Design News is part of the Informa Markets Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Could Car Batteries Back up Our Electrical Grid?

Could Car Batteries Back up Our Electrical Grid?

In the quest to supply electricity for millions of future electric cars, engineers have stumbled upon the most unlikely of energy prospects - the car itself.

If that sounds like a bit of tangled logic to you, then you're not alone. The very idea leaves most intelligent people scratching their heads.

Still, the concept is being examined by auto companies, utilities, universities and industry consultants. And many believe the electric car battery could turn out to be one of the most important sources of current for ... well, the electric car battery.

"This is very doable," says David Cole, chairman of the Center for Automotive Research and one of the industry's most respected consultants. "We're still in the early stages because we don't have high-volume battery production yet. But when that occurs, everything will change."

Indeed, if it happens, it could be a game-changer. Proponents of the idea foresee it happening a little bit at a time. In the beginning, they say, electric cars will "talk" to the grid and determine the best times for charging. That way, they'll grab the energy when the utilities have surpluses. Later on, though, monumental changes will kick in. Car batteries will dump energy back onto the grid when utilities need help. People who need energy - possibly even for their electric cars - will draw it through the grid, from cars that don't need it. Ultimately, experts even foresee a day when retired electric car batteries, connected in long strings inside giant warehouses, will supply energy back to the grid when renewable sources aren't producing.

To be sure, not everyone believes in the vision. Some automakers and utility engineers describe the concept as "interesting," but aren't willing to pencil it into their plans. Those engineers want to know if the concept poses a risk to consumers, or to electrical linemen working nearby. They want to know if repeated, two-way cycling would damage the battery and, if it did, who would be responsible for the damage.

"The business case looks good," says Mark Duvall, director of electric transportation for the Electric Power Research Institute (EPRI). "But it's not clear whether we can provide that service from millions of vehicles intended for transportation. This is not a simple problem."

Talking to the Grid

Simple or not, the idea has trickled into the technological mainstream, and it appears to be gaining momentum. Searching the term "vehicle-to-grid" on Google yields about 20 million hits, an extraordinary number by any measure. Moreover, automakers such as Ford Motor Co. are considering the lowest levels of the concept. And utilities have begun to take on vehicle-to-grid investigations, too.

The concept has built favor over the past few years as several market forces have coalesced. The stampede to electric vehicles and hybrids has highlighted the need for more electrical capacity, while a separate move toward renewable energy has left some utility engineers wondering where the power will come from.

The crux of the problem is simple but unappreciated: Wind turbines make energy only when the wind blows; solar cells generate current only when the sun shines brightly. Moreover, the electrical current created by those sources must be used immediately. With only a few minor exceptions, utilities don't have a way of storing that energy for later use.

"It's a problem," says Cole of CAR. "You have to figure out what you're going to do if the wind isn't blowing and the sun's not shining."

That's where the electric car battery comes in. One simple solution involves charging electric cars and plug-in hybrids at a time of day when demand is low. Utilities want to "incentivize" such consumer behavior by dropping the price-per-kilowatt-hour at night, and then working with automakers to enable vehicles to make such decisions on their own. The vehicles would do that by incorporating an ability to "talk" to the electrical grid, via a wireless or wired connection. Doing so, a vehicle could decide to re-charge at 3 a.m., when rates are lower.

Ford has already demonstrated the concept on a 20-vehicle fleet, using the cars' navigation screens as an interface to communicate with a smart electrical meter. The automaker accomplished that in wireless and wired fashions, using a ZigBee communications protocol for wireless and a SAE J1772 connector for the hard-wired version.

"The idea is to acquire information from the vehicle and transmit it outside," says Greg Frenette, manager of Ford's battery electric vehicle applications. "For example, if you want to communicate the battery's state of charge, there are a number of ways to transmit that signal to the charging source. But to do that, we need an open-architecture solution that crosses all the industries involved. We have to develop common codes, standards and protocols that ensure the customer in Maine has the same seamless experience as the customer in California."

The Society of Automotive Engineers (SAE) has already formed a committee to create such codes and standards. SAE J2293 is establishing requirements for transfer of electrical energy to EVs, Frenette says.

For automakers, the hardware for such transfers is likely to look like the HomePlug, a well-known product designed for standards-based home powerline networks. A digital signal will be piggybacked onto the powerline of a charging cable, enabling the exchange of information in a "smart energy profile." That way, the car communicates its needs to the grid, and the grid understands them.

"The car will want answers to some basic questions," says Duvall of EPRI. "For example, it might want to know, 'What's the price of electricity over the next 24 hours?'"

Technology companies are already springing up with new products to meet such needs. GridPoint Inc., for example, has rolled out smart charging software that manages the flow of electricity to plug-in vehicles and charging stations,

enabling the utilities to balance the grid conditions against the needs of drivers.

