Can we reduce a hurricane's power using wind turbines?

Question

Below is the abstract of an article in Nature: Taming hurricanes with arrays of offshore wind turbines, describing computer simulations that indicate that wind turbines could disrupt a hurricane enough to reduce peak wind speeds by up to 92 mph and decrease storm surges by up to 79 percent.

Hurricanes are causing increasing damage to many coastal regions worldwide Offshore wind turbines can provide substantial clean electricity year-round, but can they also mitigate hurricane damage while avoiding damage to themselves? This study uses an advanced climate–weather computer model that correctly treats the energy extraction of wind turbines to examine this question. It finds that large turbine arrays (300+ GW installed capacity) may diminish peak near-surface hurricane wind speeds by 25–41 metres per second (56–92 mph) and storm surge by 6–79%. Benefits occur whether turbine arrays are placed immediately upstream of a city or along an expanse of coastline. The reduction in wind speed due to large arrays increases the probability of survival of even present turbine designs.

My question is not about the financial, logistical or engineering challenges of building a large amount of wind turbines to "tame" hurricanes, as this is solely a computer model and it will probably be a classic case of a model saying "possibly" but in real life it will not happen.

It's the physics underlying the design of turbines blades whose purpose would basically be the opposite to that of aircraft propellors that I would like to more about, i.e. slowing air velocity, rather than increasing it.

Answer 1

While I'm not willing to spend the money to get access the paper, one issue jumps out at a casual reading of the abstract - turbine design. Honeste_vivere's answer mentions the possibility of destroying a farm, and the abstract includes "The reduction in wind speed due to large arrays increases the probability of survival of even present turbine designs." What seems to be missing at this level is the need to produce turbines which will work effectively at hurricane-force winds. Current devices are simply incapable of doing this, and since any turbine has a limited operating range for efficient operation anything capable of working when a hurricane hits will be useless most of the time.

This seems possible in principle, but among other things it would require a very large investment in R&D, the turbines would need to be far more robust than current designs (and therefore more expensive), and testing of operational units would obviously be problematic.

Also not mentioned, and not explored in honeste_vivere's answer, is just how one would dissipate the extracted power. If the power is not dissipated, the turbines can't extract it. Giant heaters out to sea which dump heat into sea water? For any heaters less than 100's of square kilometers, I suspect a successful hurricane amelioration would have catastrophic ecological consequences.

Between the need for dedicated hurricane turbines and the need for power dissipation structures, the cost would seem very high.

But then again, I didn't read the article, so I might be wrong.

Answer 2

Solution based on wind energy and cost aspects:

Typical design range 10-20 m/s: Wind Turbines are designed to produce maximum power under somewhat above normal mean wind speeds such that overall energy output per total cost of ownership is maximised. This typically results in optimum operating velocities in the 10-20 m/s range. Wind Turbines already produce energy at unsubsidised costs somewhat in excess of those from more traditional sources - so minimising capital cost is important. Assume the turbine can absorb ALL energy offered at up to 20 m/s (72 kph, 45 mph) and is "feathered at wind speeds above that to maintain power out at maximum level. (In practice a turbine may be shut down to zero output and speed at very high wind speeds, rather than being limited at maximum power.)
Typical design aspects

Wind energy rises with the cube of wind speed - doubling wind speed results in an 8x increase in the energy in the wind.

Increases in wind speed over design maximum may be survivable by feathering and preventing increased energy absorption - but increases of wind speed by a factor of 2 will completely and utterly exceed the ability to absorb the extra energy present. To reduce wind speed from say 45 m/s to 20 m/s requires removing more than 10 times as much energy as would be usually extracted at full power.
( 45^3/25^3 )- 1 = 10.39 x extra energy.

Conclusion: Economic considerations (quite apart from other practical implementation factors) make design to allow the 'occasional' reduction in hurricane strength impractical.

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Added:

Chuck Simmons has provide the following two useful related links.

