Offshore Wind Farms Guard Landscape Against Hurricanes

David Dixon. Hurricanes are seldom a problem off Walney, where this windfarm was built, but similar projects could protect the US coast from storms
The construction of wind farms in coastal waters could have a benefit besides clean energy. Turbines take energy out of the wind, and modeling shows this could be a significant enough effect to reduce the damage from major storms.
Professor Mark Jacobson of Stanford University has spent 24 years modeling atmospheric behavior, including air pollution and climate. He has used his models to study the way hurricanes form, searching for the answer to the troubling question of whether Global Warming will mean more or fewer hurricanes. He has also studied how much energy wind farms take out of windstreams, so combining the two forms of research was a logical move.
In Nature Climate Change Jacobson revealed the impact could be huge if enough turbines get built. 
"We found that when wind turbines are present, they slow down the outer rotation winds of a hurricane," Jacobson said. "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." 
Jacobson's model used enormous numbers of turbines. For example he simulated 78,000 off the coast of New Orleans. With typical offshore turbine size now above 3MW this could translate to as much as 300GW of capacity. The US has 61GW of installed wind capacity, none of it offshore, and just over 1000GW of all forms of electricity generation.
For so many turbines the effect is large. Hurricane Katrina, Jacobson calculates would have been 80-98 mph (128-157kph) slower under such circumstances, and the storm surge would have decreased by as much as 79%, almost certainly not enough to breach the levies or do any major damage at all.
The reductions Jacobson found for Hurricane Sandy were smaller, but still enough to slash the cost in lives and property damage. The bill for Sandy has been estimated at $82 billion. Not enough to pay for all those turbines on its own, but a pretty good downpayment since we'd also be getting electricity on an ongoing basis. Moreover, while it is debated whether there will be more hurricanes in a warmer future, there is general agreement that those we have will be bigger. Events like Sandy could become disturbingly frequent, giving windfarms a chance to pay for themselves several times.
Proposals to protect against hurricanes usually involve the construction of seawalls. Jacobson notes that walls protect against storm surges, but do nothing about wind speeds, and thus make a less economic investment.
Excessive winds can damage turbines, but Jacobson points out there is safety in numbers – if windfarms are big enough the storms will never become sufficiently powerful to destroy them.

Video by Kurt Hickman


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