Foundations for offshore wind turbines are changing in line with the innovations in technologies, with Scotland demonstrating what can be achieved with ambition and ingenuity.
Traditionally, offshore wind structures have been fixed-bottom models. This market is fully established and requires foundations installed on the seabed. The main drawback of this model is the limits on the depths where turbines can be installed.
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This is where floating wind offers solutions, requiring potentially lower quantities of materials for installations in areas with stronger winds. However, there are many challenges to overcome in this new sector that is still taking shape.
Both fixed-bottom wind and floating projects are being developed in Scotland, which currently has 4.3GW of generation capacity from offshore wind. Scotland could deliver more than 40GW in generation capacity if all pipeline projects are completed as planned.
The main drivers of this capacity upscale are the ScotWind and Innovation and Targeted Oil & Gas (INTOG) leasing rounds, which both comprise fixed and floating projects.
How offshore wind foundations are evolving
Fixed-bottom offshore wind is a well-understood sector with the necessary supply chain in place. Fixed-bottom projects can also currently be built more quickly and at a lower cost than floating projects.
The most common type of fixed-bottom foundation is the monopile, where steel tubes are inserted as much as 40m into the seabed at maximum water depths of 60m. For greater water depths, jacket or tripod models can be installed at depths of 80m. The model comprises numerous piles supporting lattice structures. For shallower waters, gravity-based foundations made from high volumes of concrete are installed on the seabed.
As turbines get larger and heavier, greater forces are placed on the seabed, with demand for materials to build the structures. Project sites are also limited by seabed conditions.
Floating wind opens up more potential areas for wind farms. Many concepts rely on anchoring and mooring systems. From a supply chain perspective, using proven anchoring technologies from other industries offers clear advantages for floating offshore wind.
Yet with more than 100 floating foundation concepts in development, the industry must reach a consensus to build the supply chain. Andrew Macdonald is director of development and operations at the Offshore Renewable Energy (ORE) Catapult, and chair of the Innovation Working Group at the Scottish Offshore Wind Energy Council. He predicts the industry will soon settle around fewer concepts.
“I don’t think there’s one perfect design, and it depends on the seabed conditions, water depth, and supply chain,” says Macdonald. “I think you’ll end up with half a dozen different designs, which will be credible.”
Already, the main types of concepts typically fit into either barge platforms, semi-submersibles, spar buoys, or tension leg platforms (TLPs).
Floating wind expansion in Scotland
Floating wind has much catching up to do with fixed-bottom, and a major scale-up is planned in a short timeframe to establish the industry and deliver its energy potential. Globally, there are more than 220 floating wind projects in development.
As many countries seek to finalise floating wind foundation concepts, Scotland is ahead of the curve in multiple areas. Scotland already has sites operational in Hywind Scotland and Kincardine, with more major projects in development. These include the already consented Green Volt, Pentland and Salamander projects, with several other projects in the consenting pipeline too. Furthermore, the combination of projects in the ScotWind and INTOG leasing rounds has more than 24GW of potential floating wind projects at some stage of development.
However, there are many challenges that must be tackled to deliver floating wind on this scale, not least the costs. “If we don’t get costs down, we’re not going to be building floating wind. It’s currently too expensive to be deployed at a gigawatt scale,” explains Macdonald.
Bringing the costs down of floating wind installations
As floating wind is a new industry, there are higher costs associated with developments than fixed-bottom projects. Macdonald suggests that standardisation in other industries points to how the floating wind industry could develop.
“If you look at automotive or aerospace, there are some elements that are standardised. Whether it’s tyres, wheels, or brake units. There’s a supply chain that will provide those, but the overall car is different,” adds Macdonald. “I think it’ll be the same with foundations. The supply chain might need some help identifying those common standard components. But I think the designs aren’t so different that everything needs to change every time.
“It might be that you don’t end up with the absolute optimum design. You end up with the best design that’s credible, insurable, bankable for that specific application.”
