For years, dreamers have imagined a smart grid where millions of electric cars would act as a giant back-up system, balancing energy supply-and-demand more cheaply and cleanly than today’s “peaker” stations, and offering a solution to renewable power’s intermitency. To skeptics, though, the idea always seemed fanciful--and not just for technology reasons. For one thing, why would anyone want to use their car to help a power company do its job?
Well, slowly, the vehicle to grid  (V2G) concept seems to be becoming reality. And, the answer to the question is a good one: in return for their batteries, consumers could earn lots of cold, hard cash.
Last month, NRG Energy , a New Jersey power company, announced that it wanted to commercialize V2G technology developed by Willett Kempton , a professor at the University of Delaware. Kempton, who first proposed V2G in the mid-1990s, has been developing a pilot for three years, where seven cars feed power to the grid and consumers receive monthly payments.
NRG's service, called eV2g, will consist of two elements: a bidirectional power unit, allowing power to go back and forth between batteries and grid, and an application where users can designate times when they need the car, and times when they are happy for NRG to take a battery over. "It allows the end-user to say 'I need my car fully-charged at this time, but I can make my car available on the grid at 3 o'clock in the afternoon when prices are high,'" says Denise Wilson, president of NRG’s alternative energy services.
Before you get your hopes up too soon, though, it is likely to be two years before eV2g is offered to consumers. Among the issues NRG still has to decide on: how the customer-company communication will work; whether the application will be in cars, or on a handheld device (or both); and how much users might get paid. Wilson mentions figures of $500 to $1,000 per month--though it is unclear how many batteries would need to be aggregated before companies, like NRG, might start paying out.
Kempton has said he sees groups of 100 cars generating $25 to 35 per megawatt-hour, or 30 cents per car, per plugged-in hour. Others have forecast a return of $7 to 10 a day. Either way, NRG wants eV2g ready in time for an expected surge of about 150,000 new EVs by 2013.
Unfortunately, many EV owners will have to pay to retrofit their new cars with bi-directional equipment to use the service. Wilson says it would better if car manufacturers integrated these units themselves --which some are now doing. Cars from Tesla  and AC Propulsion  already have bidirectional power capability, as will the new Smart Fortwo sold by Daimler.
Adding further grist to the market, the chairman of the Federal Energy Regulatory Commission (FERC), Jon Wellinghoff, has suggested  increasing the tarriff companies get for using cleaner, more efficient back-up power sources. If approved, that would incentivize operators to facilitate V2G, instead of relying on, say, coal or gas-fired power.
In Japan, Mitsubishi, Nissan and Toyota are developing their own V2G systems. And, according to this , Japan’s natural disasters this year have added impetus: both because the country wants alternatives to centralized power, and because consumers want back-up power during blackouts.
For less-pleasant reasons and more positive ones, vehicle-to-grid looks to have a strong future. “It could be transforming. It’s distributed storage on wheels, it can help build out renewables, and it gives consumers more choice,” Wilson says.
[Image: Flickr user Eilidh B ]