Linking electric vehicles to the National Grid could boost renewable energy

Every electric vehicle has a powerful lithium ion batteries, and nine out of 10 cars are parked at any one time. If all those parked lithium ion batteries could somehow become part of the grid, the theory goes, they could help to level out peaks and troughs of demand. When millions of kettles are switched on during TV commercials, for example, utility companies might draw energy from the cars instead of firing up another power station. And when the nation switches off its lights and heads to bed, the grid could refill batteries with cheap-rate electricity.

"Grid-integrated vehicles are beneficial to both their owners and the grid operators," says Willett Kempton of the University of Delaware in the US. "Electric-car drivers are paid for the power services they provide, while the grid maintains its reliability and balances supply and demand."

Basic V2G (vehicle-to-grid) systems are almost here. GE proudly calls its WattStation home vehicle-charger "smart-grid ready". This charger is able to wirelessly communicate with power companies to find the cheapest time to recharge. Mercedes-Benz even wants to let drivers use an iPhone to schedule their next journey with the grid. When they step out of the front door an hour, a day or a week later, their car will be waiting freshly charged.

Sophisticated systems

While saving a few pennies on recharging individual electric vehicles is nice, more sophisticated V2G (vehicle-to-grid) systems could make much larger sums. Ancillary services fine-tune the grid to its intended frequency and voltage, and their value comes in being able to call on them at a moment’s notice.

Kempton believes that a fleet of just 100 small electric cars controlled by a smart network could turn a profit of up to £30,000 a year from ancillary services alone.

"This is a new source of high-quality grid regulation for power companies and a significant revenue stream for owners," he says.

V2G (vehicle-to-grid) systems also fit well with the move to renewable energy. Wind turbines are intermittent by nature, sometimes generating unwanted surges in the middle of the night or standing still when demand is high. Instead of disconnecting wind turbines when they risk overloading the grid, V2G systems could store that power in parked electric cars and retrieve it when the wind power dies down.

The Danish island of Bornholm is already trialling such a system. Researchers hope that it will double the island’s share of renewable power from 20% to 40%, without installing any additional wind turbines.

However, not everyone is amped up by V2G systems. Car owners will have to invest in a pricey two-way charging system, and the cleverest V2G schemes will require hundreds, if not thousands, of electric cars working together.

Perhaps the biggest obstacle, though, is using batteries designed for driving to feed our ageing power-lines. Honda has already said that it would not want its electric car lithium ion batteries "stressed" by V2G technology. And with some replacement batteries costing £10,000 or more, even the prospect of supporting renewable power may not be enough to tempt tomorrow’s electric-car owners off the road and on to the grid.

Mark Harris, www.guardian.co.uk/