How To Harness the Wind

For centuries, windmills have been a distinctive feature of many landscapes, producing energy to pump water or to grind corn. Instead of the wooden shutters and fabric sails of the traditional windmills, today's new generation of wind turbines have two or usually three sleek, rotating blades that convert the energy in the wind into electricity. They operate on a simple principle. When wind turns the propeller-like blades, they spin a shaft which connects to a generator. The larger turbines – with enormous blades often around 40m long – are mounted at the top of a tall tower in order to utilise faster wind speeds. These turbines are grouped together on wind farms, which are connected to the electrical grid. The largest model, Enercon E112, is 186m tall and capable of generating 6 megawatts of power.

Mini wind turbines – typically generating 2 kilowatts of electricity – provide power for households in remote, off-grid locations. However, as wind energy is intermittent, the turbines are used to charge up batteries so that power is stored until required. In urban areas, micro wind turbines, which can be installed on the top of buildings, have an output of 400 watts – enough to run four 100-watt lightbulbs.

Consider a small wind turbine for heating and lighting greenhouses. As well as utilising free energy, you will get your investment back quite quickly. Some larger DIY superstores now stock these and can give advice on installing and using them.

Since domestic wind turbines started appearing in large DIY stores, interest in home installations has increased dramatically. As with solar panels, the pay-back period for recouping your initial outlay in energy savings is many years, but they can still make a contribution, albeit small, to reducing your home's carbon dependence.

The most efficient systems are too large for use in most domestic situations – turbines can have a wingspan of 15m or more – but smaller rooftop options can generate up to 2.5kW of electricity and simply plug into the existing grid to augment your paid-for supply whenever wind power is available.

Before you consider purchasing a wind turbine, find out whether you will need to obtain planning permission to erect it. The planning laws relating to energy-saving devices have been relaxed to encourage greater use of them in homes, but there are still some size restrictions on the diameter of the blades and the height of the supporting post and planning permission is still required in some areas and on listed buildings.

You don't need to live on a blustery mountain, but the turbine will need sufficient wind on a regular basis to be worth while, and the best way to maximise this is to mount the turbine high up. Ideally, a turbine should be 9m above any obstacle within 100m, but in an urban area this is almost certainly impossible to achieve. Turbines are heavy and the wind they need to operate can also make them unstable, so they need a firm base and strong fixings. Take advice from the manufacturer or supplier, or a structural engineer before you attempt to fit one to your house.