How Electric Cars Could Become a Giant Battery for Renewable Energy

A rather lengthy article by Dave Levitan about electric cars and the possibility of electric cars helping to smooth out the intermittent nature of wind and solar power.

Dave is a freelance journalist based in Brooklyn who writes about energy, the environment, and health. His articles have been published by Reuters, SolveClimate, IEEE Spectrum, andPsychology Today.

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How Electric Cars Could Become a Giant Battery
for Renewable Energy

Will electric cars one day become part of a network of rechargeable batteries that can help smooth out the intermittent nature of wind and solar power? Many experts believe so, pointing to programs in Europe and the U.S. that demonstrate the promise of vehicle-to-grid technology.

The United States now has more than 35,000 megawatts of installed wind energy, enough to power close to 10 million homes. Close on the heels of this ongoing renewable energy revolution is another green technology: By next year tens of thousands of Nissan LEAFs, Chevy Volts, and other electric vehicles will start rolling off assembly lines.

The electricity generation and transportation sectors may seem like two disparate pieces of a puzzle, but in fact they may end up being intimately related. The connection comes in the form of the vehicle-to-grid concept, in which a large electric vehicle (EV) fleet — essentially a group of rechargeable batteries that spend most of their time sitting in driveways and garages — might be used to store excess power when demand is low and feed it back to the grid when demand is high. Utilities and electricity wholesalers would pay the EV owners for providing that power.

Vehicle-to-grid, or V2G, is not a new idea. In fact, it’s been floating around environmental and green tech circles for a decade at least. But it has always had the tough-to-shed image of a utopian technology. Now, though, V2G — as well as simpler schemes based on smart-timed charging of the vehicles — is slowly becoming reality, evolving in quiet synergy with the worldwide push for renewable energy.

The main drawback of wind and solar power has always been their intermittency: By now it is more than a cliché to say that the wind doesn’t always blow and the sun doesn’t always shine. To some extent, that claim is specious: Existing power supplies also vary by huge amounts, and flexible generators, such as natural gas power plants, are called on to balance out the blips. This is called frequency regulation.

Those generators can handle only so much variation, though, says Willett Kempton, director of theCenter for Carbon Free Power Integration at the University of Delaware and one of the pioneers of the V2G concept. “And also, we’d rather not be using those generators at all. When you get to 40 percent, 50 percent generation coming from renewables, you need some kind of storage, and this [V2G] is a way of getting storage on the system.”

That storage takes the form of the lithium-ion battery pack on board most EVs being produced today. For V2G to work, though, the cars need to be able to communicate with system operators running the electrical grid — this can be accomplished with a simple Internet connection that could be built into the car’s plug. That communication link and a power converter that lets electricity flow both in and out of the battery will allow an overtaxed electrical grid to draw power from a group of cars, and then charge them when there is plenty of electricity to go around. If renewable energy ever supplies a sizeable portion of a nation’s power needs, using EVs as a diffuse network for storing electricity — and then feeding it back to the grid on demand — could be an important tool in decarbonizing the economy.

V2G technology is beginning to emerge in a number of countries. Japanese carmakers, including Nissan and Mitsubishi, plan to start producing V2G-ready cars by mid-decade. Small pilot projects to test the idea are also underway in Europe, from Sweden to Italy.

Increasingly-green Denmark, though, has taken the lead in V2G adoption. Wind power already accounts for about 20 percent of its electricity supply, and additional planned wind farms will raise that level to 27 percent by the end of 2012 and beyond 50 percent by 2025. At times, when the wind blows strongest, the entire country’s power demand is already met and exceeded by wind turbines. But without a way to store that excess energy, it is essentially lost.

So could a large number of EVs actually help with the huge variations in wind that can occur? According to Claus Ekman, a researcher at the Risø National Laboratory for Sustainable Energy in Frederiksborgvej, Denmark, it can, to an extent. Ekman recently published a paper in the journalRenewable Energy that modeled how well EVs could handle increasing wind power generation. He found that in a scenario involving 500,000 vehicles and 8 gigawatts of wind power, various strategies would reduce the excess, or lost, wind power by as much as 800 megawatts — enough to power more than 200,000 homes. Ekman calls this a “significant but not dramatic” effect on the grid. Scenarios involving 2.5 million vehicles and even more wind power show an even greater impact.

“The limitation is the total amount of power that the EVs can absorb,” Ekman told Yale Environment 360. “The peaks in the wind power will be too high for the EVs to absorb them completely.”

Even if a large EV fleet couldn’t handle the full extent of a 50-percent wind power penetration in a country like Denmark, which could be fossil fuel-free by mid-century, it could clearly make a dent. And Denmark has already gone beyond the theoretical, with a V2G project called EDISON running on the small island of Bornholm. The goal is to use the storage capacity of EVs to bring the island’s wind power capacity up to 50 percent of the total demand. Because V2G will reduce the need to generate power from traditional sources, researchers estimate that the price of electricity on the island could drop by 50 percent or more. Though the island is home to only 40,000 people, the project could eventually be used as a proof-of-concept for larger systems, both in Denmark and elsewhere.

In the U.S., commercial-scale V2G projects are farther off, but then again so is 20 percent renewable energy penetration. (The U.S. is currently hovering around 2 percent.) Nonetheless, some progress is being made. For almost a year, several modified vehicles based at the University of Delaware have been providing power back to the grid, and getting paid for it.

Kempton, who runs the Delaware V2G pilot program, notes that using V2G storage, rather than huge centralized aggregations of batteries, eliminates the need for additional high-voltage infrastructure, and the economic benefits of using car batteries that consumers are buying anyway are undeniable.

The potential for electric vehicles has been talked about for decades. But a game-changing infrastructure could finally make them feasible — a standardized network of charging stations where drivers can plug right in, writes Jim Motavalli.

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via environment360

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