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The idea – developed at the Center for Carbon-free Power Integration at the University of Delaware – is to allow electric vehicles not only to draw power from the grid, but to send electricity back into it. It effectively would use the cars’ batteries as a big storage system to help buffer the constantly fluctuating balance of electricity in the system — ups and downs that are expected to become steeper and more unpredictable as the share of renewable energy rises.
While electric cars are a new idea to most people, Willet Kempton, 61, Center’s Director, who teaches renewable energy policy, has had these ambitions since the mid 1990’s. While he was mulling over the problem of how to extend the use of solar power when he happened to attend a discussion of electric vehicles in Washington, D.C. Suddenly a light bulb went on in his head. “There’s going to be batteries everywhere there’s a garage or a driveway,” he recalls thinking.
His lab has been researching the idea since then and more recently testing it. Now he has applied for a grant from the U.S. Department of Energy to launch the first field-scale demonstration of the concept.
In an indication that they expect — or at least hope — electric vehicles can reach mass-scale market penetration, auto manufacturers have begun collaborating with utility companies to investigate the implications of connecting these two industries that have been almost entirely separate since their births.
Vehicle-to-grid would benefit the grid because under the current system electricity supply must match demand, immediately. Otherwise, there is the possibility for temporary brownouts, even blackouts.
“Right now, electricity is a product that is produced and consumed at the same time,” said Steven Letendre, a professor at Green Mountain College in Vermont who has modeled the economics of vehicle-to-grid.
Because demand stems from the activities of consumers, and these activities fluctuate constantly, the grid must adjust continuously. That’s not only to ensure a continuous power supply, and not waste excess electricity, but also to keep power flowing at the right frequency.
The grid sends signals to power plants every 4 seconds to tell them to make the minute up-or-down adjustments to their generating capacity, based on the needs of the grid.
Vehicle-to-grid proponents say this could just as easily be done by drawing electricity from or putting it into storage. “Right now, the power grid has … virtually very little storage,” Letendre said.
Studies show that electric vehicles could be plugged into the grid as much as 20 hours a day on average. If enough of the cars were out there, they would be a ready source of storage.
The second-to-second adjustments are called frequency regulation, and utility regulators pay power generators to provide the service. Typically, the units added to balance the grid must be at least 1 megawatt.
In 2007, the Federal Energy Regulatory Commission issued an order that would allow electric storage facilities to be treated equally to generation.
In Kempton’s plan, cars would be aggregated so that their batteries would collectively form 1 megawatt of capacity. Together, they would constitute a frequency generation unit and they would get paid. Letendre estimates that a single electric car owner could earn $2,000 to $4,000 a year by selling power from his car back to the grid.
That would not only benefit electricity consumers, but effectively lower the price of the vehicles to buyers. Experts say the cars’ relatively high prices are the largest barrier to their entry into the market.