able to prove that it is possible to move the permissible natural frequency window a little closer to the limit imposed by the wind turbine designer.
“[This] can have dramatic benefits for the design of the support structure, allowing a 25 per cent lighter structure with a wider base,” he said.
Another key technology examined by DNV GL is enhanced
control systems. Here, the Project FORCE team investigated a number of innovations within the control system of the wind turbine that they judged to be complementary to the integrated design philosophy. The most promising of these involved the adoption of what they call ‘2P’ individual pitch control, which means that the pitch (or angle) of individual blades of the turbine is adjusted twice per revolution rather than once, which Mr Phillips says is the case with current state-of-the-art models. “The team found this approach to have a significant impact
on reducing the torsional or twisting loads on the wind turbine and its support structure, again allowing mass and therefore cost savings,” he explained.
The final technology analysed in the report is slender, faster blades. Here, the Project FORCE team explored the benefits of making blades more slender. “Obviously, by doing so, you reduce the mass of each blade
and therefore costs. However, that is not the end of the story. The slender blades need to move faster through the air to capture the same amount of energy. This is good news for the rest of the machine, reducing torque and therefore mass of the drive train. Slender blades are also more flexible, thereby reducing the fatigue loads passed through to the structure. Again, reduced loads equals reduced mass equals reduced cost,” Mr Phillips explained. The report is a key output of the DNV GL Project FORCE initiative, which was established to explore how the concept of integrated design could help companies to reduce the costs of offshore wind when applied to the wind turbine and its supporting structure for a typical project. “Over the last few years, our commercial consultancy work for both offshore windfarm developers and wind turbine manufacturers has provided us with some interesting perspectives,” Mr Phillips told OWJ. “These two stakeholder groups are really those best placed to drive offshore wind forward technically and commercially at a time when we need to move the cost reduction debate from words and into action,” he added. This involved the bringing together of some 25 DNV GL expert engineers with expertise in a number of key areas, including cost modelling, offshore load calculations, blade design, controller design and structural design. According to Mr Phillips, the team has been “consistently surprised” by the inefficiencies that occur throughout the existing wind turbine design and engineering process – particularly those relating to the wind turbine and its supporting structure or foundation – where he says they discovered what he described as “an artificial commercial boundary”, which is holding back cost reduction. “So last year, we commissioned a major internal R&D
project to try to understand the magnitude of savings that might be made by removing some of this inefficiency through the adoption of a more integrated approach. This work is summarised in the public-facing summary report,” he said. Commenting on the challenges that offshore wind energy companies are likely to face in realising the potential cost savings, Mr Phillips stresses that the main barriers do not relate to technology and innovation. “Technology and innovation are not the barriers here. None
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of the technologies examined by Project FORCE are in any way radical – they are incremental. The barriers to their exploitation are purely commercial and are bound up in the way the industry organises itself,” he said. In his view, the changes needed to go beyond just better data sharing, instead demanding a new philosophy built on a collaborative ‘whole system’ approach to engineering. However, to achieve this, Mr Phillips believes that nothing less than a step-change in the level of industrial collaboration around design and engineering is required.
“This won’t happen by magic of course, and of the various options considered in the report, an industry-led JIP has the greatest probability of success in our view. Getting the key players together to jointly write a set of best-practice guidelines on how to implement this in practice will help kick-start the step-change needed,” he said. According to Mr Phillips, the reaction to the findings of the
report amongst stakeholders in the offshore wind industry has been largely positive, and some companies have been prompted to extend the recommendations into concrete action. “Since launching the report, we have had a very strong
response from industry, with several expressions of interest in forming a JIP. It seems to have really touched a nerve – it’s as if many industry leaders had been thinking along similar lines and were pleased to see the ideas brought together into a consistent narrative,” he said. “In terms of advice, in crude terms, I would suggest that all players try to look at the bigger picture. The cost of energy for offshore wind represents an existential threat to this technology. It is in everyone’s interest to reduce it if we are to secure a politically sustainable future for offshore wind at the heart of energy systems,” he noted. However, he also warned that this can only be achieved if the industry starts working together towards such a common objective – not only at an industrial level but also at the level of individual projects going through the white heat of project development, procurement and construction. “In practice,” he concluded, “this means, for example, incentivising wind turbine manufacturers into taking additional design risk for the greater [levelised cost of energy] good of the project.” OWJ
Making turbine blades more slender and faster would have a number of advantages, not least reduced costs and fatigue
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