By Mark Goalen, director of offshore engineering, Houlder

Scaling renewable energy capacity is critical to the global energy transition and the decarbonization of difficult-to-abate industries. While it is widely recognized that offshore wind can play a key role in increasing this renewable energy capacity, many people do not appreciate that for this ambition to become a reality, floating wind will have to play a significant role.

The ability of floating wind technology to open new offshore sites for high-capacity wind farms is key. For the United States, the incentive to “go deep” exists because almost two-thirds of its offshore wind resources are found in waters that would require floating platforms.

Meanwhile, the UK has increasingly ambitious offshore wind targets that floating wind farms can help the country achieve. The UK government recently announced its goal is to build 50 GW of operating offshore wind capacity by 2030, of which 5 GW will be floating wind.

A recent report by the Global Wind Energy Council (GWEC), aptly called floating offshore wind a global opportunity, highlighting that the U.S. West Coast, Ireland, Italy, Morocco and the Philippines would likely closely follow the small group of pioneers already installing the first commercial-scale floating wind farms.

However, while the offshore wind market enjoyed its best year ever in 2021, with 21.1 GW of capacity commissioned, only 57 MW of that was floating wind. So, what barriers are preventing the commercialization of floating wind technology?

As with most nascent technologies, there are still commercial barriers to overcome for floating wind technology to mature as needed. One such barrier is floating foundation structure selection.

The four main structure types (spar buoy, tension leg platform, semi-submersible platform, and square barge) are well known at this point, but decisions on which platform or variation to use are rarely underpinned by data or analysis. Demonstrators have often been driven by the floating structure designers themselves, mostly to prove their technology rather than to provide developers with an objective demonstration of each technology.

Therefore, there is still a fundamental need to identify the best technical solutions for each planned floating site to minimize costs, risk and inefficiency for developers. It’s highly unlikely that there will be a single definitive foundation type. Rather, developers will need to go beyond purely reviewing the site to identify the most suitable option for each location and specific set of conditions.

Advanced floating foundation analysis involves comparing a combination of technical and operational factors and, arguably, the latter will have a bigger impact throughout the asset’s lifecycle.

Location, infrastructure, water depth, available space for fabrication and storage are all key for ports that will support a new development. Taking the UK as an example, current options are limited. Individual ports do have plans to invest, but none will be sufficient to cover all options, so there is a risk that significant parts of the manufacture could go to Europe or Asia.

An offshore wind installation near Scotland

This lack of port infrastructure seems to be driving the choice of concrete over steel foundation. It would appear easier to manufacture concrete structures because it requires a less skilled workforce. You only need the molds and raw materials, and not the specialized welding equipment or qualified welders. Steel can be prefabricated elsewhere and assembled, but that builds in additional fabrication risk and requires additional transport of large components, increasing costs and carbon footprint.

Operations and maintenance (O&M) is an even bigger challenge facing the industry. Floating foundations are currently towed back to port for maintenance and repairs. However, this cannot be viable or economical as wind farms are located further offshore and the distance to O&M ports increases. The ability to conduct O&M on-location must be developed, because the risk and costs associated with connection and disconnection and transportation of the wind turbine generator (WTG) will prove too high over time.

A combination of modifying the WTG, as well as developing the tools and vessels required to support this O&M phase is crucial to the success of floating wind. Having the right expertise and advice available in the initial phase of the project ensures that developers gain a holistic understanding of the processes, equipment, vessels and operations involved from the outset.

The latest targets in Scotland are to deliver up to 11 GW of (fixed and floating) offshore wind capacity by 2030+, aligning with the government’s ambition to challenge Norway and China as a leader in floating wind.

The recent ScotWind leasing round awarded 24.8 GW of offshore wind, 15 GW of which is floating. Meanwhile the upcoming Innovation and Targeted Oil & Gas (INTOG) leasing round could deliver a further 5.7 GW, and the Celtic Sea Lease would deliver 4 GW.

The total capacity of floating offshore wind in the UK including ScotWind, INTOG and Celtic Sea currently amounts to 25 GW, which equates to 1,250 floating units, assuming each project uses 20-MW turbines and that one foundation per turbine if required. ScotWind is assuming mostly to use 18- and 20-MW turbines, however these are not yet available, so it’s a bold assumption on the developers’ part. For a 10-year period (2029-2039) for manufacturing and installations, this requires 125 units to be made per year.

Supply capacity for ScotWind is capable of exceeding demand. However, the actual realized capacity will likely be lower, as, due to competition with other marine activities for port use, limited areas will be available for wet storage that may hinder productivity. For this reason, not all expansion plans will be realized. Onshore crane availability may also be a bottleneck, and immature supply chain and installation infrastructure may slow progress further. Critically, many Scottish ports do not have the required areas to deliver commercial-scale floating offshore wind without significant investment and infrastructure development.

What ScotWind is still missing is a decision on which floating foundation each developer will select for a given site. Until that is known the supply chain cannot form, and investment cannot be made in the port infrastructure. There are many floating foundations to choose from, but only a handful that are practical for use with the constraints of ScotWind.

While many challenges remain, it’s not all doom and gloom; the industry is at the dawn of commercialization. The Hywind Scotland project was the first commercial-scale offshore floating wind farm in 2017. Now, there are 14 floating ScotWind projects in the pipeline.

There is no shortage of companies lining up to form the supply chain and people ready to invest. At Houlder, we believe that the challenges in Scotland, and globally, can be overcome with the right collaboration and investment. Independent marine and offshore design and engineering specialists can provide consultancy on the costs, timeframes, emissions and risks of each floating wind technology — supported by technical analysis.

Lessons will also be learned from INTOG, as well as ScotWind over time. The industry will evolve, and it is likely that future leasing rounds will have improved technology and foundations. Although this does rely on increased transparency on foundation choice and reasoning.

Vertical access turbines, or self-erecting nacelle systems such as SENSEWind’s concepts, as well as power to X will influence the direction of foundation type. But we need to put those evolutions to one side for now and choose a conservative base that can work for a site and press on to avoid major delays to ScotWind and the UK’s environmental targets.

Only the offshore wind industry and its experts can decide if floating offshore wind will be an endless dawn or a global opportunity which can drive the global energy transition. Let’s make the right decisions, supported by engineering, to ensure that renewable energy ambition is fulfilled.

Mark Goalen is a Chartered Engineer with a Master’s degree in Naval Architecture from University of Strathclyde in Glasgow. He has strong aspirations to use his skills and experience, developed in 18 years of industry, to make a positive impact on the energy transition. At Houlder, his role combines business development, engineering management and business strategy. He helps clients bring the right capabilities and knowhow to bear on current industry challenges. Starting out at subsea construction company, he worked on varied projects both in the North Sea and further afield. Mark also worked in several smaller engineering firms further developing technical skills, practicality (close to fabrication activity), and an understanding of the pressures of running a business. Managing projects for a semi-submersible owner operator increased his skillset further with exposure to regulatory requirements, operations, maintenance, and modifications of their fleet.

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