Windfarms need to be on exposed sites with constant high wind speeds. A typical turbine can produce 3-500 kilowatts of energy - enough for 150-250 homes. Typically, each turbine has 2 or 3 fibre glass blades attached to a rotor, supported by a tapering steel tower. A typical tower is 30-35 metres high, about 2 metres wide at the base, anchored to octagonal concrete foundations 2 metres deep. Each blade is 15-20 metres long. When the top blade is pointing up, the structure is 50-55 metres high. The whole thing is usually painted a pale matt grey to reduce it's visual impact. A computer system controls each turbine, ensuring that the blades face into the wind. The energy generated is routed to an onsite substation, where it is fed into (in Britain) the National Grid, to be consumed. These types of large turbine start generating with a gentle breeze of 5-6 metres per second (11mph). They close down automatically (for safety) in a strong gale force wind of 24-28 mps. The maximum generation occurs at around 12-18mps. Wind turbines make a swish sound as the blades turn and some noise comes from a gearbox (which can be designed out, by using variable electronic control, the best example of this is the Enercon E40), they are on the whole rather noisy if you stand in close proximity. Noise is one of the most frequent reasons for opposition to windfarms, another being visual impact, large windturbines look incongruous in an otherwise undeveloped or natural setting. Reasons for opposition are often politically manipulated, sometimes resulting in ridiculous or specifically inapplicable reasons being given. When the so called bad points are weighed against the problems with other generating options; nuclear (ho,ho), coal (cough, cough) or even that great poisoner of the air, orimulsion, then (with lessening consumption as a realistic proposition), wind energy can perhaps be seen as the benign and responsible technology that it really is.
