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Hurricane Damper

March 21, 2014

In my brief career in commercial radio and television broadcasting in the 1960s, I worked with many cutting-edge electronic devices of the era. These included some of the first video tape recorders, costing more than half a million dollars in today's money. This was also the era of vinyl phonograph records played by a stylus in a spiral groove on mechanical turntables by "Top-40" DJs.

Top-40, News, Weather, and Sports""It all began at a small 5,000 watt radio station in Fresno, California…""

Actually, it was a small 1,000 watt radio station in Upstate New York.

(Author's photograph, circa 1968)

Vinyl is a convenient material for making phonograph records, since the addition of plasticizers allows it to be thermally molded. However, the same properties that allow for easy molding also make vinyl records susceptible to scratching, usually by rubbing the stylus across the grooves. Some stylus types are tipped with industrial diamonds to prevent wear.

The stylus is contained in a tonearm assembly, and the desire to optimize performance of this pivoted lever assembly with movement in two axes led to some innovations. A popular tonearm in radio stations was the Gray 108 transcription arm, which used a silicone oil damping fluid to prevent sudden movements of the tonearm and prevented damage to records from accidental dropping.

Damping is the name for any process that dissipates energy from a system. In the tonearm case, this was mechanical energy, but damping is useful in electronic control systems to prevent oscillation. When controlling a motor, you don't want it to oscillate between a low and high speed state; instead, you want an even speed between these extremes. A team of engineers at Stanford University (Stanford, California) and the University of Delaware (Newark, Delaware) has proposed that offshore wind turbines can serve to dampen hurricanes.

As I wrote in some previous articles (However the Wind Blows, February 7, 2012, and Bigger than a Butterfly, "January 11, 2011) wind turbines modify the surface Air flow. A 2004 study of a large Great Plains wind farm showed that wind turbines significantly slow the wind at the turbine level, and they enhance vertical mixing of the atmosphere.[1]

As a consequence, you can't space wind turbines too closely in a wind farm, since the upwind turbines modify the airflow to decrease the wind power available to the downwind turbines. As an example of this effect, the wind turbines of the Horns Rev wind farm on the coast of Denmark are spaced seven diameters apart, but the downstream turbines generate about a quarter less power than the front row turbines.

Horns Rev Wind Farm
Wind turbines at the Horns Rev wind farm. (Photo courtesy of Rune Birk Nielsen of DONG Energy)

Mark Z. Jacobson of Stanford University has teamed with Cristina L. Archer and Willett Kempton of the University of Delaware on computer simulation of the affect of large offshore wind farms on the strength of hurricanes.[2-4] They simulated three hurricanes; namely, Hurricane Katrina, which devastated New Orleans in 2005, Hurricane Sandy, which damaged a wide area around New York City in 2012, and Hurricane Isaac, which struck New Orleans in 2012. The results of these simulations have been published in a recent issue of Nature Climate Change.[2]

Jacobson has been modeling both hurricanes and wind farms for more than two decades, so he and his team were able to combine models to determine what affect offshore wind farms would have on the strength of hurricanes. Their study found that large offshore wind farms (300 gigawatts or more of installed capacity) could diminish a hurricane's peak near-surface wind speed by 56–92 miles per hour (mph), or 25–41 m/sec, and the storm surge by 6-79%.[2-4]

Computer simulation of wind turbine affect on Hurricane KatrinaComputer simulation of wind turbine affect on Hurricane Katrina.

The right side of the screen shows wind speed reductions (less red) with placement of offshore wind farms.

(Still image from a Stanford University YouTube video by Kurt Hickman.)

Turbines were effective when placed immediately upstream of a city, or along the range of a coastline.[2] The model found that an array of 78,000 wind turbines off the coast of New Orleans would have significantly reduced the strength of Hurricane Katrina, decreasing the wind speed by 80-98 mph (36-44 m/sec) and the storm surge by up to 79%.[3-4] Turbines would have reduced Hurricane Sandy's wind speed by 78-87 mph (35-39 m/sec) and the storm surge by as much as 34%. Says Jacobson,
"We found that when wind turbines are present, they slow down the outer rotation winds of a 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."[3-4]
of course, tens of thousands of wind turbines would be expensive, but their generation of clean electricity, plus damage reduction from hurricanes, would more than offset their cost. Hurricane Sandy caused about $80 billion in damage.[3-4] Massive seawalls might protect cities, but at a cost of $10 billion to $40 billion per installation.[3-4]

Would offshore turbines withstand the onslaught of a hurricane? The present generation of wind turbines can withstand winds of 112 mph, the wind speed of a category 2 to 3 hurricane. Also, the turbines would reduce the wind speed, so survivability is even more likely.[2]

References:

  1. S. Baidya Roy, S. W. Pacala and R. L. Walko, "Can large wind farms affect local meteorology?" J. Geophys. Res., vol. 109, 2004, D19101, doi:10.1029/2004JD004763. A PDF file is available here.
  2. Mark Z. Jacobson, Cristina L. Archer, and Willett Kempton, "Taming hurricanes with arrays of offshore wind turbines," Nature Climate Change, vol. 4, no. 3 (March, 2014), pp. 195-200 (PDF file, available here). PDF file of supplementary Information, available (here).
  3. Bjorn Carey, "Offshore wind farms could tame hurricanes before they reach land, Stanford-led study says," Stanford University Press Release, February 26, 2014.
  4. Bjorn Carey, "Offshore wind farms could tame hurricanes before they reach land, Stanford-led study says," Stanford University News, February 26, 2014.
  5. Stanford simulations show offshore wind farms could tame hurricanes, Stanford University YouTube video, February 26, 2014.

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