The University of Delaware has determined that assembling offshore wind turbines in a port is the most cost- and time-effective method in the construction of offshore wind farms, since it would cost up to USD 1.6 billion less per project than conventional approaches and would take half the construction time.
The UD-led research team announced this as a result of a five-year research project, done in cooperation with industry partners and funded by the U.S. Department of Energy.
The project’s principal investigator, Willett Kempton , professor at the College of Earth, Ocean, and Environment (CEOE), said: “In planning for offshore wind power, the big question is how we generate electricity cost-competitively, and at a scale that is both a relevant replacement for aging power plants and also applicable to climate change. We’re the first people who have shown the engineering details, step-by-step, how to achieve that.”
The reference design used 10MW turbines with support structures. The key insight that allowed the team to make such optimizations in cost and deployment speed was that the entire structure, from seafloor mounting to the top of the turbine, can be assembled in one piece in port, moved as a unit, and in one step placed into the sea floor.
“Instead of today’s method, carrying out parts separately and individually assembling each in the ocean, we have an assembly line on shore,” Kempton said. “We spend more money in the port, but we spend far less money at sea.”
In addition to cost savings, shifting more of the assembly to land enables construction to proceed regardless of the weather and reduces time at sea from three days to ten hours for each turbine installed. Integral to the method is to anchor the turbines by suctioning large buckets to the seafloor rather than pounding piles. This also means that the foundation does not penetrate as deeply into the seafloor, which reduces costs for everything from the attachment process to the surveying. Without pile driving noise, installation has no acoustic impact on marine mammals.
However, as every study, this one also showed certain drawbacks. Research on turbine bearing wear and failure led the team to conclude that transporting turbines with installed blades would reduce lifetime. Transport with attached blades is also unstable. Therefore, the researchers developed a mounting for transport and a method to attaching the blades in place at sea.
To remind, the turbine assembly on the shore (at a port) has been often highlighted as one of the main advantages of floating offshore wind turbines.