At Scotland’s easternmost headland, the old fishing port of Peterhead juts out into the North Sea. Located 24 kilometers offshore, there are five towering 174-meter-tall turbines, designed by Hywind Scotland, which generates enough electricity for more than 20,000 homes, and are the first wind energy array that floats on the sea’s surface rather than being dug into the ocean bed.
What is groundbreaking about the Hywind project is that the giant masts and turbines sit in buoyant concrete-and-steel keels that enable them to stand upright on the water.
In contrast to ordinary offshore wind turbines, with long towers sunk into the seabed and bolted into place in shallow seas 18 to 48.5 meter deep, the advantage of floating turbines is that they can access large swaths of outlying ocean waters, up to 500-meter deep, where the world’s strongest and most consistent winds blow.
Another advantage is the floating turbines can be installed over the horizon, out of sight of coastal residents.
“Floating wind power has enormous potential to be a core technology for reaching the climate goals in Europe and around the world,” says Frank Adam, an expert on wind energy technology.
Some renewable energy experts remain skeptical that the high costs of floating offshore wind turbines will come down far enough to rival other clean-energy technologies. Currently the electricity they generate is often almost twice as expensive as near-shore wind turbines and three times that of land-based wind turbines.
But advocates of floating wind arrays note that the costs of onshore and near-shore wind energy have been steadily falling as the efficiency of these technologies has been rising. The same trends, they contend, are likely to lower the costs of floating offshore wind.
Walt Musial, an offshore wind energy expert, USA, says that in his country the coastal waters are often too deep for conventional offshore wind turbines. Nearly 60 percent of suitable offshore wind locations, he notes, exist in places at depths greater than 60 meter. That creates yet another opportunity for floating wind energy technologies.
Po Wen Cheng, head of an international research project on floating wind energy, says that floating turbines could produce more energy than the largest onshore or offshore technologies. Not only are winds in deeper waters more powerful than those closer to shore, he says, but the physics of the flexible, suspended rigs enables them to carry larger turbines. “The bigger the turbine, the more energy they can produce in the right conditions,” he says.
Cheng argues that floating turbines could be even taller than today’s largest offshore rigs, perhaps with 113-meter blades and towers stretching nearly 333 meter into the air. Turbines of such dimensions could generate three times the electricity of today’s most advanced onshore turbines, says Cheng. Like conventional offshore wind arrays, the floating turbines transmit electricity to coastal grid connections through heavy-duty underwater cables.
Offshore wind farms in the North Sea, Baltic Sea, and elsewhere have substantially increased clean-energy production in Europe and driven down the price to a level competitive with fossil fuels.
Investors and renewable energy companies say that the most formidable hurdle to full-scale rollout of floating wind arrays is recognition from governments, utilities, and financiers that the technology is viable and that costs will inevitably fall. Despite this, the technology of using open seas to produce renewable energy is sound.