Better batteries are making electric motorcycles possible, providing a cleaner alternative to pollution-spewing gas-powered bikes.Advanced battery technologies are enabling a much cleaner alternative to pollution-spewing gas-powered motorcycles and could help promote a larger-scale move toward electric vehicles. Yesterday, an electric scooter with motorcycle-like performance made by Vectrix, based in Newport, RI, was delivered to its first customer. And next year at least two motorcycles powered by advanced lithium-ion batteries will be sold in the United States.Although conventional motorcycles get extraordinary gas mileage--with many getting more than 50 miles per gallon--they emit more pollution than even large SUVs because they aren't equipped with equivalent emissions-control technology. Indeed, with new emissions standards, SUVs are 95 percent cleaner than motorcycles, according to the Environmental Protection Agency. So while motorcycles could help reduce oil consumption and greenhouse-gas emissions, these gains come at the price of dirtier air. Electric motorcycles eliminate tailpipe emissions, keeping pollution out of the city, and they can be powered with clean sources of electricity. What's more, electricity costs less than gasoline. Vectrix estimates that it will cost riders just a couple of cents a day to operate its scooter.
All three battery-powered vehicles are limited in speed. The fastest is the Vectrix scooter, which can go 65 miles per hour. The speeds could be increased if the manufacturers were to change the gear ratio, which is currently designed for urban settings and motocross, for which acceleration is more important than sustained high speed.
Electric motorcycles are practical today because of advances in battery technology. Lead-acid batteries, which have been used in electric motorcycles in the past, are very heavy, provide a short range, and last for only a couple of years. The Vectrix scooter ($11,000) uses nickel metal hydride batteries--the same type used now in the popular Toyota Prius hybrid. This type of battery is lighter than lead-acid batteries and more durable: Vectrix claims it has a 10-year lifetime. Lithium-ion batteries, in turn, are lighter than nickel metal hydride, and new chemistries have made them durable as well, lasting as long as or longer than nickel metal hydride batteries. The Vectrix scooter weighs about 200 kilograms, while the lithium-ion-powered Enertia ($12,000), made by Brammo Motorsports of Ashland, OR, weighs just 125 kilograms. Brammo hopes that the lighter electric motorcycles will be appealing to those who would be intimidated by a heavier bike.
The batteries' light weight also makes them appealing for motocross bikers. Zero Motorcycles, based in Scotts Valley, CA, sells an off-road motorcycle ($7,000) that easily makes 20-meter jumps and will be featured in the extreme-sports showcase X Games, says Neil Saiki, who invented the motorcycle. It weighs just 54 kilograms, which is made possible in part by leaving the battery charger off the motorcycle. The company plans to sell a street version next year that includes the charger. The batteries Zero Motorcycles uses are known for their high power. They come from A123 Systems, of Watertown, MA, the company that makes the batteries used in a record-holding electric drag-racing motorcycle that can finish a quarter mile in just 8.17 seconds, reaching 156 miles per hour. The Enertia uses battery cells and packs from Valence Technologies, based in Austin, TX, whose cells have been used in the Segway personal transport.
In the past, using lithium-ion batteries in a motorcycle would have been a bad idea because of safety concerns. Conventional lithium-ion batteries--the type used now in laptops and cell phones--can overheat and explode, which has led to massive product recalls and at least one death. In one of the electrodes, those batteries use cobalt oxide, a material that makes it possible to cram a lot of energy into a battery. But cobalt oxide is also volatile. If it begins to overheat, the material gives off oxygen, which feeds reactions that lead to "thermal runaway" and flames.
But the new lithium-ion motorcycles rely on advanced lithium-ion chemistries that don't catch fire. The new batteries use phosphate- rather than oxide-based electrodes. It takes much higher temperatures to release oxygen from phosphates, making the batteries very difficult to set on fire, even in safety tests designed to do so.
The motorcycles are limited in range, however. That's in part to keep down costs: big battery packs are expensive. Also, even lithium-ion batteries don't approach the energy density of gasoline. So while the safer lithium-ion batteries enable durable, light, and clean urban motorcycles, they're not going to allow electric motorcycles to compete with gas motorcycles for cross-country touring. The Zero motorcycle is now available with a 40-mile-range battery, and it will have an optional 80-mile pack, Saiki says. The Vectrix scooter can go up to 60 miles on a charge, while the Enertia can go up to 45 miles.
The greatest potential impact of electric motorcycles on greenhouse gases and pollution will likely be in China, where scooters are already a popular form of urban transportation. Electric-motorcycle use could increase there because the Chinese government has cracked down on conventional scooter emissions, according to electric-vehicle market analyst Peter Harrop of IDTechEx, based in the UK. Genevieve Cullen, vice president of Electric Drive Transportation Association, based in Washington, DC, says that electric motorcycles could also play a role in helping bring down the cost of advanced batteries by increasing the market for them.
Source : http://www.technologyreview.com/energy/19069/page2/
