The hand-crafted 200W, 4 ft wingspan Piggott wind turbine.
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This tutorial is based on the work of Scotsman Hugh Piggott Hugh Piggott. It was directed with the help of Aurélie Guibert, a member of the Tripalium Network in Valence, France.
It is about building a windmill of maximum power of 200W in 12V for a wingspan of 1m 20. It is designed for low power requirements such as lighting an LED or charging of a laptop.
The distribution part of the electricity and the matting are not given in detail here.
The power that the wind produces est proportional to the cube of its speed. For example, the windmill in this tutorial receives in its propeller 0.7W when the wind blows at 1m/s and a thousand times more at 10m/s.
To calculate it: P= 1/2 x Rho x S x v^3 with P: power (W), Rho: density of the air (about 1.23 kg/m 3), S: Surface swept by the propeller (m²), v: velocity of wind (m/s)
It is therefore necessary to study the land where we install the windmill to see if the wind blows relatively constant and with sufficient speed for producing minimum energy.
Like every other system, a part of energy is lost by the windmill. In theory, a windmill can never transform more than 60% of the energy that the wind provides, this is the Betz limit. In practice, with the type of windmill developed in this tutorial, the efficiency can reach up to 35%.
Generally, it is better to have land free from trees and dwellings. The windmills of the same height placed in cities or on the gables of the houses produce much less energy because of the wind's turbulence. Similarly, the wind is more constant and powerful on an altitude, therefore it is preferred to install a small windmill at height than a big windmill at a low altitude.
CostAlthough it is a Low-tech, the cost of constructing this windmill is around 350€ if all the materials are bought. Including the matting and the electronics, the cost is around 2000€. It can be interesting to install it in off-grid areas with a view to autonomy. In the case of a network connection, it is not financially attractive.
List of materials required for the propeller, refer to the chapters for details
List of materials required for the generator, refer to the chapters for details
List of materials required for the steel structure, refer to the chapters for details
List indicative of equipment, refer to the chapters for details
Note : The lower surface is the side of the blade which receives the wind, the upper surface is the back side of the blade.
1) The wood should be imputrescible, light-weighted and easy to work with. For example, red cedar, Oregon pine, spruce, larch, douglas fir may be suitable.
2) For this tutorial, the section of the red cedar plank is 150mm x 45mm.
3) The parameter which determines the energy transmitted by the wind at the propeller is the length of the blade and not it’s breadth.
1) Put the knots and defects of the wood at the end of the blade, so that the thinnest part does not become fragile (middle-end of the blade).
2) Select the leading edge ridge as neatly as possible. This ridge will not be altered during the cutting of the blade.
3) Extend the blade tip pattern by 4-5 cm to maintain a margin in case of damage.
Note: When using a circular saw for cutting, be careful to place the width of the blade always on the outside of the line.
Note: To guarantee good dimensions, the sculpture must come as close as possible to the pencil stroke without erasing it.
Note: The segment AB form an angle of 120° with the base of the blade, which will be later required for the assembly of the blades.
Note: In the case of this tutorial, the point B is situated on the perimeter of the circle. This is not always the case depending on the width of the plank.
Note: According to the thickness of the plank, it might appear that the thickness is not 17mm in section 3. Imagine a point in the space for the thickness 17mm on the rear edge on this section 3.
Note: The 30% line corresponds to the final thickness of the blade, which is why we check the dimensions at this precise location.
Note: Be careful not to crack the rear edge as it is very delicate area.
Once the work on the 3 blades is completed:
Note: The angle should be slightly less than 120° in order to be able to rotate the blades slightly during assembly.
Note: To help the propeller to fit-in on the rest of the wind turbine, it is possible to enlarge the holes of 12mm in 14mm on the thickness of the triangle and the blades, without touching the diameter 12mm of the disc.
Note: For a precise hole, point the center with a pin, pre-drill with a drill of small diameter and then at 12mm. Choose a rotation speed adapted to material and diameter of drill. Lubricate well during drilling.
Fix the two part temporarily with a few soldering points. Make the 4 drills across the base of the spindle and the cradle.
