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 utilise more wind and therefore produce more electricity, bringing down the cost of renewable energy generation.

How does a 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. Most wind turbines start generating electricity at wind speeds of around 3-4 metres per second (m/s), (8 miles per hour); generate maximum ‘rated’ power at around 15 m/s (30mph); and shut down to prevent storm damage at 25 m/s or above (50mph).

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 11kV and 132kV. The regional electricity distribution networks or National Grid transmit the electricity around the country, and on into homes and businesses. 

Internal Workings of a Wind Turbine Nachelle:

The amount of electricity produced from a wind turbine depends on three factors:

1) Wind Speed

The power available from the wind is a function of the cube of the wind speed. Therefore if the wind blows at twice the speed, its energy content will increase eight-fold. Turbines at a site where the wind speed averages 8 m/s produce around 75-100% more electricity that those where the average wind speed is 6 m/s.

2) Wind Turbine Availability

This is the capability to operate when the wind is blowing, i.e. when the wind turbine is not undergoing maintenance. This is typically 98% or above for modern European machines.

3) The way the Turbines are arranged

Wind farms are laid out so that one turbine does not take the wind away from another. However other factors such as environmental considerations, visibility and gird connections requirements often take precedence over the optimum wind capture layout.

Can we really rely on the Wind?

Wind generation is often described as intermittent, as the wind does not blow continuously. This is a misnomer as it implies and ‘all or nothing’ delivery of energy.

An individual wind turbine will generate electricity for 70-85% of the time and its electricity output varies between zero and full output in accordance with the wind speed. However, the combined output of the UK’s entire wind power portfolio shows less variability, given the differences in wind speeds over the country as a whole. Whilst the amount of wind generation varies, it rarely (if ever) goes completely to zero, nor to full output.

In order to maintain security of supplies, a second-by-second balance between generation and demand must be achieved. An excess of generation causes the system frequency to rise whilst an excess of demand causes the system frequency to fall.