Stanford Wind Farm Study Shows Tilting Turbines Improves Energy

PALO ALTO, CA — A direct hit from the wind isn't necessarily the best way to channel and redistribute the power from it, a new Stanford University study revealed.

Solitary wind turbines produce the most power when pointing directly into the wind. But when the tightly-packed lines of turbines face the force on wind farms, wakes from upstream generators can interfere with those downstream, the Stanford News Service reported.

The process is equated to 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, thus with a probability of lower operating costs, the study shows.

“To meet global targets for renewable energy generation, we need to find ways to generate a lot more energy from existing wind farms,” said John Dabiri, professor of civil and environmental engineering. “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, the news service added.

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 percent in low-wind speeds – depending on the angle of the turbines – and by 7 to 13 percent in average wind speeds. Wake steering also reduced the ebbs and flows of power that are normally a challenge with wind power.

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