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What would a world powered entirely by offshore wind look like?

A net-zero world will require thousands more wind farms

AFTER MONTHS of energy shortages in Europe, caused in part by unusually still weather becalming wind turbines, the question of how to power the world from renewable sources is high on the public agenda. This is particularly apparent at COP26, the UN’s ongoing climate conference, at which world leaders will discuss how to transition “from coal to clean power”. On October 13th Deb Haaland, America’s secretary of the interior, announced plans to open up huge sections of America’s coastline for offshore wind-farm development. These new turbines could, according to government estimates, generate as much energy per year as 30 new conventional nuclear-power plants.

Wind is a clean and renewable source of electricity. Putting noisy turbines offshore reduces the amount of disturbance they cause to people. And they are often far enough out to sea not to spoil ocean views. But just how much shoreline would be required to produce the power the world needs?

The total amount of energy needed to power the world for one year is around 556 exajoules—or 556 with 18 zeros. A single square kilometre of wind turbines produces roughly 80 terajoules (that’s 80 with 12 zeros) each year. That means around 7m square kilometres of offshore farms would be needed to power the whole world.

Projecting this area onto a map of the world’s wind-power density—a measure of wind speeds—The Economist worked out the optimal locations for these imaginary installations, using some of the same data as Land Art Generator, a public arts initiative. Locations are scattered around the globe. Some dot the west coast of America, one of the sites proposed by the Biden administration. Others cluster in the North Sea where many of the world’s most productive wind farms are already installed.

Wind will never be the sole source of the world’s energy. Farms are only effective in certain places and even then the output is intermittent, somewhat unpredictable and impossible to control. Offshore wind is also one of the most expensive forms of renewable energy. Wildlife campaigners complain that the spinning blades can be deadly to birds and that huge underwater installations disturb sealife (although turbines can also create artificial reefs which promote biodiversity).

A more realistic prediction is that in a net-zero world, in which there is an overall balance between the amount of greenhouse gas emitted into the atmosphere and the amount removed, 7.5% of the world’s energy will come from offshore wind farms. If this were to happen tomorrow it would require increasing the number of square kilometres of offshore wind installations from roughly 7,000 currently in operation, to 525,000: hardly a breeze.

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