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Stanford study shows how to improve production at wind farms

Power News - Published on Mon, 22 Jul 2019

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Four of the turbines on a TransAlta Renewables wind farm in Alberta, Canada, that were used for the wake-steering experiment. The truck in the lower left corner of the photo gives a sense of the wind turbines’ size. Solitary wind turbines produce the most power when pointing directly into the wind. But when tightly packed lines of turbines face the wind on wind farms, wakes from upstream generators can interfere with those downstream. Like a speedboat slowed by choppy water from a boat in front, the wake from a wind turbine reduces the output of those behind it. Pointing turbines slightly away from oncoming wind – called wake-steering – can reduce that interference and improve both the quantity and quality of power from wind farms, and probably lower operating costs, a new Stanford study shows.

Mr John Dabiri, professor of civil and environmental engineering and of mechanical engineering and senior author of the paper said that “To meet global targets for renewable energy generation, we need to find ways to generate a lot more energy from existing wind farms. The traditional focus has been on the performance of individual turbines in a wind farm, but we need to instead start thinking about the farm as a whole, and not just as the sum of its parts.”

Turbine wakes can reduce the efficiency of downwind generators by more than 40 percent. Previously, researchers have used computer simulations to show that misaligning turbines from the prevailing winds could raise production of downstream turbines. However, showing this on a real wind farm has been hindered by challenges in finding a wind farm willing to halt normal operations for an experiment and in calculating best angles for the turbine – until now.

First, the Stanford group developed a faster way to calculate the optimal misalignment angles for turbines, which they described in a study, published July 1 in Proceedings of the National Academy of Sciences.

Then, they tested their calculations on a wind farm in Alberta, Canada in collaboration with operator TransAlta Renewables. The overall power output of the farm increased by up to 47% in low wind speeds – depending on the angle of the turbines – and by 7 to 13% in average wind speeds. Wake steering also reduced the ebbs and flows of power that are normally a challenge with wind power.

Mechanical engineering PhD student Michael Howland, lead author on the study said that “Through wake steering, the front turbine produced less power as we expected. But we found that because of decreased wake effects, the downstream turbines generated significantly more power.”

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Posted By : Rabi Wangkhem on Mon, 22 Jul 2019
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