Over the next year, FLOWIC — ORE Catapult’s Floating Wind Innovation Centre in Aberdeen — is building a cost-reduction model to assess the multiple elements, speaking with the supply chain and developers to assure governments that cost reductions are happening. Learnings from fixed-bottom wind are informing the strategy for floating.
“We’ve just kicked off a cost-reduction monitoring framework,” says Macdonald, with a similar strategy taken for fixed-bottom wind around a decade ago.
For fixed-bottom in 2015, the target was to get below £100 per megawatt-hour. The programme looked at the scope of the industry to understand the costs and identify potential areas for savings, speaking with the supply chain to monitor where reductions were happening. Each aspect was analysed, including blades, O&M costs, ports, and vessel expenses.
“We were able to use that to give government confidence that costs were indeed coming down because you could see where the points were. After about three years, costs came down,” adds Macdonald.
He emphasises the need to get floating projects in the water sooner rather than later to enable industrialisation and allow cost reductions to start earlier.
Addressing production challenges with offshore wind expansion
Another challenge with the offshore wind scale-up is the sheer scale of the turbines and substructures to be manufactured, in terms of both individual unit size and volume across multiple sites.
Remi Zante is head of strategic planning at the National Manufacturing Institute Scotland (NMIS), part of the University of Strathclyde, and is heavily involved in solutions that address the issue of serial production in floating wind.
According to Zante, the scale of the offshore wind expansion is similar to building a ship every week. While wind turbines have fewer complexities than ships, they are similar in size and require large-scale facilities to produce them. “I don’t think anyone has the experience of building at this rate or size,” he says.
Zante emphasises the need to make the case that the scale of projects can be delivered and demonstrate the mechanisms to develop factories and facilities that provide the necessary flexibility.
“There’s an industrialisation and a pathway to scaling up the numbers. We won’t need to land one a week straight away. There are projects in a smaller pipeline, which can help prove how all this is working,” he adds. “So, there are the risk-based studies that help de-risk the decision-making, but underpinned by the technical solution for the manufacturing processes that will ultimately enable it.”
Overcoming such challenges requires a change in thinking, with Zante suggesting that established approaches need to be updated.
Automation could offer vital solutions to achieve the scale of manufacturing required. Zante highlights that the technology is already being used in Norway by the Nordic company Goodtech to produce substructures.
“It’s around a very specific use case in jacket legs, but it’s already there. It can already be done, and more of that needs to be implemented in the UK and Scotland,” says Zante. “It’s not about how things were done in the past, it’s about how they can be done in the future,” he adds.
Another advantage of automation is that it could also address the talent shortage while creating high-value jobs. Nevertheless, delivering automation technologies at a commercial scale will require substantial investment. With automation, there will also be a need to overcome the traditional trade-off between optimising processes for a specific solution and losing flexibility in the system.
“That’s going to need a mindset change from how things were done in the past to how things can be done in the future,” says Zante.
How Scotland is developing solutions for offshore wind challenges
While there are many challenges with the significant expansion of offshore wind and the establishment of the floating wind industry, solutions are emerging in Scotland.
The ScotWind and INTOG leasing rounds are strong drivers of development and indicate market demand and opportunities. Organisations and institutions such as ORE Catapult, FLOWIC, and NMIS are key players in this growing ecosystem. Then there is the talent and expertise available in Scotland from more than 50 years of operations in the North Sea. Crucially, supportive legislation is in place, as well as access to funding opportunities for innovations.
“It’s about bringing greater clarity. But the building blocks are already in place, including innovation networks across the regions, not least at NMIS, which can help drive development. And there’s a much wider network underpinning all of this,” adds Zante.
For floating wind to succeed, it requires collaboration both domestically and internationally. Scottish experience and solutions could also be exported globally in floating wind, similarly to how the oil and gas industry has historically.
“Although Scotland can, should and will take a lead UK-wide, and even internationally, in this space, it remains a truly global endeavour,” says Zante. “We work broadly across the UK and are building links to Europe. The aim is to bring all that together so Scotland sits at the centre and can lead the way, but with an international outlook.”
To learn more about the future of offshore wind, download the document below.
