Thermoelectric generator - candle and cold water

[Pirate88179]

Mags:

Thanks.  Yes, I read not to full power the 400 watt one without sinks because it will melt the solder on the hot side pretty fast.  Do I really need to use some of that thermal paste like I read about?  The ceramic substrates are pretty flat and I can  lap the bottom of my sinks on a piece of glass with some sand paper to make very flat.  It seems like overkill to me to use the paste but...if I need it, I will find some.

I did notice that on the big one, the side between the ceramic plates are sealed with a ceramic cement.  On my lower powered one, they are open.  I don't guess these are waterproof to any extent are they?  I was thinking of sealing the open one up with some high temp silicone but...I don't know.

I am just fascinated by these things.  It is a great example of how nature works: Put voltage in, get hot one one side, cold on the other.  Put hot on one side, cold on the other, get electricity out.  Beautiful.

Bill

[Magluvin]

Hey Bill

YES absolutely use the silicone compound.  Imagine looking under a microscope at the surfaces. It is used on transistors to transfer heat to the sink. Without, the transistor wont survive full power ratings. its all about getting the heat away from the component.
In our case, one side is all about getting it 'evenly' hot, and keeping the other side evenly cold, for best results. These things conduct heat well, considering the contrary belief once you feel the 2 surfaces while being powered.  ;] So heating one side, the other side gets just as hot. If we dont provide the best path for the heat to be absorbed from the 'cold' side, eff will go down. So its best to do your best.  ;] Use the compound. ;]

RS has some thin liquidy stuff that I dont care for much. Maybe they have something better now. Best to get some online. You will need a bit. Or if you have a local parts distributor. We had Vance Baldwin here, but not any more. I dont know if Alpha Electronics is still around. We have a cb/ham radio shop that carries some unusual parts. So maybe where you are there are distributors. Electronics repair shops in larger cities have places to go to get parts directly. I know some order all parts.  Just tryin to give ideas as to get things locally. ;]

My approach would be to use a large aluminum block on the cold side with fins as many as possible. This will ensure a consistent colder temp for the cold side. A small heat sink on the cold side wil get very warm from the candle powered hot side, even with a fan. So more bulk and fins will keep it cool to generate the best output.

The hot side, fed by candle, maybe not so big block, but a  cupped heat catch, even insulated with auto parts store fiberglass wrap for headers to help keep it hot as not to lose heat anywhere other than the Peltier module.  Theres lots that we can do to increase efficiency.  ;]

MaGs

[conradelektro]

Hey Conrad

The 80ma 1.3v , was that on a load?

Can you show what you have there? Its hard to tell what is what other than some heat sink, water bucket and wires.  I just want to see how the heating and cooling are done here. It might be better to have the element on the side of the container, with the candle burning under fins of a heat sink, with a thin metal shield to help hold the heat in that area.  And the rising heat wont heat the water unnecessarily more than the cold side of the chip provides it. A vid i saw on YT the guy had the candle burning right under the bare chip, with a fan and sink on top.  Ill see if I can find it.

Thanks for showing

Are you using 2 chips here?  If so, the 2 chips will transfer more heat to the water, there by keeping the 'hot' side colder, thus less output.

If you just use 1, and get better results, then what you need for 2 is 2 candles. ;]

MaGs

The 80ma 1.3v were measured on a load. The load was a Joule Thief.

The short circuit current is a bit more, about 100 mA. Open circuit Voltage (10 Mega Ohm Voltmeter) goes up to 2.8 Volt (1.4 Volt per element).

I attach some photos showing the construction around the two Peltier elements.

It is difficult to come up with a good solution to hold the heat sink (on the cold side) and the heat distribution means (hot side, flame of the candle should not touch the ceramic) against the ceramic plates of the Peltier element. A good heat resistant glue seems to be necessary. Some use 0,8 mm copper plates as spacers (but that also needs a glue).

My "heat sink" and my "heat distribution means" are both aluminium plates 60 mm x 30 mm x 4 mm, because the Peltier elements are 30 mm x 30 mm and are located next to each other.

I need two candles in order to generate enough heat.

There is an important difference between Peltier elements for cooling and for electricity generation.

- cooling element: max temperature allowed on the hot side is around 100° Centigrade, max effective temperature difference between hot and cold side about 70° Centigrade, plastic isolation is useful because it keeps moisture away from the metals

- generator element: max temperature on the hot side at least 200° Centigrade (there are elements for much higher temperatures like 1000° Centigrade), temperature difference between hot and cold side as high as possible, plastic isolation is a bad idea because it will melt

Greetings, Conrad

[wizkycho]

     Peltier is not overunity element. it means it has efficiency lower then 100% actually only 10-20%,
the best ones only 50% (but made only experimentaly, not available on market yet).
So what are you trying to do with these ? heat the house.
This ain't gona work because if you use current from peltier and connect it to some heater
peltier will apparently cool down his hot side and the current from it will dimminish.
Unless you eventually cool down cold side of peltier to temperatures colder then air or earth.
And that would take lot a energy !!!
This is not working not even in space on -273
   Guy is trying to sell peltiers this way or just yet hasen't realized that this is dead end for FE and OU.

think of it this way: Peltier element is very poor thermal isolator.
or - if it would be better isolator it wouldn't give of electric current

Igor Knitel
Perihelion Labs

[conradelektro]

     Peltier is not overunity element. it means it has efficiency lower then 100% actually only 10-20%,
the best ones only 50% (but made only experimentaly, not available on market yet).
So what are you trying to do with these ? heat the house.
This ain't gona work because if you use current from peltier and connect it to some heater
peltier will apparently cool down his hot side and the current from it will dimminish.
Unless you eventually cool down cold side of peltier to temperatures colder then air or earth.
And that would take lot a energy !!!
This is not working not even in space on -273
   Guy is trying to sell peltiers this way or just yet hasen't realized that this is dead end for FE and OU.

think of it this way: Peltier element is very poor thermal isolator.
or - if it would be better isolator it wouldn't give of electric current

Igor Knitel
Perihelion Labs

Yes, I know, Peltier elements are definitely not OU.

The idea is to use waste heat (although the efficiency is very low). The heat would be wasted any way.

I want to come up with a good design, which can be done at home (without fancy tools).

In winter I heat my house with a conventional wood stove and I want to use some of the heat from the stove to create electricity. This is not new, there is no invention, may be there will be a nice design. The idea to use part of the heat from the stove to charge a battery pleases me. It is probably not very useful and by no means a replacement of my connection to the electricity grid.

I do not sell anything, my experiments are for my personal education and enjoyment.

I posted my contraption under Conventional alternative energy systems and there in All other conventional alternative energy creation systems.

So, it should be clear, it is a conventional system for energy creation.

My contraption is "alternative" in the sense, that waste heat is rarely used. A good example for a good use is the rover Curiosity which rolls on Mars just now. In fact, the news about Curiosity inspired me to play with Peltier elements. (I will not use Plutonium for heating. I generate heat by burning wood or candles, which in itself is a bit "alternative" nowadays.)

I think it is interesting, that one can generate additional light (with a LED-lamp) when lighting candles. The waste heat from the candles is turned into electricity by the Peltier elements. (And one has the light from the candles as well.) Yes, not very exciting, no business opportunities, but nice nevertheless.

Greetings, Conrad