By Michael Reilly
updated 1:07 p.m. CT, Wed., Nov. 12, 2008
Generating wind power at sea may disturb ocean currents and marine ecosystems, according to a new study.
Offshore wind farms are common in Europe; Denmark, The Netherlands, and the United Kingdom all have several active installations. Wind power in the United States is currently confined to dry land, but three installations are planned off the coast of New Jersey, Rhode Island and Delaware, totaling about 1,500 megawatts of generating capacity.
Extracting energy from wind changes regional air currents, which can in turn affect how the nearby ocean circulates, according to Goran Brostrom of the Norwegian Meteorological Institute in Oslo.
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In a paper published this month in Journal of Marine Systems, Brostrom shows in a model that winds swirling at 11 to 22 miles per hour downwind of large farms are uneven. As they blow over the ocean they can roil the waters, causing upwelling.
The change in currents seems small — a nudge of just 3.3 feet per day — and the wind farms have to be around 1.9 square miles. But Brostrom said the effect is enough to bring nutrient-rich waters up from the depths, which marine life can thrive on.
"I think you will see a large effect over time," he said. "You will get more plankton blooming, and you will see more vibrant life overall at that place."
Plankton blooms are infamous for causing toxic red tides and for sucking oxygen out of the water. But they can also be food sources for larger animals.
"Whether or not this is a good thing is a matter of debate," Brostrom said. Though he stressed that the goal for any man-made object should be to minimize environmental impact, he added: "I'm an optimist; I think this could be beneficial to local fisheries."
Such dreams of wind farms enriching ocean wildlife — or impacting it in any way — may be a bit premature, said Michael Dvorak of Stanford University. For one thing, all current farms are situated in water far shallower than the 98-foot depth assumed in Brostrom's paper. Some deeper farms have been proposed, but maintenance costs skyrocket the further from shore windmills are.
And Brostrom's study is a very general model — ocean currents and marine life could be affected in very different ways depending on the location of the farm.
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"If you want to understand how ocean currents are really going to be affected, you'll want to include the bathymetry at the site," Dvorak said, referring to analysis of underwater depth, as well as do a detailed, specific study of the area's ecosystem.
Still, Dvorak pointed out Brostrom's study raises a point no one in the wind power industry had yet considered.
"People have looked at the climate effects of wind farms on land, but this is the first to bring up the question of ocean currents," he said. "This is something we should be looking at."
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