# Thermopile, let extract some electricity from heat without steam

1. Feb 8, 2007

### Jacquesl

I want to build a Thermopile to generate usable electricity with a heat source, like a small fire or something,
I can build something like this but, I only get 1 mA and an ant of a volt. And it subjected to 1700C blow torch, it sucks.

So does anyone have some info about that, would be nice, to light a candle and then your able to watch a DVD :rofl:

2. Feb 8, 2007

### brewnog

Find out how much heat a candle produces.
Then find out how much power a DVD player and TV take to run.

Finally, find out the efficiency of your thermopile. Factor that into the power of your candle, and you'll see whether or not you can run your TV and DVD player off it.

3. Feb 8, 2007

### Jacquesl

Lmao, it’s just a joke about that TV and DVD part. I just want to find a way to get more electricity out of heat

4. Feb 8, 2007

### Averagesupernova

Not quite. A thermocouple develops a voltage based on the DIFFERENCE between the ends of the thermocouple wire. So if you live in a climate where the temp is 50 below zero you could put the open end of your thermocouple wire outside and the joined end of the thermocouple wire inside your house held in a candle. You will have more voltage than if you had the open end at room temperature. I know it's not much, but I did say 'not quite', I didn't say 'not even close'. Obviously then the ambient inside air temp is contributing to the temp of the thermocouples heated junction. The ambient temp of course gets its energy from the furnace or whatever heating system you have in the house.
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I know a K type thermocouple junction seems to have a source imedance of around 25 ohms if I recall the testing that I did correctly. It is not very suitable for a power supply because to get any voltage out of it you have to series them up and of course you are also adding the source imepance as well. I believe a reachable voltage out of a K type thermocouple is .025 volts and to get 2.5 volts you would have enough in series to produce a source imedance of around 2500 ohms.
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Look into other thermocouple junctions. This sort of thing has always interested me. I know it's not much power, but sometimes we don't need much.

5. Feb 8, 2007

### NoTime

You can also look into Peltier Devices.
These are used for solid state cooling and electrical generation.

You can probably get enough power out a few units to run a portable DVD player.

As Averagesupernova notes the temp difference acrost the unit is important.

6. Feb 9, 2007

### Jacquesl

I’ve already checkout “Peltier effect” but it doesn’t seem to give any usable info, like building plans

I’m looking something solid state device and for something with a high wattage output.
How I see it, it sucks up a lot of watts to heat up n heating element, say like 1000W heater. But if you apply 1000W heat source to some thermocouples, you will newer get that 1000W back, It’s the same with a spotlight, 150W flood light aimed at solar panels, I wonder how many watts will you get back, solar panels have developed more efficiently than thermopiles. In wattage outputs
I belief if you can covert something to another thing, then you can surely convert it back with at least 100% back in theory, but mostly we strive near, like in transformers example.

The K type works with (Chromel (Ni-Cr alloy) / Alumel (Ni-Al alloy))
And give out approximately 41 µV/°C

But the Type J (Iron / Constantan)
Constantan is an alloy usually consisting of 55% of copper and 45% of nickel

Type J's have a sensitivity of ~52 µV/°C, it’s a little bit more, So how just with Iron/Copper and how do you know then a certain metal will give a higher voltage than an other metal?

7. Feb 9, 2007

8. Feb 9, 2007

### Staff: Mentor

Just buy one on ebay to play with - they're like 5 bucks.
They're solid state, but high wattage, uh.....
At least? Careful witht that first law of thermo.....

In any case, no, peliter devices are only single-digit efficiency afaik, and they are about the best you can do.

9. Feb 7, 2010

### rishabhjain89

Hey Jacquesl i too was thinking of making a thermocouple running device for electricity generation! can you tell me if you were able to make any device cause i too faced the same problem of low voltage generation.