How wind turbines work
Wind turns the rotor blades of a turbine. The turbine then spins a shaft connected to a generator where electricity is generated. Wind turbines generate electricity as long as there is relatively constant wind at a reasonable speed. Most small wind turbines need an average speed of 4.5 metres per second (16 km/h).
Micro and small scale wind turbines are usually mounted on towers so they’re exposed to more consistent wind with a higher average speed. Because wind blows intermittently, small wind turbines are usually combined with other energy generators in a grid-connected or stand-alone power system.
Types of wind turbine
HORIZONTAL-AXIS TURBINES
Most wind turbines are horizontal-axis turbines - like the ones you see on wind farms. The turbines are mounted on a tower facing the wind. Small scale versions have tail fins to make sure the blades constantly turn towards the wind.
VERTICAL-AXIS TURBINES
Vertical-axis turbines are less common than horizontal-axis turbines, but have the advantage of not needing to face the wind. This is useful where the wind direction varies quickly. Some are small enough to be mounted directly onto a building, others are mounted on a pole in the ground.
ROOFTOP OR WALL-MOUNTED TURBINES
Rooftop or wall-mounted micro wind turbines are a new type of turbine.
Energy output of small wind turbines
The amount of electricity a wind turbine generates depends on the wind speed and the turbine's capacity rating. If a model has a rated capacity of 1 kW, it will produce 1kWh of electricity per hour when exposed to a specific rated wind speed. This specific rated wind speed varies between different models and manufacturers, but is generally 11 to 15 metres per second. This is about 40 to 55 kilometres per hour.
In the real world a turbine will not be exposed to ideal conditions or the rated wind speed at all times. This means turbines will usually generate only 10 to 40% of their rated capacity every
Small wind turbines generally need more ongoing maintenance than solar panels and micro-hydro systems. This is especially true if your turbine is on a very exposed site.
Best sites for small wind turbines
In urban areas - even on roof tops - turbines aren’t usually very successful. Winds tend to be turbulent, weak, and erratic because of obstructions such as buildings and trees. If you live in an area that is exposed to strong and consistent wind, it may be cost effective for you to install a small scale wind turbine. Households normally usually use micro wind turbines that are smaller than 5 kW.
