Vehicle-to-Grid (V2G) Click to enlarge picture

In April 2007, California utility Pacific Gas and Electric Company showcased the first-ever utility V2G technology demonstration. Photo: PGE

OK, you're feeling really cool and smart with your purchase of a plug-in hybrid-electric vehicle (PHEV). Your daily round-trip commute to work is barely 30 miles so, recharging the batteries overnight gives you some change back from a ten dollar bill for the weekly cost of electricity. Plus, since you drive entirely on electric juice, there are zero emissions coming out the tailpipe.

Wowzer, what a feeling! But wait, there could be more euphoria in the offing.

What if the local power company was willing—maybe even anxious—to pay you to draw some of the stored energy from your PHEV's batteries while it was parked during the day? Hey, that would reduce the cost of operating the car even more.

That's exactly what Professor Willett Kempton of the University of Delaware and his colleague Dr. Steven Letendre from the Green Mountain College in Poultney, Vermont, came up with in 1966.

Called vehicle-to-grid (V2G) technology, the idea is to take advantage of the electrical storage capacity in the vehicle's battery during hot afternoons when demand is highest and most costly to avoid blackouts. During these periods, energy is worth several times more than overnight when vehicles recharge. It is also possible to provide power to a home or businesses on occasions of high electricity demands to avoid high energy prices and help prevent outages.

Kempton and Letendre's idea isn't just a theory presented in a technical journal. In April, California utility Pacific Gas and Electric Company showcased the first-ever utility V2G technology demonstration. The prototype PHEV was a traditional Toyota Prius with an added Lithium-ion battery. PG&E reversed the flow of energy from the vehicle back to an electrical outlet, then ran several lights and appliances to show how V2G could benefit its customers.

The really big potential of using V2G, however, will come from integrating the technology with renewable energy and thereby reducing harmful emissions. During times of maximum demand, electrical utilities have to buy power from expensive and less efficient fossil fuel power generating sources.

PHEVs will charge their batteries at night when energy is inexpensive and is generated with a larger percentage of renewable resources. When demand is high the next day, instead of turning on a fossil-fuel based generator, the utility can purchase the renewable energy stored in the vehicle batteries.

There are numerous hurdles in the path of V2G, not the least of which is the cost of developing and integrating the technology into the automotive and electrical generation industries on a wide scale. But, because V2G has the potential to radically change both the utility of vehicles and the ability of cities to meet peak electrical demand with significantly lower costs while reducing harmful emissions, don't be surprised if the hurdles are overcome sooner than later.

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