CC-licensed: FrankH

Proponents of renewable energy often gloss over its spiky nature, but researchers are starting to explore the possibility of using electric cars to smooth it out.

Wind, wave, solar and other forms of natural energy deliver clean, guilt-free power, but the problem is that the power doesn't come in a smooth, controlled stream like that of a coal or nuclear plant. A sunny day yields far more energy than a cloudy one, for example, but is counterproductive for wind and wave power. A blustery day means the opposite problem.

You can't really store power for long periods, so this unpredictable nature means that energy suppliers who use renewables have to rely on other sources too. In practice, that usally means ramping natural gas power stations up and down on the fly to match both the well-known demand curve of domestic and industrial customers, and fluctuating renewable supply.

Researchers have theorised for some time that massive arrays of batteries, distributed across the country, could help alleviate this problem. But no infrastructure for those batteries has been in place, until now. The tens of thousands of electric cars that are going to begin rolling off production lines in the next couple of years all contain batteries which could be used for storing power from the national grid.

This is known as vehicle-to-grid, or V2G. When demand is low but supply is high, your car battery is used to store excess power. Then, when demand is high and supply is low, it feeds it back to other local customers -- perhaps even your own house. Electricity companies would pay the owners of the vehicles for providing that power.

For this to be accomplished, however, you need to yield some control of your battery over to your electricity supplier. This can be accomplished physically by running a data connection through your power socket. Adding that and a convertor that let power move both ways through the battery, would mean that electricity grids would be able to use large numbers of electric cars to store surplus energy.

Pilot projects have begun in a number of countries -- Sweden, Italy and Japan have all begun testing the technology. Denmark, however, is taking things even more seriously. The country gets 20 percent of its power from wind farms, but on some particularly windy days those farms can supply the entire country, with energy to spare.

A paper recently published in Renewable Energy by Claus Ekman, a researcher at the Risø National Laboratory for Sustainable Energy, examines how many cars would be needed to power different numbers of homes. He discovered that 500,000 vehicles drawing from 8 gigawatts of wind power could reduce the wasted energy by as much as 800 megawatts -- 10 percent of the total, and enough to power about 200,000 homes. Ekman says this is "significant but not dramatic".

Potential problems with the technology include a worry that this excess usage could harm battery lifespan, however, this hasn't yet proven to be an issue in the trial schemes.

With many companies, including Denmark, aiming to ramp up their renewable energy production considerably in the coming decades, some way of regulating the supply will be necessary. With many countries also putting their weight behind electric vehicles and plug-in hybrids, this could prove to be a marriage of more than just convenience.


  1. Yes. Electric Cars and Renewables go together.Dr.A.Jagadeesh Nellore(AP),India  

    Jan 25th 2011

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