Using an Electrical Connection as a Heat Pipe

Sort of:

http://edge.rit.edu/content/P10451/public/Thermoelectric%20power%20generation%20from%20biomass%20cook%20stoves%20Champier%20et%20al

http://www.treehugger.com/files/2009/07/score-biomass-cookstove-also-doubles-as-electrical-generator.php

http://peswiki.com/index.php/Directory:Acoustic_Generator:SCORE:Stove_for_Cooking,_Refrigeration_and_Electricity

None of these has two peltier devices working at a distance. In fact, the second and third links don't seem to even use peltier devices: "... the cookstove converts heat into acoustic energy and then into electricity through a linear alternator.".

(BTW - fig. 13 in the first link is incorrectly captioned - I don't know whether this is the only error in the paper, but it suggests they should get a better proof-reader!).

If what I've sketched could be used practically, one great advantage would be the fact that it's all solid-state, and there are no moving parts (so it'd be rugged and maintenance-free).

I took a stab at it. I guess I was trying to give you some ideas. Aren't peltier devices already used to keep things hot or cold?

I didn't think any of them had moving parts.

http://en.wikipedia.org/wiki/Thermoelectric_cooling

I can't think of anything off the top of my head that could be accomplished by wiring two of them together. But, with my limited knowledge, that means absolutely nothing.

Is this what you mean?

The thing I'm thinking of is taking two of them, remotely located, and wiring them so that the voltage produced by one (the hot thing / 'infinite sink') is used to drive the other (the cold thing / 'infinite source'). It's obviously reversible.

It seems to me a way of shifting heat from one place to another using wires.

Depending on the relative temperatures of the hot thing and its local sink, and the cold thing and its local source, it may be able to do something useful.

The source/sink could be say a sun-warmed lake in one case, and the wall of a cave in the other (grasping at straws - but you get the idea).

Just a thought. Maybe I'll buy a couple of Peltier devices and do some 'speriments.

JohnDG:

Perhaps I am overlooking something, but there isn't much heat being shifted over the wires.

What little heat is transferred over the wires is mostly limited to:

1. the heat converted to electricity in the Seebeck portion that is converted back to heat in losses along the wire.

2. the heat converted to electricity in the Seebeck portion that reaches the Peltier portion lost to heat from assorted inefficiencies.

Neglecting losses in the wire, assuming a 5%

efficiency for the Seebeck portion, and a 0.6 COP for the Peltier portion, and assuming the goal is to heat something at the Peltier section, sounding the drastic over simplification alert, checking to making sure I have dotted my T's and crossed my eyes... I'd suggest if someone wants to transfer heat down power lines consider the transfer from the power plant to an old fashion water heater....or to the toaster.

Far and away, the heat is transferred locally to or from the sink/source. Any transfer of heat over the wire will be very small and limited to a heat transfer away from the Peltier section as losses from various inefficiencies.

If I am missing something, please upgrade my understanding.,

Interesting. Certainly not a perpetual motion machine. There could be two issues.

1. The temperature difference at the generating end may have to be higher than at the consuming end.

2. Cables may have to be large sized to transmit power at the rather low voltages involved.

Bioramani

In short, NO.

Peltier elements are wonderful, but woefully inefficient converters of current to heat flux. Having elecrical connection on the top of it invites further inefficiency.

Sorry.

Leveles has the same (or better) understanding of these thermoelectric coolers as I do. They are not as efficient as a normal refrigerator's freon (or whatever) system or all fridges would be cooled with thermoelectric. They do have advantages, but efficiency isn't one.

I did just order one for myself though and will be doing some experimenting with it this summer. I will post results here after I have made progress or failure. You can get them pretty cheap on Ebay. I had considered buying one of those car coolers with the thermoelectric chiller in it but they are much cheaper used on ebay; just make sure you get one with a heat sink and fan already fitted (just cause it is easier that way).

The Seebeck effect gives only a small voltage (on the order of millivolts per kelvin of temperature difference). Probably insufficient electrical pressure to overcome the resistance in the connecting wires.

I don't see where a heat pump is involved. A heat pipe is a sealed tube partially filled by refrigerant and having one end connected to a heat source and the other end connected to a heat sink. Capillary means disposed within the tube wick condensed refrigerant back to the hot end. Its purpose is cooling the heat source by change of state.

John, this link to wikipedia has some formulas and calculations that show the efficiency rating of peltier generators.

Wilmot, I had been looking for heat pump information, I have seen the phrase used to describe various methods of moving heat from one area to another through mechanical means. I have heard a car's engine coolant system as a heat pump. Most of the places I encounter this meaning of the phrase were not in professional HVAC circles. (I'm jus sayin)

In my recent research into thermoelectric coolers I have heard them referred to as heat pumps because with application of current they move heat from one side to the other.

When I googled heat pump all I got was a bunch of references to home air conditioning. Can you expound on 'heat pump' please?

<Please don't take my post as critical, I am only trying to give you my perspective and knowledge of the topic so you can (hopefully) see my mistake and correct it.>

I should have said microvolts per kelvin, so the total voltage produced by heat at each end of your setup would be on the order of millivolts. If the connecting wires are extensions of the thermocouples at each end you will have two thermocouples connected in series, adding their small voltages.

The Seebeck effect will produce a small voltage from the heat applied to a thermocouple (junction of dissimilar metals, e.g. iron and aluminum). The voltage will be an electrical potential between the two open ends.

Heat pump uses airconditioning type equipment, but the similarities stop there.

Airconditioning is using electricity to compress Freon gas, cool it in an external radiator, then by expanding it into gas produces a cold heat exchanger, thus cooling your room.

Heat pump, as its name implies, takes heat from here, CONCENTRATES it, and deliveres there. In winter from the wellwater to your home, in summer the other way. It does not generate it, just concentrate it. In both cases the heat source / sink is the well water. The pump is just the concentrator / transport.

Example: if you extract 10 degree temperature difference from 10 gallon of well water, and concentrate it into 1 gallon, you have so much hot water for you.

Since your equipment does not GENERATE heat, its efficiency appears to be much above 100%, as it just transport heat from here to there, and that is that much easier. Well, there is no free lunches in nature. A ground water system will cost you 10-20 thousand dollars investment. But, it is very nice to have.

Leveles;

I am confused by your effort to paint an 'air conditioner' as different from a heat pump. Most airconditioners act as heat pumps when cooling. Air conditioners are simply moving heat away from the place being cooled. It donsn't make a difference if the heat is being moved to outside air, or to a well, it is still a heat pump.

Also, I don't understand your statements about the efficiency of TEC's being over 100% and not producing heat. I liked the first answer you posted in comment #7, where you correctly identified TEC's as having very low efficiency....

Did someone hijack your computer to type seemingly self contradictory comments?

When in doubt, there is always Wikipedia. Look up "heat pump". In the chapter Efficiency you will find the detailed description of COP, as the efficiency factor. It goes into details, why heat pumps can have 400-500% efficiency. Yes, well over 100%. Because they borrow heat, then concentrate and transport it. Your electric heater have t generate heat, cannot do better than 100%. All that is available in great detail in wikipedia.

No one is disputing that COP values for some heat pumps can be well above 1.

The only problems I have with your statements are;

1. I disagree with the assertion that any TECs (even though they are a type of heat pump) have COPs above 1.

2. I disagree with the assertion that TECs produce no heat, since this would imply TECs incur no losses and are perfect machines.

3. I disagree with the need for and validity of drawing a distinction between an air conditioner cooling a home by moving heat to outside air, as opposed to one moving heat to a water heat sink. Both are heat pumps.