[font=Arial] Wind turbines use the wind to rotate blades that turn a rotor - which creates electricity. They range from very small turbines supplying energy for battery charging systems （for example on boats or in homes）, to turbines grouped on wind farms supplying electricity to the national grid. How does it work? According to the Energy Saving Trust, individual turbines vary in size and power output from a few hundred watts to two or three megawatts （one MW is equal to 1,000 kW）. As a guide, a typical domestic system for a home would be 2.5 to 6 kilowatts （kW） depending on the location and size of the house. Small-scale wind power is particularly suitable for remote locations where conventional methods of electricity supply are expensive or impractical. Most small wind turbines generate direct current （DC） electricity which is stored in a battery. The DC electricity needs to be converted to AC （alternating current） for mains electricity. You also need a controller to divert power to another useful source （such as space and/or water heaters） when the battery is fully charged. Wind systems can also be installed where there is already a grid connection. A special inverter and controller converts DC electricity to AC. Any unused or excess electricity can be exported to the grid and sold to the local electricity supply company. It‘s common to combine this system with a diesel generator for use during periods of low wind speeds. A combined wind and diesel system gives greater efficiency and flexibility than a diesel only system. What are the practicalities? It‘s best to have the turbine high on a mast or tower, as wind speed increases with height. The ideal site is a hill with a flat, clear exposure, free from strong turbulence and obstructions such as large trees, houses or other buildings. Small building-integrated wind turbines suitable for urban locations are also available to install in homes and other buildings. Ideally, you should undertake a professional assessment of the local wind speed for a full year at the exact location where you plan to install a turbine before proceeding, as the electricity generated is highly dependent on the speed and direction of the wind. The Energy Saving Trust says you should only consider a wind turbine when: the local annual average wind speed is 6m/s or more there are no major obstacles nearby such as buildings, trees or hills that are likely to reduce the wind speed or increase turbulence You also have to consider conservation and planning issues, such as the visual impact and noise. You normally need permission from the local authority to install a system. How much does it cost? Systems up to 1kW will cost around £1,500, whereas larger systems in the region of 2.5kW to 6kW would cost between £10,000 - £25,000 installed. These costs would include the turbine, mast, inverters, battery storage （if required） and installation. But it‘s important to remember that costs always vary depending on location and the size and type of system. Maintenance 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 six to ten years, depending on the type, so batteries may have to be replaced at some point in the system‘s life.[/font]