Candle Powered Fan Keeps You Cool Using a Thermoelectric Generator

This is a great example of using a thermoelectric generator for a project. [Joohansson] made both a functional, and aesthetically beautiful fan using components from a computer.

Thermoelectric generators (TEGs for high temperatures, and cheaper TECs for lower temperatures) are also called peltier elements, which look like small square pieces of ceramic with two wires sticking out of them. If you supply power to it, one side will become hot, and the other cold. The TECs [Joohansson] is using want a temperature difference of 68C between either sides. They are typically used for cooling electronics and even some of those cheap mini-fridges will make use of one with a giant heat sink on the hot side.

In addition, they can be used as an electric generator, thanks to the seebeck effect. If you can create a temperature differential between the two sides, you can generate electricity. Using a CPU heatsink, cooler, and fan, [Joohansson] was able to power a small DC fan using only a candle. It’s a brilliant demonstration of the seebeck effect.

TECs are great for getting power to remote areas — we’ve even seen someone manage to put one into a “glowing life ring” that harvests body heat to light a tiny LED!

[via Hackedgadgets]

60 thoughts on “Candle Powered Fan Keeps You Cool Using a Thermoelectric Generator

  1. A) It looks cool.

    B) I did get that right? He is using a FLAME, heating up the room, to drive a FAN to “cool” the room (basically moving the hot air from the flame into the room), right?

    C) Suggestion for enfunnyment: Direct the air stream from the fan to blow of the candle. That way you would actually make the room cooler than with the fan running, as the candle would not burn and heat the r… ah, well, you get it.

    1. You are right, but

      A) “Keeps You Cool” – this means it blows on you to cool you, not the room
      B) The amount of heat produced by the candle is tiny compared to the heat a human body produces.

      1. The relative amount of heat produced by a candle or a human body is irrelevent. The important question is whether the fan _removes_ as much heat from the body as the amount of heat _added_ to the body because the candle warms the air. The fan is used to remove heat from the TEC, so the fan is blowing air that is _warmer_ than room temperature.

        1. The title is that it “keeps you cool”. My fans in my Orlando home produce heat but the movement of air keeps me cool.

      2. Actually, the heat produced by a candle is about a third of what a human body at rest produces. Not exactly “tiny”.

          1. Just a tea light. I assumed 12 grams of wax, producing 43 kJ/g, and burning for 4 hours. That’s about 35 W. Human body in rest is about 100W.

      3. Paraffin wax contains some 10 kWh/kg. A tea candle burns for 4 hours and contains 10 grams of paraffix wax, so it produces about 25 Watts of heating, which is about a quarter of your own body heat.

    2. fans can not cool the room. all it can do it move air, in this case warmed air. so this is better described as a nice heater. It would be more effective in the winter than the summer.

      1. Fans increase airflow over your skin, which increases the speed at which sweat evaporates, which cools you down. That’s why people switch fans on in the summer.

  2. I am amazed that the fan was moving so quickly with only candles thanks for sharing this.

    BTW for those who commented about using heat to cool the room. Fans never cool the room, it is the movement of air across our body that makes it feel cooler. Besides I see this as a proof of concept.

    1. Even a small TEC can produce several Watts of power from the heat of a tea candle. At least enough to power a 2.5 Watt computer fan.

  3. Deja-vu , just watched a episode of Houshold Hacker showing the exact same thing.
    only more indepth.

  4. The title is very misleading, and the actual instructable doesn’t suggest that the fan is used to cool anything except the “cold” side of a heat exchanger. Could we light a bonfire inside a closed room to make a walk-in freezer?

    1. Yes you can, my cottage’s refrigerator runs on propane. I use FIRE to cool the interior and even freeze items in the freezer. no electricity at all, just heat used to cool and freeze.

      1. I’ve read the explanation of those a dozen times, ammonia dissolving in water etc. And I STILL haven’t any clue how they actually work! But what you say’s true, the only power input is a heating element, powered by gas or electricity, in the case of caravan fridges.

