GROW-to-GO

Removal of old monopiles

At the end of a wind farm’s lifetime, everything has to be removed. Current practice is to cut the monopiles that support the wind turbines several meters below the seabed. In the second Hydraulic Pile Extraction Scale Tests (HyPE-ST 1.2) project, Anderson Peccin da Silva and Alba Rodríguez Piedrabuena, both from Deltares, are investigating a new hydraulic pile extraction technology. In ‘Under pressure’, they tell you more about this promising decommissioning technology.

Increasing the reliability of rotor blades

In the last two decades, the length of the rotor blades for offshore wind turbines has increased significantly. Where we started with blade lengths ranging between 30 and 40 metres, we are now reaching 110-120 metres in length per blade, and this may go up towards an impressive 150 metres in the future. Despite efforts to improve control over the manufacturing process, defects still occur during production and operation that may lead to blade failures. This can significantly affect the wind farm's power output and repair costs. Therefore, the sector is looking for more reliable blades that can cope with the immense forces. Reason for David de Jager to visit Michiel Hagenbeek and Wim Castricum of TNO to dive into the world of rotor blades. Michiel runs blade models in a digital twin; Wim crawls inside actual blades to apply the sensors.

It's all about a safe tool for repair of rotor blades. Imagine that your wind turbine is installed offshore and provides significant amounts of wind energy. But then, one of the wind turbine's blades requires maintenance, or worse, gets damaged. You cannot simply take your ladder and climb up there to make the repairs like you would at home. So, Jeroen Tol and Wouter Kloppenburg from Ampelmann introduce their bright-blue “Puffer” in their production hall in Rotterdam harbour, a kind of oyster or mussel that folds around a rotor blade where you can safely stand in to do your repairs.

Rocks barely sound interesting, yet they are essential for the stability of wind turbine foundations. After all, they are used to prevent the erosion of sand around the monopile. Currently, the installation process of the scour protection requires three steps. Therefore, the Optimising Pile Installation through Scour protection (OPIS) project is researching how to improve this process. The research is well underway, and its researchers are nothing but “optimistic”.

Listen to the podcast with Ton Peters and Cihan Cengiz of Deltares and David de Jager of GROW.

Extreme conditions… in an extremely short timeframe

The Tubular Pile Pull-out Testing (TPPT) project impressively manages to mimic the conditions at sea for open tubular piles used for the mooring of floating wind turbines. Jan Kenkhuis explains: “Can we use open tubular piles for anchoring large floating wind turbines to keep the floating wind turbines on location in a harsh environment? That’s what we are testing here. We are actually simulating at this moment a storm condition. A serious storm, because that’s what we design for. Calm weather days are not really a concern.”

One ring to install monopiles faster, cheaper, and more silently.

You’d expect the fabrication of equipment for the installation of large monopiles for offshore wind turbines to occur in or near a harbour close to the North Sea. But, instead, Hein van Opstal, Charlotte van Verseveld and Rob Sprij, all working at GBM Works, can be found at the firm Kersten in Wanssum, Limburg, next to the Maas river. And not just on any day: they are here to see their jet-ring design become a reality today. A jet-ring is welded into a monopile section, which will later be part of a 13,4-meter-long monopile. And two of these monopiles will be extensively tested in an onshore test as part of the SIMOX project.

Developing the ultimate weather atlas for rain and wind in the North Sea

A meeting with Iratxe Gonzalez Aparicio and Harald van der Mijle Meijer at the beach near Bergen aan Zee in the Netherlands on a sunny January day in 2023. To talk about rain and wind in the North Sea. Why? Because the PROWESS project is investigating the relationship between rainfall at the North Sea and the observed damage to rotor blades in existing wind farms. Iratxe and Harald know quite well how raindrops can damage the blade if they collide with the blade at high speed, but a complete correlated dataset of rainfall on the one hand and wind speed and direction on the other is not available. In PROWESS, a precipitation atlas will be made for the Dutch part of the North Sea, and this will be compared with erosion data from existing wind farms.

Testing with piles in water and sand to understand the soil around monopiles.

It sounds like a beautiful beach day: playing around with water and sand in an environment that cannot be taunted by rain. But doing so can result in more than just sandcastles.

As the size of offshore wind turbines increases, monopiles get bigger as well. New installation technologies are currently being investigated, further developed, and tested in the SIMOX (Sustainable Installation of XXL Monopiles) R&D project. The aim is to enable the installation (and decommissioning) of future XXL monopiles in the North Sea sands. And all of this in a sustainable, cost-effective, societally, and environmentally acceptable manner.

Offshore wind and the winning tickets for the coming years

“The offshore wind sector is entering a new phase requiring a massive manufacturing and installation scale-up. Building a subsidy-free offshore wind farm should not mean that the companies involved make losses. We have to be economically sustainable as an industry. Therefore, it is vital to innovate to reduce costs further.” Says Jan van der Tempel, Chairman of GROW. “Mind you, we have to build 1000 turbines annually to drive the global energy transition. To make this happen, we must     speed up all processes and align the complete supply chain.”

Meet the team who loves spinning around monopiles.

The monopile foundations of wind turbines are subject to repeated (cyclic) loading by wind and waves. These forces are transferred from the foundation to the supporting soil, in a way that may affect the stability of the whole system. As the longer-term impact of cyclic loads is not yet fully understood, monopiles still tend to be designed on the safe side. If we understood better this behaviour, we could improve the design of monopiles to obtain lower fabrication costs. Federico Pisanò (Delft University of Technology) and Maria Konstantinou (Deltares) explain how the Monopile Improved Design through Advanced cyclic Soil modelling project (MIDAS) is helping to achieve that.

Improving wind measurements to optimise power performance. To gain the most power from the installed wind turbines offshore and onshore, they must operate at their absolute best. That's why the Sensor Assisted Wind farm Optimisation (SAWOP) project was initiated. Koen Hermans (TNO) and Jan Coelingh (Vattenfall) explain how SAWOP will help prove that nacelle LiDAR and spinner sensor technologies can optimise the power performance of wind turbines.