As I promised, in this post I will share the experience I made during the small wind turbine construction course, which took place in Nea Makri near to Athens from the 19th to 28th of December 2014. As adding pictures and alike is rather difficult in wordpress, I made a PDF of the text with a better format, which you can download here.
The course was arranged by Nea Guinea, a not-for-profit organization that places the self-reliance of some of our basic everyday needs, such as food, energy, health, shelter and clothing as a central objective. By offering theoretical and practical workshops in the abovementioned themes, the people involved in Nea Guinea try to gather and to spread necessary knowledge and craftsmanship in order to get actively involved in production processes and reach higher levels of self-sufficiency and autonomy. In the same vein, Nea Guinea represents the process of shaping economically sustainable and socially just processes in opposition to the dominant economic system. In cooperation with similar projects it also aims at the creation of solidarity networks that enable the transition to a more just, ecological and sustainable society.
The course instructor Kostas Latoufis, co-founder of Nea Guinea, has been active in the off-grid renewable energy sector for 10 years now, after having completed his electrical and electronic engineering degree at the Imperial College of London. He started to construct small wind turbines in 2007 and by now has several years of experience in teaching hands-on renewable energy systems.
I met Kostas during the Degrowth Conference 2014 in Leipzig and remembered his presentation on off-grid and community renewable energy as quite intriguing. Therefore, I was very excited when he announced that there will be another workshop on how to build a small wind turbine in December 2014.
In total we were five participants with various backgrounds and at least speaking for myself with little skills in craftsmanship. Nevertheless, Kostas reassured us that we will be able to finish the construction of our small wind turbine within 9 days. The wind turbine we set out to build, is based on the design of Hugh Piggott, one of the pioneers of modern do-it-yourself small wind turbines, who lives off-grid on the Scoraig peninsula in North West Scotland.
The main components of the DIY wind turbine are the rotor, the alternator (an axial-flux generator), the tail and the mechanic frame that connect all of the other parts. The rotor of the wind turbine we built has a diameter of 2.4 meters, which means each of the three wooden blades has a length of 1.2 meters. The alternator, basically two magnet disks that rotate with the blades and the stator, which consists of the assembly of the coils, has a power rating of around 700 W, but the output varies according to the wind speed. Both the magnet disks and the assembly of coils had to casted in vinyl ester resin by using moulds. This is necessary to prevent corrosion of especially the magnets and to provide stability for the parts of the alternator. The task of the tail, which is a plywood vane bolted to flat steel bars on a steel pipe, is to turn the rotor into the wind direction (to yaw) in order to capture a maximum of the power and to allow the turbine to swing out of the wind in case of too high wind speeds (furling) to prevent damages.
All of the above might seem quite complicated and difficult to imagine, so in the following I will present a walkthrough of the construction of our wind turbine including photos to ease the understanding and to provide some feel for the construction work.
Obviously a variety of different tools had to be used during the construction process, which I will not be able to elaborate on here. Most of us did also not have much experience in handling them, but through superb explanations and supervision of our instructor Kostas, we were able to use the tools without bigger problems (with some exceptions, so be aware of the spoke shave).
The first day:
On Saturday morning we set out to have our first day at the workshop, which was located in the garden of a residential house near to the Mediterranean Sea. With around 15 degrees Celsius, a bright sun and blue sky we were eager to start building the blades of our wind turbine.
After some preparations and the explanations of the tools we started to turn the three wooden planks into the blades. The wooden planks had to be cut and carved in order to achieve the appropriate shape of the blades. All of the measurements for cutting and carving (as well as for all the other steps and parts of the wind turbine) are detailed in Hugh Piggot’s “A Wind Turbine Recipe Book”.
With 6 people at the workshop, two could work on one blade and try the different tools.
Below you can see our workshop, basking in sun and surrounded by lush Mediterranean vegetation. A perfect place to create a wind turbine, reminding us of a more natural and sustainable way of life.
Further chiseling is also required to create a twisted shape of the blade along its length. This is necessary for capturing more force of the wind along the blade the width of which changes along its length.
We finished about half of the work needed to complete the blades on the first day.
The second day:
On the second day we continued working on the blades, and cut the pieces that sandwich the blades in the end. Further, we also started to build the device for winding the coils and started to wind them.
After two days of wood working the blades where finished and now really have the shape they should have, including the airfoil-like shape along the width of the blade.
For the pieces that sandwich the blades, a triangular and a circular piece of plywood have been cut with a jigsaw. Afterwards all the pieces needed some filing in order to bring them into shape and to reduce the risk of chippings.
In order to wind the coils into a specific form a template had to be created and assembled onto a block of wood. The block of wood was then fixed to the vice and by threaded crank shaft, the template could be turned and thus wind the coil into the appropriate form.
