Fire Power: Electricity From Heat





Introduction: Fire Power: Electricity From Heat

Lego created a robotics contest that focused on the advance of technology in students at schools and other organizations. This contest is known as FLL (First Lego League) and uses Lego's robot kit- Mindstorms. Each year, a theme is chosen to correlate with the robot and the other aspects of the contest. This year's theme is titled "Natures Fury", and it involves natural disasters. A table is set up with "missions" (also made of Legos and relating to natural disasters) that must be completed by a robot built and programmed with Mindstorms.

As well as the robot part of the contest, a project or innovative solution must also be built that solves a problem in a natural disaster. This Instructable is a collaboration of our efforts on the project and will serve as a means to present our information to judges at the FLL competition that we will be attending this month.

The grading rubric used to judge the project design states that the project should be "shared with multiple individuals or groups who may benefit." What's a better place to share than on Instructables? We would like to thank all of the viewers like you in advance for the support and the helpful feedback you will surely give.

If you would like to read about the process in which we decided to build this project, then follow along, but if you want to skip right to the building instructions jump to Step 2.

Please do not forget to vote for this Instructable in the contests if you like it. Thanks

It has finally warmed up (from -10), so I was able to get outside and test for voltage and amperage on the project. Please refer to step 4 (Use Your Stove) for more details.

FLL Website-
FLL Rubric-

Step 1: The Problem

First, we chose a community and natural disaster to study. From there, we selected a common problem in the disaster. Here is a diagram of how we narrowed down the broad topic to our project idea.

Community: Northern Wyoming > Storm: Thunderstorm > Common Problem: Power outages > a need for electricity > using available resources > fire > HEAT POWERED BATTERY CHARGER!!!

As you can see, a long process occurred between choosing a community and selecting a project. One of the many reasons that we selected power outages as a major problem was because we felt that it was a somewhat overlooked topic. In thunderstorms, many people worry about the immediate consequences (lightning, heavy rain) but forget about the prolonged problems. Power outages can last anywhere from hours to weeks. That is weeks without power. Say goodbye to phones, lights, heaters, and all electronic appliances/devices.

For our project we selected an electricity generator that uses heat to produce electricity (more on that later) because 1.) You can recharge batteries on essential things such as flashlights, radios, and phones. 2.) We killed a couple birds with one stone with this project... While you wait for your batteries to charge, you can soak up the warmth of your heat source, cook food, and have a source of lighting.

Now we realize that there are a few amazing solutions already out in the wild that could potentially solve this problem, but we still feel that our project is quite useful.

Solar power/chargers- Solar power can still be quite expensive, despite the fact that prices have dropped greatly in recent years. Also, the sun is not out all of the time. What if you would like to generate electricity after dark or when the sky is overcast?

Hand crank devices- These are great, but would be potentially harder to build and are already readily available to many people. We wanted to create a project that was innovative.

Wind generators- Hey, the wind doesn't blow all the time.

Biolite Camp Stove- We also found that a commercial version similar to our was project available. However, it only charges usb devices, and it is quite expensive at $129.95.


Step 2: Introduction/Materials

As you have probably gleaned from the previous steps, this project has something to do with using heat to generate electricity to charge batteries. This is all true, but there is much more in the science of the project than what first appears. Even for someone completely oblivious to all of the little components that make up our everyday electronics, our goal is for this project to be easy for all to build in case of a disaster.

The entire project can be built for roughly $30.

The key component of this entire project is a device called a Peltier Module. Also known as a TEC or a thermoelectric cooler, this small, 40x40mm, white ceramic square is really where the magic happens. A peltier module is normally used in small cooling applications such as wine coolers and novelty pop chillers.
A peltier module basically consists of a sandwich of a ceramic plate, a thin metal film, a semiconductor, another thin metal film, and finally an additional ceramic plate. When DC electricity is applied to the two wires protruding from the device, it pulls in heat from one side to the other; one side of the device gets cooler while the other gets hotter, creating a temperature differential. This is useful for applications such as cooling.

However, if a temperature differential is placed on the peltier, such as one side being placed over a heat source, and the other side cooled, electricity is generated!!! This process is known as the Seebeck Effect. (for further information on the science behind the peltier module, please check out the sources listed at the end of this step. This is the principle that we will be using to generate electricity.

Here is a list of parts that are needed to construct this project.


Step 3: Build!!!

The first step for building is to solder the circuit together. If wanted, you can prototype the circuit on a breadboard before permanately soldering. Please reference the above diagram created in Fritzing to help with the soldering process. If you need help soldering, a very thorough source can be found at:

To attach the peltier module to the heat sink, we cut an inch hole in the lid of a large can. We then centered the peltier over the hole and sandwiched it between the heat sink and the lid. We used screws and soft wire to securely fasten them together. Another option to attach the heat sink to the peltier is to use thermal compound, a sort of thermally conductive glue. Lastly, we shrunk heat shrink tubing over the peltier's wires to shield them from the heat. For the convenient carrying case we cut to fit a square out of the small plastic box and screwed the spring terminals into the box. After screwing it in, we proceeded to solder in the appropriate wires and components. In addition, we printed out labels and glued them to the spring terminals for easy connecting.

