Offshore wind farms could help to weaken hurricanes before they make landfall, according to a new study.
Using a sophisticated computer simulation of hurricanes Katrina, Isaac and Sandy, scientists have shown that arrays of tens of thousands of turbines offshore wind turbines could reduce hurricanes' wind speeds, wave heights and flood-causing storm surge.
Hurricanes are unusual, isolated events that behave very differently to normal long-term weather patterns, which prompted University of Delaware's Professor Cristina Archer and Stanford University's Professor Mark Jacobson to hypothesize that they might be more affected by wind turbines than normal winds.
"We found that when wind turbines are present, they slow down the outer rotation winds of a hurricane," Prof Jacobson said. "This feeds back to decrease wave height, which reduces movement of air toward the centre of the hurricane, increasing the central pressure, which in turn slows the winds of the entire hurricane and dissipates it faster."
The highest reductions in wind speed found by the study, published online in Nature Climate Change, were by up to 87mph for Hurricane Sandy and 92mph for Hurricane Katrina.
According to the computer model, the reduced winds would in turn lower the height of ocean waves, reducing the winds that push water toward the coast as storms surge. The wind farm decreased storm surge – a key cause of hurricane flooding – by up to 34 per cent for Hurricane Sandy and 79 per cent for Hurricane Katrina.
"This is a totally different way to think about the interaction of the atmosphere and wind turbines," said Archer. "We could actually take advantage of these interactions to protect coastal communities."
Turbines are designed to keep spinning up to a certain wind speed, above which the blades lock and feather into a protective position, but the study showed that wind farms would slow wind speeds so that they would not reach that threshold meaning the hurricanes would not damage the turbines.
Jacobson and study co-author Professor Willett Kempton, also of the University of Delaware, also carried out a cost-benefit analysis of using offshore wind farms as storm protection. This found the net cost was less than the net cost of generating electricity with fossil fuels and building sea walls when health, climate change and hurricane damage were taken into account.
"This is a paradigm shift," Prof Kempton said. "We always think about hurricanes and wind turbines as incompatible. But we find that in large arrays, wind turbines have some ability to protect both themselves and coastal communities from the strongest winds."
However, though sensitivity tests suggested benefits even for smaller numbers of turbines, the study looked at wind farms with tens of thousands of turbines – much larger than commercial wind farms today – and assumed a mature offshore wind industry.