While fixed-bottom developments account for almost all the world’s operational capacity today, floating wind has been widely acclaimed as the future — and rightfully so.
With fixed-bottom wind farms limited to depths of up to 60 metres, the ability to deploy turbines irrespective of sea depth is a game-changer in terms of potential offshore generation capacity.
But despite its potential to speed up the transition from fossil fuels, floating offshore wind presents unique challenges, because it requires an understanding and analysis of additional data sets to optimize operation and performance.
A new dataset
While floating wind can repeat the spectacular cost reduction we’ve already seen in fixed-foundation offshore wind with vast economies of scale - industry and academia face constant challenges around data measurement.
Our current understanding of the complex interaction of wind within an offshore wind farm was reached by observing and analyzing the performance of fixed-bottom turbines. But the interaction of a turbine within a new plane of movement upon a floating platform is a new field of study and we must understand the most effective balance between the natural behaviours of wind and wave conditions to optimize performance.
Floating platforms introduce new types of data to be considered. Factors include the motion of the floating platform (which may have its own controller to shift ballast), mooring line tensions and parameters of the sea such as wave height, frequency and period all acting on the floater. Projections of energy yield will need to consider the availability of the floating platform as well as the turbines.
Risks, rewards and opportunities
For companies broaching the floating offshore wind market for the first time, starting earlier with the data is important.
The challenge lies in determining exactly what data is necessary and valuable to optimize the performance of the coupled turbine-floater unit. While turbine OEMs such as Siemens, GE and Vestas have an established structure for providing operational data and know its pitfalls, manufacturers of floating platforms are still refining what a good quality and well-structured dataset looks like. Data integrity must be ingrained from the start and not be overlooked in the race to deploy the physical structures.
For companies which fail to acknowledge the complexity of this new plane of data, it may be an expensive oversight. Failure to manage conflicting sets of requirements brings inherent risks including potential mechanical overloading, increasing fatigue of critical structures and a reduction in the safe operational life of the asset.
Learning from oil and gas
From a data gathering perspective, the industry should draw from decades of oil and gas experience, developing and operating floating platforms. Much can be learned from the sector’s knowledge on optimal sensor placement, frequency of data sampling and modelling assumptions.
However, some caution should be used because floating oil platforms are not designed to accommodate a dynamically loaded structure, or the consequent changes in behaviour.
As with traditional offshore wind, data analysis platforms will evolve to accommodate the demands of floating wind data. These tools will help to dissect and interrogate the data in a way that is valuable to better understand our floating platforms.
Exploring and analyzing new data through the likes of experimental sites such as the National Floating Wind Innovation Centre in Aberdeen, Scotland will be crucial in determining the optimal combinations prior to scaling up to ensure lower overall costs.
Spar, semi-submersible or tension leg?
At this early phase of development there is a proliferation of floating offshore platform solutions, such as spar, semi-submersible and tension leg. Each is designed and optimized for a particular range of water depths and ocean conditions. Whereas the interaction of a turbine with a static foundation is universal, this is not so with floating foundations.
The intensive research required to understand and optimize the interaction of both wind and sea states on the coupled turbine and floating platform must be multiplied by the number of platform solutions.
It has taken the focus of the entire industry to reach our current level of understanding on the behaviour of wind within an offshore wind farm. A comparable effort may be needed to get the most from each type of floating platform. Collaboration and knowledge sharing within the industry will help to accelerate the learning curve. However, due to the material differences in behaviour of each floating solution, many learnings will apply uniquely to specific floating solutions.
A new horizon
Successful deployment and upscaling of floating wind will be made possible by rapidly filling the knowledge gaps in managing and optimizing the coupled wind turbine and floater unit. This demands industry collaboration, cross-fertilisation and the brightest minds to explore the challenges of floating wind.
Accruing this knowledge will be highly data-driven and acquiring genuinely useful data will be the foundation of analysis and understanding.
Bronwyn Sutton is offshore principal at Clir Renewables