The future floats

July 1, 2017

Elaine Maslin surveys a variety of floating offshore wind projects due onstream in the near future.

Statoil’s Hywind project.  Image from Statoil.

This year, floating offshore wind will make a significant splash in UK waters with not just one, but three floating offshore wind farms – albeit demonstrators – being built, alongside others around the world.

Fixed foundations such as monopile and jackets are a popular choice for shallow water (in areas such as the North Sea). However, floating could be used in areas such as offshore Japan or Hawaii, where steep shelves are unsuitable for fixed installations and government mandates call for increased renewable power generation, as well as other deepwater areas.

Hawaii, for example, has the potential for 28GW of offshore wind resource in <1000m water depth, according to the US National Renewable Energy Laboratory (NREL). Alpha Wind Energy says that Hawaii has decided to become 100% renewable for all electricity consumption by 2045. Alpha Wind Energy proposes to develop two, 400MW floating offshore wind energy projects near Oahu, Hawaii, and has submitted unsolicited applications for the projects. Each would involve 50 floating turbines, 15mi (24km) or further from the coast in >600m water depth. Úna Brosnan, Atkins offshore wind growth manager, told the All Energy conference and exhibition in Glasgow in early May that there are a further 800MW in unsolicited bids for projects offshore Hawaii.

Meanwhile, NREL says that 80% of the offshore wind resource in Europe is in water over 60m deep and has the potential to produce 4000GW of floating wind. NREL says that there’s 2450GW potential offshore the US and 500GW potential offshore Japan. The UK’s Energy Technologies Institute (ETI) says that the UK has many high-energy offshore wind sites within 70-100km of the coast in 50-100m water depth – prime for floating wind, which is most suited to 50m+ depth, it says.

Another factor that could be in floating wind’s favor is the ever-increasing size of turbines. Burbo Bank Extension in the UK came online in May with 32, 8MW turbines, each with 35-tonne a piece, 80m-long blades. There’s talk of 10MW turbines and even 20MW units. Could they be more viable on floating structures?

“This is the technology that has the potential to enable us to reach the high-energy yield sites without being limited by water depth, etc.,” said Johan Slãtte, senior consultant, DNV GL, at All Energy.

Furthermore, “Floating wind means more wind and less turbulence,” Brosnan adds, as well as not being restricted to water depth or ground conditions. They can also be towed to shore, she says.

According to wind energy association WindEurope, floating offshore wind is no longer confined to research and development (R&D). It has now reached a high technology readiness level.

“While floating offshore wind technology was previously confined to R&D, it has developed to such an extent that the focus is now moving into the mainstream power supply. The technology readiness level (TRL) related to semisubmersible and spar buoy substructures has entered a phase (>8) in which the technology is deemed appropriate for launch and operations. The barge and the tension leg platform (TLP) concepts are projected to reach this stage in the coming years,” says WindEurope in its June Floating Offshore Wind Vision statement.

There are currently about 30 different floating offshore wind concepts, which mostly fall into certain concepts: spar, semisubmersible, TLP, multi-turbine and hybrid units, which combine with other technologies, Brosnan says. Atkins is involved in several projects, including Kincardine Offshore Wind (KOW), Hexicon’s Dounreay Tri project, and Statoil’s Hywind, all offshore Scotland, as well as Principle Power’s Windfloat concept.

There are challenges, however. The Hywind, Hexicon, and KOW projects are at TRL5-6, she says. Questions remain if they’ll reach TRL7 to meet a renewable obligation certificate (ROC), a form of funding, by a 2018 deadline and, what will replace that funding. Access to the grid and consenting processes are other challenges, alongside making floating offshore wind competitive with other technologies.

But, while it’s not that long since the first floating wind demonstrators went into the water, “We are well on way to demonstration, the next step is commercialization,” Brosnan says. And, oil and gas technologies, such as turrets and moorings, could play a role in the build out of this technology.

Hexicon’s system, artist’s illustration. Image from Hexicon. 


“The density of pilot projects is a sign of the maturity of the industry,” Ole Stobbe, business development manager northern Europe for design and engineering company Ideol, told All Energy. “The next step is commercial scale arrays.”

