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Info Bite 6 - Floating Foundation Technologies

Floating Wind Technologies
Potential Opportunities in OW

Several companies have put forward designs aimed at generating power off the Pacific Coast of the USA, where the waters are deeper and less amenable to fixed foundations.

Despite a groundswell of support and interest, it is still unclear how floating wind will be deployed off California. One frontrunner in field of floating platforms Equinor’s Hywind concept. Equinor has the only commercial wind farm operating on floating platforms and has already achieved major cost reductions and performance improvements in the technology over the last decade.


Hywind floating platform cost reduction. Source: Equinor, June 2019.

“We’re getting great results,” says Daniel Rogstad, project director for business development at Equinor, noting that the platform has worked well with larger turbine sizes and can be maintained using traditional crew transfer vessels.

But Equinor’s spar-buoy platform design is only one of several being mooted for Californian waters. The costs for these first-of-a-kind designs will naturally exceed those of fixed-bottom offshore wind, says Randy Male, head of the Boston office at Green Giraffe. “There will be some premium initially,” he says.

However, research by Cierco Corporation, carried out on behalf of the UK government, indicates that by the time 12 MW turbines are in the water, around 2024, floating foundations could technically be competitive with fixed jackets and piles.


Floating offshore wind cost optimization with next-generation, 12 MW turbines. Source: Cierco, June 2019.

“If we make the assumption that build is in 2024, a shallow floater on 50 meters, 40 kilometers from shore, lands at about $70 [per MWh],” says Mikael Jakobsson, managing director of Cierco.

Although there are many floating foundation concepts in train, most are variants of three major families:

  • Spar: a simple structure, stabilized by ballast, offering excellent stability but only suitable for waters in excess of 100 meters, without the potential for quayside installation.

  • Semi-sub: a low-draft, buoyancy stabilized concept that can be used in shallow water, allowing for simple, quayside installation, but with larger motions requiring a complex control system.

  • Tension-leg platform (TLP): a lighter structure stabilized with mooring lines, offering excellent stability and quayside installation but requiring a complex mooring system.


Floating offshore wind concepts. Source: Joshua Bauer, US National Renewable Energy Laboratory.

Equinor’s Hywind design belongs to the spar family, while another developer, Principle Power, is working on a steel semi-submersible variant called WindFloat that is now technologically proven and is in the process of demonstrating commercial viability. “We have been able to extend the design lifetime from five to 25 years,” declares Samuel Nelis, offshore wind product and business development manager, Tractebel, which is involved in a WindFloat program in Europe.

“The installation procedure has been improved,” he says. “We still need to ensure cost reduction.”

By the mid-2020s, the company hopes to achieve an LCOE of less than €100 ($112) per MWh, he says. “The WindFloat is in a sense its own installation vessel, which reduces costs quite a lot,” says Antoine Peiffer, senior manager, global supply chain and development at Principle Power.

Several other designs could also enter into operation on the West Coast. “TLPs, spars, semi and hybrid systems, they’re all feasible in one way or another,” comments Professor Habib Dagher, principal investigator at the University of Maine’s Aqua Ventus Project.

Furthermore, the experience so far means the more advanced designs are increasingly bankable, says Hans Petter Øvrevik, head of field development at Aker Solutions. “The first element of getting anybody to put money behind something is to have something that you know works,” he says. “The industry has proven through WindFloat and Hywind that the technology works.”

As on the East Coast, however, a challenge for offshore wind in California might be finding suitable port facilities. Manufacturing floating foundations will add to this challenge, says Yvan Leyni, engineering and projects director at Bourbon Subsea Services. Because of the size of the foundations, “it’s not that straightforward to find a fabrication site,” he says. “[The foundations] have to be stored somewhere before being towed to site.”

Ultimately, though, the opportunity in California could be unparalleled elsewhere in the US, believes Jim Lanard, CEO at developer Magellan Wind. “Once we resolve some of the siting issues, I think we’re going to see California really taking off and leading the country with the size and scale of what offshore wind can be,” he says.

The US offshore wind market is probably the most rapidly-developing renewable energy sector in the world. Follow #USOW20 for the latest news and expert opinions.

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By Julian Jackson – writer on technology, arts, blockchain and cryptocurrencies

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