Taming Hurricanes With Arrays of Offshore Wind Turbines

Mark Z. Jacobson Cristina Archer, Willet Kempton Wind Energy Symposium University of Delaware February 27, 2013

[Stanford Report, February 26, 2014 Offshore wind farms could tame hurricanes before they reach land, Stanford-led study says]((http://news.stanford.edu/news/2014/february/hurricane-winds-turbine-022614.html)

Note the quantity and scale of the turbines above and their peak required capacity compared to the energy that would be available to them on all other occasions. To be economically justified such an installation would probably need to be costed solely on the basis of their hurricane damage reduction capability. This may prove to be justifiable in some contexts, but the quantity required are not "useful" or financially justifiable in energy production terms. (eg a 2 MW turbine typically costs $3M - $4M installed. Start by erring on the low side due to economies of scale. An array of 78,000 large turbines as suggested in the above article would cost
~= 78,000 x 3,000,000 =~ 240 Billion dollars. As these are offshore and necessarily at the extreme upper end of the robustness range, costs would be liable to be higher, or much higher.
Hurricane Katrina (the 6th most damaging US Hurricane ever) had an estimated cost of about 125 billion dollars - with somewhat higher and lower figures also being suggested. The WT array will not prevent all Hurricane damage. If it could reduce damage by 10% it saves 12.5B. If by 25% then 60B. A Hurricane here and a hurricane there and after a while all these amounts start to add up to real money - but you'd want to stave off a lot of them over the lifetime of your storm slayer to justify its 240B (and maybe double that) cost. As savings occur in the future and distant future discounted cash flow amortisation of the savings means you'd need to substantially ameliorate dozens of hurricanes to pay its way. Could such an array do so? Maybe so but very probably not.

Note that if energy dissipation without everyday energy generation is the sole focus then other means of hurricane energy dissipation may be possible at lower cost.

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FWIW: Contrary to suggestion in the editing note, I did read and understand the information that was cited and free to read. Scrubbing energy off the outside of a hurricane is "a good start" but ultimately the array must dissipate substantial energy to be useful. The papers suggested that by slowing peripheral winds the hurricane can be persuaded to "wind down" of its own accord. A good trick, if you can do it. Can you? TBD.

Answer 3

I think you need to be careful here.

The total power contained within a hurricane ranges from $1 \times 10^{12}$ to $6 \times 10^{14}$ Watts or 1 to 600 TW. The world energy consumption in 2008 was 20,279 TWh. There are 8760 hours/year, thus our consumption rate was ~2.31 TW (1 TW = $10^{12}$ W).

The point being, the energy you would need to dissipate per second is up to ~260 times the total world energy consumption rate.

So the short answer to the question posed by your title of this post is no.

Whether wind farms can help reduce the strength of hurricanes prior to striking land is another issue. If the purpose is to weaken a storm, then producing large enough wind farms may be more costly (in production and repairs after each storm) than the effects of each hurricane, depending on strength. Obviously, some hurricanes will produce several billion dollars (USD) worth of damage but others are not as financially costly. Unfortunately, money is the primary driver for policy makers, not feasibility, logic, or human life. So I think the main part of your question is one of economics rather than physics.

The article reference you cite states one would need 300+ GW-sized wind turbines to have these effects. A recent report shows that the average cost of wind power is ~\$31,000/MW. Therefore, a 1 GW production level is \$31 million just for basic operations and maintenance costs. 300+ GW-sized wind turbines would run over \$9 billion. So it might be a hard sell, especially if one storm could effectively destroy an entire farm which would add to the total cost of storm damage.

Answer 4

A quick Google search turns up a couple of additional resources besides the free paper abstract. Stanford has a summary of the paper, and the University of Delaware has slides associated with a talk on the paper.

Offshore wind turbines currently exist and do act the opposite of an aircraft propellor: wind energy is converted into electricity, slowing the wind as a result. For this reason, modern large wind turbines are placed about half a kilometer apart: 4 turbines per square kilometer. This is the spacing used in the paper (see the slides). (Also, the Whitlee windfarm has 215 turbines spread over 55km².)

One of the primary take-aways from the summary, which other answers seem to have overlooked, is that the hurricane is "tamed" when wind turbines interact with the relatively slow, outer winds of the hurricane. "This feeds back to decrease wave height, which reduces movement of air toward the center of the hurricane, increasing the central pressure, which in turn slows the winds of the entire hurricane and dissipates it faster."

The hurricane's power is reduced before the stronger central winds can become a problem for the wind turbines, which can, in any event, withstand category 2 to 3 hurricanes (112 mph winds).

Wind turbines are designed to dissipate energy efficiently, mostly by transmitting the generated electricity into the power grid. Wind turbines are designed to dump loads when the grid cannot consume all of the available power. A standard design is to heat up the water filled monopile that supports the turbine.

The paper discusses an offshore wind farm spread over 20,000 square kilometers. So when dumping load, the energy is being dissipated over a large area.

