Emergency Light/Charger From Fire & Water




About: I like to design, construct and experiment with both old and new technology, especially when it includes mechatronics. I'm also devoted to photography, computers, programming and technology in general.

DIY a really simple Thermoelectric Emergency Generator from very few parts.
Optimized for powering with tealights/candles.

With inspiration from my previous projects:

This was made as an experiment to test efficiency when using water as cooling component in a thermoelectric system. The result was very interesting and as it was really easy to make I thought I could share this too.

It converts heat energy (from candles) into electricity. Main usage is to power LED lights to act as an emergency product. It could also be scaled up and used in homes where electricity is not very given. It could also be used as a battery charger or power other electronic devices. I´m well aware of the commercial product tPOD1 which I think is a great idea but I´m more interesting in a DIY solution for everyone.

I´m using a thermoelectic module, also called peltier element, TEC or TEG. You have one hot side and one cold. The temperature difference in the module will start producing electricity. The physical concept when you use it as a generator it's called the Seebeck effect. Thermoelectic modules are mainly used for the opposite effect, the Peltier effect. Then you apply a electric load and it will force a heat transfer from one side to the other. Often used in smaller refrigerators and coolers. Read more about i here:

First I used a cheap TEC-module (8€) but it was unfortunately destroyed due to high temperatures. It was specified to handle 200ºC max temperature but somehow I got higher temp than I measured. I ran it without load, that might be the cause. I now use a 40x40mm TEG-module that produce 5.9W (4.2V/1.4A) at 180ºC difference. It has a maximum operating temp of 350ºC (180ºC cold side). It was the same module I used in my other charging project. It´s quite expensive though, about 50€. TEGs are a bit hard to come by but I think there are cheaper ones available.

To transport away all heat and cool it with air you usually need a large heat sink, or a small heat sink with a motor and fan. In this project I use water instead. That make the contruction really compact and the temperature on the "cold" side will never exceed 100ºC. Water will eventually boil but it´s easy to refill, as long as you have water.

To power LEDs you need higher voltage than the module itself produce. In my previous project I built an adjustable regulated voltage Step-up. That could be used (and is better) but I choose to use a $1 step-up from Ebay.

The best choice of heat source is 3x tealights. That produce about 0.2W electric power.


  • 90g (without LED)
  • WxH=85x78mm
  • Built in voltage step-up
  • Support for 3x tealights

Mainy constructed to power LEDs but can be used for other things as well:

  • Battery/smartphone charger
  • External fan (cooling effect, fire booster, etc.)
  • Electronics
  • Charge super capacitor and power high intensity SOS signals

Could also be heated with lots of stuff:

  • Candles
  • Spirit burner/stove
  • Gas burner/stove
  • Wood stove
  • Camp fire
  • Barbecue
  • Hot water

Step 1: Materials

  • 2x cans of tuna-fish or similar (diameter=85mm). You need as flat bottom surface as possible, larger than TEC/TEG-module. Make sure it fits 3x tealights inside.
  • 2x 40x40x3mm sheets of aluminium
  • LEDs (I used a "USB notebook light" with two LEDs)
  • TEC or TEG module. I bought mine "TEP1-1264-1.5" at http://termo-gen.com/
  • Voltage step-up (1 to 5V). Search Ebay for "emergency aa battery portable dc charger". Another cheap circuit is this one: http://dx.com/p/usb-dc-1-5v-to-dc-5v-voltage-step-up-boost-module-green-143571
  • Thermal paste (better if specified for high temperature, 200+ºC
  • Optional: 3x pull springs to add stability and heat transfer
  • 6mm drill
  • File
  • Sand paper and/or steel wool
  • Optional: Soldering iron

Step 2: Construction

Prepare Can 1:
This will be used to absorb heat from the candles. Fire needs air and that is why you need to make lots of holes in the can. Most cans are covered with some kind of varnish. That smell really bad when you heat it up. You need to remove that.
  1. Remove labels with hot water
  2. Drill 18x3=54x 6mm holes
  3. Use the file to reduce sharp edges
  4. Heat up the can, outside! I used a gas stove. It will burn and smell really bad. Then you can remove the varnish quite easy with a file or steel wool.
Prepare Can 2:
That does not need to be prepared much. It will just contain water. Remove labels with hot water.

