Induction motors: The Difference Engine: Tesla's revenge

Some in Washington are wringing their hands over possible shortages of so-called “critical materials” for America’s high-tech industries. In particular, the Department of Energy frets about certain metals used in manufacturing wind turbines, electric vehicles, solar cells and energy-efficient lighting. The substances in question include a bunch of rare-earth metals plus a handful of other elements which—used a pinch here, a pinch there—enhance the way many industrial materials perform.

It is not as though the rare-earth elements—scandium, yttrium and lanthanum plus the 14 so-called lanthanides—are all that rare. Some are as abundant as nickel, copper or zinc. Even the two rarest (thulium and lutetium) are more widely spread throughout the Earth's crust than gold or platinum. But because they have similar chemical properties, and tend to be lumped together in rocks along with radioactive thorium and uranium, extracting and refining them can be difficult, expensive and messy. Disposing of the toxic waste is one of the biggest headaches.

A decade ago, America was the world’s leading producer of the rare-earth metals. But its huge open-cast mine at Mountain Pass, California, closed in 2002—a victim of China’s much lower labor costs, America's increasingly stringent environment rules, and delays in renewing the mine’s operating license. Today, China produces 97% of the world’s supply of rare-earth metals—a by-product of the country’s vast iron-ore mining operations in Inner Mongolia. Over the past year, the Chinese authorities have cut back drastically on exports of rare-earths, as China's own high-tech industries absorb more of the output.

The rare-earth the Department of Energy seems particularly paranoid about is neodymium. This is widely used for making super-strong permanent magnets. Over the past year, the price of neodymium has quadrupled, as electric motors and generators that use permanent magnets instead of electromagnetic windings in their rotors have proliferated. Cheaper, smaller and more powerful, permanent-magnet machines have been one of the main factors behind the increasing popularity of wind turbines and electric vehicles.

That said, not all makers of electric vehicles have rushed to embrace permanent-magnet motors. For one, the Tesla Roadster, an electric sports-car based on the Lotus Elise, uses no rare-earth metals whatsoever. Nor does the Mini-E, an electric version of BMW’s recreation of the iconic 1960s car. Meanwhile, the company that pioneered much of today’s electric-vehicle know-how, AC Propulsion of San Dimas, California, has steered clear of permanent-magnet technology. More recently, Continental AG, a German car-components firm, has developed an electric motor for a forthcoming European electric vehicle that likewise uses no rare-earths. Clearly, a growing number of car companies think the risk of depending on a single (and not so reliable) source of rare-earth metals is too high.

The latest car-maker to seek a rare-earth alternative is Toyota. The world’s largest car-maker is developing a neodymium-free electric motor for its expanding range of hybrid cars. Following in AC Propulsion’s footsteps, Toyota has based its new design on industry’s electromotive mainstay, the cheap and rugged alternating-current induction motor patented by Nikola Tesla, an American inventor, back in 1888.

http://www.economist.com/blogs/babbage/2011/04/induction_motors&fsrc=nwl