Ideol’s floating foundation, an artist’s illustration. Image from Ideol. 

Ideol has developed a floating substructure for floating offshore wind floating, which is due to be used in the single 2MW Floatgen project demonstrator, being built at Saint Nazaire in 33m water depth, 12mi offshore France. The demonstrator is one of four demonstration projects commissioned by the French government. The project involves Ideol’s ring-shaped surface platform, with a moonpool, which acts as a damper to wave motion, with three clusters of mooring lines at 120 degrees from each other.

Ideol, which recently gained investors Siem Offshore Contractors and the Japanese company Hitachi Zosen, is also part of the four-turbine, 24MW EolMed pilot farm project, which will use the damping pool concrete floater, offshore southern France. It is due online in 2020. Another 24MW project, also due online in 2020, is being developed by Engie, EDP Renewables, Caisse des Depots, GE, and Principle Power (which was behind the Windfloat concept and one of the first floating wind demonstrators offshore Portugal in 2011). It will use four 6MW GE Haliade turbines.

Principle Power is also part of the WindPlus consortium’s Windfloat Atlantic project offshore Portugal, a three, 8MW farm 20km offshore in 85-100m water depth. JDR Cables recently announced it had won preferred supplier status for the farm. This could see the first application of JDR’s 66kv cables on a floating wind project.

Meanwhile, EDF EN is working on the Provence Grande Large project, offshore France, with SBM Offshore and IFP Energies Nouvelles producing the foundations, with three 8MW Siemens turbines and support from Technip.

Ideol also has a contract for the design of two of its structures, one steel and one concrete, to be commissioned next year by Marubeni and the University of Tokyo. It is also working in Taiwan, where it is due to commission a floating turbine, next to a bottom fixed turbine, in 2019. And the firm is working with Atlantis Resources on a UK floating offshore wind project, and with Gaelectric on a project offshore Ireland.


Ideol’s Floatgen, taking shape in Saint-Nazaire (France). Photo from Ideol.

KOW is one of three Scottish floating offshore wind pilot projects being built this year. Allan MacAskill, its director, worked in the oil and gas industry for Talisman, where he was involved in building the first Beatrice offshore wind turbines. In 2008, he wrote a European Commission report that said floating offshore wind was something for after 2030. Then, he got involved with WindFloat.

“I saw that I wasn’t right,” he told All Energy. “In the 1970s, in the oil and gas industry, very little was done floating,” he says. “Companies were proud to have big fixed facilities. Then Amerada (now Hess) and others came in with floating facilities and within a decade it was a norm. That same application is coming now to offshore wind.”

The first turbine for KOW, a demonstrator project 15km off Aberdeenshire, Scotland, will be installed and begin operating this year. Construction work is due at Kishorn Port (OE: May 2017), on Scotland’s west coast, a site which has been out of use for more than 20 years. In total, eight 6MW turbines, no less than 1km apart, and with 176m maximum blade height, are due to be installed on a semisubmersible structure, moored with drag embedment anchors in about 45-143m water depth. KOW was originally looking at using one of Principle Power’s Windfloat substructures, but then switched to a Cobra semi-spar concrete substructure, due to being easier to manufacture, assemble and not requiring heavy lift crane capacity.

“The big benefit of concrete is the speed with which you can build. We could build one in four months and could build more,” MacAskill says. The technology consists of a central column connected to three outer columns by rectangular pontoon sections, with the outer columns about 6m below the water surface when operational, allowing support vessels to approach from all directions.

Interarray cables and two 33kv or 66kv export cables to the Redmoss substation south of Aberdeen will also be installed. KOW is a joint venture between Pilot Offshore Renewables and Atkins.

Dounreay Tri

Founded in 2009, Sweden’s Hexicon has been working with Atkins and RES Offshore on an 80m-wide, 180m-long, triangular semisubmersible platform design, supporting two 5MW turbines, offshore Dounreay, northern Scotland. It will be moored using a turret and electrical swivel, enabling it to weather vane. Construction started in April, with assembly due at Nigg, near Inverness, Scotland. The site is near the former Dounreay nuclear power station, which means there’s a 33kv substation connection to the grid. The project is due to be commissioned by September 2018.


