We have been working on creating a stable way to charge our electronics while camping for a while. Solar panels work alright, but I find that when you really need your cell phone and GPS it is dark, sinister, and stormy out.
This Thermoelectric Generator can produce energy from common temperature differences such as snow, tail pipes, engines, candles, wood stoves, campfires, and anywhere else there is a temperature difference.
Check out this video of building and testing! :-)
What you will need for this instructable:
- Peltier Plates (Seebeck Plates)
NOTE: Make sure the optimal and maximum operating temperatures suit your application.
- Copper pipe
- Copper heat sink
NOTE: Aluminum may be substituted for copper, but the generator will have reduced efficiency
- Thermal Paste
- Mechanics Wire
- Crimp Type Electrical Marrettes (crimp type wire connectors)
- Screw Type Electrical Marrettes (screw type wire connector)
- Small Computer Fan
- Voltage Regulator (with spare connection cable)
- Metal Working Bench Vice
- Drill Press
- Wire Brushes
- Sand Paper
- Side Cutters
- Wire Strippers
- Clopping or Hack Saw
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Step 1: How It Works (Scientific)
Peltier plates "pump energy" because of thermal and electrical continuity differences in the materials they are produced from. At first glance, many people wonder if conductors may work better than the semiconductors, this is where the major predicament of the Seebeck effect falls. If a material has a low electrical resistance, it also usually has a low thermal resistance. If a material easily allows heat to pass directly through it, then it will disperse the temperature gradient the Peltier plates require to function.
Inside of the Peltier plates are many pairs semiconductors, the two semiconductors are placed thermally parallel (but electrically in series). The two semi-conductors (usually referred to as "P" and "N") have different electron densities (the measure of the probability of an electron being in a certain position, higher the density, the more electrons and the higher chance of hitting one), this difference causes electrons in the P semi-conductors to flow along with the heat, while allowing the electrons to flow against it in the N. This creates an electrical current as the heat flows through the Peltier.
Peltier plates are also able to force heat to move a certain direction, if an electrical current is applied in one direction it will flow through the semi-conductors pulling the heat in the direction of the current in the P semiconductor and against the flow of the heat in the N. If the current is reversed the heat pump will reverse as well, the heat will always flow in the direction of the current in the P semiconductor.
Because of the properties of Peltier plates they will hit a "wall." The plates can only disperse a certain volume of heat flux. To increase this volume there are multiple Peltiers in this generator are they are wired in series, this allows the plates to consume any excess energy passed on from the voltage regulator to pump heat. This increases the total heat flux volume of the generator.
We chose to use copper for our plate and heat sink because of its high electron density, meaning that it has an extremely high thermal transfer, allowing for energy production at very low thermal differences. This is why our generator can generate power from melting snow and solar rays, when ones with aluminum heat sinks are unable to. The animated heat sinks above show a simulated comparison of a copper and aluminum heat sink of the exact same dimensions, observe how the plate is cooler under the copper heat sink (on left) than the aluminum one (on right). Copper also has a higher melting temperature than aluminum, reducing the risk of accidentally melting our generator.
Step 2: Preparing Your Plate
Part 1 - Mark out the width and length of the heat sink onto the copper plate.
Part 2 – Cut the plate to height and width using a hacksaw.
Part 3 - Now use wire brushes and sandpaper to polish the copper, this will remove any corrosion, tarnishing, or debris. Polishing will improve the bond of the thermal paste and thermal transfer.
Part 1 – Measure the circumference of the copper pipe, ensure that is wide enough to cover the Peltier Plates.
Part 2 – Mark out the length of the Peltier Plates onto the copper pipe, then cut the pipe using a clopping saw to approximately 1/6” longer than the Peltier Plates.
Part 3 – Place the copper pipe in a vice, and starting from one end, cut through one sidewall along the entire length of the pipe.
Part 4 – Now use pliers to open the pipe until it is bowed to an arc with a radius larger than 6”
Part 5 – Pound the copper pipe into a flat plate using a hammer on a rigid surface (such as an anvil or metalworking vice).
Part 6 - Now use wire brushes and sandpaper to polish the copper, this will remove any corrosion, tarnishing, or debris. Polishing will improve the bond of the thermal paste and thermal transfer.
