Aeroelastic flutter is the back and forth motion of an object caused by the air flow. An example is the shaking of a plane’s wings during turbulence. This phenomenon has been used by Instructables user DylanD581 to produce electricity and is even more effective than a wind turbine in low winds.
Wind turbines only work with wind that’s not too slow nor too fast and that is blowing in a specific direction. Aeroelastic flutter energy harvesters can work with any type of wind, take up less space. They usually produce more voltage (but less current).
STEP 1: Technical Explanation and Materials
In order to produce drag, Dylan used a 3D printed object (of any basic shape) at the end of the flexible metal beam. This is to make for a constructive feedback loop (producing a twice larger waveform, by adding the waves). In order to trigger it, there should be a right amount of drag force (created by the object at the end).
He then glued piezoelectric discs to the beam to generate electricity. They are special crystals that generate electricity as they move.
- 1/2″ PVC Pipe
- ABS 3D Printer Filament (or another strong material, such as nylon – feel free to experiment)
- Printed STL Files
- Ribbon Wire
- Full Wave Bridge Rectifier (individual component, or a homemade circuit)
- Piezoelectric Crystals
- Ferroelectric Materials (man-made piezoelectric crystals – these are the flexible, film-style ones)
- Super Glue
- Hot Glue
- Acetone (for smoothing 3D prints – optional)
- Aluminum, Brass, or Copper 3/4″ Beams
Step 2: 3D Printing and Post-Processing.
First of all, load ABS filament into your 3D printer. Dylan chose ABS because of its toughness and resilience, but you can choose any other filament. After that, use a Printrbot Simple Metal, printing at 230C with a heated bed temperature of 60C. Make sure to print everything at a layer height of 0.1 mm. After that, use acetone vapor, for a smooth surface finish.
Step 3: Assemble the Beam
You will need an 18″ long beam. You can cut it to the desired length using a metal-cutting blade. As a material for the beam, aluminium is appropriate, because it is flexible and cheap enough. Next, you will have to insert one of the “PVC Pipe Attachment” fitting into 1/2″ PVC pipe of any length. You can use “Dual PVC Pipe Attachment” if you want to place more than one generator on one length of PVC piping.
After that, adhere the piezo elements to the beam with super glue. Place them near the ends and in the middle, since most flutter will occur there. If you want to produce more electricity, you can use ferroelectric materials. However, it will be much cheaper to buy dozens of small crystals off Aliexpress/ebay and to put them all over the beam. Finally, let everything dry and put the printed object on one end, and the other end will go into “PVC Pipe Attachement”.
Step 4: Wire the Electronics
Now you have to connect wires to the piezoelectric crystals. Use two wires for every crystal and solder one to the positive (silver) pad and another one to the negative (gold) pad. Keep in mind that you will need to bring the wires down to the control box, so choose the proper length. You can use rectifying diodes for every crystal in order to prevent the interference of the voltages. However, if you don’t want to spend a lot of money, you can wire them all together without diodes. The final output voltage will be lower in this case, since some of it will cancel out. Diodes are dirt cheap, too.
Next, connect everything to the full wave bridge rectifier, since it will prevent any voltage from going back and powering any of the piezo transducers. Additionally, the power will be converted from AC into DC electricity. Optionally, you can use a buck/boost converter to reduce the voltage and gain more current.