Magazine article The Futurist

Harvesting Vehicles' Waste Heat: An Innovative Car-Exhaust Mechanism Could Raise Cars' Energy Efficiency by 20%

Magazine article The Futurist

Harvesting Vehicles' Waste Heat: An Innovative Car-Exhaust Mechanism Could Raise Cars' Energy Efficiency by 20%

Article excerpt

Most of gasoline's stored energy never actually powers a single car, according to General Motors (GM) researchers. Half to three-fourths of gas energy is lost as waste heat spilling out of the cars' tailpipes. But GM and competitors BMW and Ford are all separately working on ways to capture that heat energy before it leaves the tailpipe and convert it back into mechanical energy that the cars can use.

"You've got a lot of this waste heat. Let's try to turn it into a mechanical heat and put it to work," says Jeffrey Brown, vice president of Dynalloy Inc.

Dynalloy is helping GM design a thermal recovery system that would be installed near a car's exhaust system and use the escaping heat to generate enough electricity to fully power the car's radio or airconditioning. The system consists of a thin belt of nickel-titanium alloy that loops around three pulleys to form a triangle. One corner of the triangle lies close to the thermal exhaust system, where it is very hot; another corner is farther away, where it is cooler.

The belt automatically expands and contracts in response to changes in temperature: Heat makes it tighten up, while cold causes it to loosen. So as the different areas of the belt are exposed alternately to blasts of hot and cool air, the belt moves along and turns the three pulleys, which in turn move a shaft that drives a generator. The more heat that strikes the belt, the more electricity the generator creates.

"It uses low-grade waste heat that can't be used in a conventional motor," says Alan L. Browne, a GM Technical Fellow and one of the project's leading team members. "We're just harvesting this stuff that is otherwise being dumped into the environment."

The U.S. Department of Energy awarded GM an $8 million contract for waste-heat recovery R&D this year. Ford and BMW are working separately with partner firm BSST.

"This is one of many [waste-heat recovery concepts] that are being explored, but it's also the newest boy on the block. And right now, we are now producing some outputs that are looking very competitive," says Browne.

So far, a 10-gram strand yields 2 watts, enough to power a small nightlight. That would amount to harvesting 4% or 5% more energy. Since the typical combustion engine's energy yield is now just 25%, that would constitute a 20% overall energy-efficiency increase. …

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