Did you know that Pacific Hydro's installed wind farms save as much as 380,000 tonnes of global warming pollution from being emitted each year?
That benefits the environment as much as keeping almost 90,000 cars off the road.
Electricity-producing windmills were first used in Europe, and today are found right across the world. In Australia, wind is still a relatively new source of clean energy – our country’s first wind farm wasn’t built until 1987.
Windmills
Windmill blades are modeled after airplane wings. They’re designed so that they rotate because of a difference in pressure, caused by air moving over the surface of the blade. The blades cause a rotor to turn, which then drives an electrical generator.
The windmills installed at Pacific Hydro’s wind farms are ‘smart machines’ – able to operate without human intervention. Each windmill uses its own internal computer system to monitor the direction and speed of the wind, with electricity production commencing automatically at wind speeds above 14 km/h.
The amount of electricity produced continues to increase with the wind speed until the wind generators reach their maximum or ‘rated’ capacity at winds of around 55 km/h.
With blades rotating slowly at 17 revolutions per minute, the wind generators continue to operate at their maximum output until the wind speed reaches 90 km/h, at which point the windmills automatically shut down and turn out of the wind to avoid being damaged.
However, winds of that speed are not very common. In fact, only one windmill needed to shut down at Challicum Hills in the development’s first eight months of operation.
Glossary of windmill terms
Blades: Most windmills have either two or three blades. Air passing over the blades creates a difference in pressure and causes them to lift and rotate. Some windmills are designed to operate upwind, with their blades facing the wind; others are designed to run downwind, facing away from the wind.
Gear box: The rotor turns about 22 revolutions per minute (RPM) but the gearbox has to turn at about 1500 RPM. The gearbox connects the main shaft to the small shaft and converts the 22 revolutions to 1500 revolutions.
Generator: The generator makes electricity when it turns. The current is then sent down through the tower in large electricity cables.
Small shaft: The small shaft runs at about 1500 RPM – that’s very quickly. It leads the power from the gearbox to the generator.
Main shaft: The main shaft is turned by the rotor. It has to be very thick as the rotor uses a large force. The main shaft is connected to the gearbox.
Nacelle: The rotor attaches to the nacelle, which sits on top of the tower and includes the gear box, main and small shafts, generator and brake. A cover protects the components inside the nacelle. Some nacelles are large enough for a technician to stand inside while working.
Rotor: The blades and the hub together are called the rotor. The rotor is bolted on to the big main shaft.
Tower: It’s a lot more windy high up in the sky than down on the ground, so taller towers mean windmills are able to capture more energy and generate more electricity. Towers are usually made from tubular steel, which is very strong, or steel lattice, which is less expensive.
Wind vane: Measures the wind direction and allows the yaw drive to direct the windmill properly depending on the direction of the wind.
Yaw drive: On upwind windmills, the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don't require a yaw drive: the wind blows the rotor downwind.
Yaw motor: Powers the yaw drive.
Capacity factor: The capacity factor is simply the windmill's actual energy output for the year divided by the energy output if the machine operated at its rated power output for the entire year.
Capacity factor (%) = Actual Output (MWh )/ Rated Capacity (MW) x Time Elapsed (h) x 10
Sources:
http://www.nrel.gov/wind/animation.html#animation
http://www.windpower.org/en/kids/intro/intronac.htm