Understanding Micro-Wind Turbines
Can we downsize wind turbines effectively?
Most turbines work best with wind speeds of 6m/s, although some manufacturers quote figures as low as 4m/s…
As a renewable energy source, large–scale wind farms are highly successful, generating enough electricity to power 1.2 million homes. Downsize this technology and locate it on homes and offices and surely a combination of solar power in the summer and micro–turbines on cold and windy winter days should be the ideal renewable energy solution?
Unfortunately, despite being the latest ‘must have fashion item’, micro–turbines have yet to fully live up to their promise.
Two kinds of turbines
- Horizontal–axis turbines are fitted with devices such as tail fins to guide the blades towards the direction of the wind.
- Vertical–axis turbines are more attractive, don’t suffer with wind direction problems and are quieter, but efficiency tends to be lower.
The shaft of the turbines is connected, usually via a gearbox, to a generator that produces electricity.
Most turbines work best with wind speeds of 6m/s, although some manufacturers quote figures as low as 4m/s. Modifications are possible in areas where wind speeds are low, including using five bladed rotors instead of three, but efficiency levels are lowered.
Turbines should also avoid turbulence caused by other buildings, chimneys, parapets, etc. This means that many densely populated areas fail on both accounts, unless turbines are mounted very high, which can cause planning problems, and only isolated rural dwellings look set to benefit.
Roof mounting can also be problematic, as pitched roofs often don’t have the strength to resist the bending forces of the turbines, although most flat roofs can.
The amount of power micro–turbines produce can also be a bone of contention. Most manufacturers tend to refer to peak output figures, which are only reached when wind conditions are perfect.
Very small–scale turbines—found in many DIY outlets — have a peak output of 1kW while larger sizes from can range from 1.5kW to 6kW. Manufacturers estimate cost pay–back periods of 10–12 years, but this can vary depending on where the turbine is sited and local wind conditions.