After reading about this device, you are probably curious about how the circuit works. Here is a basic rundown of the workings. First, the Peltier module produces electricity due to the temperature difference. On one side of the module extreme heat is placed, while on the other lies a heat sink. See all of those wavy bits of metal? These aren't just for beauty, they are designed to maximize the surface area for heat to be dissipated, cooling this side of the peltier. This is similar to the ridged metal surrounding the engine on a motorcycle.

Next, the electricity reaches the diode in the circuit. A diode only allows the electricity to flow one way- towards the battery. If a diode was not placed in the circuit, than the battery would drain itself by putting electricity into the peltier module and creating the cooling effect described earlier. Finally, the electricity reaches the battery and, if the voltage is higher than that of the battery, will began to charge it.


Step 4: Use Your Stove

To use the device, simply plug the red peltier wire into the voltage input (labeled VIN) spring terminal, and the black peltier wire into a ground (GND) terminal. Finally, insert the positive wire of the battery into the voltage out (VOUT) terminal, and the negative wire into the other ground terminal. It is very important to note polarity when connecting the wires. Place the peltier and heat sink over a heat source with the lid facing down. Once the peltier has heated to a high enough temperature, a suitable amount of electricity can be generated to charge the battery. To ensure that the device is working properly, first measure the voltage of the rechargeable battery at the beginning of charging time. After a little while, measure the battery again. You should find that the battery voltage increases!

Heat source ideas:
Although there is many different possibilities to heat your generator with, we have found that a rocket stove works quite well. A rocket stove is essentially some kind of a container (such as a tin can) with a hole poked into the bottom so that air can flow in. A fire in the rocket stove is very easy to light, and, after lit, becomes extremely hot. For instructions on how to build your own rocket stove check out this instructable:
For fuel, we made some fire starters using egg carton, wax, and dryer lint. They work marvelously. Check out this instructable:

I have tested the stove and recorded various readings concerning volts and amps. Here are my findings:

Heat Source: rocket stove with direct flame
Load: 1.2 volt "D" rechargable battery
Air temperature (this will effect the temperature differential): 14 degrees Fahrenheit
Volts produced: 2.2-3.2
Amperage: 350-400 mA
Watts: .77-1.28 watts

Step 5: In Closing...

Thank you to all of the viewers of this instructable. We encourage you to try this project. If you need any help or have any suggestions just post a comment below. Our main goal was to solve a problem in a thunderstorm. We feel that this has contributed to the many already available resources to prepare for a power outage. Now that the project is completed, I think that we have realized that this project could not only be useful in natural disasters, but also for camping and just getting free electricity. Thanks for viewing and good luck building.

Here are some ideas for future updates to the design.

  • a battery charge-status monitor
  • USB compatibility
  • a switch to turn the charging circuit on and off
  • a more elegant design
  • A circuit built into a stove
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100 Discussions

I was wondering if it is possible to connect 2 Peltier's in series so that the voltage doubles. Would I have to add any extra Schottky diodes then?

This is a great idea, if you need more powerful output thermoelectric coolers in series for higher voltage or in parallel for more current for charging more divices

Maybe an other idea: if you would us 2 peltier modules, the voltage would be around 5V. If you then connect it to a power bank, you've got your USB port. You would only need a micro USB for the input though. Is this realistic you think?

well i waiting for delivery two peltier module, will check and report :)
also with this booster i successful charge mobile with 2 AA battery.

I was wondering if it is possible to connect 2 Peltier's in series so that the voltage doubles. Would I have to add any extra Schottky diodes then?

I have tons of expendable heat in my region. Dallas, Texas, US. But I wanted to throw this out there.

Solar panels lose efficiency when over 25° C. This is a year round situation here since the panels are black. My roof without panels measures 140°F on an 80° day in cool April in the morning. Why not ($, i know) put TEGs (thermal energy converters) on the back of the solar film (the shady side) to beef up output by cooling the solar panels. Still need heat sinks of course. Then, simply series these guys up with the solar panel to add heat generated power before the optimizer makes the most of this marriage and essentially collect solar energy from all wavelengths that the panel doesn't reflect including radiant heat (very long wavelength infrared) and really, a panel maker can always add absorptive pigments and materials on the back to just collect whatever reflects off, and to the surface of the TEGs to collect everything that passes right through the panel and boost panel output and efficiency. I realize I am leaving out some things but I am throwing the concept to "paper" to stimulate thought.

