Wind turbines use the wind's lift forces to rotate aerodynamic blades that turn a rotor which creates electricity.

In the UK we have 40% of Europe's total wind energy. But it's still largely untapped and only 0.5% of our electricity requirements are currently generated by wind power.

Most small wind turbines generate direct current (DC) electricity. Systems that are not connected to the national grid require battery storage and an inverter to convert DC electricity to AC (alternating current - mains electricity)..

Wind systems can also be connected to the national electricity grid. A special inverter and controller converts DC electricity to AC at a quality and standard acceptable to the grid. No battery storage is required. Any unused or excess electricity may be able to be exported to the grid and sold to the local electricity supply company.

There are two types of wind turbines:

• Mast mounted - which are free standing and located near the building(s) that will be using the electricity.
• Roof mounted - which can be installed on house roofs and other buildings.

Wind power is a clean, renewable source of energy which produces no carbon dioxide emissions or waste products.

Individual turbines vary in size and power output from a few hundred watts to two or three megawatts (as a guide, a typical domestic system would be 1 - 6 kilowatts). Uses range from very small turbines supplying energy for battery charging systems (e.g. on boats or in homes), to turbines on wind farms supplying electricity to the grid.

You should consider the following issues if you're thinking about small scale wind. An accredited installer will be able to provide more detailed advice.

• Wind speed increases with height so it's best to have the turbine high on a mast or tower.
• Generally speaking the ideal site is a smooth top hill with a flat, clear exposure, free from excessive turbulence and obstructions such as large trees, houses or other buildings.
• Small scale wind power is particularly suitable for remote off grid locations where conventional methods of supply are expensive or impractical.

Small-scale building-integrated wind turbines suitable for urban locations are also available to install in homes and other buildings.

Please note that the electricity generated at any one time by a wind turbine is highly dependent on the speed and direction of the wind. The windspeed itself is dependent on a number of factors, such as location within the UK, height of the turbine above ground level and nearby obstructions. Ideally, you should undertake a professional assessment of the local windspeed for a full year at the exact location where you plan to install a turbine before proceeding. In practice, this may be difficult, expensive and time consuming to undertake. Therefore we recommend that, if you are considering a domestic building mounted installation and electricity generation is your main motivation, then you only consider a wind turbine under the following circumstances:

• The local annual average windspeed is 6 m/s or more. An approximate figure for your location can be checked on the BERR website. (They accurately point out that the windspeed at our office in Hebden Bridge is too slight.)
• There are no significant nearby obstacles such as buildings, trees or hills that are likely to reduce the windspeed or increase turbulence

If you are in any doubt, please consult us.

Planning issues such as visual impact, noise and conservation issues also have to be considered. System installation normally requires permission from the local authority, so Green Refurb will always check with your local authority about planning issues before you have a system installed.

Roof mounted

These are relatively cheap. The amount of energy and carbon that roof top micro wind turbines save depends on several things including size, location, wind speed, nearby buildings and the local landscape. At the moment there is not enough data available from existing wind turbine installations to provide a figure of how much energy and carbon could typically be saved and, here at Green Refurb, we harbour doubts about the effectiveness of this type of installation in most types of urban environment.

Mast mounted

Larger systems in the region of 2.5kW to 6kW would cost between £10,000 - £25,000 installed. These costs are inclusive of the turbine, mast, inverters, battery storage (if required) and installation; however it's important to remember that costs always vary depending on location and the size and type of system.

Turbines can have a life of up to 20 years but require service checks every few years to ensure they work efficiently. For battery storage systems, typical battery life is around 6-10 years, depending on the type, so batteries may have to be replaced at some point in the system's life.