Generating electricity from alcohol

thermoelectric-generator-lamp

Here’s a thermoelectric generator which [x2Jiggy] built. The concept uses heat from a flame, biased against cooler temperatures produced by that huge heat sink making up the top portion of the build to produce electricity via the Peltier effect.

The build is passively cooled, using a sync assembly that takes advantage of heat pipes to help increase the heat dissipation. A nearly flat heat sink makes up the mounting surface for the hot side, which faces down toward a flame driving the generator. [x2Jiggy] started the project by using a can, wick, and olive oil as the heat source. He managed to get about 2V out of the system with this method. What you see here is the second version. It swaps out the olive oil lamp for an alcohol stove. The cans with holes punched in them act as a wind screen while also providing a stable base. This rendition produces about 3V, but it doesn’t sound like there are any precise measurements of what it can do under load.

50 thoughts on “Generating electricity from alcohol

    1. Having worked on furnaces and water heaters, the norm for me is a standard thermocouple, which is what this is. the fact that applying electrical current to two dissimilar conductive metals to get a delta t, and providing a delta t to two dissimilar conductive metals to get a current is not only easily understood, but rather mundane. I did like the build though, really top notch. great for demonstrating the thermoelectric effect in science class.

  1. Thermolelectric effects, although often very convenient for sensing & spot heating/cooling, are VERY inefficient! At best this setup would only deliver a few % of the fuel’s energy as usable electricity – much larger “stove pipe” systems are needed for even quite simple battery charging etc. A cheap solar PV would far out perform it in daylight, & may even deliver viable electrical energy under indoor ambient light.

  2. My research into the Seebek effect a year or so ago led me to believe it would be an order or two of magnitude less effecient than a traditional generator. That is to say while it might be interesting to burn alternative fuels like wood, while in the boonies for a month, it makes no sense to carry fuel to run a peltier-junction style generator.

    1. My company produces TEGs that are around 10-12% efficient at these kinds of temperature gradients. We normally have parasitic losses on top of this, but there shouldn’t be any in this case. Though an IC engine would be more efficient, a small gas generator is typically only 20-25% efficient. This is going to be much smaller, lightweight and have no moving parts as well as burn any fuel source for heat. Though, in the back woods a small solar cell would work just fine.

      1. Am I right in thinking a traditional 2-metal type thermocouple would be more efficient? Since Peltier devices are heaters / coolers run backwards in this situation. Any tips on the latest thermocouple-generating tech?

        Just to mention the old Soviet thing, where they had a thermocouple rigged to an oil lamp powering a radio. It deserves mentioning.

        My other thought on this was, perhaps to run the alcohol in a loop around the cold end of the peltier stack. Same way rocket engines run their LH / LOX around the engine bell to stop it melting, as the LH / LOX is on it’s way to the engine for combustion. If he did the same, and the alcohol happened to evaporate int the process, it wouldn’t matter for burning it, but it would give a greater heat difference, therefore more power. Even if it’s still a bad idea.

        Maybe our guy could start twisting some wires together, you don’t hear much of home-made thermocouple stacks.

    2. My company produces TEGs that are around 10-12% efficient at these kinds of temperature gradients. We normally have parasitic losses on top of this, but there shouldnt be any in this case. Though an IC engine would be better, a small gas generator is typically only 20-25% efficient. So definitely not orders of magnitude. This is going to be much smaller, lightweight and have no moving parts as well as burn any fuel source for heat. Though, in the back woods a small solar cell would work just fine.

    3. I’ll dumb your comment down: It uses too much fuel and produces too little power for practical uses… Unless you consider a big furnace for powering a single LED…

  3. I remember seeing peltier devices engineered to work this way….I think they tolerated much higher temps. more efficient too..

    1. Could one combine the two, and solar power? Have a parabolic reflector focus light onto a photovoltaic cell which is sitting on top of a peltier which is attached to the bottom of a stirling engine. Would that work?

      1. I think the idea is that heat transfer is slowed down on it’s way through a peltier, or a Stirling engine, or any kind of heat engine, and that’s where the work comes from. Like the opposite of a heat sink. So the peltier would act to reduce the efficiency of the Stirling engine by more than you’d gain from using it. Same thing vice-versa, the Stirling engine would stop the peltier’s cold end cooling down enough. So overall you’d lose out. Which I believe is covered by the first law of thermodynamics.

    2. IIRC, and I may not, a stirling engine large enough to produce usable power is about the size of a city bus. Efficient but not yet practical.

      1. You do not remember correctly, an integrated unit of stirling engine and generator (200W) weighted about 30kg and was 40x45x27 cm in size. For proof google: “Philips MP1002CA”

    1. You know, after all the coverage of HeatSync Labs in Arizona, dude probably picked up some bloggy muscle memory he has to overcome. I can see it being a pretty natural mistake.

  4. The build have the same problem as one i built, the fins are horizontal, so once the heatsink is hot, it cannot dissipate the heat. You need a Heatsink with vertical fins to utilize the convection cooling…

    1. Stick a heatsink on the hot side of the peltier, turn the whole assembly sideways and place the new heatsink in the chimney of the stove.

  5. It also seems to me that a voltage measurement here is not very informative. I would want to know how much current it can pump.

    1. I would guess between 100 and 350mA. That’s what mine would produce when I was trying similar arrangements. A mini steam boiler or pretty much anything else would work better. Thermoelectrics just can’t cut it as a primary power source.
      They are a hell of a lot of fun to experiment with, though! This one is a nice, clean build.

  6. Somewhat less green because it burns alcohol. A rocket stove like this that burns small sticks that otherwise are only good for compost would be more green. It would be interesting to see stats on how much energy you would have to get out of it you equal the amount of energy it took to make the heatsink and peltier unit. That kind of math is beyond me though, maybe Randall Munroe at http://xkcd.com would be up for it.

    1. I’m fascinated by this as well but I haven’t found much else about it on the internet. I would love to see this work but without any data I can’t get my hopes up.

  7. Around the same time 1960 our school encyclopedia had a picture of a hookah powered radio in India. It was new it was progress, getting it on in the modern world.
    Being able to push a TEG up to edge of a campfire with the cold side away from the fire, would be elegant.

  8. What about using something like this on an internal combustion engine’s exhaust? Granted you won’t get much power, but you’ll get some that would otherwise be lost to the environment as heat.

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