Wind Turbine

posted in: Energy, Open source design | 0

The construction of the wind turbine came about from conversations with a friend who lives around these parts and who was thinking about running training courses in making low cost environmental energy products. It seemed to me that many components necessary to build the turbine, designed by Tim Piggott, were ideally suited to be made on a CNC router. These included the moulds for making the stator and the alternator, the coil winder and of course the turbine blades themselves. Keen to get involved with possible training activities I decided that the only way to get to grips with the technology was to build one for my self. The manual has all the information needed to build the turbine, but wood working and metal working skills are essential.

I borrowed the construction manual and set about buying components and materials. The Scorraig turbines are incredibly well designed, requiring mostly hand work to construct, the only thing that needs to be machined are the disks that that are part of the alternator. The five main areas of construction are briefly described below:

The blades

The blades were modelled in blender, a 3D CAD package, from the dimensions and instructions for hand carving them given in the manual. A 3D tool path was then generated in free CAD and the blades cut using the CNC router. They each took about an hour to cut and a further hour to sand and smooth. The three blades are then screwed to 2 plywood triangles to make up the full turbine. And after 5 coats of linseed oil they were ready to take on any weather.

Moulds for the stater and magnet disks

Both the stator windings and the magnets on the magnet disks are encased in resin to keep them in place, requiring moulds to be made for each component. Both of these moulds were drawn up in CAD and machined on the CNC Router

Coil winding mandrill

The mandrill for winding the coils was also drawn up in CAD and cut on the CNC Router, It was then bolted to a rectangular box section of steel and a handle added.

The frame

The frame is the main part of the machine, shown at the top of the photo . It incorporates the wheel bearing that allows the blades and magnet disks to rotate . A plain bearing that allows the generator to follow the wind and another plain bearing for the wind vane that keeps the blades perpendicular to the wind. This then sits on top of the tower. It has some quite complex angles that keep the blades from hitting the tower, and allow the machine to rotate out of the wind in a storm. Once welded it was all galvanized. The tower has a hinge system welded to the bottom, a number of tabs to connect the guy wires to, and a steel plate to attach the connection box too.

Frame, stator, and magnet disks
Resin coil block mounted on galvanised steel frame
Assembling the alternator

The stator and the magnet disks

Both the coils for the stator, and the magnets for the alternator, are encased in polyester resin which require moulds to be made so they can be cast in place. The magnets are fixed to two steel disks that were laser cut by a local firm. The wire coils have to be wound on a wooden mandrill, soldered together in sequence ,and then embedded in resin. These are then bolted to the frame such that the two magnet disks rotate on the wheel hub and the stator is stationary between them.

Setting up the infrastructure, wires battery and load controller

This was physically quite demanding. Five, 1 metre deep, foundation holes were dug and filled with concrete, one for the tower to sit on, and four to anchor the guide wires to. Then a 40 meter trench had to be dug to take armoured cable to the load controller in the house. Two 12v batteries were housed in a box outside the house and also connected to the load controller.

Erecting the tower

Once the generator, tower and wiring are complete, the whole assembly can be erected. For safety reasons it is best to put up the tower on its own first, without the generator, so that the guy ropes can be set to the right length and tensioned, and you can test the gin pole and raising mechanism. Once satisfied, that everything is safe and secure lower the tower, push the generator onto the tower, and connect it to the wiring system. The blades can be bolted on, the wind vane attached, and the braking system turned off. Winch the whole structure up, secure all the guide wires remove the gin pole and raising rope and wait for the first gust of wind to take the turbine for its first spin.

Final thoughts

Regulations would not allow us to tie the turbine into the grid, so we have connected it to the hot water tank, taking some of the load off the air source heat pump. On a good day it seems to generate about 400 watts resulting in a very special bath. I found it an extremely enjoyable project to take on involving a wide range of skills including woodworking, metal working, electrical engineering, resin casting, concreting, and the finished object it is an extremely satisfying edifice, generating not only electricity but also a considerable amount of joy and satisfaction.

Anyone interested in knowing more, or even wanting to come on a training course please get in touch.

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