Wind farms: How much power does a wind turbine produce? How reliable are they?

Credit: PA

Prime Minister Boris Johnson has promised to power every home with offshore wind by 2030, but how much power is generated by wind turbines?

How much power can one wind turbine produce?

The largest wind turbine in operation produces just over eight megawatts of power.

The biggest offshore wind farm in the world, Hornsea One, located in the North Sea off the Yorkshire coast, consists of 174 wind turbines of seven megawatts.

Overall the wind farm generates 1.2 gigawatts of power.

What would 1.2 gigawatts power?

A kettle uses electricity at a rate of 1,000 watts or one kilowatt.

One gigawatt is equivalent to a thousand million watts, so a gigawatt would generate electricity for a million electric kettles.

How many homes can a wind turbine power?

The energy used by every house in the UK is variable, but the average domestic electricity consumption rate for a home is 0.5 kilowatts or 500 watts.

An eight megawatt offshore wind turbine would generate 8,000 kW (kilowatts) when it is operating at its maximum capacity.

So it would be able to supply 16,000 homes at a rate of 500 watts each.

Credit: PA

How many wind turbines are there in the UK?

At the moment there are 2,000 offshore wind turbines in the UK waters.

The UK has the most offshore wind turbines than any other country globally.

There is currently just under 10.5 gigawatts of wind in the seas around the UK, generating around 10% of our electricity.

What is the difference between onshore and offshore wind turbines?

Onshore wind turbines are inherently cheaper than offshore wind turbines.

The base of an onshore wind turbine is buried in the ground, whereas with an offshore wind turbine, you have to bury the turbine base into the seabed.

When a turbine is operating on shore, someone can drive up and fix it easily, but with offshore wind turbines, you have to travel to the site by boat, which can take several hours and the sea conditions have to be right to get off the boat and onto the turbine.

From a cost point of view, you would want to install wind turbines onshore if possible, but they are unattractive and generally people do not like living near wind farms.

Which is why the UK government incentivised offshore wind farms and cut back subsidies for onshore wind farms

The UK also has a great asset when it comes to wind turbines, the North Sea.

It is less than 50 metres deep, which means you can pile the turbine foundation straight into the seabed.

The North Sea allows the UK to have a large area that is striking distance from the shoreline where we can install wind turbines.

Onshore wind turbines are much more cost-effective compared to offshore wind turbines. Credit: PA

How reliable are wind turbines?

Wind turbines can produce power when the wind is blowing and if the turbines are operational.

They work with a cut-in speed, so they will not turn if the wind speed is very low, but they start operating at wind speeds of 4 to 5 metres per second and reach maximum power output at around 12 metres/second, which is just over 25mph wind speeds.

When the wind gets higher than that, the turbine stops increasing in power, the turbine continues to turn and generate power but at the same level.

At very high wind speeds, turbines shut down and do not generate at all, which means its service life does not get affected by gale-force winds.

A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs depending on the wind speed.

Over the course of a year, a turbine will generate about 30% of the theoretical maximum output, which is known as the capacity factor.

How much power will wind farms need to generate in 10 years time?

Boris Johnson has pledged that offshore wind farms will be able to generate power for every home in the UK in 10 years time.

He said he was raising its target for offshore wind power capacity by 2030 from 30 gigawatts to 40 gigawatts.

At the moment, the UK does not generate 40 gigawatts of energy, but in a decade, we will rely on electric vehicles more and ground source heat pumps as the source of energy, and the UK will stop using fossil fuels as much, so demand for electric energy will grow.

This article has been compiled with the assistance of Professor Simon Hogg, Head of Engineering at Durham University and Ørsted Chair in Renewable Energy.