1 November 2007—Thanks to an uncommonly stable lithium chemistry and high-surface-area nanopatterned electrodes, Altair Nanotechnologies’ lithium-ion batteries for electric vehicles (EVs) charge up fast. Very fast. One of the Reno, Nev.based battery developer’s 35-kilowatt-hour packs, capable of propelling an EV pickup truck for 160 kilometers, can fully charge in just 10 minutes—a feat that would be downright dangerous with most lithium batteries. What remains to be seen is whether such rapid charging will prove practical on the street. Although some EV developers, battery experts, and utilities see a breakthrough that will take battery-powered EVs mainstream, others see a technological dead end [See ” California to Rule on Fate of EVs”, IEEE Spectrum, November 2007.
At issue are the awesome power levels required. To charge a 35-kWh battery in 10 minutes requires 250 kilowatts of power—five times as much as the average office building consumes at its peak. That rules out rapid charging at home. Even rapid-charge ”filling stations” stretch the imagination, as you’d need a megawatt power feed—generally available only at electrical substations—to simultaneously operate four power pumps. That is a stretch too far for even some staunch EV proponents. ”I look at 10-minute charging as a gimmick because of the power requirements,” says Andrew Burke, an EV engineering pioneer at the University of California, Davis.
Altair CEO Alan Gotcher acknowledges these difficulties, saying installation of equipment to rapidly charge and discharge modules has slowed Altair’s own R&D program. ”It’s just a lot of power to manage,” says Gotcher.
But what critics see as barriers, Gotcher sees as challenges that can be overcome. He predicts that rapid charging will likely take off first in fleets of delivery vans and other commercial vehicles—a controlled environment where trained personnel will be familiar with each battery and where EVs can be scheduled to minimize the strain on the electrical service. In fact, Gotcher says that Altair is working with an undisclosed energy company considering a rapid-charge station at San Jose (Calif.) International Airport to service EV cabs. (A local cab firm has already ordered 20 five-passenger EV pickups from Rancho Cucamonga, Calif.based EV start-up Phoenix Motorcars, which uses Altair batteries.)
Meanwhile, officials at San Franciscobased utility PG&E Corp., which has ordered four of Phoenix’s rapid-chargeable EV trucks, are excited by the concept of a rapid-charge station. Sven Thesen, supervisor of PG&E’s Clean Air Transportation group, stresses that the utility is still evaluating the business case for rapid charging. But it is safe to say he is undeterred by the power flows required. PG&E has plenty of experience with power and plenty of substations—31 in San Francisco alone.
Thesen says one idea PG&E is exploring is the installation of battery storage at its substations to support rapid charging. The batteries would be charged overnight, thus easing the need to bring in electricity over congested power lines during peak midday hours. Thesen points out that such super -substations present more than a new business opportunity for utilities such as PG&E. The battery banks could do double duty, providing bulk power for rapid charging while simultaneously helping stabilize local power lines. PG&E will be putting some of these ideas to the test in 2008 when it plans to install an EV charging station capable of rapid charging at its Davis, Calif., facility thanks to a US $170 000 grant from the California Air Resources Board.
Looking further out into an EV-rich future, utilities imagine that the EV’s batteries could themselves become a stabilizing force for the grid. PG&E has partnered with EV start-up Tesla Motors to test so-called vehicle-to-grid power controllers by which utilities can draw on the energy stored in EVs plugged into the grid. ”If there’s a power outage, you have energy right there,” says Thesen.
Ironically, such distributed energy storage could also support grid nodes strained by rapid-charge stations, in which case hundreds or thousands of grid-connected commuter vehicles might sell back surplus power to rapid-charge an EV battery that’s on empty.
Ultimately, the challenge for rapid charging may be the notion that something as mundane as power grids—largely ignored by the public and politicians alike—can be catalysts for a radically altered view of power and personal transportation. PG&E demoed vehicle-to-grid technology at the Society of Environmental Journalists’ annual conference this September, showing how power from a modified Toyota Prius could be shifted to the Palo Alto, Calif., grid, in the process running a conventional electrical meter backward. ”It’s nothing sexy,” Thesen admits, ”but it has huge ramifications for society.”
About the Author
Contributing Editor Peter Fairley has reported for IEEE Spectrum from Bolivia, Beijing, and Paris.