Box 1. Plug in, turn on...sell out

"Forget hydrogen, forget hydrogen, forget hydrogen." James Woolsey, a former CIA director, reckons that there's a faster and cheaper way to solve America's energy problem — plug-in electric cars, acting as a massive distributed battery for the electricity grid.

Woolsey, founder of Set America Free, an organization based in Washington DC that advocates the reduction of US dependence on oil, was speaking in January 2006 at the launch of Plug-In Partners, an advocacy group led by the city of Austin, Texas. Its members have already pledged to buy almost 10,000 cars for municipal fleets.

The idea is to replace millions of gas guzzlers with electric vehicles that are powered by off-peak mains electricity. Millions of vehicles could be charged without building any new power stations, as existing plants rarely run at full capacity. Part of the stored energy could then be sold back to the grid at periods of peak demand.

Integrating vehicles and the electricity grid, the two largest consumers of energy, makes a lot of sense, according to a study published last month by the Pacific Northwest National Laboratory. It concluded that the existing grid capacity could power 217 million light-duty vehicles (three-quarters of the light-duty fleet).

Moreover, because the light-duty vehicles consume 97% of the petrol supply, switching to plug-in hybrid electric vehicles (PHEVs) could save 6.5 million barrels of oil a day — or half of US imports. The scheme would require running power plants at higher constant levels, but because they are more efficient than car engines, the net balance would be a 27% reduction in greenhouse-gas emissions.

PHEVs are similar to today's electric car, but they have bigger and more expensive batteries to cover average daily driving needs (53 kilometres), with a fuel engine kicking in for longer trips. Assuming that PHEVs would cost US$6,000 to $10,000 more than a regular car, the study estimated a user would recover the investment in 5–8 years. Those economics would improve further once batteries could be mass produced, says Steven Letendre, an expert in vehicle-to-grid economics at Green Mountain College in Vermont.

The snag is that for now, very few PHEVs are available. Only one small company, AC Propulsion in California, currently makes them, although General Motors, Toyota and DaimlerChrysler, are working on prototypes. "The real key to making PHEVs work is the vehicle — they must be attractive in terms of performance and cost to the US consumer — or the high penetrations we studied will not come to pass," says Robert Pratt, one of the authors of the study. A 24 January executive order by US President George W. Bush may give PHEVs a federal boost, by requiring US agencies to adopt them as soon as their life-cycle costs become comparable to those of gas-fuelled vehicles.

Without such incentives, or with continued hikes in oil prices, Pratt reckons that it could take 20 years before PHEVs make a serious dent in the US vehicle fleet. Woolsey thinks that they still make much more sense than the hydrogen economy, which requires changing the entire energy and transport structure. By comparison, he said, PHEVs demand "a bigger battery, and yes, an infrastructure investment: an extension cord. Every family would need an extension cord."

 K. KENNELL/ZUMA PRESS/NEWSCOM

Declan Butler