This effect combines with another one relating to changes in wind direction as it blows over the hill, driving up the intensity of forces across the turbines.
Finding ways to increase the efficiency of windmills has been on scientists’ innovation agenda for some time. While some innovators are working on radically different designs to achieve that goal, a recent study yields a rather unexpected finding — placing wind turbines behind hills could produce significantly higher amounts of energy than those out in the open.
Conducted by researchers at the University of Twente in the Netherlands, the study aimed to explore how, in some circumstances, wind turbines could actually benefit from being placed behind hills. As part of their experiment, the scientists used an aerodynamic modeling technique called large eddy simulation, which allowed them to model the effects of a three-dimensional hill on the performance of downwind turbines.
The simulation was based on a 90-meter-tall (295-ft) turbine with 63-meter (207 ft) blades, being placed 756 meters (2,500 ft) behind a 90-meter-tall (300-ft) hill. To their surprise, the researchers found that under some conditions, this particular arrangement actually increased the power generation capacity of the turbine by 24 percent.
“The wind speed immediately behind the hill is slower, which creates an area of low pressure,” explains study author Dr. Richard Stevens. “This low-pressure area sucks in air from above, where the wind is much stronger than it is close to the ground. This means that a wind turbine does not need to be higher to take advantage of the strong winds at higher altitudes.”
As explained by New Atlas, this effect combines with another one relating to changes in wind direction as it blows over the hill, driving up the intensity of forces as they sweep across the turbines.
Scientists are now further investigating this phenomenon to see whether the same findings could hold up on actual terrain where the conditions are much more complex.
Study source: Renewable Energy — Effects of atmospheric stability on the performance of a wind turbine located behind a three-dimensional hill