Powering Britain: How Offshore Wind Turbines Work

Source written for Revision Library (original, copyright-free).

Along the coastline of the United Kingdom, hundreds of enormous white towers rise out of the sea. Each one stands taller than the Big Ben clock tower, with three blades that can be longer than a football pitch. These are offshore wind turbines, and together they generate a huge amount of the electricity used in homes and schools across Britain.

In 2010, offshore wind supplied less than one per cent of the UK's electricity. By 2025, that figure had grown past twenty-five per cent, making Britain one of the world's largest producers of offshore wind power. A single large wind farm, built several kilometres out to sea, can contain more than one hundred turbines and generate enough electricity to power over a million homes.

Building a giant

Every turbine is built from three main parts. The tower is a hollow steel tube that can be over one hundred metres tall. At its top sits the nacelle, a metal case about the size of a double-decker bus, which houses the gearbox and generator. Attached to the nacelle is the rotor: three fibreglass blades fixed to a central hub. The blades are shaped like aeroplane wings, so that when wind flows over them, it creates a force that makes the rotor spin.

Each part is manufactured separately, often in different factories, before being transported by specialist ships to the wind farm site. There, cranes mounted on floating platforms lift the pieces into place and bolt them together, one on top of another, until the finished turbine towers above the waves.

From wind to electricity

The process of turning wind into electricity begins the moment air pushes against the blades. As the rotor spins, it turns a shaft connected to a gearbox inside the nacelle. The gearbox increases the speed of the spinning motion, driving a generator that converts the movement into electrical energy. Cables run down through the tower and along the seabed, carrying the electricity to an offshore substation, where its voltage is increased before it travels through further cables to the mainland. From there, it joins the National Grid and is shared out across the country.

Why build turbines at sea?

Wind speeds over open water tend to be stronger and steadier than on land, where hills, buildings and trees slow the wind down and make it turn and gust unpredictably. A turbine positioned several kilometres offshore can therefore generate considerably more electricity than an identical turbine built inland.

However, working at sea brings its own difficulties. Saltwater is highly corrosive, so every metal part must be specially coated and regularly inspected. Engineers usually travel out by boat, though in rough weather a helicopter may be the only way to reach a turbine safely. Because of these challenges, offshore wind farms are expensive to build and maintain; a single large turbine can cost several million pounds before it generates a single unit of electricity.

'People sometimes think a wind farm just appears overnight,' explains Priya Nandwani, an engineer who has worked on wind farms off the Yorkshire coast for nine years. 'In reality, each turbine takes years of planning, and the maintenance never really stops. But once it is running, a single turbine can power thousands of homes without producing any carbon dioxide, which makes the effort worthwhile.'

Looking ahead

The government has set a target for offshore wind to supply enough electricity to power every home in the UK by 2030. Meeting that target will mean building thousands of additional turbines, training many more engineers, and developing new technology such as floating turbines that can be anchored in deeper water, far from the coast.

Not everyone agrees that expansion should happen quickly. Some fishing communities are concerned about losing access to traditional fishing grounds, and conservationists continue to study the effect of turbines on seabirds and marine life. Wind farm developers are now required to fund research into these effects and to design turbines that reduce the risk to wildlife wherever possible.

Whatever challenges remain, one fact is clear: the turbines standing along Britain's coastline are already reshaping the way the country makes its electricity, one gust of wind at a time.