Since earliest times, man has harnessed the power of the wind, with the first mill recorded as long ago as the 6th century AD. The technology has diversified over the years to include pumping water, grinding grain, powering sawmills and most recently generating electricity, now the fastest growing energy sector worldwide.
Wind turbine technology has developed rapidly in recent years and Europe is at the hub of this high-tech industry. Wind turbines are becoming more powerful, with the latest turbine models having larger blade lengths which can utilize more wind and therefore produce more electricity, bringing down the cost of renewable energy generation.
The first commercial wind farm in the UK, built in 1991 at Delabole in Cornwall, used 400 kilowatt (kW) turbines, while the latest trials have involved turbines ten times more powerful, of four megawatts (MW) and above.
The average size of an onshore wind turbine installed in 2005 was approximately 2 MW. Wind turbines have an average working life of 20-25 years, after which the turbines can be replaced with new ones or decommissioned. Old turbines can be sold in the second hand market and they also have a scrap value which can be used for any ground restoration work.
How Does a Wind Turbine Work?
Wind turbines produce electricity by using the natural power of the wind to drive a generator. The wind is a clean and sustainable fuel source, it does not create emissions and it will never run out as it is constantly replenished by energy from the sun.
In many ways, wind turbines are the natural evolution of traditional windmills, but now typically have three blades, which rotate around a horizontal hub at the top of a steel tower.
Wind Turbine Technology
Generating electricity from the wind is simple. Wind passes over the blades exerting a turning force. The rotating blades turn a shaft inside the nacelle, which goes into a gearbox. The gearbox increases the rotation speed for the generator, which uses magnetic fields to convert the rotational energy into electrical energy.
The power output goes to a transformer, which converts the electricity from the generator at around 700 Volts (V) to the right voltage for the distribution system, typically between 11 kV and 132 kV. The regional electricity distribution networks or National Grid transmit the electricity around the country, and on into homes and businesses.
Offshore wind farms are an exciting new area for the industry, largely due to the fact that there are higher wind speeds available offshore and economies of scale allow for the installation of larger size wind turbines offshore. Offshore wind turbine technology is based on the same principles as onshore technology.
Foundations are constructed to hold the superstructure, of which there are a number of designs, but the most common is a driven pile. The top of the foundation is painted a bright colour to make it visible to ships and has an access platform to allow maintenance teams to dock.
Subsea cables take the power to a transformer, (which can be either offshore or onshore) which converts the electricity to a high voltage (normally between 33 kV and 132 kv) before connecting to the grid at a substation on land.