Introduction: Fan Powered by Any Heat Source
How to build your own portable thermoelectric device with a quadcopter motor.
This project might not have an electrifying impact to the world but it´s a baby brother to my first instructable (Thermoelectric Fan) and just had to be built. It´s much smaller than most similar projects and the top power device can be detached from the lower heat source base and be used as experiment in other areas. What does it do? It converts heat energy into kinetic energy, looks nice and sounds awesome!
It uses a thermoelectric generator module (TEG) to power a motor with a fan. The heat source (candle) heat up the lower aluminium plate => creates a temperature difference over the module => generates electricity to the motor => increases air flow through heat sink => increases temperature difference => more power. Without the fan it would eventually stop generating power since the heat sink would get almost same temperature as the plate.
Almost any heat source with enough temperature can be used to power the motor and this makes this small device easy and fun to experiment with. It´s very sensitive to temperature differences. I could run it on water with only 20C difference (23C air temp and 43C water temp). As seen in the video it´s powered from fire, hot water, food, and even used to cool a computer processor. The latter is an idea I had when i created my first build in 2013 and people said to me it cannot be done. It can and it´s stable for normal use but with further optimizations it could probably be even better. I don't think it can replace a regular CPU cooler but as it uses no electricity from the computer it´s somewhat environmental friendly. More information on last page.
- Size base: 56x64x40mm
- Size power device: 56x56x40mm (including fan)
- Size total: 64x64x79mm
- Weight base: 27g
- Weight power device: 85g
- Weight 3D print: 2.7g
- Weight total:114.7g
- Cost: ~12$
It require few parts, easy to build and you do not need any knowledge about electronics. You just need some mechanical tools for cutting, drilling and polishing the aluminium. If you want to build it, please read further.
Step 1: Materials and Tools
I think you can find everything on Ebay. Prices are estimated. Aluminium and bolts not included in price since it´s basically scrap metal.
- 1x Motor: Hubsan x4 20x8mm (20x7mm also works) [$3]
- 1x Propeller: Hubsan x4 propeller [$1]
- 1x TEG: 40x40x4mm (My module is same as used in Powerpot5, but most TEG or TEC will work) [$4]
- 1x Heatsink: 43x43x16.5mm (ICK PGA 17X17 8.6C/W by Fischer Electrinics) [$4]
- 1x Aluminium sheet: 56x56x3mm
- 1x Aluminum sheet: 75x65x3mm
- 3x Bolts: M4x40mm
- 2x Bolts: M3x15mm
- 1x Wire: 0.5x150mm
- 1x shrink tube: 30mm (optional)
- 1x CPU thermal paste (optional for better heat transfer, I highly suggest it): For example Keratherm KP 92
- Screw driver
- Drills: 2.5mm, 3.3mm, 4mm & 7 or 8mm depending on motor
- Screw taps: M3, M4 (optional for better stability)
- Soldering iron (optional)
- Sandpaper: Different types from 100-1500 grit for smooth surfaces (optional for nice finish)
- 3D printer with T-glase filament: For my special design part (optional)
Step 2: Construction
Wire (Used for fixating the heat sink)
- Fixate the two M3 bolts (CC=50mm) to use as template
- Bend the wire around the bolts and twist the ends
If you use a 8mm motor you will need a 8mm centered hole in the heat sink.
- Use pliers to cut the middle parts of the heat sink if possible
- Drill a 8mm hole (not all way through the bottom)
- Check that motor fits into the hole (wire goes beneath the motor if possible)
Bottom Aluminium Sheet
- Use hacksaw and file to make it nice 75x65mm
- Wait to cut it triangular to make easier to fixate in machines
- Draw edge lines (red) and mark up for three M4 holes, see image for measurements
- Drill three holes with 3.3mm drill if you want to use M4 threads, or 4mm if no threads
- [Optional] Create M4 threads with thread tap
- Cut the edge with hacksaw to get the triangle
Top Aluminium Sheet
- Use hacksaw and file to make it nice square 56x56mm
- Use the bottom sheet as template and mark up same three holes, see image for measurements
- Drill three 4mm holes (half way through), we use no threads here to make it easy to attach/detach
- Use the heat sink as template or my measurements to mark up the two M3 holes
- Create M3 threads with thread tap
- Chamfer all corners (10mm long (diagonal) bottom chamfers, 8mm long (diagonal) top chamfers
- For nice design, use sandpaper or other tools to create a nice finish of the two aluminium parts. I used step by step paper grit 200 up to 1500.
Step 3: 3D Printing (Optional)
For design purpose you can print this special part if you have a printer and transparent filament like T-glase.
I used a wanhao duplicator 4x printer and simplify 3D software. If you want it lower or higher you can simply scale it along Z.
Link to model:
- Layer height: 0.37mm (single outline corkscrew method (vase mode)
- Shells: 1
- Infill: 0
- Top and bottom layers: 0
- Extrusion multiplier: 1.15
- Extrustion width: 0.5mm
- Speed: 600mm/min (10mm/s)
- Temp extruder: 235C
- Temp bed: 80C
Step 4: Assembly
- The TEG module is placed between the heat sink and top aluminium plate
- Use thermal paste for better heat transfer on both side of the TEG
- Place motor in heat sink with both motor wires and steel wire loop beneath it
- Screw the heat sink using two M3 bolts and through the wire loop
- Connect the motor to TEG and solder it using shrink tubes (optional)
- Screw the M4 screws all way through bottom plate
- Place the module on top of base and use 3D printed part if you want (Gives a little more power as it shields the candle flame)
Step 5: Self-regulating CPU Cooler
The module could be used in a computer to replace a conventional CPU cooler. It uses only heat from the CPU to power the fan, which in turn transfer the hot air away from the CPU. It might not have enough efficiency for a modern CPU but this is more or less a proof of concept. It does not require a sensor, electronics or motor controller as the fan speed is self-regulated by CPU temp.
Currently tested on an AMD Athlon 64 3800+, 2400MHz single core, 89 Watts. Normal computer use was stable but I also did a 5 min stress analysis both with and without the motor fan compared to stock cooler. Clearly the fan helps to cool the CPU. The stock cooler is a 80x70x70mm heatsink (402g) plus a large fan compared to my small device (85g with motor & fan). Last thing I tried was to only use the small heat sink without any TEG in between but the result was exactly the same. The TEG surprisingly conduct heat quite good and with that I can finally conclude that using a TEG gives better cooling than without (with equal build volume).
- Idle [stock cooler]: 30C
- Idle [TEG-fan]: 37C
- Idle [TEG-noFan]: 60C
- Idle [Only heat sink, no TEG]: 60C
- 100% load [stock cooler]: 49C
- 100% load [TEG-fan]: 75C
- 100% load [TEG-noFan]: Cancelled at 95C to not damage CPU
- 100% load [Only heat sink, no TEG]: Cancelled at 95C to not damage CPU
After the test the CPU went back to stable 37C and fan RPM went to normal. Also be aware that I did not apply any down force on the device, it just rested on top of CPU and if you´re a computer builder you know that is not very efficient. The device is also way smaller than stock cooler and a larger TEG and heat sink would probably do a better job. Would be great to see someone else experiment with this! Though, I will not be held account for any CPU damage. This particular CPU has a rated max temp of 69C so I would not recommend the build as it is.
Update 1 (Second picture):
Also tested with added small heat sinks on the bottom plate for better cooling from left-over air. I did this to show that parameters can easily be optimized further. Just to be sure, I removed the extra aluminium during the test and temp increased to 75C as before.
- Idle [TEG-extra cooling]: 37C
- 100% load [TEG-extra cooling]: 71C