I read that scientists are developing a panel that collects light in 3 different ways, each designed to be most efficient in its band of light, all visible bands, BTW. If you made it past Jr high you saw that visible light is just a sliver of solar radiation so tiny it was represented by a line on a whole page. What of everything else that will soon be cutting the power of my rooftop PV system--stuff that may or may not be visible, regardless of the source-- energy. Energy that CAN be collected by a "solar" panel and can be converted to electricity?

The answer? Well, redundantly, it can be electricity too and it would make a darn good radiant barrier too, a third benefit by reducing the amount of energy my AC unit has to pump outside. Hey, just a thought.

Those 3 band solar cells won't hit the market for 35 years. Don't hold your breath please.

These TEGs that are too expensive now (many would say), if made in the billions for radiant energy panels formerly known as solar panels, would drop in price as economy of scale does to things. So yes, thats the cost: cost. But in a disaster zone, even if cloudy a solar cell will do ok, today. Now, it will do how much better? I don't know. It depends. Try it and measure your results and conditions.

My point is that in a disaster the sun is always there, whether the clouds matter or not depends only on what wavelength we measure or utilize. Now, why not utilize all of them that reach down here and keep your panels cooler and more efficient too and generate enough, without a fire, to get somewhere safe from forest fires caused by other people's TEC projects. I'm joking about the fires, lol.

Well, if you are in a disaster, a fire can be mighty hard to make, illegal, or it can be dangerous too, I suppose. I'm likely to hurt myself trying to do the bow and stick thing. I'm too old. A better solar panel helps everyone, everywhere, anytime, disaster or not. Maybe. I think probably so.

It looks like about 20,000 watts input to produce 1 watt output!

3 replies

Just what I was thinking. The ONLY practical use I can imagine for this is when one MUST have a fire AND one has no access to electricity for small batteries. I CAN imagine such a scenario following a significant weather event when ALL electricity is out AND you have NO ACCESS to a generator, AND you HAVE to start a fire AND you NEED to use your cell phone for an emergency. Otherwise,

Build a FIRE to charge a small batter? REALLY?

If this was applied in a different way, this would be practical. Think of waste heat.. i.e. water heater, exhaust pipe, stove/oven, roof of your car on a hot day...

Fair enough. A source of WASTE heat is a good place to put one of these. However, waste heat is going to be difficult to find in a "disaster area". Still, I would offer that my comment was reasonable, (even if incomplete), in the context that the author posed, AND in the unlikelihood that "waste heat" would be available in a "disaster area". Maybe better rephrasing of my assessment would have been - This device is really only practical/reasonable where waste heat is available or when you HAVE to build a fire and thereby have some waste heat available and NO other source of electricity.

Please keep up the good work, far 2 many great ideas have been lost over the years. For example; The URINE POWERED ELE. GENERATOR, invented back in the 80 or 90's, and due to lack of interest, forgotten about!

Please keep up the good work, far 2 many great ideas have been lost over the years. For example; The URINE POWERED ELE. GENERATOR, invented back in the 80 or 90's, and due to lack of interest, forgotten about!


2 years ago

Just get a $11, 10 watt, 12 volt solar
panel from ebay and hook your usb charger to it. It even would trickle charge your
car battery or 4-wheeler to keep the batteries charged.

And in
cloudy days it still would produce 10% to 50% of the power output,
depending how dark the clouds are and how many clouds you have.

A solar panel that has more power for less money compare to the thermo electric.

i dont know where this guy is getting 30 bucks from a peltier cooler is only 6 dollars or less on ebau.. and you dont need a battery holder some rare earth magnets for 1 dollar and some bolts and nuts on the end of the wire then just put on the magnet it will stick to the bolt and stick to the battery ends.. and wire thats lieing around the house.. and heat sink use a old laptop one etc it needs to be fairly big to disapate more heat than its getting or the peltier will be damaged..


2 years ago

Since the peltier junction runs on temperature differential, instead of heat sink, try a can full of snow. When the snow melts, toss the water and refill with snow.

Hi. I know this Intractable was ages ago but I was curious to know how big the heatsink you used was, and what side of the Thermoelectric Cooler you put it on. I used to be in FLL for 3 years and won 2 awards in the Australian comp, the Natures Fury year was my last and I used to absolutely love it. It's interesting what other teams thought of for their solutions. :)

2 replies

My heatsink was from a computer and was used to cool a CPU. Its dimensions are 3" x 2.5" x 2.5" (l x w x h). I just did a test, and it doesn't appear to matter which direction the peltier is orientated. Nature Fury was my first and last FLL competition. I have since moved onto the First Tech Challenge (FTC) which is a ton of fun.

have either of you tried FRC?I was a student all 4 years of Highschool, and mentor for 2 years, tons of fun, and the comunity is beyond helpfull