Though today still a fledgling sector by almost any measure, floating wind power is fast approaching industrial lift-off, with arrays in development in all major maritime regions and over 20GW of commercial-scale projects in early planning.

Many analysts in fact see floating wind as a booster rocket for a wider offshore wind multi-100GW build-out from 2030, as its levellised cost of energy (LCOE) falls to the sub-€50/MWh range now being seen in conventional bottom-fixed fleets.

This year will be a crucible for the sector and the following five projects will be instrumental to its future, during what Sebastian Bringsvaerd, head of floating wind at Norwegian energy giant Equinor – which brought the world’s first floating wind array, Hywind Scotland, online in 2017 – calls “a critical period on the pathway to a floating wind industry where scaled, low-cost, high-performing assets are the standard”.

WindFloat

Being built off Portgual in the Atlantic Ocean, the 25MW WindFloat Atlantic (WFA) project is continental Europe’s flagship floating wind array – and only the second on the planet (if you exclude the now partly-decommissioned Fukushima Forward demonstrator installed off Japan in 2014). Developed by the EDP-led WindPlus consortium, WFA is based around a trio of semisubmersible platforms designed by US pioneer Principle Power, which are mated to 8.3MW MHI Vestas V164 turbines.

First power was reached on the last day of 2019, and once all three units are connected to the grid, the array will contribute to producing power to supply 60,000 homes.

WFA represents a milestone for the floating wind industry in Europe as the first project to reach switch-on since Hywind Scotland, but it also has the wider significance of having been built without heavy-lift construction vessels, a key cost-reduction area for the sector as it tries to shave down its LCOE to be on par with bottom-fixed offshore wind.

Principle Power CEO João Metelo believes the project “marks the beginning of a new era, where floating wind enables the true globalisation of offshore wind and firmly establishes this industry as the renewable energy source with the highest growth for the coming decades”.

The floating platform technology being used on WFA was prototype-tested as a 2MW unit from 2011-2016, also off Portugal, and has gone on to become a leading concept, with WindFloat in the frame for projects including the 50MW Kincardine off the UK, 30MW Golfe de Lion off France, and the up-to-150MW Redwood Coast Offshore Wind Project off the US West Coast, as well as others in a 10GW pipeline.

TetraSpar

Brainchild of wind power grand homme Henrik Stiesdal – who was laurelled as the 2019 Recharge Floating Wind Power Player of the Year – the TetraSpar is designed as an antidote to the offshore oil engineering-inspired spar, semisub and tension-leg platform concepts that have informed the first wave of floating wind projects.

The innovative design – a modular tetrahedral structure made up of standardised components and steel-work that can be manufactured in “local factories” and transported to quayside for assembly to cut construction time and reduce per-unit delivery to “weeks rather than months” — features a unique triangular float-keel that is tucked up during construction in harbour and tow-out to site, and then lowered using air-filled ballast tanks to provide deep-draft stability for the unit as sea.

“We have built up an extremely good knowledge-bank in the wind industry over the last decades and in bringing costs down,” says Stiesdal. “We need to bring this to bear on floating wind so we don’t spend years teaching shipyards and fabrication yards, which come from the high-cost oil and gas sector, to ‘do’ low-cost floating wind.”

Backed by substantial investment from oil giant Shell and utility Innogy, the first TetraSpar is currently in piece-work construction in Denmark, with plans to install the prototype topped with a 3.6MW Siemenes Gamesa turbine this spring as part of a €18m ($20.3m) demonstrator project at the Marine Energy Test Centre off western Norway, where the first-ever industrial-scaled floating wind turbine, the Hywind Demo (now an R&D unit) has been turning since 2009.

After a programme of trials in the North Sea, the TetraSpar is being looked at for a number of international, industrial-scale projects, as well as being included in developer Magellan Wind’s planned bids for leases off California, construction at manufacturer Welcon’s new factory on the US East Coast, and even for developments in North America’s Great Lakes.

SATH

One of several Spanish designs now heading for – or in – the water, the SATH (Swing Around Twin Hull) being developed by engineering outfit Saitec is to be installed as a “medium-scale” prototype in the Cantabrian Sea in the first quarter of this year.

The 1:6 demonstrator, based on a 10MW design built around conjoined cylindrical pre-stressed concrete hulls anchored to the seabed via a single-point mooring system that allows the unit to ‘weathervane’ to face the wind, will undergo a 12-month testing programme version as part of the so-called BlueSATH project.

The concept, which received €2m from the European Commission last year, will be tested for its dynamics in the open sea, as well as for the robustness of its assemblies and the choice of concrete mixtures for the hull, but also to accelerate the commercialisation process toward an ultra-large model.

A final investment decision on a full-scale 2MW unit, known as DemoSATH, is about to be taken to start construction this summer.

Along with its work in European waters, Saitec in 2018 tied up via a special purpose company with Spanish-Japanese renewable energy developer Univergy International to develop floating wind projects off Japan, last year securing a key patent for its innovative platform concept.

W2Power

The world’s first twin-rotored floating wind power platform, W2Power’s eponymous design, was brought online off the Spanish island of Gran Canaria last year, by developer EnerOcean.

The 1:6 scale unit – a triangular steel semisubmersible with angled turbines at two corners that ‘weathervanes’ into the wind – was put through its paces in 65 metres of water in a fast-track testing programme, as the launch-pad for the developer’s plans for a maiden full-size array in the coming years.

The 40-tonne prototype, which will fly two “generic” 100kW machines, has a shallow-draft design that can be adjusted to get in and out of harbour. At full-scale, the W2Power platform is conceived of for a “sweet spot” of water-depths ranging from 35-300 metres.

The W2Power concept, which has gone through several incarnations since being launched in 2009 as a hybrid offshore wind-wave power design, is engineered to ultimately support a pair of “off the shelf” 6MW turbines, giving each unit a 12MW nameplate capacity.

“We want to show that our concept, with its two turbines, can be built on a light, robust platform ... [and that] there is high value in generating high power from this design, which includes some real innovations in terms of the weathervaning and the leaning towers that allows [the rotors] to reach-out beyond the base of the platform,” says EnerOcean president Pedro Mayorga.

SeaTwirl

Sweden-based SeaTwirl stands apart from other concepts now floating out by being a vertical-axis design. It is engineered to rotate as one unit, from blade-tip down the length of its axle, turning a direct-drive permanent-magnet generator, with seawater drawn into the structure through the shaft by centrifugal force, and then released during low-wind periods to maintain the turning momentum — like a figure-skater pirouetting — so that the turbine works as a flywheel.

In 2018, SeaTwirl inked a deal to supply electricity to Norwegian regional utility Haugaland Kraft for power from its planned first ‘S2’ unit, a 1MW prototype, and last year, it picked up fresh tailwinds with a long-term collaboration deal with engineering giant Siemens and the appointment of former MHI Vestas CEO Jens Tommerup to the company board.

Having first launched the concept in 2011, SeaTwirl appears to at last be approaching its breakthrough, in April 2019 adding SKr70m ($7.5m) to its war-chest from Belgium’s Colruyt Group and Norway’s Norsea,to finance development and installation of the company’s flagship off Norway this year.