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Old 08-11-2008, 06:40 AM   #1
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Exhaust Thermoelectric Generator

I would take this with a grain of salt...
http://www.physorg.com/news137649222.html
A claim of 5-10% (depending on which part of the article you are looking at) increase in fuel economy is overly optimistic in my opinion.



Note the tiny tubes. Since there are no heat sinks on the TEC devices I will assume that these are for a liquid coolant, which means there is some method of pumping and a heat exchanger involved.

The best TEC devices only have about 5% efficiency, and the voltage output is small. A good number of then would have to be wired in series to produce a usable voltage for a car.

I experimented with these devices last year:
http://flapdoodle.250free.com/cooler.html
For those of you wondering how cooling relates to generating electricity, the devices work in reverse as well, but the efficiency is lower.
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Old 08-11-2008, 07:17 AM   #2
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I ran some calculations on these and got figures I didn't like. It's potentially possible though that a specific for application device engineered for mass production could be considerably better than the retrofit device I was contemplating, that would have to be made out of available parts.

NASA's thermoelectric devices have some quirks that I can't see translating into useful features for automobiles. Firstly they'll be working off a radioactive source that can be completely surrounded, secondly their "cold sink" is the background energy of the universe 6 Kelvin or something like that. Probably working with a 500 Kelvin differential.

I do have several approaches in mind for messing with exhaust gas energy extraction though.
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Old 08-11-2008, 08:03 AM   #3
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Quote:
Originally Posted by RoadWarrior View Post
I ran some calculations on these and got figures I didn't like. It's potentially possible though that a specific for application device engineered for mass production could be considerably better than the retrofit device I was contemplating, that would have to be made out of available parts.

NASA's thermoelectric devices have some quirks that I can't see translating into useful features for automobiles. Firstly they'll be working off a radioactive source that can be completely surrounded, secondly their "cold sink" is the background energy of the universe 6 Kelvin or something like that. Probably working with a 500 Kelvin differential.

I do have several approaches in mind for messing with exhaust gas energy extraction though.
In another thread that I can't remember right now I had looked into using commonly available thermoelectric generators from gas furnaces to be strapped to the cat and power a HHO setup. By my calculation it would require about 16 of them to produce a usable voltage, and at ~$70/ea I just dismissed it as being too expensive to be practical.

-Jay
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Old 08-11-2008, 08:35 AM   #4
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I just came up with an evil plan today though... I was trying to think of a 2-300mV source for an O2 sensor offset, then I thought, thermocouple!
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Old 08-11-2008, 10:12 AM   #5
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By my calculation it would require about 16 of them to produce a usable voltage, and at ~$70/ea I just dismissed it as being too expensive to be practical.

-Jay
They are fairly cheap on eBay (like $11 including shipping), BUT even 16 would be $176 and I would expect an output of maybe 120Ma.

Speculation:
GM posted a 2nd quarter loss of $5.5 billion this year. GM in the past systematically went city to city buying up all the natural gas public buses, then had them crushed for scrap. The TEC generator is but one in a series of pie-in-the-sky promises of better FE "just around the corner".

Could it be that it is a feeble attempt to persuade the public to stay with gasoline? Why is the photo they released 10 years old? What were they doing in those ten years, and why not some solid output figures if this is a such ground breaking device?
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Old 08-11-2008, 10:17 AM   #6
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I thought GM bought up trolleys and electric busses that ran on overhead wires leftover from old trolley lines to sell gasoline and diesel busses in the 50's.

-Jay
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Old 08-11-2008, 10:20 AM   #7
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I found the post... Here it is...

Quote:
Originally Posted by Jay2TheRescue View Post
I have a question... Would the extra 40 - 50 pounds from carrying an extra battery negate any gains from using said battery to power an HHO setup?

-Jay

EDIT: I looked into thermoelectric generators. There is a quite common one used in boiler controls. The downside is that it only generates 750 mv, and costs $70. 16 connected in a series and strapped to the cat would generate the voltage required using waste heat, making it "free" without adding any load to the alternator or having to lug around an extra battery. The problem comes with that it would cost over $1,100 for this thermoelectric setup.
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Old 08-11-2008, 10:30 AM   #8
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I thought GM bought up trolleys and electric busses that ran on overhead wires leftover from old trolley lines to sell gasoline and diesel busses in the 50's.

-Jay
After you posted that I realized you are correct. I did find this:

GM Executive Raises Natural Gas As Alternative To Gasoline
Tuesday, August 05, 2008
CNN Money -- DETROIT -(Dow Jones)- General Motors Corp. (GM) may add natural gas to the arsenal of energy alternatives it hopes will one day make gasoline a scarcity on U.S. roads.

GM's top researcher said in a recent blog posting that the auto maker considers natural gas an "enticing" alternative to petroleum, signaling a new interest in the fuel by GM as it struggles to combat the effects of soaring gasoline prices.

"It is abundant, affordable and relatively clean," Larry Burns, GM vice president of research and development, said in a posting on GM's Fastlane blog.

The world's auto makers are scrambling to find new, commercially viable alternatives to gasoline as the reality of $4-per-gallon gasoline wreaks havoc on the U.S. auto industry.
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Old 08-11-2008, 10:31 AM   #9
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some people have said that the optimum voltage for an HHO cell is somewhere around 1.2 volts. if this is true than you could get away with just two but how much current would this thing be able to produce before the voltage started to dip away.

I still have my doubts about HHO but hey this is another idea
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Old 08-11-2008, 10:38 AM   #10
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It would still take a Brazilian of them (Bush reportedly thinks a Brazilian is a very big number). A watt is a watt regardless of voltage.
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