Wind Generator

Wind generator for sale.

Wind energy is both green and fun, so the idea of building one's own wind generator is a good one. The following will give you an idea of what is involved and point you toward sources of information on the subject.

Wind energy on a large scale is now competitive with other sources of electricity on the national grid. However, small domestic-sized wind generators have not yet reached this point. The wind is free, but small wind turbines are expensive in relation to what they produce, and cannot realistically compete with mains electricity. Building your own machine saves some of the cost, but please do not underestimate the difficulty of the task. If it were easy to save money by using small wind turbines, then they would be a major feature of the landscape by now.

Wind generators work with thin air, so they need to be large in relation to the power they produce. To power a modern home on a good site, the blades would need to span about 5 metres from tip to tip. This is known as the rotor diameter. With careful conservation of energy a smaller machine may suffice. A rotor diameter of 2 metres might yield about 500 kWh of electricity per year, compared with an average annual household consumption of roughly 4,500 kWh.

Most small wind generators are used for charging batteries, to provide a reliable stand-alone power source where grid power is not available. The obvious choice of generator for self-build is the car alternator. However this has major drawbacks. It must be driven at a high shaft speed (over 2000 rpm) to give full output, so you will need to gear it up or modify it in some way to drive it with rotor blades, which typically only manage a few hundred rpm. This reduces the efficiency. In low windspeeds there is very little power available in the wind, and you need a highly efficient generator to capture it. Most, if not all of the power in light winds will be used up energising the magnetic field in the alternator, so the results are disappointing. Nearly all small commercial wind turbines use purpose-built permanent magnet generators for this reason. The DIY enthusiast can make one too, but this is not simple to do. Or you can reuse a permanent magnet motor as a generator. The generator is the key to success or failure of the project, and by far the hardest part to get right.