The early pioneers of wind power were the Russians, who in 1931 built a 100kW generator at Yalta in the Crimea. This provided much important information until its destruction during the war twelve years later. However, in 1940 during the Second World War, the Danes took up the mantle. They had no oil and coal was in very short supply, leaving them with little choice but to turn to the wind for electricity. Soon they had converted over 80 windmills into wind-powered generators, some of which are still operational.
The largest wind generator to date was built at Vermont, USA. Until it broke down and was subsequently abandoned, it generated electricity into the local grid sufficient for around 600 homes. Many other countries have since carried out research into the commercial viability of wind power, and many individuals have designed and built working wind generators, although usually with very limited output.
Many were essentially similar in design, the blades driving through gears to a generator. The blades often had an adjustable pitch to make best use of the wind. A version built in Britain based on a design by French engineer J. Andreau, had some advantages over the conventional method. Operating on the `depression principle,' the system used hollow rotor blades which were open at the ends. The hub was also hollow and the generator was mounted at the bottom of the tower. As the rotor turns, the centrifugal force pushes the air out of the rotor at the ends, creating a low pressure, or depression. Thus air is sucked in through the turbine, which is linked to the generator by ducting, causing the turbine to rotate. Advantages with this system are that the generator, which can be very heavy, is kept at ground level, and there is no direct connection or gearing between the rotor and the turbine.
