of the expensive back-up generators. Eventually, plug-in hybrids could eliminate the peaks and valleys in electricity supply, and bring the cost of electricity down to the price of the always-on ("base load") generators.

Here comes the sun
Vehicle-to-grid is unlikely to happen soon, says Don Hillebrand, a transportation expert at Argonne National Laboratory. "It's nice in theory, it's a Holy Grail, but I believe it's much further out [than plug-in hybrids]. It would take five years or longer before there would be enough plug-ins to make an impact on vehicle-to-grid. It's something we really want to pursue, but it will be the last thing we do."

Car is at center of energy flow that includes ethanol, solar and wind power, and the utility grid.
Plug-in hybrids could offer a new path through the energy maze, helping to boost the use of alternative energy. Adapted from Efficient Drive Trains, Inc.

But, Hillebrand concedes, vehicle-to-grid will get a big boost "when solar and wind are technologies that are widely distributed, and we'll need a backup from the car."

Battery storage in plug-ins creates a natural synergy with wind and solar electricity, Frank says, and could initiate a major leap toward electric transportation and green electricity -- without requiring much change in transportation patterns.

Blow, baby, blow!
One beneficiary of cheap storage would be wind electricity, which is limited by wind's fickleness. "I got back from Germany, where 18 percent of the kilowatt-hours come from wind," says Frank. "But the Germans realize the theoretical maximum is 20 percent, because for every megawatt of wind, they need a megawatt of backup power, and all these plants are sitting around, doing nothing when the wind blows. But if you had energy storage in your society, you could shut down the backup plants, because the [car] batteries become the backup."

Or you could increase your wind generation and store more energy in the batteries.

Solar electricity is another possible beneficiary of burgeoning batteries, Frank says. "If you buy a plug-in hybrid and a solar panel, with today's cost of gasoline, you could pay off the solar panel in three to four years, and that means for the next 25 years, you get to drive your car for free."

With big batteries in every garage and solar panels on roofs and at employers' parking lots, Frank says, "The primary energy source is the sun, and the grid and the gas station become the backup."

Back up? No. Forward to the bibliography!


Megan Anderson, project assistant; Terry Devitt, editor; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive

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