The coils moreover have to have a certain amount of windings, so that the right amount of voltage is induced by the changing magnetic field of the magnets.
In order to cast the magnet disks and the assembly of coils into an encapsulating form of vinyl ester, moulds had to be created. Those were made of wood and have specific sizes and shapes all indicated in “Wind Turbine Recipe Book”. The moulds are needed to keep the liquid vinyl ester in the place it needs to be, while it slowly dries and hardens up (4-5 hours).
Similarly, a template for placing the neodymium magnets onto the metal disks, which together constitute the rotor of the alternator (i.e. the magnet disks) had to be designed. Each metal disk houses 12 magnets, which have to be exactly 30 degrees apart in order to produce a stable alternating magnetic field and thus voltage.
Fourth and fifth day:
As by now, most of the wood work has been finished, we started to work on the yaw bearing and alternator frame, which involved primarily metal work. So, with an angle grinder we had to cut metal rods, pipes and bars of different sizes. These pieces were then welded together to form the main mechanical parts of the wind turbine.
The final adjustments of the mechanical part had to be done while using a vice, as different parts had to be connecting in different angles. This is important for the yawing and furling of the rotor to happen successfully.
After all the metal work, the two magnet disks had to be assembled, the coils had to be soldered together and finally these three pieces had to be cast into resin.
The template for the magnet disks was fixed to the metal plate and the magnets were carefully placed into the openings of the template. Those neodymium magnets are very strong and even if that sounds funny, working with them is probably the most dangerous part of constructing the wind turbine.
Each of the magnets had a north and south pole on the opposing sides of their biggest surface. In order to arrive at an alternating magnetic field, when the rotating, the magnets have to be placed onto the metal disk in such a way that each magnet had a magnet with an opposing magnetic field (measured with the small device you can see) as its neighbor.
Furthermore, the magnets were glued to the metal disk, so they would not move after the wooden template is removed.
Soldering the coils was a tedious task, as three out of the nine coils had to be connected in series (with two coils in between). Joint effort and the support of our animal companion made sure we did not make the mistake of connection the wrong coils.
After finishing the magnet disks and the assembly of coils, we prepared for casting the stator, i.e. the coils and the two rotor disks of the alternator. For this we needed the moulds, we created before, and some resin, in our case vinyl ester. The vinyl ester had to be mixed with some catalyst, for a faster drying and hardening process and the addition of talcum powder helps in dissipating the heat involved in the reaction of the catalyst and the vinyl ester.
All the single pieces of the turbine were now ready to be assembled. This included the assembly of the rotor, the alternator and the tail, while finally all of the parts where put together to form the DIY wind turbine.
As long as a certain weight and surface area of the tail vane is kept, the shape can basically be randomly chosen.
After long discussions on the form of the tail vane which is needed to both, keep the wind turbine facing perpendicular to the wind and turning the turbine out of the wind if it is too strong, we went for a simple but recognizable form, the banana.
The final assembly of the three blades to form the rotor takes some time, as the sandwiching plywood pieces have to be screwed in order to hold the blades together. Furthermore, the blades need some balancing to avoid dynamic unbalance and heavy vibration during its operation. The assembly of the alternator requires some detailed work as well. The hardened pieces of resin containing the magnet disks and the assembly of coils have to be fixed onto the alternator frame while leaving an air gap of 1-2 mm between the stator and the two magnet disks.
In the end, we connected all the bits and pieces of the turbine and our turbine was completed.
Notice the 4 big threaded rods that go through the triangular shaped plywood and which connect the rotor blades to the magnet disks of the alternator. The tail and the banana tail vane were also connected to the stator frame.
On the last day of the workshop we set out to install our turbine at an off-grid community near to Nea Makri.
Having lifted the entire tower plus our wind turbine, we connected the cables and electronics and measured the power output. Our turbine proved to work perfectly and produced an average power of 500 Watts.
Obviously, the turbine we built cannot be compared with the commercial and industrially produced ones, which you might be all familiar with. Those big wind turbines feature towers with more than 100 meters in height and rotor diameters up to 160 meters. Our small do-it-yourself wind turbine did of course only realize a fraction of the above proportions.
Nevertheless, building a small wind turbine by yourself, not only helped us to get familiar with some tools, but gave us a feeling for how much energy our society actually produces and consumes. It helps to put things into perspective, while also empowering local people with knowledge and the possibility to produce their own electricity.
During the entire course we had an awesome time and enjoyed to get some hands-on experience. I hope, I could offer a glimpse of what the entire workshop entailed and can only encourage you to take such an opportunity if you have the chance to. The next workshop at Nea Guinea will either be held in April or September 2015.