6.4 Wind Power

When solar radiation enters the Earth’s atmosphere it warms different regions of the atmosphere to differing extents – most at the equator and least at the poles. Since air tends to flow from warmer to cooler regions, this causes what we call winds, and it is these air flows that are harnessed in windmills and wind turbines to produce power.

Wind power, in the form of traditional windmills used for grinding corn or pumping water, has been used for centuries. But the use of modern wind turbines for electricity generation has been growing rapidly since the 1970s, following pioneering work in Denmark. The size and power of land-based turbines has increased from machines producing 100 kW in the 1980s up to over 5 MW today (2024).

UK wind power has increased dramatically since the early 1990s, initially with onshore wind farms. The Ardrossan wind farm in Scotland constructed in 2004 (see Figure 23) is a typical UK example. It is equipped with 2 MW turbines with blades 40 metres long and these turbines are expected to continue operating into the 2030s. The photograph does demonstrate the visual impact, which has given rise to planning objections elsewhere.

A significant development came in 2002 with the construction of the first large-scale offshore wind farm in Denmark. Offshore construction is more difficult than for onshore wind farms, but the expertise of the oil and gas industry in constructing offshore structures has proved very useful. Placing turbines offshore has many advantages:

• they can intercept stronger winds, both by virtue of being out at sea, and also by being taller
• single turbines can be physically larger; the largest 15 MW designs have blades over 100 metres long
• if they are manufactured at waterside locations, they can be moved to wind farm sites by ship
• they can be freed of some objections of visual intrusion in landscapes.

Since 2005 there has been extensive development of offshore wind power in the UK, Denmark and Germany. In 2023 the UK obtained nearly 30% of its electricity from wind power, with an increasing proportion coming from offshore sources (DESNZ, 2024).

There is plenty of scope for further expansion. The UK resource for offshore wind turbines mounted on the seabed is larger than the country’s total 2023 electricity demand. The world resource for land-based turbines alone is several times current world electricity generation.

Wind power is now the world’s second-fastest-expanding source of electrical energy (after solar PV), having achieved a growth rate of over 15% per annum between 2010 and 2023. In 2023 it supplied nearly 8% of the world’s electricity.

The IEA’s Net Zero by 2050 scenario requires a continuing high growth rate. The amount of electricity generated globally from wind power (onshore and offshore) needs to increase from its 2022 value by a factor of 8. If this was all done using offshore wind turbines, globally it would require an area of sea roughly equal to three times that of the North Sea.

This video visits a wind turbine in the Hornsea 1 wind farm in the North Sea, 75 miles off the Yorkshire coast. The wind farm was completed in 2020 and can produce over a gigawatt of electricity. Each 7 megawatt turbine has blades 75 metres long (and the turbines for more recent offshore wind farms are even larger!) The video demonstrates the sheer scale of the wind turbines and gives a sense of the engineering expertise required to construct them in a relatively hostile environment.