Fuel Efficiency Increases 20%

A new approach to harvesting the waste heat from a car's engine could improve fuel efficiency by more than 20 percent. The key component is a nickel-titanium alloy that expands and contracts with changes in temperature.

A thin belt of the alloy is looped around three pulleys, forming a triangle. One pulley is located close to the exhaust system, where it can pick up heat. Another is placed further away, where it's cooler. As the temperature differential increases, different areas of the belt expand and contract to move the pulleys. This motion can be captured to drive a generator shaft and could create enough electricity to power the air conditioning system or radio, for example.

A mere 2-gram strand of the alloy will generate up to 2 watts of power. At current typical levels for a gasoline engine, that amounts to a nearly 20 percent increase in energy efficiency. But the technology is not limited to cars; diesel trucks and trains that run continuously for long periods are excellent candidates for waste-heat recovery systems.