28 Φεβ 2015

Article from Simon Goess who participated in the December 2014 wind turbine construction course

Posted by neaguinea

photo-27-12-2014-12-02-11

“Build a small wind turbine” construction course by Simon Goess

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).

Figure 1: THE spoke shave, a tricky tool

Figure 1: THE spoke shave, a tricky tool

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”.

Figure 2-3: Arni is cutting the wooden plank in order to create blocks of wood that can easily be chiselled off

Figure 2-3: Arni is cutting the wooden plank in order to create blocks of wood that can easily be chiselled off

With 6 people at the workshop, two could work on one blade and try the different tools.

Figure 3-4: By using a draw knife the remaining parts of the blocks can be removed, while the wood plane serves to create a smooth and plane surface

Figure 3-4: By using a draw knife the remaining parts of the blocks can be removed, while the wood plane serves to create a smooth and plane surface

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.

Figure 5: View of our workshop in Nea Makri, while we were busy working on the blades

Figure 5: View of our workshop in Nea Makri, while we were busy working on the blades

Figure 6-7: Kostas, our instructor, showing us how to check if the surface of the blade is truly plane using a square and giving the final polish to the three blades

Figure 6-7: Kostas, our instructor, showing us how to check if the surface of the blade is truly plane using a square and giving the final polish to the three blades

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.

Figure 8-9: Paul chiselling near to the root of the blade (the thickest part, where all blades will finally be connected to from the rotor). The final product of the first day of work. The transformation of the blank is not finished, but slowly resembles a blade

Figure 8-9: Paul chiselling near to the root of the blade (the thickest part, where all blades will finally be connected to from the rotor). The final product of the first day of work. The transformation of the blank is not finished, but slowly resembles a blade

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.

Figure 10-11: Some more cutting and subsequent chiselling of the blocks, while Michael using “heavy” machinery to give some shape to the blade

Figure 10-11: Some more cutting and subsequent chiselling of the blocks, while Michael using “heavy” machinery to give some shape to the blade

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.

Figure 12: The final blade, now they only needed to be assembled to form the rotor.

Figure 12: The final blade, now they only needed to be assembled to form the rotor.

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.

Figure 13: Me filing the circular sandwiching piece

Figure 13: Me filing the circular sandwiching piece

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.

Figure 14: The single pieces of the coil winder template

Figure 14: The single pieces of the coil winder template

Figure 15-16: The coil winder connected to the crank shaft and two big spools of copper wire and Paul and me winding coils

Figure 15-16: The coil winder connected to the crank shaft and two big spools of copper wire and Paul and me winding coils

Third day:

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).

Figure 17-18: Gotzon taking measurements for the rotor moulds, while Arni is cutting the pieces for the rotor moulds with the jigsaw

Figure 17-18: Gotzon taking measurements for the rotor moulds, while Arni is cutting the pieces for the rotor moulds with the jigsaw

Figure 19: The open stator mould, in which the assembly of coils will be put

Figure 19: The open stator mould, in which the assembly of coils will be put

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.

Figure 20: Cutting the template for the placing the magnets on the metal disks

Figure 20: Cutting the template for the placing the magnets on the metal disks

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.

Figure 21-22: While Michael was happily grinding some rod…Kostas introduced us into serious welding

Figure 21-22: While Michael was happily grinding some rod…Kostas introduced us into serious welding

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.

Figure 23-24: The stator frame (big square metal piece) with the yaw bearing (thick pipe) and the tail hinge (thin pipe on top) and the frontal view onto the stator frame. In the front the round hub on which the alternator (two magnet disks and the assembly of coils as the stator) is connected to the assembled rotor blades. In the back the tail can be seen.

Figure 23-24: The stator frame (big square metal piece) with the yaw bearing (thick pipe) and the tail hinge (thin pipe on top) and the frontal view onto the stator frame. In the front the round hub on which the alternator (two magnet disks and the assembly of coils as the stator) is connected to the assembled rotor blades. In the back the tail can be seen.

Sixth day:

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.

Figure 25: Placing magnets on the metal disk

Figure 25: Placing magnets on the metal disk

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.

Figure 26-27: Joint soldering of the coils while being observed by our animal companion and the assembly of coils after successful soldering

Figure 26-27: Joint soldering of the coils while being observed by our animal companion and the assembly of coils after successful soldering

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.

Figure 28:-29 Pouring the resin into the mould with the magnet disk inside (wearing protective gloves and masks is highly recommended, because of the chemicals and the fumes that develop). The mould of the stator with the assembly of coils inside, already covered by the resin.

Figure 28:-29 Pouring the resin into the mould with the magnet disk inside (wearing protective gloves and masks is highly recommended, because of the chemicals and the fumes that develop). The mould of the stator with the assembly of coils inside, already covered by the resin.

Seventh day:

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.

Figure 30: Gotzon’s magnum opus, the banana shaped and coloured tail vane

Figure 30: Gotzon’s magnum opus, the banana shaped and coloured tail vane

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.

Figure 31-32: Using the drill press to drill holes for the threaded rods into the rotor assembly and putting together the alternator using the hardened forms of resin, while scrutinizing the air gap between the two rotor disks and the stator.

Figure 31-32: Using the drill press to drill holes for the threaded rods into the rotor assembly and putting together the alternator using the hardened forms of resin, while scrutinizing the air gap between the two rotor disks and the stator.

In the end, we connected all the bits and pieces of the turbine and our turbine was completed.

Figure 33: The fully assembled small DIY wind turbine

Figure 33: The fully assembled small DIY wind turbine

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.

Eighth day:

On the last day of the workshop we set out to install our turbine at an off-grid community near to Nea Makri.

Figure 33-34: Putting the turbine onto the tower. By using a gin pole (short pole on the right) which is lowered by a rope hoist (not visible here) the tower with the wind turbine on top can be lifted.

Figure 33-34: Putting the turbine onto the tower. By using a gin pole (short pole on the right) which is lowered by a rope hoist (not visible here) the tower with the wind turbine on top can be lifted.

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.

Figure 35-36: The 12 meter tower with the wind turbine on top, being stabilized by four guy anchors. You can see the measured voltage (left), which is determined by the battery bank the turbine is connected to and the current produced (right), which in that instance was 19 Ampere. The instantaneous power produced was thus 520 W.

Figure 35-36: The 12 meter tower with the wind turbine on top, being stabilized by four guy anchors. You can see the measured voltage (left), which is determined by the battery bank the turbine is connected to and the current produced (right), which in that instance was 19 Ampere. The instantaneous power produced was thus 520 W.

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.

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