Siting a wind turbine behind a hill would not likely appear to be an appropriate choice for optimal power generation. While wind farm designers typically focus on open landscapes to harness prevailing wind resources, researchers from the University of Twente in the Netherlands have demonstrated that in some cases wind turbines can actually produce more energy in hilly terrain.

Simulations placed a 90 m tall turbine with 63 m blades at a site 756 m behind a hill that is 90 m high. Under some conditions, this arrangement increased the power production of the turbine by around 24%.

Researcher Richard Stevens explained “The wind speed immediately behind the hill is slower, which creates an area of low pressure. 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 wind above the hill blows in a different direction to that close to the ground, slow-moving air bends away from the turbine, leaving the turbine behind the hill to benefit from the strong current.”

These effects cause the wind turbine to produce more energy than in the same conditions without the hill.

The research detailed in Renewable Energy demonstrates that vortex shedding induced by the hill can result in the entrainment of the high-velocity wind from the low level jet to the turbine area. This can result in an unexpected increase in turbine power production compared to a reference case without hilly terrain.