Statoil’s Hywind project continues to make progress offshore Scotland. Statoil, which installed a 2.3MW demonstration floating turbine off Norway in 2009, is now building a 30MW, five-turbine pilot park on spar structures, moored with suction anchors. It will spread out over 4sq km in 95-100m water depth, with 10.1m/sec average wind speed and 1.8m average wave height, off Peterhead, northeast Scotland. The turbines will reach 258m-high, including the 80m-long blades.

Halvor Hoen Hersleth, operations manager, Hywind Scotland Pilot Park, Statoil, told All Energy that all 15 suctions anchors had been installed in April, using the Deep Explorer, and that all five substructures, built at Navantia, had now been shipped from Spain on the Albatross by Offshore Heavy Transport under contract to Technip. The turbine towers, built by Navacel, with their nacelles and blades, have been assembled onshore in Stord, Norway, on temporary flanges. In late June, they were lifted and mated on to the spar structures using the Saipem 7000. Tow-out – one at a time – to the Buchan Deep site, 25km off Peterhead, is due in the middle of July using two tugs. The mooring chains were be installed in late June.

Operations out of Peterhead will see technicians traveling on crew transfer vessels to the turbines for commissioning and then future maintenance work. Subsea 7 will install the Nexans 33kV export and infield cables in July-September, with first power is due in late Q3, or early Q4.

Scaling up from the initial 2.3MW single turbine will hopefully achieve cost reduction and demonstrate the project, Hersleth says. The nacelles will be instrumented, lidars and strain gauges installed, with all the data being used to qualify the concept.

It’s not been entirely smooth running, with the number of contractors and interfaces proving a challenge, he says, “some our own fault because we were not clear enough, but that needs to get better. We also see improvements we can make in our marine operations. Having the Saipem 7000 waiting on weather is very expensive.”


Gicon’s semisubmersible. Image from Gicon.  

Away from Scotland, Iberdrola is working on a floating wind foundation, called TLPWind. It is based on a “shipyard friendly” cruciform pontoon structure, with a single main column. Moorings connect to the ends of each cruciform, with a tension mooring spread which can be engaged using two vessels. Iberdrola has also designed a transport and installation system for its concept, based on a semisubmersible barge, with a bow slot to accommodate the cruciform structure, complete with its installed tower and turbine. This could be towed out using a tug or anchor handler, Juan Amate López, Ibedrola, told All Energy. TLPWind is looking at up to 10MW turbines in more than 60m water depth. “Key to the solution is that it is something easy to manufacture,” López says.

Meanwhile, Principle Power and Mitsui Engineering & Shipbuilding agreed to collaborate on promoting floating wind projects in Japan, having already achieved approval in principle for Principle Power’s WindFloat concept by Japanese classification society, Class NK. US-based Glosten Associates, which is behind the Pelastar TLP concept, and Germany’s Gicon, which has developed a similar technology, agreed earlier this year to work together on floating wind for 20-350m water depths.

Cobra, part of the ACS group, which owns offshore construction yard Dragados, is developing the Flocan5 demonstrator in the Canary Islands, with a concrete semi-spar incorporating three outer cylinders and a central column. Five floaters with 5MW turbines are planned. FID is due in 2018.

Saitec, based in Biscay northern Spain, is looking to bring its SATH (swinging around twin hull) concept to market. It has a DemoSATH 2MW single point moored, twin hull low draft concrete platform able with heave plates. It will be able to weather vane and be “plug and play,” Amaia Martinez, Saitec, told All Energy. The firm hopes to start construction on its first prototype in 2018 and be fully operational in 2019.


With fixed structure offshore wind costs falling, floating wind will need to focus on cost reduction to give it a chance of finding a viable market, says director of policy and innovation Jan Matthiesen at the Carbon Trust, a not-for-dividend company that supports carbon reduction initiatives. “We think floating can take a similar path, if there is more competition,” he says. “More players in the supply chain, optimization and doing things smarter, learning through doing and scaling up.”

