SAN DIEGO—Widespread adoption of plug-in electric vehicles could dramatically cut greenhouse gas pollution and reduce U.S. dependence on foreign oil. But results of an electric-car pilot project presented here today at the annual meeting of the American Association for the Advancement of Science (which publishes ScienceNOW) provide added incentive to go electric: Car owners could return unused electricity back to the grid and make real money while doing it.
Electric cars need big, powerful batteries to accelerate to highway speeds and travel scores or even several hundred kilometers on a single charge. But because most drivers drive just a few dozen kilometers a day, most of that battery capacity sits unused. To take advantage of that storage capacity, Willett Kempton, director of the University of Delaware's Center for Carbon-Free Power Integration in Lewes, teamed up with an electric car maker, several utilities, a software company, and PJM Interconnection, one of 10 regional organizations that coordinate and control the U.S. electrical grid.
To ensure that electricity flows steadily and without interruption, the U.S. government requires PJM Interconnection and its counterparts to have reserves of power to tap into in case a generator goes down and other electrical reserves to maintain the 60-hertz frequency of alternating current that our appliances and devices are accustomed to dealing with. Today, PJM Interconnection and its counterparts pay conventional power plants to maintain this reserve power. But as renewable energy sources such as wind and solar, which provide energy cleanly but intermittently, come online, these grid operators need to ramp up their storage capacity to ensure a steady electricity supply. So Kempton, electrical engineer Ken Huber of PJM Interconnection, and their colleagues set out to provide some of the backup power from a fleet of parked electric cars.
Kempton's team used an electric car from AC Propulsions, a San Dimas, California, company, that was custom-built to provide electricity back to the grid. They used commercially available software and hardware that companies such as PJM Interconnection use to monitor and control energy flow. In November, the company hooked the grid up to the car, and Kempton's team's electric car became the first car in the world to earn its keep as a backup electric power source. At the rates that PJM Interconnection pays today to maintain power reserves, a hooked-in electric car could generate $1800 a year for its owner.
"I think it's tremendously exciting," says Kathryn Clay, director of research for the Alliance of Automobile Manufacturers. "The extra dollars an electric car provides will not be enough by themselves to get consumers to adopt grid-enabled vehicles en masse—for that we also need better and less expensive batteries and tax incentives to give the market a nudge." Nevertheless, "it's an incentive to push in the right direction."