What is wind energy?

Wind represents a vast source of energy and has been used for hundreds of years in Britain to grind corn and pump water.  It can now be used to make electricity and, for onshore installations, it is one of the cheapest sources.  As the UK is the windiest place in Europe, wind power is one of the most promising renewable energy technologies and already provides electricity for nearly 250,000 homes.

What is a wind turbine?

Wind turbines range from small units of around 30 watts, used to charge batteries for caravans and boats, to giant structures of 3 Megawatts, with 50 metre long rotors extracting enough energy to run 3000 small homes. 

A turbine, basically, is a set of blades designed to rotate as the wind blows past them.  The shaft to which the blades are attached is coupled to an electrical generator.  The more wind that passes the blades, the more energy can be extracted, so we have a situation where doubling the length of the blade increases the 'swept area' by a factor of four.  The bigger the turbine, the more economic generation of power.

What happens when the wind doesn't blow?

If the wind isn't blowing, wind turbines do not produce energy.  In fact most wind turbines have a 'cut-in' wind speed of around 3 m/s (approx 6mph).  This is why wind energy is known as an 'intermittent' energy source and as such it needs to feed into either a storage system, such as battery (for small scale applications), or into the electricity network - the national grid - where it can be combined with electricity from other sources.

Can I run my house on wind power?

An average house uses 3300 Kilowatt hours of energy in one year.  A 300 watt wind generator working at peak output for maybe 30% of the time would provide you with about a quarter of this.  Due to the intermittent nature of wind energy a storage system would be required, as it cannot be guaranteed that power will always be needed as soon as it is produced.

How much electricity does one wind turbine produce?

One 600kW wind turbine at a reasonable site would produce enough electricity to meet the annual needs of 375 households.

What are the environmental aspects of large wind turbines?

Wind turbines occupy very little ground space and so can co-exist with livestock or even cereal crops.  The only permanent use of the land is the concrete turbine foundations, service road and the transformer building.  For good wind speeds, the turbines need to be sited on high exposed land.  However, as technology has developed and system costs have reduced it has become more feasible to locate wind turbines in less windy sites.

The turbines, like other conventional infrastructures and power generation plants such as power transmission lines and power stations, can be visually intrusive.  There is therefore a delicate balance to be struck between the change in the landscape and wind power's environmental benefits.  Offshore wind farms, although more expensive to install, are less visually intrusive.

Noise from modern turbines is less than from many other everyday activities.  Careful design, siting and operation has ensured that the noise is no longer a nuisance.  Electromagnetic interference with television reception is not usually a problem and any remedial action is simple and cheap.

Wind turbine manufacturers and wind farm developers have by now substantial experience in minimising the ecological impact of construction work in sensitive areas such as moors, or mountains, or when building wind farms in offshore locations.  Restoring the surrounding landscape to its original state after construction has become a routine task for developers.  After the useful life of a wind farm has elapsed, foundations can be reused or removed completely.  The scrap value of a wind turbine can normally cover the costs of restoring its site to its initial state - this is in stark comparison to the cost of decommissioning a nuclear plant, which for Dounreay in Scotland is estimated to take over 50 years at a cost of over £4billion.

For future generations electricity will have to come from renewable sources as the finite supplies of fossil fuels will by definition run out.  Using renewable energy will help offset the man made carbon dioxide emissions that have arisen from burning fossil fuels.

How long does it take for a turbine to 'pay back' the electricity used to manufacture it?
The comparison of energy used in manufacture with the energy produced by a power station is known as the 'energy balance'. It can be expressed in terms of energy 'pay back' time, i.e. as the time needed to generate the equivalent amount of energy used in manufacturing the wind turbine or power station.

The average wind farm in the UK will pay back the energy used in its manufacture within three to five months, and over its lifetime a wind turbine will produce over 30 times more energy than was used in its manufacture. This compares most favourably with all fossil fuel and nuclear power stations which do not take any of the associated environmental costs into account.

How much does it cost?

A 1kW wind turbine can, on average, generate 120kWh per month (depending upon site conditions) and may be installed complete with all system components, for around £4,000 with grant assistance - for more information on the available grant aid, visit www.clear-skies.org.