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Why wind farms make more power over water than land

A Greenland-sized wind farm on land would struggle to produce the 7 terawatts needed to power both the US and China, the world's largest consumers of energy. But the same wind farm over the sea could produce 10 terawatts, capable of lighting up China once and the United States twice, according to a study published Monday. All told, there's enough wind energy over the sea to power all of civilization, writes Chris Mooney in the Washington Post.

Why it matters: As countries switch to renewable energy, they will run into land use issues. Wind farms and solar panels take up space, and can damage habitats or harm migrating birds. A smaller farm at sea might have different—and potentially smaller—environmental impacts than one on land. "I would look at this as kind of a greenlight for that industry from a geophysical point of view," study author Ken Caldeira told the Post.

How it works: Each time wind passes through a turbine, some of its energy is converted to electricity. That means that it's less windy on the other side of the turbine. Eventually, rows of turbines on land lose so much wind they become ineffective, so there's a maximum amount of energy a land-based farm can create. Researchers already knew there was more wind over water, and that smooth ocean surfaces had less friction. This study shows the downward movement of air over the ocean replenishes wind as it moves through the farm, which means ocean farms have a much higher energy cap.

But, but, but: "It's very unlikely that we would ever build out open ocean turbines on anything like that scale — indeed, doing so could even alter the planet's climate, the research finds," writes Mooney. But this study shows that ocean turbines can be a part of a larger energy grid.