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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."

The
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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RE: Potato meet exhaust pipe...
By masher2 (blog) on 6/7/2008 1:51:13 PM , Rating: 2
> "So, it doesn't block the exhaust and cannot create an increased back pressure."

Yes, but remember the function of that exhaust is to allow heat to exit, not just hot air. Even without any additional backpressure, a wrapper around the exhaust pipe (or even the engine itself) will have a minor insulating effect, and will thus reduce engine efficiency somewhat.

I have no doubt the overall effect will be very small, possibly even negligible, but it most definitely exists.


RE: Potato meet exhaust pipe...
By MisterChristopher on 6/8/2008 5:17:12 AM , Rating: 2
Masher, your comment does not make sense. The point of a unit like this would be to collect energy in the form of heat and convert it to electrical energy. Therefor instead of insulating, you may actually find that if used in conjunction with an effective heatsincing system, this could potentially convert more heat to electrical energy than energy you might naturally dissapate via radiant heat off your muffler system.

Basically think of these things as a reverse peltier. They could potentially be attached to other radient heat surfaces like the engine block, the radiator, the hood of the car, or any other part of your car where there is a temperature differential between two surfaces because of air flow or coolant channeling. Effective car designs could easily channel air over certain areas.

The amount of current created is based solely on the difference in temperature. This means that when there is only a small difference in temperature between the two surfaces of the peltier, there will only be a small current. But, with well designed heat transfer systems, I can see a potential for creating several zones on the car which make hotspots for this for of energy harvesting. These areas should be able to generate very decent current. Definitely enough to completely replace your alternator, or enough to charge batteries in hybrids very effectively.


RE: Potato meet exhaust pipe...
By masher2 (blog) on 6/8/2008 5:26:05 PM , Rating: 2
> "Therefor instead of insulating, you may actually find that if used in conjunction with an effective heatsincing system, this could potentially convert more heat to electrical energy "

Converting heat energy to another form is more difficult than simply exhausting heat -- all else being equal, any system which attempts to capture the energy of exhausted heat is going to radiate slower than one which does not.

Now while its feasible that this might be outweighed by an "effective heatsinking system", you're then not comparing apples to apples. One could easily put such a heatsink on just the radiator itself, without adding the thermoconverter itself.


RE: Potato meet exhaust pipe...
By MisterChristopher on 6/9/2008 4:01:11 PM , Rating: 2
I'm not comparing apples to apples. I am trying to show a way that this technology could easily equal or surpass the heat dissapation qualities of our current muffler systems. This technology is totoally plausible without creating any additional heat load or insulating effect compared to what we have now. It could possibly even reduce the average heat level dependant on your design and the temperature differentials that design creates.

This technology is excellent. You could go get a peltier right now and start using it to generate electricity without any complicated heatsincing and no insulating. Just get one and strap it onto your muffler. See what kind of current it produces. I bet if you had a few of these thermoelectric units attached to your car, you could power an HHO creation process via waste energy.


By masher2 (blog) on 6/9/2008 4:32:51 PM , Rating: 2
> "Just get one and strap it onto your muffler. See what kind of current it produces"

You're still missing the point. Sure it'll produce current...but it'll also the heat level inside the muffler itself.

A single peltier won't raise it measureably...but it also won't create much current either. Cover the entire muffler surface with them, however, and you'll see not only a higher internal muffler temperature, but a slightly lower fuel efficiency as well.

The laws of thermodynamics are quite rigid. If you want to cool a system, you're going to have to input energy. You can't achieve a cooling effect simply by processing waste heat.


"And boy have we patented it!" -- Steve Jobs, Macworld 2007














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