Developing a next-generation floating wind design brings with it challenges both foreseen and unforeseeable – and needed a mix of ‘determination and ingenuity’ to get our technology tested and a key step closer to market, writes X1 Wind's Alex Raventos
By Alex Raventos
Powering up was a bigger milestone than any of us could have imagined. The prototype of our PivotBuoy floating wind design was brought online earlier this year in the Atlantic off the Canary Islands, but getting to this point was not only the product of pure determination over years as a start-up engineering outfit developing a novel technology – a downwind-facing turbine on a slimline triangular steel tension leg platform (TLP) with single-point mooring – it was also the result of regular lightning flashes of ingenuity as we figured out solutions to the many challenges faced along the way.
From the outset of our prototype project, we faced the significant challenge of selecting the right scale for the part-scale flagship – not least that despite a limited budget of €3.9m ($4.25m), the team needed to demonstrate the technology in a real offshore environment. Initially, 1:10 and 1:6 scale units were considered, but after careful consideration, a 1:3 scale was selected as the best scale for the test site even if it meant more investment than for a smaller unit.
There was also the matter of finding a suitable turbine for the X30 prototype – and adapting it to the downwind configuration. Due to the need for equivalent mass at the 1:3 scale, a relatively small nameplate machine was selected – a 225kW Vestas V29 – and then converted on the fly by our engineering team using a new set of gears that allow the gearbox to counter-rotate, and blades turned 180º to reorientate the rotor.
This work proved crucial. The decision on scale led to a size of the prototype that valiantly weathered storms with ferocious sea-winds, affirming the choice to design the floater and mooring to withstand extreme wave heights at that scale, and it also led to the option of a flying a turbine with pitch-regulated blades – better for downwind. By adding an ABB full-power converter, we were able to successfully test out modern control system strategies while offshore.
'Engineering on several secondary subsystems was not fully closed and steel for the prototype was already arriving at the manufacturing facility in Spain.'
X1 Wind CEO Alex Raventos
Behind the scenes, our company was growing at a pace. At the time of receiving our first EU grant in 2021, the X1 team was made up the two founders, me and CTO Carlos Casanovas, and three engineers. While the system design – still in the concept stage – had to be brought to manufacturing readiness in record time of about one year, the team size doubled. This challenge could have been hugely problematic, were it not for the involvement of other consortium members on the prototype project, including Intecsea, DEGIMA, and DNV which all provided crucial know-how.
The onset of the Covid pandemic towards the final stretch of detailed design also added to the challenge of finalizing the engineering in a timely manner, with several secondary subsystems still not fully closed and steel already arriving at the manufacturing facility in Spain.
Local knowledge is power
Once the prototype was ready for load-out and installation – it had been one of our primary objectives to demonstrate this could be done using local contractors – we had to work with an improvised plan that avoided costly heavy-lift cranes or submersible barges using tension leg platform buoy as a barge while employing locally sourced mobile cranes for a synchronized operation – and was only viable in spring tides, roughly 2 days a month, and had to be perfectly timed.
On 3 March, the X30 prototype began feeding power into the offshore smart grid through the underwater cable, becoming Spain’s first floating wind prototype to export electricity.
Since switch-on, it has been a thrill to see the system demonstrate excellent downwind self-alignment and power performance when exporting – and exceeding expectations in the process. And the data collected has already provided valuable insight into the system’s behavior and confirmed its stability, even in the most adverse weather conditions.
We have with the PivotBuoy X30 project overcome significant challenges by applying innovative strategies and solutions. By gathering the insights from our experience – particularly in the installation and operation of the world’s first operational floating wind TLP without the need for large construction vessels, will help the wider sector accelerate its own industrialization efforts, and we hope pave the way for the widespread deployment of floating wind arrays around the world.
· Alex Raventos is CEO and co-founder of the Spanish floating wind technology developer X1 Wind
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