Thermoelectric generator - candle and cold water

[conradelektro]

It is a very old idea, electricity from a temperature difference. The effect is called "thermoelectric effec" or "Seebeck effect", see for instance http://en.wikipedia.org/wiki/Seebeck_effect#Seebeck_effect .

I used two Peltier elements in series with a size of 30 mm x 30 mm x 3.6 mm each http://uk.farnell.com/multicomp/mcpe-127-10-13/peltier-cooler-38-1w/dp/1639751

Each Peltier element is held between two flat aluminium bars, one hot and the other cold. Heat is provided by a candle and coldness by cold water (in a container).

See the attached photos showing a crude contraption. The output is up to 2,8 Volt (no load, 10 Mega Ohm digital volt meter, two Peltier elements in series) and up to 80 mA (short circuit current).

When running a Joule Thief driving a gutted CFL or a 220V 1W LED lamp, the Voltage holds at about 1,25 Volt and the current is about 68 mA (about 80 mW). Of course neither the gutted CFL nor the 220V 1W LED lamp have full brightness.

An output of 80 mW is not much, but with a better design and more powerful Peltier elements an output of 1 Watt seems to be feasible.

I found very good Peltier elements for electricity generation at http://thermalforce.de/de/product/thermogenerator/index.php?uid=f06c1126a7b53e606196e78a328e41e9&ref= but one probably can also find some in the US or elsewhere.

A design I will try next is depicted in the attached drawing.

The difference between cooling elements and generator elements is in the temperature resistance. There are generating elements which can be run at several hundred degrees (centigrades) of temperature difference. The cooling elements are designed for a temperature difference of about 70° (centigrades).

The basic idea:

During winter (where I live) one just has to put a bucket of water outside to cool it to freezing temperatures. In the house one then uses a candle as heat source (and cold water) to drive a thermoelectric generator which could power a small reading or novelty lamp.

I like to light a tiled stove during winter, which could also provide heat for a thermoelectric generator (again coldness from cold water).

The cold water is of course heated up over time and has to be exchanged every hour or so (depending on the volume of the cold water container).

Greetings, Conrad

[Pirate88179]

Conrad:

I was thinking of exploring this area myself after reading a 1951 Physics book explaining thermocouples.  They said it was just 2 dissimilar metals, they used copper and iron, and one coil at one end cold and another coil at the other end hotter than the other coil...and....electricity!!!!  No degradation of materials and you could use a whole bunch of them I am guessing and add up the power or volts.  I also am rethinking the Stubblefield coil in that...it used copper and iron wire and a coil was in the ground.  Well, here in KY where he lived, the ground temp is 54 degrees year around as that is the average temperature.  Well, it gets well over 100 degrees here in the summer so, that is a pretty good differential.  So maybe that is part of how he did all of that?  Who knows.  I will follow your experiments here with much interest.

Bill

[Magluvin]

I havnt tried using them as a gen yet but with 2 modern cpu heasinks and cpu blower fans(squirrel cage) and a peltier chip, with 12v at 1 amp per fan and around 4 amps for the chip, it is a small solid state A/C unit.

Sitting on the bench, blowing the cold side on me and the warm side elsewhere, I had to tun it off after a while as I was a bit chilled. ;]

A guy has a candle powred deal on YT where he actually runs a fan to cool a PC cpu heatsink, for the 'cold side' , with a candle on the hot side.
The cooling fan runs off of the output of the chip.     Candle powered fan.

I have that on my list. ;]

They have campfire chargers also. Charge and run devices on a camping trip with the camp fire. Survival outlets have them.

If ya think about it, per square area, these might give out more in a solar application that solar cells. The cooling side will have to be dealt with. The hot side is easier.

Now, there was the woman who was a biologist, that invented a sun powered micro refrigerator, using what she learned in biology about how our bodies get rid of heat.

2 aluminum containers, same height, 1 is smaller in diameter to have some space between the container walls if we insert the smaller one into the larger one.

The outer container has many small holes or larger holes with a screen wrapped around it.  In the space between the container walls, you put sand, dirt, sponge, what ever that might absorb water.

Put an insulated lid on it and put it in the sun. The evaporation through the screen/holes brings down the inner container to 42 deg F.   

Now, if those efforts were combined, the sun can be used to 'power' the hot side of the chips, and the 'cold' side. And if we consider the amount of heat on the hot side of the chip from the sun, then the solar refrigerator would be better than just running a lot of water for the cold side. ;]

Very neat devices. And ebay has them in bulk for great prices. And many sizes to choose from.  I think they come in 6in x 6in.   

MaGs

[Pirate88179]

Mags, I like the solar aspect to this...never thought about it.  What about a bunch of peltier junctions floating on a lake or pond, with the cold side in the water, and the hot side facing the sun?  I believe that there is a lot more that can be done with these than is being done at the moment.  Or, perhaps mounted in the back of our freezers with the cold side...and the hot linked to the cooling coils that are very hot.....we pay for this cooling anyway so....sort of "free" electricity?

Bill

[Magluvin]

Hey Pirate

Well, we could use the heat of the fridge to power the hot side. If you look around for info, the ratio for hot side and cold side to get decent power out is 'hot' and 'cold'. So heat from the fridge for the hot, where do we get the cold? If we get our cold side from A/C in the home, then the A/C has to work harder to keep the fridge coils cooler, through the peltier gen, So maybe the energy from the peltier is free? And all from heat just passing from the fridge to the home A/C unit? ;]  Being that the fridge is heating the house anyway, that the A/C cools, that loss is inherent. So the peltier gen output is a gain. The heat from the fridge through the gen, then into the open air, wont make the house any hotter.  ;] It is what it is.  ;]

So put 50 of these chips on the back of the fridge, mount aluminum heat sinks to the cold side of the chips, lol, then power and inverter to run the fridge, with inherent losses that exist in the house already.  lol  im nuts.  Maybe not.


There is a lot of vids on YT that are inspiring with these chips. Their efficiency is not great.
That when I decided that the candle power, if it could charge a phone, that would make me forget about the efficiency fast. The outcome would be worth it in power outages, or other things like disasters like hurricanes. 

Thinking about it further, then I came up with the sun powered hot and cold side. ;]

I want to get like 10 of these and try to make a small solid state A/C unit. Just to see what a larger scale of what I did with 1 works like.

The single is about 70 watts fans and all at 12v. Times 10, 700 watts. Like a smaller wall shaker unit, maybe less.  And 20 fans included in that estimate would create a lot of wind. These are not the simple bladed pc fans.

I find that it is best to use more fan and fins for the hot side. The faster you get rid of the hot side heat, the better the cooling on the cold side.  Like in your car, if you put the ac blower on low, the air coming out is colder.

So maybe the 20 fans could be divided to have more of them on the hot side, and less on the cold. Then if you want the solid state ac to be a heater, just reverse the chips input polarity.  ;]  They supposedly run best at near 16v input. As a gen, the voltages are more like less than 10v, closer to 5v, depending on the heating and cooling design. As a gen, the candle will get the hot side hot, so in the gens case, we also want to get rid of the heat from the opposite side of the chip as fast as possible for best results.

You can series and parallel them for greater outputs.  And series the chips physically also, so 10 chips for the SS A/C unit, 5 stacks of 2 chips would do close to the same job as all 10 laid out on heat sinks.

Computer shops will sometimes have boxes of these heat sinks and fans that you can get from them dirt cheap, from the right guy. Comp usa has good prices on new also.

The chip is only as good as the design of the application. ;]



MaGs