        1. The pilot light in an r.v. fridge perculates the freon through a check valve, causing flow.
          The pressure drop through the capillary tube allows for heat removal in the evaporator
          coil (in freezer) . The perculation takes place of the compressor witch the fridge may also have…
          Napervillian

          later

        1. Not really. They just operate on the principle that mixtures of different gasses and liquids have different boiling points. It’s a continuous distillation machine where heat is used to distill ammonia out of water, and dissolved back into it. The pumping action of the device works exactly like a coffee maker.

          The separated liquid ammonia inside the fridge starts to boil because the ammonia vapors dissolve in the water that is coming out of the distiller portion, and that creates a vacuum. The ammonia water then simply drips into the boiler where it gets distilled and separated again, and the cycle continues.

  5. I built one of these for my father-in-law for Christmas last year. He heats his garage with a wood stove and this works great to circulate the warm air surrounding the stove.

    1. Was just considering that…

      If only I could build something with a high WAF, I could use it to circulate the air when the wood burner is on in the living room!

  6. I like this. It’s fun, shows basic principles of physics and is a nice build. This would be a good science teacher project.

  7. Would this be more efficient if you incorporated a second heat sink on the cool side and directed the air stream over the fins?

  8. I find it clever that the fan is set up next to the heat sink, moving air across it, likely further cooling the heat sink and thus creating a larger temperature difference across the peltier. Very cool.

    1. No, it’s a fan, powered by heat. Fans make you cool. If the fan’s cooling is greater than the candle’s heating, from the point of view of whoever’s using it, then it cools you.

      I’m sure everyone realises that candles give off heat. We didn’t need that pointing out, thanks.

        1. A fridge also gives off heat, yet strangely works really well at encoldulating food. The heat is part of the mechanism, not all of it. As someone pointed, the motor in an electric fan creates heat. Yet still people turn on fans when it’s hot. Why could that be? Are they INSANE!?

          It’s a fan. Blows room-temperature air. Makes you cooler. It even works on a wet thermometer. This is an old idea, back when emperors used to have flunkies wave big leaves at them. Fans make you cooler. It’s a fact, however autistically you focus on the one element being a candle.

          1. It actually blows slightly-warmer-than-room-temperature air, moving as much heat as is being absorbed from the candle minus what is transmuted into electrical energy. It’s not a very good forced-air heater because the air is only *slightly* above room temperature.
            Also the fact that moving air over a person’s surface aids in evaporative cooling is a very very good thing. No idea why anyone would doubt that a fan blowing on a hot person makes the person more comfortable, but this is definitely not the first time I’ve seen that debate on hackaday.

  9. Some people are missing the point that: while this does move air like a fan and thus could give the effect of making you feel ‘cooler’ because of sweat evaporation, the air it is moving is being heated beforehand by movement through the heatsink. Using this to cool yourself via air-movement would be like using a space heater to cool yourself in summer because it has a fan inside. It is highly unlikely the small amount of phase-change induced cooling it causes will be noticeable over the increased temperature of the air it is circulating.

    Regardless, awesome project. I just wish the HackADay writers would be more careful with entry titles considering it is the first impression people get of an article.

    1. Actually at a decent distance I think the airflow’s cooling will dominate the candle’s heating. Tho as you point out, that’s the essential argument of this device’s usefulness.

      From knowing the heat output of a candle, and the cooling of a small fan, by feel, I think it would work. If anyone can be bothered getting the figures for how fast a person sweats and the specific heat of evaporation or whatever, we could conclude this. I bet $5 it cools the user more than it heats him.

  10. This gives me an idea for the group I am involved in for an easy project to help homeless living in tents this summer. It would not cool a room but it could help in a 2 man tent I think.

  11. Guys, isn’t this a Peltier cooler being used, so in theory, shouldn’t the side he has heatsinked towards the fan get cold?

