Offshore wind turbines are big and getting bigger. The 62 turbines currently under construction off the coast of Massachusetts (Vineyard Wind) will produce 13 megawatts (MW) of power, each. Their blades will be 837 feet above the sea, perched atop towers 476 feet tall. By contrast, the five 6 MW turbines that comprise the Block Island wind farm have a maximum blade tip height of 593 feet. This move toward bigger turbines stationed miles out to sea is partially the result of the current economic realities of offshore wind turbine installation.
Patrick Gilman is a program manager at the U.S. Department of Energy’s Wind Energy Technologies Office in Golden, Colorado. “There is a significant opportunity for offshore wind development in the U.S. Floating offshore wind is crucial to that picture,” Gilman said. On the West Coast and in the Gulf of Maine, most of the offshore area is too deep (greater than 60 meters depth) for conventional fixed wind turbine construction; installation of floating wind turbines will be crucial to tap into that opportunity.
The market for energy produced by commercial offshore wind farms is tied to the renewable energy targets set by states, just as it was for land-based wind turbine development. In Maine, Governor Mills recently signed an offshore wind bill that calls for the state to procure 3 GW of offshore wind energy by 2040.
However, the costs for construction of any type of offshore wind farm have skyrocketed in the past few years. The federal government is addressing some of the increased costs with tax policies and provisions contained within the 2022 Inflation Reduction Act, but it can’t entirely erase them.
International companies that bid on offshore wind energy leases in the past decade calculated possible increases in inflation that have proved wrong. The U.S. inflation rate hit a 40 year record of 7% in 2021 and 6.5% in 2022. As a result, interest rates have climbed as governments around the world try to stem steep inflation growth. In addition, the war in Ukraine affected the worldwide cost of steel, a key element in turbine and blade construction. European countries acted swiftly to reduce their dependence on Russian oil, leading to a reemphasis on renewable energy resources.
The University of Maine Advanced Structures and Composites Center has been working on floating wind turbine designs for nearly two decades. Its 1/8-scale floating wind turbine prototype was successfully tested off Castine in 2013. The floating wind turbine sector in the U.S., however, is still at an early stage of development, according to Gilman.
“It will take time for the macroeconomic situation to settle down before floating wind development matures,” Gilman said. But when the economic dust does settle, offshore energy companies are likely to focus on larger turbines.
Floating wind turbines are still a new technology. The costs associated with assembling and installing them, digging undersea trenches for electric cables, and maintaining the structures remains a financially risky proposition for any developer. It makes economic sense to construct fewer and larger turbines in order to keep costs under control.
The Block Island wind turbines commissioned in 2016 are 6 MW. Today, offshore wind turbine manufacturers are starting to develop wind turbines in the 16 to 18 MW range. Increasing the size of offshore wind turbines, however, introduces new supply chain needs, including bigger ships to move the parts and expansion of ports.
Whether or not it would be wise to pause on the rush to larger turbines is an open question.
At the the American Floating Offshore Wind Technical Summit, held in Portland in early October, Walt Musial, chief engineer for National Renewable Energy Laboratory’s (NREL) offshore wind research program, spoke about the issues such larger turbines pose.
“In the United States, several regions, including the northeast, are expected to rely significantly on floating wind technology for future offshore wind development initiatives. However, ongoing economic challenges within the fixed-bottom industry might decelerate progress in the floating wind sector in the short term,” Musial said at the conference.
He favored slowing down the race to larger turbines and focusing on learning how to make the 15 MW turbine prototypes more economical.
“The new 15 MW class turbines promise to lower project costs for both fixed and floating technologies when the supply chains mature,” Musial said in a later interview. “Further turbine upscaling before the industry builds the supply chain for these new prototypes and gains solid experience in operating fleets of them could slow progress and introduce unnecessary risk. I believe there is much more to be gained in reducing the cost of offshore wind by becoming proficient in manufacturing and deployment of these new jumbo 15 MW class turbines than in making even bigger turbines.”
In five years, there may be an entirely new set of questions related to floating offshore wind turbines. “In Europe commercial floating wind projects will be online,” Gilman said. “That will be important because it will give us a better understanding of how you deploy the turbines. There will be advancements in technology, some of which we at the Department of Energy are working on now. States will have more certainty to move on energy procurement after seeing what the cost outcomes are.”
Gilman emphasized the role that the states, rather than the federal government, have in fostering a demand for offshore wind energy. “The states make the markets. Just like with land-based wind and solar when they were first being developed 20 years ago, the prices will be higher at first. But once the first generation of projects are in the water you could see really significant growth in production and reduction of costs.”
Emerging U.S. Offshore Wind Industry
- BOEM held three auctions in 2022 and sold 13 offshore wind lease areas for $5.44 billion
- Energy procurement mandates in seven eastern states equal 42,730 MW
- 42 MW currently installed in the U.S.
- 2,032 MW approved and under construction
- 19 Projects (20 MW+) have submitted Construction and Operating Plans