Energy

Surprising study shows how wind turbines can work better behind hills

Surprising study shows how win...
Wind turbines could benefit from placement behind hills, according to a new study
Wind turbines could benefit from placement behind hills, according to a new study
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Wind turbines could benefit from placement behind hills, according to a new study
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Wind turbines could benefit from placement behind hills, according to a new study
Aerodynamic simulations have shown that wind turbines might be able to produce more energy when placed behind hills
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Aerodynamic simulations have shown that wind turbines might be able to produce more energy when placed behind hills
A simulation shows the wind flow at low wind speed (blue) turns upwards behind the hill, putting the wind turbine (the vertical line) in a stronger wind flow (red)
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A simulation shows the wind flow at low wind speed (blue) turns upwards behind the hill, putting the wind turbine (the vertical line) in a stronger wind flow (red)
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Engineers go to great lengths to maximize the exposure of wind turbines, placing blades atop tall towers on the crests of hills or miles off shore over the wild, unprotected ocean. A new study has thrown up an interesting curve ball that could open up new avenues for the generation of renewable energy, demonstrating how turbines nestled behind hills could actually produce higher amounts of energy than those out in the open.

The research was carried out at the University of Twente in the Netherlands, and sought to explore how, in some circumstances, wind turbines could actually benefit from being placed behind hills. The scientists did this through an aerodynamic modeling technique called large eddy simulation, which allowed them to simulate 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 meter (2,500 ft) behind a 90-meter-tall (300-ft) tall hill. Counterintuitively, the team found that under some conditions this particular arrangement actually increased the power production of the turbine by around 24 percent.

Aerodynamic simulations have shown that wind turbines might be able to produce more energy when placed behind hills
Aerodynamic simulations have shown that wind turbines might be able to produce more energy when placed behind hills

“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.”

This effect combines with another one relating to changes in wind direction as it blows over the hill, which drives up the intensity of the forces as they sweep across the turbine.

A simulation shows the wind flow at low wind speed (blue) turns upwards behind the hill, putting the wind turbine (the vertical line) in a stronger wind flow (red)
A simulation shows the wind flow at low wind speed (blue) turns upwards behind the hill, putting the wind turbine (the vertical line) in a stronger wind flow (red)

“In addition, the wind above the hill blows in a different direction to the wind close to the ground," says Stevens. "This causes the slow-moving air to bend away from the wind turbine (see above), leaving the turbine behind the hill to benefit from the strong current."

While the study demonstrates that some turbines placed behind hills in certain environments could produce greater amounts of power, there are other factors to consider. The simulations show that this increase in wind leads to higher amounts of turbulence, which would cause greater wear and tear on the turbines. The scientists are continuing to research whether the benefits outweigh the type of damage the turbines might incur, and whether this uptick in performance can be replicated across broader, real-world settings.

“For this particular situation, with only one hill, energy production is higher but real-life terrain is much more complex,” says Stevens.

The research was published in the journal Renewable Energy.

Source: University of Twente

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6 comments
6 comments
niio
Wind turbines have rotating heads because the wind direction is always changing. Having a turbine aligned to a hill means this would work about 5% of the time. Seems like a waste of effort to even investigate.
Signguy
There are newer, more efficient power generators using wind than these gigantic blade windmills that are inefficient, cost tons of money, have tremendous maintenance, and are polluting in disposing all the materials.
jerryd
Well duh! As they say, it depends. Winds will follow terrain and terrain can amplify winds. The question is how often and time of day these happen. A valley across the normal winds will make a lot less than a valley aligned with the regular winds.
The valleys between mountains have always been a favorite WT site.
What you need is no obstructions above the WT plus 20' for small ones for a good ways especially in common strong wind directions. A lot of tract housing resembles this.
paul314
I wonder whether the non-ridgeline location would also be less objectionable to the NIMBY types who complain about towers spoiling the landscape.
Gordien
Concerning wind turbines, I've always heard that the higher the better. I live in North Central Idaho near the rolling hills of the Palouse, and it appears that the land concentrates wind in certain locations - it can be rough on the crops. I imagine that horizontal rolling turbines could get a lot of energy there. Just a thought.
SpieroFantasio
Where in the whole Netherlands you may find a hill with the height of incredible 90m / 300ft? All flat land like a table top there.