Can Heat Be Used to Charge a Small Battery?

[mishima]

Hi, I don't know so much about electronics but...

I know when you have a junction of two metals that is heated you can get a small voltage. Like wrapping a piece of wire around a nail and holding a flame over it produces a very small but measurable voltage. This is a thermocouple as far as I know.

Now I've heard different metals can produce larger voltages. I was wondering if it might be possible then to make something that could use heat to charge a small battery. It would only have to be enough to light a single LED for 4-5 hours.

So, you could put the junction in some charcoal that is burning all day (like charcoal ovens in 3rd world countries), and then come nighttime have a battery that has enough charge to make a light for you.

I don't really know how a battery charger works, I'm just wondering if something like this is possible. Thanks.

 

[russ_watters]

Yes: http://en.wikipedia.org/wiki/Thermoelectric_generator

 

[NascentOxygen]

So, you could put the junction in some charcoal that is burning all day (like charcoal ovens in 3rd world countries), and then come nighttime have a battery that has enough charge to make a light for you.

No matter what metals you try, one junction doesn't produce anywhere near enough voltage from realistic temperatures to charge a battery. You need lots of junctions.

I have read of these devised around a large kerosene-burning lamp for Soviet peasants in isolated regions to listen to a small radio. Mostly this would be while indoors at night, with the lamp providing meagre room lighting and heating, cooking or water heating, together with the daily propaganda broadcast.

 

[mishima]

russ,
Yes I've been playing with a cheap thermoelectric generator like the one in that wiki pic. Its not really a steady voltage, and pretty small. But if my goal was just to charge a small button type battery for a single LED, could I do it with some kind of voltage multiplier and regulator?

Nascent,
That sounds great, I'll see if I can find anything more about that.

 

[alphysicist]

I can confirm that it is indeed possible to charge a battery using heat. This process is known as thermoelectric power generation and it involves converting temperature differences into electrical energy. The device used for this purpose is called a thermoelectric generator (TEG).

TEGs work based on the Seebeck effect, which is the principle that states when there is a temperature difference between two different materials, an electric potential is created. This potential can then be used to charge a battery.

To charge a battery using heat, a TEG is placed between a heat source (such as charcoal) and a heat sink (such as the surrounding air). The temperature difference between these two surfaces creates a voltage, which can be used to charge the battery. However, it is important to note that the amount of energy produced by a TEG is relatively small, so it may not be enough to fully charge a battery.

Additionally, the efficiency of TEGs is still being improved, so they may not be the most efficient way to charge a battery at this time. However, with further research and development, it is possible that TEGs could become a viable option for charging batteries using heat.