Prepare aluminium distance plates
They will act as a distance between the cans. Depending on what can you use, you might skip those. But I think they also are good to get a more even heat transfer.
  1. Make them 40x40mm, that make them compatible with different TEG-modules. I had to also make 10x10mm chamfer on the corners to fit the flat surface of the cans.
  2. Use fine sand paper or steel wool to make them flat and nice
Assemble Mechanics:
  1. Prepare one side of plate 1 with thermal paste
  2. Place plate 1 on top of can 1 (with thermal paste facing down)
  3. Optional: Prepare plate 1 with thermal paste (depending on what TEC/TEG you use)
  4. Place the TEG module on top of plate 1
  5. Optional: Prepare TEG with thermal paste (depending on what TEC/TEG you use)
  6. Optional: Place a thermal resistor on top of plate 1 if you want to monitor temperature
  7. Place plate 2 on top of TEG
  8. Prepare plate 2 with thermal paste
  9. Place can 2 on top of plate 2
  10. The order is: Can1-Paste-Plate1-Paste-TEG-Paste-Plate2-Paste-Can2
  11. Optional: Add pull springs to hold the cans together, see pictures.
Assemble Electronics:
  1. Connect the two cables on TEG-module to your step-up booster (check polarization)
  2. Connect LEDs to output of step-up booster (check polarization)
I used a soldering iron and screw the cables to a terminal block. The terminal block was glued to can2.

Step 3: Result

Lit your candles and enjoy! Be careful with the temperature and make sure your TEG-module can handle it!

Output power from TEG at different water temperatures:
30ºC:  0.25W
40ºC:  0.23W
50ºC:  0.22W
60ºC:  0.21W
70ºC:  0.21W
75ºC:  0.22W

It never got over 75ºC with three candles. Water vaporizes at a rate of approx. 40ml/hour.

The efficiency of the booster/voltage step-up measured to 70% (Input=0.23W, Output=0,16W). That is enough to power some LEDs!

  • I used the can of water and replaced the heat sink and fan in this project: Smartphone Charger
    I managed to charge my iPhone 4s with 1W power at very low gas output. I could have used only this construction to charge the phone with the gas stove but I didn´t want to mess up my thermal paste with that kind of heat.
  • Once it has started (must exceed 1V), one candle is actually enough to power the LEDs! It will vaporize less water.
  • If you don´t have fire, then just take a glass of hot water and fill the upper can with ice. That gives light for 30 min!
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    26 Discussions


    2 years ago

    Hie sir,
    I was thinking to charge a smartphone through this project is it possible get a output


    2 years ago

    I try to do it with a SP1848 Teg but it doesn't work. Any suggestions?


    2 years ago

    sorry tons of lagging autocorrect, where did you get your aluminum plates?


    2 years ago

    hi Iantto nd the aluminum plates. Where did you get yours?t c

    Mark LesterV

    3 years ago

    Cool project! Me and my classmates would like to do this and we were just wondering how many volts is needed for it?

    Mark LesterV

    3 years ago

    Coll project! Me and my classmates would like to make this an we were just wondering how many volts needed to make it work?


    6 years ago on Introduction

    Please mail me detail layout of TEG or TEC module.

    Is it possible to make peltier module at home.

    Thanks a lot

    1 reply

    Reply 4 years ago

    it probably is, but the homemade variant will actually cost more in materials, and will be worse in every single way


    6 years ago on Step 3

    Very well done! Thank you do much for this guide. I can't wait to try this!


    6 years ago on Introduction

    I love these projects. Great work. I have often thought about lining a chimney flue with peltier modules. I live off grid and during winter solar is down especially with cold batteries. We pretty much run a fire 24/7 and an external flue seems perfect to line with these modules, ie sub zero outside very hot inside. Granted you need maybe 30 of them but comparing the costs and wattage output to a solar panel it really isn't that bad and they run at night! These projects are very inspiring. Thanks!!!


    6 years ago on Introduction

    Great instructable!!

    Really awesome to see your progression through the various peltier projects you have made.

    Voted :-)


    6 years ago on Introduction

    your project reminded me the peltier projects i did some years ago but then were very expensive and not so many size varietes. Very good instructable!!!


    6 years ago on Introduction

    These are they type of projects I love to see at instructables.