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New technology promising to cut CO2 and save gas

Alternative energy comes from unusual sources -- huge rivers, massive arrays of silicon panels, nuclear reactions, and massive spinning metal blades.   But German researchers are getting power from a source that might strike scientists from decades past as particularly peculiar -- they're making power from automobile exhaust gases.

In an era of ultra-expensive fuel and concerns about emissions fueling global warming, the automobile has come under increasing scrutiny with users looking for ways to extend gas mileage and cut emissions.  Fraunhofer-Gesellschaft, a leading German research organization, is developing materials and designs for a thermoelectric generator which will help to solve both problems.

In automobiles, two-thirds of the fuel used is emitted as waste heat. In total, 30 percent of the energy is lost in heat from the engine block and a further 30 to 35 percent is lost to exhaust fumes.  Many teams of researchers have began to look at how to recapture some of this heat and heat from similar industrial engines and transform it into electricity.  Such devices are known as
thermoelectric generators or TEGs for short.

The TEG generator takes a temperature gradient, driven by the difference between the waste heat and the ambient temperature and uses that gradient to produce electricity.  Greater temperature differences yield great results.  The
Fraunhofer Institute for Physical Measurement Techniques IPM has a number of thermoelectric materials under development that will harvest this heat in automobiles. 

Dr. Harald Böttner, head of the Thermoelectric Systems department states, "The temperatures in the exhaust pipe can reach 700 degrees Celsius or more.  The temperature difference between the exhaust pipe and a pipe carrying engine cooling fluid can thus be several hundred degrees Celsius."

thermoelectric converter the team is developing takes the gradient created by the exhaust gas and uses it to drive charge carriers through a semiconductor.  This creates a looped current flow similar to a battery.  The technology is relatively straightforward, but the real challenge is finding optimal thermoelectrics with high carrier mobility.  The research team is hoping that the device will make the alternator obsolete, providing power to the car's consumer electronics, onboard computers, and charging the battery.  Böttner states, "This would make it possible to cut gas consumption by between five and seven percent,"

Researchers point out that with 50 million cars on the road in Germany with an average on-road time of 200 hours a year per car, if only one kilowatt each was produced by the TEGs, this would amount to
ten terawatt hours per year. 

The researchers are hoping to begin to construct prototypes of their designs very soon.

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Seems expensive
By FishTankX on 6/6/2008 3:18:09 PM , Rating: 2
Wouldn't it be easier to just have the turbo drive the alternator?

RE: Seems expensive
By MrBlastman on 6/6/2008 3:27:16 PM , Rating: 2
That would have a negative effect on the amount of compression the Turbo could achieve creating parasitic drain on the total power output of the engine.

In this case - I think it'd be far greater than the parasitic drain that an alernator hooked directly up to the pullies and belt system.

Or, look at it this way, no longer do you have to wait until 2500 RPM's for your Turbo to spool up and enter boost, but now you have to wait for 5000 RPM's.

That'd suck. Royally.

RE: Seems expensive
By mmatis on 6/6/2008 5:10:58 PM , Rating: 2
Isn't that what turbochargers are supposed to do? I mean after all, superchargers blow...

RE: Seems expensive
By stryfe on 6/6/2008 5:56:48 PM , Rating: 2
Not at all. They both "blow" if you want to put it that way. They both pressurize the engine's intake charge, they just use different methods to do so. A supercharger is belt driven while a turbo charger uses the kinetic energy of the exhaust to drive it.

RE: Seems expensive
By Rugar on 6/6/2008 3:27:17 PM , Rating: 5
Any mechanically driven generator, however it is attached to the engine, will decrease the power available to deliver to the drive train. By using a thermoelectric generator like this, it takes power that is currently lost to waste and recaptures it as electricity. If it can be constructed so that it recovers even a tiny percentage of lost power, it should result in dramatic fuel savings over the lifespan of an automobile.

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