Wheel Magnets May Soon Power Electric Cars

Cars have traditionally been wasteful beasts. Every time a drop of gas explodes inside a cylinder, the energy gets passed along from the piston to the crankshaft, flywheel, gearbox, drivetrain, and axles. By the time the wheels actually turn, four fifths of the original energy has disappeared. The electric car goes a long way toward reducing wasted energy by replacing the internal-combustion engine with batteries. Even so, electric cars destroy about 60 percent of the energy because mechanical parts are still used to deliver energy from the batteries to the wheels. Lately, though, engineers have come up with a far more efficient way to accomplish the same task: by using magnets in the wheels.

Wheel motors promise to wring more efficiency from the electric car, bringing the truly energy-efficient car another step closer to reality. The mechanism is surprisingly simple. Each wheel hub has a ring of electromagnets inside. Another ring of magnets lines the rim of the wheel, which fits over the hub. A rapidly alternating pulse of electricity through the electromagnets in the hub changes the polarity of magnets many times each second, causing the wheel to turn. The only moving parts, aside from the wheel itself, are the ball bearings.

About 200 test cars, buses, and trucks have been built with wheel motors, according to Frost & Sullivan, an automotive consultancy based in Mountain View, California. Roughly 20 companies are developing or studying the technology, including BMW, Ford, General Motors, Honda, Mitsubishi, Renault-Nissan, Siemens, and Volvo, as well as wheel and tire makers Bridgestone and Michelin. Two- and three-wheeled vehicles that use wheel motors are already being sold, especially in China, and four-wheeled models are poised to enter production this fall.

ZAP Electric Vehicles, an electric automaker in Santa Rosa, California, will soon start manufacturing wheel-motor passenger cars—a roadster, a pickup, a sedan, and a minivan—at a factory in Franklin, Kentucky. CEO Steven Schneider says the firm can make a pair of wheel motors for less than the cost of a combustion engine with its "ungodly amount" of moving parts. Auto labor is going cheap, and the state of Kentucky pitched in $68 million for the factory. Schneider expects sticker prices of between $14,500 and $35,000.

In July the first of four city buses retrofitted with wheel motors began carrying passengers in the Dutch city of Apeldoorn. The technology, developed by e-Traction, a Dutch company supported by Volvo, has more than 600kg of batteries, which are charged by the bus's internal-combustion engine. The system is expected to reduce diesel consumption (and emissions) more than 30 percent. Wim Kurver, an executive at Veolia Transportation, a French company that operates city buses in the Netherlands, estimates that in five years more than 200 Veolia-operated buses in the Netherlands will use wheel motors. Buses are driven long hours, so they will likely recoup the cost of wheel motors with fuel savings much faster than family cars.

Although costs are falling, wheel motors are generally more expensive than conventional drivetrains, and they don't handle as well as conventional cars. Wheel-motor vehicles may not catch on in a big way for a decade or so, but improvements in the technology and the push for efficiency could transform ring magnets into a new standard for powering cars.