What's more, automakers and utilities are envisioning other ways of empowering vehicles. Hybrids with electrical architectures supporting 300V, 400V, 500V and even 600V have sprung up, enabling cars to power a home during an outage or handle the electrical loads temporarily when electricity prices run high.

"Let's say it's really hot out and electrical prices are high," Duvall explains. "You could use a vehicle-to-home arrangement. Instead of pulling power off the grid at 30 cents per kilowatt-hour, you pull it out of your vehicle. Then you recharge it at 3 a.m., when electricity prices drop to 5 cents per kilowatt-hour."

Two-Way Power Flow

Such concepts, however, pale by comparison to the true vehicle-to-grid vision. That vision, often credited to Willett Kempton, an associate professor and senior policy scientist at the University of Delaware, calls for vehicles to dump power back onto the grid at key times.

Kempton, who published peer-reviewed papers on the topic as far back as 1997, says he believes the two-way flow of electrical current offers far more potential than the one-way scenario. "What we are doing has 10 times more economic value," he says.

Kempton's vision involves a connection between the electrical grid and a centralized server, which would track all the cars under its jurisdiction.

"In a business, you would have cars that subscribe to the service," he explains. "And when the cars are plugged in, the server would know where they are. It knows their state of charge and the size of their plug. And when the grid says, 'I have too much electricity or not enough electricity,' the server meets its needs." In essence, Kempton says, the server would initiate flow of current from parked cars back to the grid, where the additional current would relieve the utility's temporary load imbalance.

Kempton's idea of vehicle-to-grid might use a wireless Internet connection or an SAE-approved hardware link, such as the J1772 plug. Either way, he says, the key would be the server's ability to instantaneously allocate electrical current from thousands, or even millions, of vehicles back to the grid in a momentary time of need.

Although automakers and utilities won't openly commit to the concept, they agree with Kempton on one critical point: The technology's success depends largely on its ability to motivate automotive owners to unload their battery charge back onto the grid. Such motivation, they believe, would have to come in the form of cash.

"If you're going to put equipment on a car that allows bi-directional power transfer, then you need to offer the consumer an almost-daily return," Duvall says. "Vehicle owners will be interested in something that pays them a non-trivial amount of money. If we can convince the owners that they'd net $500 a year, then they'd be very interested."

Designed correctly, Kempton says he believes the concept would have a "negative cost" - in other words, a gross monetary gain for the consumer of between $1,000 and $5,000 a year.

Automakers and utilities are still unsure whether the idea is workable, however. They point to a multitude of potential problems: Can the vehicle transmit energy back onto the grid in a safe manner? Is there risk to the consumer? If a $20,000 lithium-ion battery is damaged, who's responsible? The utility? The automaker? Most important: Will electric vehicle batteries stand up to the repeated cycling?

Kempton argues that new batteries, capable of multiple thousands of cycles, are already on the horizon. Altair Nanotechnologies Inc., for example, has produced a lithium-titanate battery that connects directly to the electrical grid and stands up to 5,000 cycles.

Still, the auto industry is withholding judgment for now. "There's been an awful lot of hype around this topic for the past several years," says Frenette of Ford. "But we really need detailed, data-driven information that government and industry can build a consensus around."

Battery Backup

Even if vehicle-to-grid fails to capture industry support, many experts say they believe EV batteries will still provide storage for the electrical grid. In a separate scenario, engineers say utilities could link long strings of used lithium-ion batteries in vast battery farms that would provide balance for the grid at a moment's notice.

"After the battery is done with its life in the car, it still has a lot of years remaining," says Cole. "It may not have quite the capability you'd like in a car, but it can do fine in a battery farm."

Utilities are already employing such battery farms. Golden Valley Electric Authority in Fairbanks, AK uses a nickel-cadmium Battery Energy Storage System capable of producing 27 MW of electricity for 15 minutes. Similarly, a lead-acid battery farm in Sabano Llana, Puerto Rico provides 20 MW for 15 minutes.

Ultimately, the use of such storage could depend on the spread of renewable energy. As wind and solar gain momentum, utilities are likely to reach for alternative means, and the most thoroughly understood solutions are likely to appear first. That's why most industry engineers believe simple grid communication and one-way current flow are likely. In a few years, they say, vehicles with grid-ready interfaces could start to reach production.

Whether two-way, vehicle-to-grid energy transfer will be adopted in the next few years is another matter. "There are still a lot of open questions," Frenette says. "People will consider it more seriously when we understand the implications from a vehicle standpoint and from a consumer standpoint."

Still, automotive experts say they're optimistic over the long term.

"The technology is here; no invention is necessary," Cole says. "Don't bet against it."

Click here for a list of vehicle-to-grid technology peer-reviewed V2G articles.

Hide comments


  • Allowed HTML tags: <em> <strong> <blockquote> <br> <p>

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.