Driving changes on the grid

Researchers in the US believe that electric-drive cars will be capable of supplying up to 20 percent of the power required by the electricity grid in North America by 2050.

Electric-drive cars can supply to the USA’s power grid as much as 20 percent of the power that it will need by mid-century, suggests research by professors at Green Mountain College in Poultney, Vermont and the University of Delaware.

The concept is called “vehicle to grid” or V2G. The idea is that during the 90 percent of the time that most electric-drive vehicles are sitting parked, they could supply power to the electrical grid.

“This could alleviate electricity shortages and actually make money for vehicle owners when they sell power to the grid,” says Steven Letendre, associate professor of business, economics and the environment at Green Mountain College.

“Most analysts agree,” he says, “that electric drive transportation will be required in the not-too-distant future. We already are seeing hybrid (gas / electric) vehicles becoming popular with the car-buying public. Fuel cell technology is being developed and is viewed by many as having the potential to replace the internal combustion engine. Finally, some still have hope for the battery electric vehicle. Regardless of technology, future vehicles will likely have at least a partial electric drive system. With proper planning, these vehicles could be connected to the electric grid, offering a huge resource for the electricity industry.”

In a previous study done for the California Air Resources Board and the Los Angeles Department of Water and Power, Letendre and Willett Kempton, of the University of Delaware, showed that battery-driven cars, the increasingly popular hybrids, and fuel cell cars each have roles to play as utility resources.

“Battery-powered vehicles must already be connected to the grid to recharge their batteries,” explains Letendre. “Adding V2G capability requires little or no modification to the charging station and about $400 worth of on-board power electronics to the vehicle itself.”

An auto-charge controller in the car would allow the owner to stipulate how much power he or she is willing to sell to the power grid. The driver might, for example, direct the vehicle to always maintain enough charge for a trip of 40 miles, while selling the excess power to the grid.

Hybrid cars – at least 20 models of which are planned for 2005 or 2006 production by major auto companies – could also be configured with specially designed two-way meters to run backwards to sell power to the grid. Hybrids combine an internal combustion engine with a battery and electric motor.

For the future, car makers estimate that fuel cell vehicles could be generally available to the public in the next 10 or 15 years and these, too, could sell excess electricity to the grid.

Letendre and Willet say that while the cost of electricity from electric-drive vehicles appears too high to make it attractive for utilities to buy during “baseload” power times, it is quite marketable for “peak power” times and what are called “spinning reserves” and “regulation services.”

Spinning reserves are generators that are spinning and synchronised with the grid, ready for immediate power feed into the grid if needed in case a power plant would drop off line unexpectedly.

Regulation services involve a generating facility that can ramp power up or down to match the generation of power to consumption. In certain markets, such as California, regulation services comprise a separate power market.

Letendre and Willet calculated that the owner of a hybrid car could net more than $1,500 annually by selling electricity to the “spinning reserves” market. Battery powered electric cars could net from $311 to $720 annually. And fuel cell cars with hydrogen recharge could profit their owners from $2,430 to $2,685 per year by selling in that market.

“Formulas were derived to calculate the power capacity of each vehicle type,” says Letendre.

The total power capacity depends on charger capacity, residential and electrical service capacity, fuel needed for the next trip and several other factors. Vehicle technical parameters were derived from production or prototype electric-drive vehicles.

They found that battery vehicles have power capacity of around 10 kilowatts. Fuel cell vehicles have around 40 kilowatts. Hybrids come in at about 30 kilowatts.

“There are no significant technological barriers to the implementation of the V2G concept,” states Green Mountain’s Letendre.

“V2G could improve grid stability and reliability. It could make electric-drive vehicles more attractive to buyers. These developments could have substantial benefits to the electric industry, to the environment and to society as a whole.”