Improvements in electrical systems, different mooring designs, logistics, and understanding wake models for floating wind, are also on his list, alongside the need for high voltage wet- and dry-mate connectors and a solution for floating – or even seafloor – substations.

Indeed, in early June, oilfield services firm Petrofac was awarded a floating offshore wind research project by the Carbon Trust’s Floating Wind joint industry project. It is to investigate the key electrical system challenges associated with large scale floating wind farms including deepwater substations, dynamic cables, cable connectors, and array cable layout and burial.

Mid-June, verification house Bureau Veritas issued a preliminary design approval for a floating offshore wind turbine designed by France’s DCNS Energies, based on a semisubmersible floater.

The design is part of GE (ex-Alstom) and DCNS’ Sea Reed project, supported by the French Environment and Energy Management Agency. Other areas that need to be explored include anchor and mooring types and layouts, including sharing mooring lines, Matthiesen added.

Offshore Floating Winds Projects List

Name Capacity Country Expected commissioning date

Dounreay Tri

2 x 5MW Scotland 2018



Hywind Scotland

30MW Scotland 2017
WindFloat Atlantic
30MW Portugal 2018-2019
49MW Scotland From 2018
French pre-commercial farms
4 x 25MW France 2020
100MW UK 2021

Data from WindEurope.

Testing a new wave energy converter

CorPower’s resonant wave energy converter, the CorPower S3, has started a dry test program following system commissioning.

The first power was delivered to the Swedish grid in April 2017, with the device operating in simulated waves using a 500kW hardware-in-the-loop (HIL) test rig in CorPower’s integration facility in Stockholm.

CorPower hope that dry testing will accelerate product development and de-risk an upcoming ocean test. The HIL-rig is used to supply the device with mechanical loading representing the full range of sea states, allowing debugging and stabilizing the system in simulated waves, including storm conditions.

Multiple earlier prototypes have been tested at smaller scales in Portugal, France and Sweden since 2013. Once it has been through dry testing, the latest 1:2 device will be deployed at the European Marine Energy Centre’s (EMEC’s) Scapa Flow test site in Orkney, Scotland.

HiDrive is the most advanced project funded by Wave Energy Scotland, scheduled to complete Stage 3 testing within 2017. A total of €6.5 million has been invested in the Stage 3 program by InnoEnergy, the Swedish Energy Agency and Wave Energy Scotland.

Buckets and bases

While most offshore wind farms are built on monopile and jacket foundations, there are projects testing alternatives, including suction buckets and gravity based foundations.

Vattenfall’s European Offshore Wind Deployment Centre (EOWDC) is set to trial number of new technologies, including 11, MHI Vestas v164-8.4MW turbines (the first commercial 8MW turbines were deployed this year), with 80m-long blades, and JDR Cable’s 66kv inter array and export cables.

Meanwhile, Smulders Projects will carry out the work on the 11 suction bucket foundations at its Wallsend-based manufacturing facility, which Smulders acquired from OGN Group, at the end of last year.

The project, off Aberdeen Bay, is believed to be one of the first UK offshore wind projects where suction buckets will be deployed on a large scale. Construction is due to be complete by April 2018.

EDF Energy Renewables 41.5MW Blyth Offshore demonstrator project will also use 66kv cables, but it is going to be built on hybrid gravity-monopile foundations in up to 45m water depth about 5.7km off the coast of Blyth, northeast England. Installation is expected in Q3 2017.

The gravity based foundations comprise two elements, a concrete caisson and a steel shaft. The caissons are being constructed in the Neptune dry dock on the Tyne by BAM. The shafts were fabricated in the Netherlands and due to be shipped to Newcastle where BAM would install them into the caisson. The complete foundations were due to be floated out of the dry dock and towed to Blyth in May/June. From there, they will be immersed to take up their permanent position on the seabed. They will then be ballasted with sand and the wind turbine generators installed.

EDF says that the structures are potentially economical in 35-60m water depth, depending on ground and/or environmental conditions.

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