For hurricane Sandy, the paper discusses dissipating 1/16th of 2030 worldwide electricity generating capacity. This is roughly comparable to the electricity generating capacity of the U.S. East coast. So, yes, you would want an efficient grid capable of shunting a significant portion of the generated electricity somewhere useful. In this context there would be numerous massive arrays of turbines in the Gulf and along the eastern seaboard. All of these turbines would share the work of dumping excess load.

The cost of the arrays is offset by: * The cost of the electricity produced; * The cost of the damage avoided; * The avoided cost of other structures (e.g. sea walls) that would be built instead.

So the physics of the existing wind turbines isn't an issue; the physics of energy dissipation isn't an issue; and the cost of the turbines isn't an issue. Now, whether or not you want millions of turbines dotting the southern and eastern coasts of the United States... that may be an issue.

[I do not have sufficient reputation to post links to my sources. I invite a reader to edit my text to remove '@' signs used to mask the links from the software, and then remove this comment.]

Answer 5

Interesting question which even made me laugh. As already pointed out the Power of an hurricane is too high to be connected to any grid. My laugh came about this; "Giant heaters out to sea which dump heat into sea water?" -Why?

Because it's basically the heat of the sea which feeds the energy to the Hurricane, and thus this kind of system would not do anything. The main rotation would simply happen above these wind turbines. To understand this all, we need to study the Functionality of a Hurricane;

Basically the Heat of the sea has too high Pressure compared to the upper atmosphere pressure. Heat is radiated to the space, and the clouds reflect the Sun's energy back. This causes an extreme cooling of the atmosphere, and thus amazingly low pressures there.

"High Pressure"/Temperature in Sea, Low Pressure/Temperature on Sky. This is the primary cause to drives the Hurricane. It's simply nature's way to balance this difference.

So the point of this Question is this; It's the physics underlying the design of turbines whose purpose would basically be to slowing air velocity, rather than increasing it.

As mentioned above, with Turbine blades and Generators, it would be impossible. There is simply no place you could put the energy in to.

But the question is "Slowing air velocity" and this would be needed to be made in away, which helps the Nature to find it's balance.

The easiest way to Slow down the Air velocity is to reduce the Pressure difference, which causes the velocity in the first place. The nature does it by evaporation. But it could be made more efficiently by sort of mechanical Transpiration.

If the Energy of Windmills is used to pump and spray the sea water behind the Turbine, the sum of "Evapotranspirated" water would be increased enormously. The airpressure difference at the windturbine would be locally decreased, and this would thus even protect the windturbine from the highest winds.

But the Water condensates behind the blades, like seen in airplanes? Yes it does, but the reason is temperature. The velocity is increased, and thus the pressure drops, but also the temperature. The Pressure drop Increases the vaporization, it's the Tempereture drop, which forces it to condensate.

So behind the Windturbine, there is quite optimal Conditions to vaporize water. The energy amount of energy, which must be dissipated is extreme;
If we calculate with 60 TW, we should produce 26 500 000 kg Watervapour / second.

Let's look what A single Windpowerplant could do; 6 MW WindTurbine has 126 m turbine diameter, and maybe it's tower is 100 m High. It reaches the Nominal Power at 14 m/s Windspeed. Cut out at 30 m/s. As Wind power goes to V^3, the Peak-Power is mostly only a Grid connection problem.

The Area of this Turbine is 12500 m2, and with 14 m/s the wind Power is (With Betzlaw) 13.2 MW, so the Turbine works with approx 50% efficiency. Thus only with 18.5 m/s and 30% efficiency, it would be already really realistic to have 3 MW power to pump Water. If the Water is pumped to 100 m hight, and as we want to vaporize it, we need to use 100 bar pressure; this means total 110 bar, or 1100 m Pressure head. With 3 MW could be pumped 278 kg/s. If simple Sprinkler nozzle would be enough, then with 20 bar the amount could be 1529 kg/s; The dissipation power is 3 470 MW, which with 30 MW Brt-power of Windturbine sums up quite exacatly to 3.5 GW.

ANSWER; 11.6% of the energy of the 600 TW Biggest Hurricanes;

70 TW could be dissipated with 20 000 Windturbines. The costs of these Turbines would be 120 Billion Dollars, which sums up to be approximately the same order as The costs of Hurricane Katarina. The Peak power production might just be absorbable 120 GW, as the Average Consumption in USA is 500 GW.

But this means that the Waterspraying has a postive impact, otherwice this idea is Nonsense.