Wind Energy Creates a Warming Effect, Study Finds

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Clearly, wind energy is favored to its fossil fuel counterparts in terms of its environmental footprint. Zero greenhouse gas emissions. Zero global warming potential. Zero heat islands. Simply, wind energy seems to be a perfect part of the solution to a climate change problem.

At least, this is what we thought.

Until recently, when scientists discovered a surprising link between wind farms and rising land surface temperatures. As it turns out, wind farms may stir air in an atmospheric boundary layer a bit too much – enough to produce a noticeable warming effect after the sundown.

The study, which was published in Nature Climate Change in April, is one of the first ones to consider interactions between wind turbines and the atmospheric boundary layer near the land surface. A team of scientists from State University of New York at Albany and several other institutions presents a long-term observational evidence of the effects of wind farms on surface temperatures. Over the span of nine years, they carefully observed land surface temperatures around four wind farms in west-central Texas. Guided by the satellite data, the team found that wind farms are responsible for “a significant warming trend of up to 0.72°C per decade, particularly at night-time”.

“We attribute this warming primarily to wind farms”, the study confirms.

The Cause

The researchers suggest that the observed warming effect is created by an enhanced vertical mixing behind the wind turbines. When wind turbines rotate, they create wakes behind them. The turbulent wakes can travel long distances downwind – and stir up air as they go. This is similar to wakes created by motorboats on a lake’s surface.

Yet, during the nighttime, the atmospheric boundary layer is very stable and thermally stratified. Because of the efficient radiative cooling of land surface, air lying closest to the land surface is coldest. From there up, its temperature increases. Therefore, warmer air will typically loom above cooler air. As wind turbines continue to spin during the dark hours, they bring warmer air close to the surface. This creates a warming effect, which is not observed in the absence of wind farms.

Conversely, during the daytime, the atmospheric boundary layer has warm air on the bottom and cool air on the top. As a result, the mixing could produce a cooling effect to some degree, as suggested in the paper. But instead, the results show only negligible effect in daylight temperatures.

Land Surface Temperatures

Satellites used in the study measure Earth’s surface temperatures, which are different from air temperatures we see in weather forecasts. As viewed from the sky, land surface temperatures depend on a number of variables, such as land cover, nature of the surface (for example, roof, road, or forest), reflectance, etc. Plus, land surface temperatures show greater day-to-night variability than air temperatures. The study acknowledges that it is, therefore, possible that the resultant warming effect on air might be slightly less than the calculated effect on the land.

Possible Atmospheric Interactions

Most likely, the role of a wind turbine goes beyond the conversion of kinetic energy into mechanical energy. If the turbine has an active role in vertical air mixing, it changes the moisture content within the atmosphere, too. The amount of moisture present in the atmosphere depends on temperature – warmer air can hold more water vapor than colder air. How this mass and moisture transfer during daytime and nighttime affects regional climate is not yet clear.

Sure, an increase by 0.72°C in a decade doesn’t seem a lot. Yet at the same time, wind power is rapidly expanding all over the map. For example, over the next decade, European Wind Energy Association predicts more than 200% increase in wind energy production in EU countries. Plus, many other countries are joining the race to the top of the global wind industry. With new wind turbines being added each day, the way they interact with environment might be something to think about.

Article by Adela Kuzmiakova

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About Author

Walter’s contributions to CleanTechies over the past 4 years have been instrumental in growing the publications social media channels via his ongoing editorial and data driven strategies. He is the founder and managing director of Sunflower Tax, a renewable energy tax and finance consultancy based in San Diego, California. Active in the San Diego clean technology community, participating in events sponsored by CleanTech San Diego, EcoTopics, and Cleantech Open San Diego, Walter has also been a presenter at numerous California Center for Sustainability (CCSE) programs. He currently serves as an adjunct professor at the University of San Diego School of Law where he teaches a course on energy taxation and policy.

4 Comments

  1. Finn McGowan on

    I don’t feel like paying $32 for the privilege of reading this study, so my comments are uninformed and may be unfair, but I’ll make them anyway.

    If all their work and conclusions are correct, why does this matter? Raising a few hundred acres of local farmland by a couple degrees on windy nights seems unlikely to ruin crops or habitats. There doesn’t seem to be any suggestion that this contributes to *global* warming – their speculation is that the turbines are churning air, not so much heating it.

    But I doubt all their work is correct. How can they infer that the effect increases “per decade”, when they considered only 8 years of data?

    I don’t even know if we can generalize what happens “over a region in west-central Texas” to regions in other terrains, altitudes, latitudes, and climates.

    It’s good to have this data. But it’s not actionable intelligence yet – it’s unclear that this study implies anything for policy makers.

    An engineer doesn’t look for a perfect solution, he looks at the available trade-offs and chooses the one with the best balance of cost to benefit. Until wind farms are shown to have more environmental costs than their fossil-fueled and nuclear competition, they should be considered a positive addition to our energy portfolio.

  2. I can’t believe this has been reposted. Time to dispel myths again. *Sigh*

    Other media reports have thoroughly debunked this erroneous story about turbines causing global warming. See Washington Post’s story at http://wapo.st/IQk6DC

    “Scientific studies are misrepresented all the time. But now and again the distortions get particularly bad. That was the case Monday, when Fox News ran the headline, ‘New Research Shows Wind Farms Cause Global Warming.’ A number of other media outlets did the same thing. And it’s… not true at all.”

    This is just stirring the (hot) air on what people are talking about–farmers have done this for decades to keep the frost away from crops–albeit, most of these single bladed fans are noisy–that’s another, annoying another issue. No heat and no heat-trapping gasses are being added to the climate, so it couldn’t possibly cause global warming. As the study author himself says here: http://mediamatters.org/blog/201204300004

    The researchers, led by Liming Zhou, said it is “[v]ery likely” that “wind turbines do not create a net warming of the air and instead only re-distribute the air’s heat near the surface, which is fundamentally different from the large-scale warming effect caused by increasing atmospheric concentrations of greenhouse gases.” The turbines pull down warm air, increasing land surface temperatures, which already have “a larger day-night variation” than the surface air temperatures featured in daily weather reports.

  3. Many of the wind power farms arcoss PRC are infact transpiting thermals in sun drenched deserts and outward no signs of winds that prevail in February March. Clearly one feels the moisture and indeed condensation at night.The4 true Carbon acounting of wind and solar fabrication erection in remote region hook to grid in their short life cyle actually makes them a liability to lowering CO2

    Robert Vincin Adviser t6o PRC since 2005 growing soil food fodder in deserts with C4 array lowering CO2e.

  4. Those are local effects, and while they may have some significance for local areas, wind power adds no net energy to the overall planetary system, unlike fossil fuels or even nuclear energy, which take heat-generating materials from their resting places deep underground to release their latent heat energy (and in the case of carbon, increased heat retention) into the atmosphere.

    Newer turbine designs that minimize vortexes and smooth air flow may also alleviate this problem.

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