Members
2nD CIC Batxillerats
Anna Recasens
Pol Bayés
Jaume Domènech
Introduccion
A wind turbine is an electrical generator that works by converting the kinetic energy of the wind into mechanical energy through a helix inelectrical energy thanks to an alternator, a current generator altern
ating current
Our project consists of the construction of a shaft wind turbine vertical It falls within our capabilities when it comes to building it and it can accept the wind in any direction. However, after already having it once created, we believe we can take the project to a large scale changing many things, such as the turbine as the previous idea was create it from a vertical axis and this way is a little less efficient than the more common way of turbines that are axis horizontal.
1.1. What are we inspired by?
Last quarter we were a little lost when it came to choosing what our project was and where we wanted to focus it. That’s why, thanks to MIT students, we started the project with inspiration in the Savonius wind turbine model.
The design of the wind turbine by the Finnish engineer S.J. Savonius created in 1922 was very similar to the model we wanted to create. The his idea was to mount two semi-cylinders on a vertical axis and it was simple to build and could accept the wind in any direction. Although and
this, was a little less efficient compared to the more common turbine horizontal axis The reason for the difference has to do with aerodynamics. The turbines horizontal axis have blades that create a lift to turn the rotor, while the vertical axis design we used inspired by the Savonius wind turbine works based on drag: a side creates more drag on the moving air than the other, causing the rotation of the axis.
1.2. Our idea
Well, after creating a model of a wind turbine that was not finished to function at all, at the beginning of this quarter we met heartily to focus our idea a little more and to create another wind turbine brought to a large scale and worked more thoroughly. It was at this time, that Covid-19 appeared and everything had to change radically. The our idea was to improve, in an extreme way and with all the resources that we had at school, our project and, as we have already said, take it to the big one ladder We wanted a new wind turbine model that created its own electricity with a simple generator that produced current pulses or alternating current It would do this by passing strong magnets over coils of fine wire Every time a magnet passed over a coil, the coil would be energized with electricity. With 4 coils connected in series, the result would be a quadruple of the tension, but ours intention was to put 8 coils instead of 4. This is the easiest and possibly most effective way to generate electricity and is the same basic principle used in almost all the wind turbines, even in large-scale commercial ones. The electricity of a wind turbine varies with the wind speed, therefore, for to make practical use of it, it must be possible to store it in batteries or change it to a form that gives a stable and constant voltage. Electricity from wind turbines is usually converted into electricity alternating to direct current, which can be used to charge batteries.
The fact of not being able to finish the course at school and under normal conditions has unfortunately meant that the final project is not what it really should have been. That is why during these months of confinement we have had to do a little of what we could. Everything that we had started and advanced at the beginning of the 3rd quarter has been lost since we did not have time to get the materials and everything created before the quarantine, and this has meant that we have had to find some way to carry out the last and strange project of the course. For this reason and much more, the work process has been very different but we have tried to follow the instructions and steps to make the aerogenerator.
Materials and tools
To develop the project, a series of materials and tools are needed that allow the assembly of the different structures that you want to create.
1 plastic bottle
1 14×15 wooden base
Enameled magnetic wire
2cm diameter magnets
1 wooden stick LED bulb
Cardboard
Tape
Glue gun
Ruler
Scissors
Cutter
Screwdriver
Compass
Pencil
Hook saw
Air compressor
Sandpaper
Safety glasses
Procedures
First we started the project by creating a series of ideas and sketches of how we wanted it to end up. Once we had this done we got the necessary materials to carry out the project and started creating it. The steps to do it were the following.
1. Frame and base:
We took a pencil, a ruler and a compass, with these tools we drew a circle with a 6 cm radius and drilled the center of the circle with a drill, then we crossed the wood with a wooden stick and later fixed it with hot glue.
2. Making the coils:
Next we took pieces of cardboard and made a structure where we could wrap the copper and have the desired coils. We wrapped the wire around the structure, as shown. We made 4 coils, each with 200 turns of wire, and made sure that there was ample space between each coil. Then we soldered the coils, closing the circuit and using the voltmeter we helped to make sure that electricity could be obtained through all of them.
3. Stator Construction:
We smoothly placed all 4 coils on the base, as shown in the diagram:
We also made sure that the turns of wire could carry electrons clockwise in each coil. Once we were sure that the coils were positioned correctly, we glued them onto the circle we had previously drawn on the base. And finally we connected the free ends of the coil wires to the light-emitting diode (an LED).
4. The Rotor
Using the compass we made a 12 cm diameter circle in the wood, then we cut this circle with a jigsaw. Using a ruler, we marked one side of the rotor disk with perpendicular lines. We made sure that the two lines are perpendicular. To finish this part of the procedure we glued the magnets to the wood following the lines already marked, we put 6 magnets on each line on each side of the piece of wood
5. The turbine
First we took a template that the MIT members provided us and traced it onto a piece of cardboard. Then, as we drew, we cut out the marked part of the cardboard with a cutter, and we had to make 2 of these figures, one for each side of the plastic bottle.
