h a l f b a k e r yOn the one hand, true. On the other hand, bollocks.
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Use a bank of thermocouples to harness all
waste heat from engine to charge the car
Battery, thus eliminating the need for an
altenator and useing all that power going to
waste as heat. Could be integrated into the
head, block, radiator, exaust manifold you
name it. More power from your engine
and
more efficient.
Hi-Z
http://hi-z.com/doc...Z.Brochure.2006.pdf
Recovers exhaust heat as electricity. <edit>6 years later, link juggle - but mostly the same info [lurch, Sep 22 2005, last modified Feb 25 2011]
Another possibility in a similar vein
http://www.powerchips.gi/
A more efficient method of converting heat to electricity [NoOneYouKnow, Sep 24 2005]
[link]
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"The second law of thermodynamics holds, I think, the supreme position among
the laws of nature. If someone points out to you that your pet theory of the
Universe is in disagreement with Maxwell's equations - then so much the worse
for Maxwell's equations. If it is found to be contradicted by observation -
well, those experimentalists do bungle things up sometimes. But if your theory
is found to be against the second law of thermodynamics I can give you no hope;
there is nothing to do but to collapse in deepest humiliation." |
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~ Arthur S. Eddington (British Astrophysicist, 1882-1944) in The nature
of the Physical World (1928) |
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This would recover an extraordinarily small amount of heat, and increase the efficiency of your engine imperceptibly. |
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""This would recover an extraordinarily
small amount of heat, and increase the
efficiency of your engine imperceptibly."" |
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But would it charge the battery? and if so
could it eliminate the alternator? if so i
think that you would gain from no
altenator. |
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In my car, when I turn on a high power electric device like the rear window defogger, there definitely is a perceptible change in the load on the engine. This means two things. One: eliminating the alternator would produce a perceptible change in performance. And two: some high power devices like head lights and window defoggers probably use more power than could be produced by thermocouples. Could someone who is familiar with the power characteristics of thermocouples second that? |
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I know nothing, but google found me "High-Power Thermocouple,100 kHz to 4.2 GHz, 25W". Alternators push out in the region of 500W-1kW, so you'd need about 20-40 high power thermocouples in a bank. I doubt this would really work, but the figures seem to hold up so I'm bunning until anyone points out that I don't know what I'm talking about. |
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Sorry, [wags]. The thermocouple you cite is a measurement device, and provides a small signal proportional to RF (Radio Frequency) power in a waveguide. In no way does it produce 25 W of useable power. |
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Thermopiles (large quantities of thermocouples in series/parallel) do produce useable energy, but to be useful, must run on much wider temperature differences than seen on an IC engine. |
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Uh, guys, sorry to distrupt the flow of 'bad technology' calls here, but - and this feels wierd because I am usually the one trying to drag people to look at the thermodynamics laws - if you extract heat from your exhaust system, your IC engine does not lose output efficiency. If anything, it might gain just a smidge because you are allowing it to work across a higher delta-T. Anyway, this solution is feasable, a bit on the expensive side, needs a lot of heat input to produce a worthwhile output, doesn't quite entirely replace the alternator, and is Baked. See link. |
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Nice - I want one. But only if the Mack comes with it. |
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Thanks for the link i'm glad someone is
doing it already, but i'd like to see it go
further put them in the radiator on the
head everywhere, but as mentioned before
money is the problem. |
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This has been experimentally baked, but as some have said already, a usefully-sized thermopile is very expensive, and somewhat heavy. Simply carrying around this extra weight around will negate most of the benefit. The little bit of savings left will not be enough to offset the cost of the device over the life of the car.
So, not a bad idea, but not presently viable as a marketable product either, purely due to economics. |
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There really is an engine that has very high effeciency and it is related to the old German WWII Pulse Jet engine. I know, this is not related to this thermocouple idea...much...but this engine is reported to have produced 95% efficiency...impossible, I know. And I have searched for a link to the story unsuccessfully. I did see an engine that operated in the oilfield and produced only very mild temp exhaust gasses (you could hold your bare hand in the exhaust pipe with no trouble at all)...this thing operated a rather large generator...allmost all energy was "recycled" in some kind of converter. I only saw this thing once and never heard of it again. So, I think something like this T-couple may have some merit in terms of increasing output. Am I thinking wishfully? |
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Our physics lab at school had a kettle which was 109% efficient. I know - I measured it. |
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[Blisterbob], sadly yes I think you are. Any reliable evidence of something like that would be found easily on google. |
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[moomintroll] - I'll buy your kettle for a billion zillion pounds. |
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I guess I need to back off from one of my statements. I said //needs a lot of heat input to produce a worthwhile output// but apparently it is all in what you call "worthwhile". The aforelinked Hi-Z people worked with DARPA on a 15 cm UAV (an unmanned airborne vehicle that will fit in a 15 cm box) and used this same arrangement - thermoelectric converters around the exhaust - with a common .049 cu. inch(!) model airplane engine, and produced sufficient power to run the onboard video camera, thus negating the need to carry batteries. The drawback was with the added weight. However, the longer the flight duration went, the more it favored thermocouple generation. If I can get the abstract in linkable form, I will post it. |
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What [Blisterbob] is referring to with respect to the stationary engine is called regeneration. Very common on large steam turbines, like power plants. |
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On the original idea, I have posted a link to a company (Powerchips) that is starting to produce a device based on electron tunnelling that does the same thing MUCH more efficiently. |
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I can't find the link now, but I believe this was baked for a truck (as a demonstrator), saving about 1 KW of power... (+) |
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[wagster] had better get a good lawyer. It all depends on how you define "efficient". It would be easy to make an electric kettle that added more than 109 KJ of heat to the water, while consuming less than 100 KJ of electrical energy; using thermocouples, for example. |
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