Small-scale wind turbines
A good option, in the right place. Mounted on the roof of a building or on a small mast, micro wind turbines can provide useful amounts of electricity, particularly in rural or ‘off-grid’ settings.
Domestic wind turbines generally range from between 1kW to 6kW and will be either building mounted or free-standing depending on their size. There are two main designs of turbine, vertical axis and horizontal axis.
Horizontal axis turbines are the more common design. They have turbine blades that look like an aeroplane propeller. The towers that support this design need to have strong foundations in order to prevent the turbine from blowing over and on domestic systems they will often have guy wires to provide additional support.
Vertical axis turbines have the main rotor shaft running down vertically which allows them to have the gearbox located at the base of the turbine. The turbine does not have to directly face the wind in order to rotate and is considered by manufacturers to be more suited to areas where the wind is turbulent.
Average wind speed is a key factor to consider for any wind turbine installation and the recommended annual average wind speed for a location is 5 metres per second (11 mph). There are a number of factors that can affect wind speed such as nearby buildings, trees and the height of the turbine from the ground. An ideal location will have no significant obstructions such as tall buildings that are likely to either reduce wind speed or create a turbulent airflow.
Turbines sited in urban areas are unlikely to perform well and locations such as the bottom of rural valleys are also probably unsuitable. There are a number of online wind speed calculators you can use to find out if you live in an area that is suitably windy, including:
However, before making any significant investment in a wind turbine it is recommended that you invest in an anemometer to measure the average wind speed at your proposed location. To get the most accurate picture, you should run the anemometer for a minimum of three months, and ideally over the course of a year.
The cost of installing a wind turbine does vary depending on factors such as the size and type of system.
• A roof mounted 1kW system costs around £2,000
• A 2.5kW pole-mounted system costs around £15,000
• A 6kW pole-mounted system costs around £30,000
A well made and well maintained wind turbine will last between 20 to 25 years, but regular maintenance checks should be carried out to ensure that the system is running efficiently. The turbine inverter (which converts the DC current produced by the turbine into AC current that most household appliances use) will need replacing at some stage, and off-grid systems will probably need new batteries every 6 to 10 years.
Wind turbines will not only provide you with free electricity, but will earn you money through the feed-in tariff which is a payment that the owners of small-scale renewable energy installations receive for both generating and selling their electricity*.
The following table will give you an idea of the savings you may make with a 6kW turbine, sited in an appropriate location and assuming that the system is eligible for the feed-in tariffs:
|Feed-in tariff (generation)||£2,800|
|Feed-in tariff (export)||£160|
|Savings on electricity bill||£260|
|Total income and savings||£3,220|
[These calculations are based on a generation tariff of 28p/kWh and an export tariff of 3.2p/kWh assuming that 75% is exported. Fuel bill savings assume an electricity unit cost of 14.39p/kWh. Figures from Energy Saving Trust. Note that the tariffs are reviewed periodically by the government and may be reduced, and are also index-linked which means that they will increase or decrease with inflation. The most up-to-date figures can be found online at www.ofgem.gov.uk/fits.]
Due to permitted development rights it is now possible in some cases to have domestic wind turbines installed without the need for planning permission as long as specific limits and conditions are met. In some cases planning permission will be required and it is recommended in all cases to first approach the local planning authority to determine regulations for the area.
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