"Change we can believe in" was President Barack Obama's campaign slogan, and whether anyone believes in it, change is exactly what the U.S. is getting. One example is the federal government's policy on energy. The Obama administration crafted the comprehensive New Energy for America Plan, the centerpiece of which is putting 1 million electric vehicles on U.S. roads by 2015. But that aggressive plan raises a concern: Can the country's aging electric grid support these new plug-in hybrid electric and plug-in electric vehicles?
Experts would say yes. In fact, with the right technology, electric vehicles could do more to help the grid than harm it. Through vehicle-to-grid (V2G) technology, plug-in vehicles are capable of adding power capacity to the grid during high demand - known as peak shaving - and also storing renewable energy that can be returned to the grid during peak hours. V2G technology also may benefit consumers who could sell that excess power back to grid operators.
For V2G technology to work, however, plug-in electric vehicles must be grid-integrated. This would require car manufacturers to make vehicles with two-way connections that let them take energy from the grid for charging and give back excess power. They'll also need a control system that grants grid operators access to vehicles' batteries and a way to track energy exchange between the vehicle and grid. Finally concerns remain about the electric grid's stability, despite demonstrations of how the grid and plug-in vehicles can have a mutually beneficial relationship.
Photo: Cadillac Converj concept car/Photo by Kenavt/Wikipedia
The nation's power grid is designed to support peak energy loads, so when electricity demand is low - typically between midnight and 6 a.m. - unused energy is produced by coal- and gas-fired power plants. Charging plug-in vehicles during off-peak hours could use that excess energy, which is what some researchers call "filling the trough." And if plug-in vehicles charge while demand is low, it wouldn't be necessary to increase the grid's delivery capacity.
Additionally grid-integrated vehicles would include a timer to control when charging cycles begin and end. Controlled charging would mitigate too many people charging at any given time, which could overwhelm the grid. "If you have some kind of controlled charging, impacts on the grid will largely be positive," said Paul Denholm, a senior energy analyst for the National Renewable Energy Laboratory.
Willett Kempton, a University of Delaware professor and father of V2G technology, said a Super Bowl broadcast will tax the grid more than plug-in vehicles. "On average a vehicle pulls something like 400 watts, which is about the same as a plasma TV," he said. "The thing about the Super Bowl is everybody turns their TVs on at the same time ... more of a problem than cars, which are plugged in at varying times throughout the day and night."
So the question isn't just if the grid is up to supporting plug-in vehicles, it's also whether these vehicles are up to supporting the grid.
Cars have come a long way since Henry Ford's first Model T produced in 1908. The modern array of energy-efficient vehicles is a showcase of technological advancement.
Plug-in hybrids, like the Chevrolet Volt, have an electric motor and an internal combustion engine, similar to conventional hybrid vehicles. But they differ because their high-capacity lithium-ion batteries can be recharged through an external electrical outlet. The internal combustion engine kicks in when the batteries are depleted, giving the vehicle more range. Full electric plug-in vehicles, like the new Nissan Leaf, are powered solely by rechargeable lithium-ion battery packs, which are recharged by an external power
In either case, the potential benefit to the grid lies in their high-capacity battery technology. According to the U.S. Department of Energy, lithium-ion batteries store three times more energy per pound than the nickel-metal hydride batteries used in the Toyota Prius. But researchers and manufacturers say lithium-ion batteries haven't been developed to support V2G services, and using the batteries to push power back to the grid could significantly shorten their lifespan.
Thomas Turrentine, director of the Plug-In Hybrid Electric Vehicle Research Center at the University of California, Davis, one of the leading institutes in plug-in hybrid development, echoed this sentiment. "For the manufacturers of these vehicles, they're probably not very excited about people using their batteries to provide those services," he said. "Manufacturers first just want to get the vehicles on the road and working properly before they take the next step toward those types of services."
Another stumbling block is a lack of standards for how plug-in vehicles will link to the grid. Tracy Woodard, director of government affairs with Nissan North America in Nashville, Tenn., cited this as one reason Nissan didn't make the Leaf grid-integrated and V2G-compatible. "There's not a communication standard right now between cars and the utilities," Woodard said, "and we really need to see a common standard before we really proliferate that."
Kempton said a committee is working on implementing a communications standard for V2G, including 20 participants from the University of Delaware. He said he anticipates standards will be developed soon.
"From the standpoint of Nissan or any OEM [original equipment manufacturer], of course if they're going to make 50,000 cars a year, which I think Nissan plans to do with the Leaf, they'd like to have a standard already agreed upon, and I can understand that," Kempton said. "On the other hand ... there are other auto manufacturers that are saying, 'We want to try this out on 600 vehicles.'" He said these manufacturers will be prepared when standardization finally arrives.
Some say lack of standards could delay mass production of V2G compatible plug-ins for years. But Kempton said grid-compatible plug-ins could arrive sooner than many observers expect. "I have a fleet running right now, cars that are doing not only grid integration but they're actually also doing vehicle-to-grid," he said. "So that doesn't seem like it's five years away to me."
The framework for energy exchange between vehicles and the grid, according to Kempton, is firmly established although it hasn't yet been deployed on a large scale. He's managing a tracking system that monitors what energy is pulled from and pushed to the grid by vehicles that are part of a larger fleet.
But power from plug-ins won't be attractive unless it's aggregated across multiple vehicles. Grid operators want to attain energy in megawatts (MW), and single vehicles can only deliver power in kilowatts (kW) or tenths of kilowatts. For instance, Kempton estimated that 200 or 250 Nissan Leafs would be needed to generate 1 MW.
For consumers who want to sell power to the grid, energy from their vehicles would have to be packaged with power from other vehicles. This fleet would be managed by an individual who would monitor when and where cars are plugged in, and how much money each vehicle earned. This kind of service is ideal for large companies like FedEx or UPS, as well as government entities with large vehicle fleets like the U.S. Postal Service. Parked cars can turn a profit through V2G connections.
"Right now, we've got four vehicles that are online and they're providing a total of 42 kW to the grid operator [and] getting paid for it," Kempton said. The University of Delaware has six vehicles combined with a larger
fleet to produce 1 MW, which is sold to a grid operator. "Other than the size, which is so small it hardly matters, we are providing a valuable service to the grid; we are getting paid for it, and we have money to redistribute to cars when you get to a size that it's worth setting up an accounting system," he said.
But whether grid-integrated, V2G-compatible vehicles are close to taking to U.S. highways in droves, academics and manufacturers agree that they're coming. Turrentine said the market will be ripe for plug-in electric vehicles once manufacturers start producing the models and integrating them with the grid so they can provide V2G services. "The market for plug-in hybrids in particular ... will be quite solid, especially with the incentives, so we will see consumers buying these vehicles," he said.
Nissan's Woodard agreed. "I definitely see it coming; it's just a matter of getting it implemented."