Having decided what size of turbine is required, and secured the promise of funding, the next hurdle is to choose a manufacturer and an installer. In the range of 50 kW to 100 kW, there aren’t actually that many turbines to choose from, perhaps no more than half a dozen. You can’t really choose on price, because they are all much the same, and no one will give you a quoted installed price. You can’t even really choose on generator output because they all only work at capacity in high winds which are relatively rare. A good measure is rotor diameter, as the power output is proportional to the swept area covered by the blades. Another good comparator is the start-up wind speed, because some turbines need 4.5 m/s to start generating, whereas others will start at only 3 m/s. You get a lot of wind at those low speeds where one machine will be generating, another not. But even that’s not the whole story, because all that sophisticated control gear actually consumes power so although the turbine may be spinning and generating, you may not actually be gaining anything.
But in the end, I have chosen a Dutch machine with an 18 m diameter rotor on a 30 m tower, driving an 80 kW generator. One unusual factor is that it only has two blades not three. I’m not sure if this is a good thing or a bad, but certainly the swept area is the same, and there is less of that expensive carbon fibre material, and less springs and flanges in the hub.
The next issue is the choice of installer, and again there are half a dozen companies advertising themselves as agents for the manufacturer. I have decided to go with a small company whose enthusiasm and lack of overhead cost will, I hope, make up for their shortage of resources.