Note: If the 4 initial screws of the spindle are in good condition, they can be recovered by drilling only the cradle and screwing directly into the base. In this case, care should be taken that the original threading should not get damaged (which is a mechanical threading and cannot be used with other screws). It is sometimes necessary to shorten these screws so as to avoid problems during assembly.
Note: The stator is the fixed part of the generator.
1) If a clamp is used to maintain the threaded rod while cutting, wrap the threaded rod in a cloth at the jaws before tightening, to avoid damage to the screw pitch.
2) Before cutting the rod, screw a nut on the part of the rod that will be cut in order to reform the pitch of the screw at the level where it is been cut through the repeating passage of the nut.
Notes: The coils will be wound between the 2 discs of the plywood (thickness minimum 15mm), which are known as "ears". The small plywood rectangle between the two ears is the spacer: which determines the thickness of the coil. The inner shape of the coil is determined by the outer edges of the 4 large nails, this forms a rectangle of 46mm x 30mm. This rectangle corresponds to the dimensions of the magnets that will pass in front.
Notes: For the easy slippage of the wire, you can bevel the inner edges of the ears. Make markings with a marker on the edge of both ears to count the turns more easily.
Notes: The stator is composed of 6 coils made with 76 rounds of 1.4mm diameter enameled copper wire. This allows the generator to produce maximum 200W in 12V without damaging the wires. In order to make 6 coils, 1.5kg of copper wire is required.
Notes: It is important that all coils are positioned with the coils turning in the same direction, either clockwise or anti-clockwise. If this instruction is not respected, the generator will not function as expected.
2) Connect the output of 1 to the input of 4.
3) Connect the output of 2 to the input of 5.
4) Connect the output of 3 to the input of 6.
Notes: This step includes use of dangerous elements (resin, fibers, etc. ) Make sure to put on the latex gloves and safety glasses till the end of the molding.
Notes: the talc not only charges the resin using a cheaper material but also diffuses the heat during the drying of the resin and also during the future operation of the windmill without damaging the stator.
Allow to harden (it might take several hours). Then demold, deburr and varnish or paint.
Note: The rotor is the rotating part of the generator triggered by the propeller.
1) It is important that the disk is made of steel so that it can conduct the magnetic fields. It will not work with aluminum or stainless steel.
2) Il can be easier to get the disk prepared from craftsmen who have precise cutting tools (plasma, laser)
Note: This step consists of gluing together strong magnets on the steel disk by alternating the poles of the magnets. If the alternation is not respected, the generator will not function and there is risk of damage.
Note: Be very carefully during the manipulation of these magnets. Being very powerful, they can damage electronic devices, attract all kinds of metal objects and squeeze them very hard.
1) If there is repulsion, stick it in the adjacent notch keeping this direction: the 2 magnets have the polarities positioned in an opposite way.
2) If there is attraction, turn it over in your hand, check if there is repulsion now and then stick it in the adjacent notch.
Prepare two 150g container of polyester resin and two 2.25ml syringes of the associated catalyst.
2) A tube of external diameter of 42.2, length 100mm: Pivot windmill.
3) A tube of external diameter of 33.4mm, length 150mm: Rudder Pivot.
4) The cradle previously made.
Note: The heat released by the solder have a tendency to work the metal, deform the pieces and their positions. To avoid this problem, make a few weld points at a few strategic locations around the perimeter of the weld and then pull the weld bead.
1) A tube of external diameter of 42.2, length 130mm: Rudder Pivot.
2) An iron plat of 50 x 50 x 6mm: Cover of the rudder pivot.
3) A tube of external diameter of 33.4mm, length 700mm: Tail rudder.
4) An angle of 30 x 30 x 5, length 250mm: Rudder Support.
5) A plywood cut according to the desires of each, thickness 6mm and 0.1m ² of surface (for example a right-angled triangle of height 300mm and base 600mm): the Rudder.
"'Note"': To charge the 12V battery, it is necessary to transform the AC produced by each phase into a DC.
Remarque: Il sera nécessaire d'installer un contrôleur de charge entre l'éolienne et la batterie.
Vous pouvez télécharger une fiche pédagogique créée par le Low-tech Lab dans la partie "Fichiers" du tutoriel (onglet au niveau de la section "Outils-Matériaux").