Step 3: Prepping Your Heat Sink
Part 1 - Scrape off old thermal paste if you have a used heat sink
Part 2 - Remove the screws and springs from the mounting bracket with a screwdriver
Part 3 - Drill out the mounts, make sure the drill bit is small enough to pass through the holes in the heat sink without damaging it, but will still make contact with the mounting bracket.
Part 4 - Some of the mounting brackets may fall off after being drilled out, but others may require a little encouragement with pliers.
Part 5 - Polish the contact surface of the heat sink using wire brushes and sandpaper to remove any debris, corrosion, or tarnishing. Polishing will improve the bond of the thermal paste and thermal transfer.
Step 4: Preparing Your Copper Plate for Mounting
Part 1 - Place the heat sink on top of the thermal plate and mark the holes onto the plate using a hammer and punch.
Part 2 - Using the same drill bit used to drill out the mounting brackets, drill holes into the plate using the punch marks as a guide.
Part 3 - Remove any debris and sharp surfaces created by drilling out the holes using wire brushes and sandpaper.
Step 5: Assembling the Generator
Part 1 - Before you can mount your Peltier (Seebeck) plates you will need to wipe them off with a damp cloth to remove any dust or debris to ensure a good bond with the thermal paste.
Part 2 - Apply a thin layer of thermal paste to each plate and place them onto the heat sink using an angled motion (to prevent air bubbles). Ensure that the plates are evenly spaced and make good contact.
NOTE: Both too little and too much thermal paste will inhibit heat transfer, make sure your coating is thin and even.
Part 3 - Apply a thin layer of thermal paste to the copper plate and place it top of the Peltier (Seebeck) plates, making sure to line up the holes on the copper plate and heat sink.
Part 4 - Cut 4 pieces of mechanics wire at least 1.5" long
Part 5 - Poke the mechanics wire through the holes in the heat sink and copper plate. Then fold over the wires and twist the ends of each wire together using pliers. (If you use zip ties, be careful not to melt them off during use)
WARNING: Do not over tighten the mechanics wire, you can crack the Peltier plates
Step 6: Wiring
The Peltier (Seebeck) plates must be wired in series, if they are wired in parallel and one Peltier plate begins to over heat and stops using up its fair share of the excess energy, the others will begin to transfer heat even faster, frying the Peltier that began to loose efficiency. Because they are wired in series, if one plate begins to over heat all of the plates will experience a voltage drop, causing less heat to be transmitted to the heat sink, allowing all of the plates to cool.
It is because of this unstable efficiency that a digital energy regulation device must be wired into the output. If you were to hard wire a transformer into the system you run the risk of either under powering or of frying your electronics.
NOTE: As pointed out by user UberGeeknz wiring the fan in parallel with the pelters wired in series will increase the efficiency of the generator.
Part 1 - Observe the above wiring diagram, trim and strip the wires between the Peltier Plates and between the Peltier Plates and the fan to be between 1” and 2” in length. Leave the leads to the voltage regulator at full length and only strip the ends of the wires.
Part 2 - Use crimp type marrettes on the orange connections (between the Peltier plates), and screw type marrettes on the blue connections (Peltier to fan and Peltier to voltage regulator). Since the polarity of the current will change depending on which side of the generator is hot, the polarities will need to be reversed.
Part 3 - Cut and strip the cable to your voltage regulator, remember that the center of the plug must always be the hot wire (positive). Make sure to mark it.
Step 7: Testing
Because Peltier (Seebeck) plates are capable of pumping heat in both directions, you must be careful not to back charge your voltage regulator. Once you know your generator you know it's polarity based on its heat direction.
For your first test I recommend a hot plate for a heat source and an incandescent lightbulb for a power test, as the bulb will light up with either direction of polarity. After the bulb lights up, change to your voltage tester and mark the hot wire, this wire will always be the positive when heating the copper plate, and negative when cooling the copper plate.
I have been able to Generate measurable levels off of electricity using snow in a warm room, a tea light candle, my truck's tailpipe, and a black metal plate in the sun.
When using a wood stove it is possible to stack two generators plate to plate, to produce more energy, and increase the efficiency of your generator, it also reduces the risk of melting the plates.
Step 8: Enjoy Your Reclaimed Power :-)
Now you can charge your devices (Cellphones, GPS Units, Cameras, iPads) almost anywhere that you can find a temperature differential.
If you have any suggestions for improvement, or have any questions, we would love to hear from you and see what you have built. Feel free to comment below! :-)
Have a great day!
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