Will You or the Grid Control Your Electric Car?

Simply controlling where and when electric cars charge could go a long way to easing any spikes in electricity demand

By David Biello

PECAN STREET: A new development near Austin, Texas boasts the largest concentration of electric car owners in the U.S. Image: Courtesy of GM

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There's a place in Austin, Texas, where the residents have agreed to be the test subjects for a renewable energy and smart grid future?and it's named after a nut. The Pecan Street demonstration project?part of the newly built 280-hectare neighborhood known as Mueller?has become the largest concentrated community of electric vehicle (EV) owners in the world. The community now has nearly 60 Chevy Volt owners alone, thanks to the demonstration project's commitment to match the federal government's $7,500 rebate incentive, effectively halving the price of the hybrid electric cars. And, in addition to learning where and when EV owners charge up their cars, Volt manufacturer General Motors is hoping to learn from the folks in the Pecan Street project how a residential fleet of electric vehicles might change the electric grid.

Such a dense cluster of electric vehicles might strain the grid if all owners try to charge them at the same time?say, on returning home in the evening?and that does indeed seem to be the case based on preliminary monitoring. So GM is considering a new program that delivers so-called "demand response" that can ease back the amount of electricity each car's battery pack consumes. For example, on a hot summer evening when electricity is in high demand for air-conditioning, the system could drop the amount of power going to an individual car from 3.3 kilowatts to just 1.2 kW or even less, explains Paul Pebbles, GM's global manager of Electric Vehicle and Smart Grid Services.

The technology works through the now ubiquitous OnStar technology for GM cars and is applicable to all the EVs GM makes, from the Volt sedan to the new Spark EV minicar. (OnStar can also be used to help the new Spark EV find charging stations while en route?because the all-electric car only has an 132-kilometer range?as well as plot a route to that plug.)

Such demand response is different from using electric vehicle batteries as a form of storage or backup for the electricity grid, which can put undue strain on batteries as they constantly cycle from fully charged to nearly drained. Demand response doesn't cycle the battery this way but rather throttles the flow of electrons into the battery when it is recharging. "When you're driving, you're pulling out a lot more kilowatt-hours and putting them back in with braking than anything we could do remotely," Pebbles argues. The idea is to still deliver what the customer wants: a fully charged car and electricity bill savings via some kind of payment from the utilities or grid operators that benefit from the reduction in demand.

Of course remote control of your car may seem a little off-putting at first, especially because it could be done invisibly, but "we would never do this without customer consent," Pebbles promises, noting that the program will be entirely opt-in. "Anything we do there has to have a benefit in it for the customer. If not, there's no reason to do it." One hope is to coordinate EV charging with the electricity pulled from the rooftop solar panels on many of the homes in the new development, although that would require the cars to be home during the day.

Source: http://www.scientificamerican.com/article.cfm?id=remote-control-of-electric-cars

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