In the center of the figures we made a hole the same size as the one we had made in the wooden base so that the stick could go in. Meanwhile, the other part of the group dedicated themselves to cutting a plastic bottle in half so that it was divided into 2 parts. Once we had the bottle in 2 parts and the 2 cardboard figures cut out, we joined the templates and the bottle bands with hot glue so that they would stay fixed.
6. Final steps
We carefully pushed the pointed end of the turbine shaft through the top of the rotor disk to its exact center and checked that the turbine was turning properly. The wind turbine looked like this:
Cientific Corpus
SUMMARY:
The wind turbine consists of a front rotor, a stator and a rear rotor. Both rotors are connected by a longitudinal axis. The stator contains copper wire coils, in which the voltage is induced as a result of the variable flux produced by the magnetic field of the permanent magnets located in the front and rear rotors. The stator is mounted on a fixed, immobile base. The permanent magnets are positioned in such a way that the magnetic flux passes from one rotor to another, crossing through the stator coils, while the rotor shaft rotates; thus, the sinusoidal voltage is induced at the terminals of the coils. The process of converting wind kinetic energy into electrical energy must go through three transformation processes: aerodynamic, mechanical and electrical. At each step, some of the energy is lost and as a consequence, the electrical energy that a wind turbine can develop is less than the wind energy that hits it. This is not specific to wind energy, since all energy production processes have losses.
AERODYNAMIC EFFICIENCY:
By means of an elementary physics calculation, it can be demonstrated that a certain mass of air, with a density “r”, moving at a speed “v”, transfers in a time “t” an amount of mechanical energy to the blades of a rotor that sweep an area “A”, given by the following expression:
E = 1/2·tpAv^3
MECHANICAL EFFICIENCY:
The turbine shaft drives a gearbox that changes the speed of rotation caused by the wind to a speed that best suits the electrical power generator to which it is connected.
ELECTRICAL EFFICIENCY:
At the output of the gearbox, the high-speed shaft is coupled to the rotor of an alternator, which converts the mechanical energy of rotation into electrical energy, which can be continuous or alternating, depending on whether it is a direct current generator or an alternator. In the latter case, it happens that due to the variability inherent in the wind, the speed of rotation, logically, is not stable, so that the frequency of the current generated does not coincide with the exact 50 Hz of the electrical network. Therefore, it is necessary to couple complex electronic power circuits to convert the frequency of the energy produced to the exact value of 50 Hz, necessary to be able to dump it into the electrical network.
Problems
Our main objective when we decided to carry out this project again and do it again was to be able to solve all those problems that in the first attempt prevented us from operating the wind turbine. The first of the problems we had was that the magnets we bought were mainly too weak for the power that our work required, but we solved it quickly and efficiently. We had to buy a type of magnet called neodymium magnets that are much more powerful than the ones we had bought at the beginning. The second problem we had was the lack of good copper that we solved the same day by stripping a cable from a lamp that we had used for a job that was already finished, we got a few more meters of copper that we finally twisted and could use for our project.
The third was the bulb that we intended to use for the final function of our work, which was to turn on a light bulb through the energy produced by the wind. The bulb that we wanted to use was a normal lamp bulb, but the MIT members told us that it was impossible for us to turn it on and that we needed a very small LED bulb. Having said that, we took a green LED bulb, but we couldn’t turn it on either, and a few days later they told us that this green LED bulb was also too powerful and that it was better to try a red LED bulb that requires less energy to turn on. And finally, the last problem we had was that we realized that perhaps one of the reasons why our work didn’t work was that we had placed the magnets alternating North-South-North-South and in reality they should all be placed North-North-North-North.
However, the problems we have had to face during this confinement undoubtedly exceed those of the last quarter. It has been much more complicated to try to overcome them since at first we thought that we only had to overcome those explained above and that refer to the first attempt at an air generator. But to these were added the problems of the confinement that Covid-19 has brought. We have tried to finish the project by solving those problems that caused the air generator not to work last quarter but we have run out of time and resources.
Conclusions
The conclusions we have reached after the end of the quarter and the course are not what we would have wanted at the beginning. Helplessness is the word that could best define our feelings towards this last quarter, since we took this last one with immense desire because we wanted to prove that we were really capable of making a good wind turbine that could work and create energy. But luck was not with us and we found ourselves trapped in a lockdown and unable to return to school to work and have all the materials and tools necessary to fulfill our initial objective. We would have loved to be able to finish the wind turbine in a better way and that would meet all our requirements, but well, we have learned that as people we have to face everything that life puts in front of us and always find a solution to those problems or discomforts that we have to solve.
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