It’s a hot and smoggy day in Washington, DC, and things aren’t going well for Les Goldman, a longtime energy lobbyist whose latest project is a new kind of car that is supposed to slash gasoline consumption and reduce greenhouse-gas emissions. We’re outside his office, a block from the White House and a quick trip down Pennsylvania Avenue from Capitol Hill. And Goldman is sweating at the back of the “plug-in” hybrid that I’m supposed to test-drive, checking electrical connections and trying to figure out why it isn’t working.
The car is a modified Toyota Prius with an extra battery installed in the spare-tire compartment. Conventional hybrids like the Prius run on an electric motor part of the time, but the electricity they use is generated by a gasoline engine and by capturing energy from braking. In the plug-in version of the car, the extra battery can be recharged from an electrical outlet. The battery stores about 40 miles’ worth of electricity; if it’s depleted, the car reverts to conventional hybrid mode.
The few plug-in vehicles on the road today are prototypes that, as Goldman is discovering, aren’t always reliable. But recent advances in battery technology have attracted the attention of major manufacturers, raising the possibility of a mass-produced plug-in car. General Motors has announced that it is developing plug-in hybrids that use advanced lithium-ion batteries and could be ready within a few years. One of the GM designs–for a car known as the Volt–calls for a gasoline engine that kicks in after 40 miles just to recharge the battery. Toyota also says it is researching lithium-ion batteries and testing plug-in vehicles.
An electric battery with a 40-mile range could nearly eliminate trips to the gas station for many drivers, since Americans drive just over 30 miles a day on average. But unlike earlier, all-electric cars, the new hybrids could handle longer commutes; the Volt is designed to travel 600 miles using its backup gas tank to charge the battery. And electricity from the grid is cheap: the equivalent of a gallon of gas costs less than a dollar.
A123 Systems' Automotive Lithium-Ion Battery
The environmental arithmetic is also favorable. Generating the electricity to power plug-in cars causes less greenhouse-gas pollution than burning gasoline does, according to a recent study by the Electric Power Research Institute and the National Resources Defense Council. Even in the worst-case scenario, in which a plug-in vehicle got all its electricity from coal-fired plants (in reality, electricity in the United States comes from a mix of sources that on average release less carbon dioxide than coal plants do), it would still be responsible for a third less greenhouse-gas pollution than a conventional car. And though plug-ins and conventional hybrids would account for similar amounts of greenhouse-gas emission in most parts of the country, plug-ins in areas with clean sources of electricity, such as hydroelectric power, would be responsible for about half the carbon dioxide emissions of other hybrids.
Unlike other alternative technologies, such as cars powered by hydrogen fuel cells, plug-ins don’t require any significant new infrastructure. Existing gas stations would provide the fuel for long trips, and electrical outlets in garages would provide the power for short commutes. (Eventually, charging stations could be installed for city dwellers.) And plenty of electricity is available, particularly overnight. According to a study from the Pacific Northwest National Laboratory, there’s already enough excess generating capacity at night to charge 84 percent of the cars, pickups, and SUVs on the road today, if they were all suddenly converted into plug-in hybrids.
A couple of weeks after my ill-fated attempt to test-drive the plug-in car in Washington, I’m outside the headquarters of battery maker A123 Systems in Watertown, MA. Out front is the shiny, aggressively styled GM Volt. The car is there because GM has selected A123 as one of two companies that could end up providing the battery technology for the Volt.
A123 makes a new type of lithium-ion battery. Lithium-ion batteries, which are now used widely in laptops and cell phones, pack a lot of energy into a small space. They take up just one-sixth the space of the lead-acid batteries used in previous types of electric vehicles, and they weigh one-sixth as much. They also take up less than half the space of nickel-metal hydride batteries, the kind used in today’s conventional hybrids, while weighing just a third as much.
But the type of lithium-ion battery that’s used in laptops and cell phones has problems, including the occasional tendency to overheat and, in rare cases, burst into flame. Troubling as this instability is in personal electronics, it could be even worse in a car, which uses a module that consists of hundreds of times the number of batteries found in an electronic device. On top of that, although prices have been coming down gradually, lithium-ion batteries are still expensive.
All that could change as a result of A123’s batteries, in which electrodes based on cobalt oxide have been replaced with iron phosphate electrodes. At relatively low temperatures, oxides release oxygen, which can drive reactions that might heat up a battery and cause it to explode. But phosphates continue clinging to oxygen at much higher temperatures. What’s more, iron is far cheaper than cobalt.
Volt or Bolt?
There is a giant “if” in all this, though. To become practical and economically viable, plug-in vehicles will need to be mass-produced.
Will automakers follow through on their highly publicized announcements about plug-ins? GM, for one, has a reputation for quitting on innovative engineering; the company’s executives scrapped an earlier all-electric vehicle. And even though GM had an early lead in conventional hybrid technology, it failed to bring hybrids to market until after the success of Toyota’s Prius. What will happen to plug-in plans if gas prices drop, or if interest in reducing greenhouse gases wanes?
No one can predict the results of the carmakers’ fickle decision-making process. But a few things are clear. Plug-ins are the most practical and enticing alternative to the internal-combustion engine that has been developed in years. And their fate will depend on whether automakers learn from the success of conventional hybrids and fully embrace the new technology.
I did at last drive a working plug‑in. The converted car glided noiselessly along the streets of Boston as I eyed a gauge that estimated my mileage at more than 150 miles per gallon. But on the day that I saw the Volt on display at A123’s offices, GM wasn’t giving rides; the car was just a mock-up, without the new batteries. As I sat in the driver’s seat and grasped the steering wheel, sunlight streaming through the clear roof, it was easy to believe that plug-ins are on the way. But the mock-up was also a harsh reminder that when it comes to green innovation, U.S. automakers have long been more eager to show off flashy concept cars than to manufacture vehicles that work.
Kevin Bullis is the nanotechnology and materials science editor at Technology Review.
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