Engineers go to great lengths to maximize the orientation of wind turbines, placing them on the ridges of hills, mountains or miles from the coast in the middle of the ocean. A new study has taken an interesting twist that could open up new avenues for renewable energy generation, showing that turbines behind hills could produce more power than those in the open.
The research was conducted at the University of Twente in the Netherlands and sought to explore how, in certain circumstances, wind turbines could benefit from being placed behind hills.
To do this, the scientists used an aerodynamic modeling technique called large turbulence simulation, which allowed them to simulate the effects of a three-dimensional hill on the performance of wind turbines downwind.
The simulation was based on a 90 meter high turbine with 63 meter blades, placed 756 meters behind a 90 meter high hill. Unexpectedly, the team found that, under certain conditions, this particular arrangement increased the power output of the turbine by 24%.
The wind speed just behind the hill is lower, creating an area of low pressure. This area of low pressure draws in air from above, where the wind is much stronger than near the ground. This means that a wind turbine does not need to be taller to take advantage of strong winds from above.
Dr. Richard Stevens, author of the study.
This effect combines with another related to changes in the direction of the wind as it blows over the hill, which increases the intensity of the forces as they sweep the turbine.
Also, the wind above the hill blows in a different direction than the wind near the ground. This directs the slow moving air away from the turbine, leaving the turbine behind the hill to benefit from the strong current.
Dr Richard Stevens.
Although the study shows that some wind turbines placed behind hills in certain environments could produce more energy, other factors must be considered. Simulations show that this increase in wind causes a greater amount of turbulence, which would lead to greater wear on the turbines. Scientists are continuing to study whether the benefits outweigh the kind of damage the turbines can sustain, and whether this increased performance can be replicated in larger real-world environments.
In this particular situation, with a single hill, the power output is higher, but the actual terrain is much more complex.
Dr Richard Stevens.
More information: www.sciencedirect.com
Going through www.utwente.nl