    1. No, normally if you put electricity in, one side gets hotter, one cooler.

      This is working in the inverse mode, where having one side hot and one side cooler produces electricity. Which drives the fan.

  12. In ye olde days they used to make candle powered fans that used a stirling motor… No peltier device required.

    1. I just saw one of those in an old B&W movie. I was kinda surprised at first, I saw the fan, and it was running, then I thought about it for a second, and “hey! They’re in Africa, turn of the century, in the bush, and HAVE NO ELECTRICITY!!!”
      Then looking at it, I noticed it looked like a Stirling engine driven fan.
      I would LOVE to have one of those, the old antique fan, that would be sharp sitting there.
      Can’t remember the movie, but it was Angi Dickinson as a nun/missionary that went to Africa and the guy she was there to help, died, rather soon, leaving her along and all manner or troubles.

  13. Is there a formula for working out how much energy went in (candle) vs. how much is actually used by the fan?

    Or generally speaking, what’s the efficiency of those TEC/TEGs?

  14. I like how the fan draws air through the CPU-cooler, increasing heat dissipation and creating a better difference in temps. This thing looks so neat, I may have to try making one myself.

  15. Very aesthically pleasing! Although a -ah- FANtastic way to move air around, especially if it’s layered in a still room, best keep in mind that the thermoelectric Seebeck effect is very inefficient.

    Although waste heat applications (furnaces, fireplaces, deep space nuclear heated probes etc) may appeal, even the best designed thermopiles will only develop a few % of electrical power from the thermal source. For simple day time work even a small solar PV panel is usually superior!

  16. That is an excellent build, neat and well finished. Regardless of the present pragmatics it is a great demonstration of alternate application outside the norm. Going off grid people use similar applications. Who would of thought Leonardo DaVinci understood the principles of helicopter flight given the technology of his day. Yes, the device would make an excellent teaching aid. Now what can the Steam Punk community make out of that. Once again not very pragmatic, but then again, people do watch sport.

  17. Very aesthically pleasing! Although a -ah- FANtastic way to move air around, especially if it’s layered in a still room, best keep in mind that the thermoelectric Seebeck effect is very inefficient.

    Although waste heat applications (furnaces, fireplaces, deep space nuclear heated probes etc) may appeal, even the best designed thermopiles will only develop a few % of electrical power from the thermal source. For simple day time work these days even a small solar PV panel is usually superior (& with no fire risks either…)!

    Those interested in exploring Seebeck effect further should check the superb historical overview => http://www.douglas-self.com/MUSEUM/POWER/thermoelectric/thermoelectric.htm Scroll down to the marvellous 1959 Russian Kero lamp radio !

  18. I’m kinda curious how cold you would need to get it in order to reverse the process, Say sitting it on a ice cube or dry ice?

  19. Haven’t yet read all the comments. But am wondering, could you use the fan to force more air on to the candle, in order to make a small furnace, which would burn much hotter, and therefore produce an increase in thermo difference, and in turn create a higher source of power?, ie, like a mini turbo? Or … in theory, could this cause a run-away process. Produce higher voltage, increases speed of fan, more air to candle, burns hotter, produce higher voltage… etc, until the mini furnace flame melts the alloy heatsink? Interesting to ponder. Be great if you could run strip lights on your ceiling to light your house off a few candles. Brilliant and wonderfully crafted concept though.

  20. I recently saw one of these in an old B&W movie. Beautiful fan too.
    They were located in the African bush at the turn of the century or so. No electricity and had a candle powered fan.

  21. I built a similar item for our fireplace at our old home in PA. I used 1/4 in copper tubing under the wood, and had 400ml of ferro fluid move up to the 4 peltier fans. I had two harvesting the electricity and running the other 2 as heat exchangers. Since the hot fluid would naturally convect, this made a huge difference to the amount of heat in our home. I should have done a writeup, but I didn’t follow this stuff at the time.

    Great build!

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