The last couple of days in the Master Class are marvelous! On 8 september, my birthday, the group finished the first turbine. It is a Piggott design with a rotor diameter of 1.8 meter charging one 12V battery. During the afternoon, the wind picked up. It was fantastic to see the wind turbine speeding up suddenly, when we were still balancing it on the ground pole (see picture).
In low wind the turbine does not start, because we use a somewhat too heavy car hub. But when the initial static friction has been overcome, the turbine spins like crazy. If you have not seen it before it looks like magic. The physics of the aerodynamic shape is causing this surprisingly high speed. Everybody was amazed of the speed.
Today we put the turbine for the first time in the new tower. It is a 12 meter guy-wired pole. When erecting the turbine, the electrical connections are short-circuited to break. The turbine reached the top smoothly after a couple of minutes hoisting. Again today, enough wind was present. When I released the break, the turbine speeded up immediatly. It goes from zero to high speed without encountering any resonances. It is really nicely balanced. All participants are very happy.
After a couple of hours charging, our batteries were full. In this case the load control switches the power from the turbine to a so-called dumpload to prevent damaging the batteries by overcharging them. For the Tanzanians, this is unbelievable: “we are throwing away electricity!” Followed by a lot of discussion in the group about adding extra batteries. I explained to them that batteries are very expensive, and that this is the reason that you cannot add them for free. I think they are not convinced yet. I can feel that electricity has much more value to them than to our Europeans.