|May 27, 2020|
Will floating turbines usher in a new wave of offshore wind?
|At Scotland's easternmost headland, the old fishing port of Peterhead juts out into the North Sea. "On a clear day," says Alastair Reid, an economic development official with the Aberdeenshire Council, "from the harbor you can just make out the turbines of the Hywind park."|
In windswept northern Scotland, where abundant wind arrays both on land and off the coast vie for limited space, the distant location of the five towering 574-foot-tall turbines, 15 miles offshore, is just one novelty of this renewable energy project. Indeed, Hywind Scotland, which generates enough electricity for more than 20,000 homes, is the first wind energy array that floats on the sea's surface rather than being dug into the ocean bed. Proponents say the technology heralds a new generation of green energy.
What's groundbreaking about the Hywind project, located in more than 300 feet of water, is that the giant masts and turbines sit in buoyant concrete-and-steel keels that enable them to stand upright on the water, much like a fishing bobber. The turbines' nearly 10,000-ton cylindrical bases are held in place with three taut mooring cables attached to anchors, which lie on the seafloor.
In contrast to ordinary offshore wind turbines, with long towers sunk into the seabed and bolted into place in shallow seas 60 to 160 feet deep, the advantage of floating turbines is that they can access large swaths of outlying ocean waters, up to half a mile deep, where the world's strongest and most consistent winds blow. In Europe, where the density of onshore and near-shore wind turbines in places like Germany, the United Kingdom, and Norway has spurred increasing opposition to new arrays, 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 at the University of Rostock in Germany.
The ocean space beyond the reach of conventional offshore turbines makes up 80 percent of the world's maritime waters, opening the way for floating arrays, Adam says. "In the past few years this technology has made great strides, and Hywind shows that it can work as a whole park," says Adam. "Now the farms have to grow bigger to show governments and investors that they're feasible on a really large scale."
Some renewable energy experts remain skeptical that the high costs of floating offshore wind turbines --- 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 --- will come down far enough to rival other clean-energy technologies.
"It will always be cheaper to build turbines on land, and that is where the emissions-reduction targets are going to have to be reached," says R. Andreas Kraemer, founder and director emeritus of the Ecologic Institute, a Berlin-based think tank. "Even though the floating parks may be cheaper in some cases than fixed offshore wind power plants, and deployable over a larger sea area, it is still maritime engineering --- and that makes it expensive to build, deploy, and maintain. Lifespans of the stations are short because of the corrosive nature of the marine environment."
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. The Hywind Scotland array --- 75 percent owned by the Norwegian firm Equinor, formerly Statoil --- has been in operation for nearly three years and remained afloat and generating power during Hurricane Ophelia in 2017 and throughout other harsh winter storms with 100 mile-an-hour winds and 27-foot waves.
Other floating wind projects, some with turbines larger than Hywind, are now being built in Europe and Japan. In Portugal, the WindFloat Atlantic project, now under construction, is expected to produce enough power for 60,000 homes when it is completed later this year. France has floating wind power written into its clean energy plans and says it aims to be a world leader in deploying the technology. It has dedicated sites and price supports for wind farms off of Brittany and the Mediterranean coast. Scotland, which aspires to cover all of its electricity needs with renewables this year, has new floating parks in the works, including one just south of Hywind Scotland.
Walt Musial, an offshore wind energy expert at the National Renewable Energy Laboratory, a research institute funded by the U.S. government, says that in the United States the coastal waters of both coasts 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 200 feet. That creates yet another opportunity for floating wind energy technologies.
Po Wen Cheng, head of an international research project on floating wind energy at the University of Stuttgart, 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 400-foot blades and towers stretching nearly 1,000 feet into the air --- as tall as the Eiffel Tower. Turbines of such dimensions could generate three times the electricity of today's most advanced onshore turbines, says Cheng.
Experts say that while some of the floating turbines' finer mechanics are still being tweaked, the technology is sound. The oil and gas industry has used similar marine know-how for decades. (Hywind Scotland's chief owner, Equinor, is Norway's largest oil and gas company.) And the masts and rotors are identical to those of conventional offshore wind turbines. "Floating turbines can adopt a lot of knowledge and experience of the wind power development of the past 10 years, which gives them a huge jump," says Adam. Like conventional offshore wind arrays, the floating turbines transmit electricity to coastal grid connections through heavy-duty underwater cables.
In Europe's ambitious plans to be carbon-neutral by 2050, wind energy of all types figures prominently. Although onshore wind parks are the most cost-effective solution, they have been met with stiff opposition from activists, who object to their marring the landscape, the proximity to their homes, and the impact on nature, particularly birds. In some countries, such as Germany and Norway, citizen opposition has nearly ground onshore wind to a halt.
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. But Europe's current offshore production is roughly 5 to 10 percent of the wind power supply that the International Energy Agency (IEA) and the European Union says Europe should reach by 2050 to meet its goals under the Paris Agreement. The problem is that a massive increase in near-shore wind arrays simply isn't feasible, in part because of growing opposition from fishing fleets, conservation groups, and coastal residents.
This is where floating parks enter the equation, says Jonathan Cole, the managing director of offshore wind energy at Iberdrola, one of the world's leading producers of wind power. "Green energy is going to be needed in all sectors of the economy," says Cole. "Fixed-bottom offshore wind will be expanded far beyond what it is today, but it will run out of space, too, like onshore has in some places."
Ib Krag Petersen, a wildlife ecologist at Aarhus University in Denmark, says birds such as eagles, ducks, griffins, storks, and gannets can collide with the mammoth blades of offshore rigs. But deep-sea wind arrays, he says, where the density of the turbines and the communities of birds are more thinly distributed, have less of an impact on seabirds than near-shore wind arrays.
The Hywind project enjoys broad support in Aberdeenshire, Reid, the local economic development administrator, says. Among other things, Equinor has worked with the prominent fishing sector that docks at Peterhead so as not to interfere with its operations.
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. "We need commitments from governments, the way France, Scotland, and Japan have done, to help get bigger floating parks off the ground," says Bruno Geschier, chief sales and marketing officer of Ideol, a multinational offshore wind developer.
Adam of Rostock University says, "It's easy to produce one or half-dozen floating turbines, but 10 or 20 or 100, that's another story." This requires supply chains, shipyards, and ports that can handle such enormous structures, and factories for serial fabrication, he says.
Despite these challenges, the promise of harnessing so much of the open seas for renewable energy generation remains an enticing proposition. As the IEA has noted, in theory, offshore wind power alone could eventually meet the entire electricity needs of Europe, the U.S., and Japan many times over.