A recent study supported by the U.S. Department of Energy found it is possible to significantly reduce the time and capital required to get offshore wind turbines in the water. Researchers at the University of Delaware say the cost of building an offshore wind project can be slashed by 37 percent by completing much of the construction and assembly on land.
“Nobody had said, ‘Let’s back up a second here and ask: How do all these things fit together?’” said Willett Kempton, who led the study, in an interview. Kempton is a professor at the College of Earth, Ocean, and Environment and research director for the Center for Carbon-Free Power Integration at the University of Delaware.
What separates the process outlined in the study from existing methods, said Kempton, is integrated design. This entails not viewing any one stage of an offshore wind project -- be it marshaling components in the port, carrying the components out to sea, or on-the-water construction -- in isolation.
“All those things together should be evaluated as a whole, and then let’s choose the cheapest and fastest-to-build method on that basis," he said. "We spend more money in port, but we spend far less money at sea.”
Integrated design at work
The study was designed around building 10-megawatt turbines, assuming the use of caissons (suction buckets) instead of cylindrical steel piles for the foundations. In this scenario, everything from the caissons to the nacelle would be assembled at port and partly commissioned. The assembled 2,500-metric ton structure would be moved to a pier with a self-propelled modular transporter. Then the structure would be lifted atop a shear-leg crane vessel, carried to the project site, and lowered to the seabed.
While they aren't commonplace today, it won’t be long before the base-case 10-megawatt turbines become commercially available. Greentech Media recently reported that Danish wind turbine maker MHI Vestas, for instance, will test the gearbox and main bearings of its 9.5-megawatt offshore turbine at Clemson University in South Carolina. The company’s 8-megawatt offshore turbine was deployed commercially for the first time at the Burbo Bank Extension project in the U.K., which opened in May of this year.
Kempton said the process laid out in the study is suitable for much of the East Coast of the United States, the North Sea, and most other offshore project sites located in water less than 60 or 80 meters deep. The method specifically requires a port with open access to the sea and no overhead obstructions, such as bridges.
The United States’ offshore wind industry is just starting to build a supply chain and lacks the infrastructure found in Europe, but Kempton said those realities don’t necessarily put the sector at a disadvantage under the construction process envisaged in the study.
“For vessels, it’s the opposite of a disadvantage," he said. "If you build the whole thing onshore, and then you take it out to sea in one shot and put it down on the bottom, you have a simpler and less expensive installation vessel.” For instance, the process wouldn't require the use of a jack-up staging vessel.
Shifting much of the assembly to land also reduces expensive time at sea from three days to 10 hours per installed turbine. Faster installation would enable 1 gigawatt to be deployed each year from a single port.
Additionally, the study found it would be possible to reduce costs beyond the 37 percent estimate by scaling up to 20-megawatt turbines, performing additional commissioning in port, co-locating component fabrication and assembly, and further industrializing the assembly.
Analyst and developer response
“Promisingly, a big part of this proposal’s benefits come from its use of suction buckets, a technology that’s already proven and project-ready,” Anthony Logan, an analyst with MAKE Consulting, said in an email. MAKE Consulting is owned by Wood Mackenzie, Greentech Media’s parent company.
“The proposal’s reduction in on-site labor time should pay dividends in mitigating the Jones Act,” he added. “Labor’s share of operating costs on Jones Act ships is significantly higher than on foreign-flagged ships.” The Jones Act requires that goods shipped between U.S. ports be carried on U.S.-built ships. GTM reported last month on how Jones Act restrictions could stifle the U.S. offshore wind market.
“We appreciate the University of Delaware’s commitment to offshore wind and are excited to see people studying new approaches to developing utility-scale offshore wind projects,” said Lauren Burm, head of public affairs for Ørsted North America, in an email. “These innovations will help foster new opportunities to advance the technology in the U.S.”
Ørsted, formerly Dong Energy, has built more offshore wind farms than any other developer.
Burm noted that Ørsted’s extensive experience building offshore wind demonstrates the ability for experiential learning to lower costs. “Over the past two decades of developing offshore wind resources, Ørsted has established a standardized, integrated and streamlined model to drive down costs and maximize efficiencies,” she said. “Our learnings have helped produce a 63 percent decline in costs over the last seven years in Europe.”
In search of proof-of-concept pilot
Kempton said the initial feedback he and his team have received from developers basically amounts to: "The industry has to move this way. This is the future." Ideally, he said, the method could be piloted in a two-, six- or eight-turbine project and then scaled to a commercial 50- or 100-turbine offshore wind farm.
"[Developers] can’t start a large project with something that hasn’t actually been done before. These are $2 billion projects. For anything that size, you’re going to have a cautious approach,” said Kempton.
“On the one hand, the U.S. would be an excellent test ground for these technologies since we’re a bit of a blank slate without much in the way of existing, competing EPC [engineering, procurement, and construction] resources," said Logan. "On the other hand, bankability will be a challenge as many of these technologies are so untested.”
Asked about developer interest in a demonstration project, Kempton wasn’t ready to announce details.
“We’ve had some initial conversations,” he said, “and there’s definitely some interest.”