Wind turbines save your city
Mark Z. Jacobson, Cristina L. Archer and Willett Kempton have written a paper in Nature: Climate Change that provides a magnificent excuse to build more wind farms. Hurricanes are causing coastal damage as they come onshore at greater and greater velocities. Clean electricity is one thing, but any reduction in the damage done by storms would be just as welcome.
The energy extracted by wind turbines has to go somewhere, which is, of course, to be converted into electrical and heat energy. The natural source is the kinetic energy of the sub-surface winds. This kinetic energy has to be reduced during any transfer of energy, so a lot of wind turbines would theoretically reduce wind force by a large amount. The same effect happens whenever a hurricane hits land-its energy begins to reduce, while over the ocean, it builds up its power. Large arrays of turbines produce more than 300GW of energy for electrical grids. This would reduce near-surface wind speeds by between 25 and 41 metres per second. That is equivalent to 56 -92 mph. The storm surge could equally be reduced by 6-79%.
The place for these arrays to have the most benefit would be to the windward side of a city or exposed coastal strip. Costs would be alleviated by the added benefit of prevention of hurricane damage, leaving fossil fuels even more expensive s power station fuel sources. Sea walls can cost between $10 million and $40 million in some exposed sites. This cost could also be reduced where storm damage was less, although it would be a brave man or woman to declare that sea walls would not be needed!
The turbines can currently run up to wind speeds of 112mph. This matches the speed of a smaller hurricane of category 2 or 3, the advantage being that these wind speeds would be dramatically reduced if a very large array of turbines combated the storm. On to actual case studies, a computer model reveals that Hurricane Katrina could have been reduced significantly by a massive array of 78,000 turbines in the Gulf. Amazing though that sounds, the model indicates a reduction of 36-44 m/sec (80-98mph) while the storm surge would have been reduced by a possible 79%. Hurricanes Isaac and Sandy would have been reduced in effect in a similar way, thought the storm surge from Sandy would only reduce by 34%.
For reference, Hurricane Sandy caused $82 billion worth of damage in the 3 states it blew over. Reduce that by 34 % for a fair estimate! Many factors influence the argument for wind energy. Though politically in the US, it is dynamite, with objections even to a few hundred turbines. Despite the objections, global warming, air pollution, energy wastage, storm damage and flood caused by storm-surge all reduce, giving Professor Jacobson good reason to state that, "these factors, each on their own, reduce the cost to society of offshore turbines and should be sufficient to motivate their development."
The three authors hail from Stanford University and the University of Delaware and used Mark's GATOR---GCMOM atmospheric---ocean model that he developed at Stanford. More on wind energy and its fruitful take up in other places can be found in The Future Offshore is Wind.