A new Dutch invention can make cars, busses and other vehicles no less than 50 percent more efficient and thus more environmentally friendly. Better still, the technology is already available; it all comes down to a smart combination of existing systems.

This winter, in the city of Apeldoorn, a city bus will be used to prove that the claims about the new invention are true. These are quite bold. E-traction, the company that developed the bus, boasts fuel savings of up to 60 per cent, with emissions down to only a fraction of the soot and carbon dioxide an ordinary bus would blow out of its tailpipe.

In addition, the test bus requires no adaptation, its drivers need no extra training and there'll be no discomfort for passengers. It will simply run on diesel, just like all the other buses, and it should be just as reliable. One thing however will be very different; the Apeldoorn bus hardly makes a sound, hence its nickname "the whisperer".

In-wheel engine All this is made possible by an �in-wheel' electric engine, in fact nothing more than a normal electric engine turned inside out.

The outer wall of a traditional electric engine is a cylinder lined on the inside with copper wire. If electricity is fed into the copper wire, the current will circle the cylinder on the inside at high speed. Cylinder and wire together are called the �stator' (because it doesn't move). To change the electricity running along the inner wall of the cylinder into movement, another part of the engine comes into play: �the rotor'. This is in fact an axle, mounted in the centre of the cylinder, with permanent magnets attached to it. The electrical current in the stator pulls the rotor magnets along and the axle starts to turn.

The wheel works precisely the other way around. The fixed part of the engine - the stator - is now on the inside. The wire is wrapped around it.

The moving part of the engine � the rotor - is no longer an axle fitted with magnets but a ring running on the outside of the stator.

The magnets are fixed on the inside of this ring. If power is fed into the engine the magnets will � as before - follow the current, but now it's the ring on the outside, which will turn.

Eureka And that's what makes �the whisperer�revolutionary; a ring functioning as a wheel. By just putting a tire on it you can drive a bus, a car, anything with it. Since the wheel is in fact the engine, no axles or any other friction-producing and therefore energy-wasting mechanical parts are needed.

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