Wind turbines are used to generate electricity from the kinetic power of the wind. Historical they were more frequently used as a mechanical device to turn machinery. There are two main kinds of wind generators, those with a vertical axis, and those with a horizontal axis. Wind turbines can be used to generate large amounts of electricity in wind farms both onshore and offshore.

Large wind turbines are now available from 100 kW to over 5,000 kW. Wind turbines can be sited offshore, where the wind blows harder and larger turbines can be installed. Many offshore wind farms are being proposed and developed today in densely populated Europe, where there is limited space on land and relatively large offshore areas with shallow water.

However, the urgent need to respond to climate change means that we will need to use as many renewable resources as we can, as quickly as possible, and that means both onshore and offshore wind.

The amount of power a wind turbine can generate depends on the rating of the wind turbine and the wind regime in which it is to operate. The ‘rating’ is the maximum amount of power the turbine can generate after a certain wind speed. The power that a wind turbine can generate varies according to the cube of the wind speed, so that doubling the wind speed will produce eight times as much power. It is therefore important to ensure that wind farms are installed on tall towers on windy sites with exposure to the prevailing wind directions.

That said, wind farm developers must choose sites carefully in order to ensure that whilst there is enough wind to make the project commercially viable, there will also be the least possible adverse impact on the local environment. Factors that need to be considered in the early stages of a wind farm project are the visual impact, noise pollution and shadow flicker impact on local residents, the impact of construction and operation on protected areas and important or protected flora and fauna, and the impact of the development on aviation, television signals and other communications. These negative impacts must be weighed up against the positive impacts, such as reduced levels of carbon dioxide emissions and the creation of jobs.

If a site has been carefully chosen and planning consent is granted for the wind farm, it can then be constructed and will generally operate for approximately 20 years. After this period, one may decommission the project and return the land to its original state or re-power the project with new turbines for a further 20 years. Wind farms therefore offer a sustainable source of energy which will last for as long as the wind blows.