Wind turbines as hurricane brakes

A team led by Stanford professor Mark Z. Jacobson calculated that offshore wind turbines could weaken hurricanes. However, this would require tens of thousands of turbines. The researcher nevertheless believes it is possible.

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Symbol of destruction: these Rollercoaster on the New Jersey coast was swept into the Atlantic by Hurricane Sandy in 2012. Storms like this are piling up – and they’re causing more and more damage.

Harvey, Irma, Jose, Maria: The 2017 hurricane season kept America and the Caribbean on edge. The immense forces of such storms cause devastating damage – but could also produce vast amounts of electricity if they hit offshore wind farms.

Researchers at the renowned Stanford University in California, however, go one step further. You say wind turbines at sea can even mitigate hurricanes and protect the coastline. EnergyWinds talked about this with Mark Z. Jacobson spoke to the study’s leader.

Mr. Jacobson, In your model, wind turbines have different impact on Sandy and Katrina. Why do the results turn out so differently?
Mark Z. Jacobson: Sandy and Katrina were very dissimilar hurricanes. Sandy was a very large-scale storm where the force was spread out, making the hurricane weaker overall. Katrina was concentrated in a smaller area and thus much more intense. If you put the same number of wind turbines for both storms, they have a stronger impact on Katrina because all the turbines are directly in the path of the storm. Sandy, on the other hand, is more sprawling, so the wind turbines can do less of a job. Also, due to sheer size, Sandy had slower winds. That’s why the effect of the wind turbines is weaker.

Mark Z. Jacobson is a professor of civil and environmental engineering at Stanford and director of the university’s Atmosphere and Energy Program.

How do wind turbines affect a hurricane?
Jacobson: The biggest benefit is that wind turbines reduce wind strength. Because strong winds whip up the waves, this directly affects the height of the tidal surge.

And how exactly do they do it?
Jacobson: When a hurricane is in full swing, the winds move in a circular pattern. Waves whipped up by the wind create a strong friction on the surface, which directs the winds slightly inward. They circulate inward until they meet the eye of the storm. However, they cannot enter the eye because they are moving too fast.

You have to think of it like a race car driver: He can’t turn on the spot at 200 miles per hour, doing so would cause him to roll over. At such high speeds, it always travels around a certain point.

Exactly the same thing happens to the winds in a hurricane: they move insanely fast inland, but then circulate upward around the center. Higher up, there are even faster winds that really suck out the air. This will pull more winds up to replace the escaped air. This process causes the air pressure in the eye to drop dramatically – and for as long as the air is escaping at the top faster than it is flowing in at the bottom. This, in turn, strengthens the winds at the surface because the air pressure is low in the eye of the storm, but higher outside it. This difference drives the winds, which then create higher waves, which in turn create more friction on the surface and direct more winds into the eye of the hurricane.

If you bring the wind turbines into this scenario, they reduce the wind strength in the outer area of the hurricane by taking energy from the wind and converting it into electricity. Weaker winds reduce wave heights, reducing their friction, so the circulation of wind into the interior of the hurricane is weaker. As a result, the pressure in the eye of the storm increases, because less air is transported upwards and pulled out of the eye. The higher air pressure inside takes the strength out of the winds, weakening the whole cycle.

The turbines can survive extreme weather. This is what wind farms in the North Sea show

Can’t a hurricane just destroy the wind turbines?
Jacobson: The wind turbines protect each other. The more wind turbines there are, the stronger their effect is on the approaching hurricane. The wind turbines weaken the hurricane from the outside in, even as it begins to approach. By the time it finally hits the wind turbines, it’s already too weak to destroy them.

In our model, we calculated using standard wind turbines, which shut down when the wind force reaches 33 meters per second and withstand winds up to 50 meters per second. In the case of Katrina, they were so effective that winds never reached 50 meters per second. And in the meantime, it’s easy to build larger turbines with more powerful engines to play it safe.

We know about conventional turbines that can withstand extreme weather conditions. This is shown by wind farms in the North Sea, which are regularly exposed to heavy storms.

How many wind turbines are we talking about here??
Jacobson: Any number of wind turbines has a positive impact. The more you have, the better it is, of course.

In our energy transition master plan, where 100 percent of energy in the U.S. comes from clean energy sources, 15 to 20 percent of that is for through offshore wind farms. According to our calculations, we would need around 200 for this.000 wind turbines along coasts.

You wouldn’t place them all right outside New Orleans or New York. The chances of a storm hitting that exact park are too low. They also compete for the same winds when they are close together. So it’s smarter to spread them out. Ideally, divide them into clusters of 10.000 or several thousand on.

These are incredible numbers. With so many wind turbines, would there even be room left for shipping traffic?
Jacobson: Yes, because the turbines would not all be located along the coastline, but would extend out to sea in the individual clusters.

America’s first offshore wind farm: The five GE turbines from Block Island are located off the coast of the state of Rhode Island. They went into operation in 2016. Jacobson’s plans would require thousands of such farms to be built.

How far would the farms be from the coastline?
Jacobson: They can be far enough away that they can’t be seen. When the first row of wind turbines is five to seven kilometers from the coast, they are about the size of a thumbnail to the observer. On most days, there is so much sea salt in the air or it’s so cloudy that visibility doesn’t reach that distance. And in the meantime, there are floating wind turbines that no longer have to be firmly anchored in the seabed, but can be moved around.

200.000 wind turbines cost a lot of money?
Jacobson: Not compared to current energy sources: In the U.S., direct costs are currently about 13 cents per kilowatt-hour and 30 cents per kilowatt-hour in health and climate costs. Offshore wind farms have only direct costs.

In addition, the parks’ effect on hurricanes also reduces their immense financial damage. In 2017, extreme weather caused $300 billion in damage in the U.S. This sum is not accounted for by hurricanes alone, but the effect of wind farms could avoid a good part of it.

You have to keep in mind that the wind turbines are put up to mainly generate energy – their effect on hurricanes are only a positive side effect.

Offshore wind farm in the North Sea: There are now far more than 1,000 wind turbines in German waters alone.

Currently, the Block Island Wind Farm off Rhode Island is the only offshore wind farm in the U.S. How realistic is it that one day there will actually be 200.000 wind turbines along the coast?
Jacobson: From the technical and also from the economic point of view it is definitely realizable. It’s within the power of the states to have a coastline.

The State of New York has just presented a program according to which hundreds of turbines will be placed along Long Island. Some companies are already working on applications for more wind farms, but that process takes a while.

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