Wind Farms May Warm Local Land While Fighting Global Warming

If the US’s entire electricity demand was met by wind energy, it would warm up the average surface temperature across the country by 0.24°C, a study finds. For the same amount of energy generated, the climate impacts of solar farms would be ten times less.

Wind power of course benefits the climate by replacing fossil fuels and cutting greenhouse gas emissions. But any energy technology has environmental impacts even if it reduces carbon emissions, say the Harvard University researchers behind the study published in Joule. There is no simple answer regarding the best renewable energy technology, and it is important to weigh the pros and cons of each as the world transitions to a carbon-free energy system.

Lee Miller and David Keith compared the impacts of wind and solar by using a high-resolution climate model of the continental US. They covered the windy grass plains of the Midwest with enough turbines to produce about half a terawatt of electricity, which would meet 100 percent of the country’s electricity demand. Using solar panels to produce the same amount caused a local warming of 0.024°C.

Unlike the burning of fossil fuels, wind turbines do not produce heat-trapping greenhouse gases. Instead, they redistribute heat. Rotating turbine blades draw down warmer air from higher up in the atmosphere. The warming effect of the turbines is strongest at night when temperatures increase with height and the air is calmer without the sun warming it and causing it to move up. Surface temperatures increasing by up to 1.5°C, the computer models showed.

Wind’s climatic impacts could be reduced by increasing the height of the turbine rotor to reduce interactions between the turbulent air behind them and the ground, or by switching the turbines on or off depending on meteorological conditions, the researchers say.

The climate impact of wind power and fossil fuel emissions they reduce are different in two important ways, they add. One is that the impact of wind power is immediate but would disappear if the turbines were removed, while the benefits of cutting emissions grows with the cumulative reduction in emissions and persists for thousands of years. Second, wind power’s impacts are predominantly local to the wind farm region, while the benefits of reduced emissions are global.

“The direct climate impacts of wind power are instant, while the benefits accumulate slowly,” Keith said in a press release. “If your perspective is the next 10 years, wind power actually has—in some respects—more climate impact than coal or gas. If your perspective is the next thousand years, then wind power is enormously cleaner than coal or gas.”

Source: Lee M. Miller and David W. Keith. Climate Impacts of Wind Power. Joule, 2018.

Image: giphy

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