Researchers work to turn car's exhaust into power
Researchers are competing to meet a challenge from the U.S. Department of Energy: Improve fuel economy 10 percent by converting wasted exhaust heat into energy that can help power the vehicle. That's not a trivial improvement: 10 percent savings would amount to more than 100 million gallons of fuel per year in GM vehicles in the U.S. alone.
So this is where a group of researchers have created a metallic device which is attached to the exhaust pipe, producing electricity from the otherwise wasted heat: a thermoelectric generator, a device that uses temperature differences to create electricity. When installed on a Chevy Suburban, it improved by 1mpg (which is 5 percent). The generated electricity was used to reduce the load on the alternator, therefore using less fuel through reduced parasitic losses. A Suburban produces 15 kilowatts of exhaust heat energy during city driving, which is enough to power three or four air conditioners simultaneously. When cruising between 50 and 60 mph, the generator can produce about 800 watts of power, which is enough to power the GPS device, the DVD player and potentially the water pumps. This device will be installed in a 2009 Suburban and a BMW to check how effective it becomes in real life.Thanks to my friend Chuck for the tip.
[Source: Associated Press]
Reader Comments (Page 1 of 1)
Mike Silva 5:42PM (8/11/2008)
When cruising between 50 and 60 mph, the generator can "produce about 800 watts of power" There's something wrong with this, that's about 20x less heat than stoped. This means the heat is being released without being catched by this system.
Cut this BS of ICE engines and jump on EV's once and for all.
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meme 6:15PM (8/11/2008)
So, in short, a vehicle with a 320hp engine is producing 1hp worth of electricity via this generator. A big wow there :P
Mike: Thermoelectric generators are very inefficient. This being low level heat, they're even less efficient here (nothing is efficient with low-level heat; it's an impossibility, via Carnot's law).
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dm789 6:06PM (8/11/2008)
Nice.. this is interesting.
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dmmb 6:12PM (8/11/2008)
"converting wasted exhaust heat into energy"
Isn't that exactly what a turbocharger does?
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mrbell 7:33PM (8/11/2008)
Yes, but a turbocharger is used to produce power, and they are generally an on-demand device. This doesn't produce any more power, it reduces parasitic losses and it does so relatively continuously where the turbo only does its work under high load conditions.
But of course, you're probably right that a better solution would be to power the suburban 1L to a turbo... On the other hand, there's nothing to stop something like this being used in conjunction with a turbo.
Brent 7:31PM (8/11/2008)
No, they don't use heat for power.... they use the exhaust flow... if they used the heat, you wouldn't need an intercooler. :)
Tyler 7:56PM (8/11/2008)
They do use heat for power. There wouldn't be flow if the exhaust wasn't 1600F. Exhaust flow comes essentially from the expansion of gases as they heat up in the cylinder. You need an intercooler because compressing gases(as a turbo does to the intake air) increases their temperature. Exhaust gases post-turbo or generally quite a bit lower than pre-turbo. That heat energy went into compressing the intake air. But even post-turbo exhaust gases are hot.
BillySharps 6:58PM (8/11/2008)
The only question is how much it will cost. If it's cheap, it doesn't really matter if the amount of waste heat converted is small. If it is expensive, it's probably not worth it.
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killroy 10:33AM (8/12/2008)
The efficiency increase would be a lot more if they just switched to much simpler electric motors to power the car.
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ryan 11:41PM (8/11/2008)
Cool!
Anybody know of any other examples of this idea being used on vehicle exhaust systems?
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rj 11:54PM (8/11/2008)
This has also been done on a large diesel truck.
http://www.hi-z.com/tp2001.php
The output of the generator is dependent on engine load.
The 15 KW is the heat energy not the electrical output of the generator. Thermal electric generators might return 5% of this energy as electricity or ~ 750 watts.
Are those tubes around the outside for cooling water?
An alternator is a hunk of copper, steel etc pretty common materials. A TEG is made up of some pretty rare stuff.
A 20 watt TEG will set you back $200+
http://www.hi-z.com/store.php
where a 1300 watt alternator can be had for $100
Quality vs quantity
Think of energy as currency. You can have the same quantity of money in different forms. A 100 dollar bill has the same face value as 10000 pennies, but the bill is far easier to spend.
Gasoline is a high quality energy, a 100 bill
waste heat is pennies or pesos.
If you see a $100 bill on the ground you pick it up, if you see a penny chances are you don't.
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Serge 12:45PM (8/12/2008)
Waste heat is far from being measured in pennies. To use your monetary analogy you get 20 cents on a dollar when using gasoline. You get even less for your efforts to recycle the other wasted 80 cents of exhaust or radiator-vented thermal engine. Time to retire the ICE.