The installation of large diameter monopiles for offshore wind turbines presents new challenges as turbine sizes and water depths increase. Traditional deck-based upending methods are constrained by vessel capacity and workability. Seaway7’s Monopile Upending Smart Tool (MUST) enables suspended upending using crane based rigging and grommet connections, offering a more flexible alternative. While time-domain simulations have been recommended in prior studies, a fully coupled, continuous implementation has not yet been applied to this operation.

This thesis investigates how hydrodynamic effects influence the upending phase of a monopile suspended from a crane vessel. The increasing added mass due to larger submergence of the monopile generally increases the natural period of the pendulum oscillation. Partial submergence of the monopile causes intermittent slack in the upending lines, resulting in snap loads that are considered unacceptable for safe operation. For head seas conditions, the 60 degree upending angle was identified as the critical upending angle and governing configuration for the operation, due to the likelihood of snap loads in the upending line. However, the results also show that proposed mitigation measures, including damping strategies and monopile design, can significantly improve operability at this upending angle and thereby improve the overall feasibility of the operation.

A coupled time domain model was developed in OrcaFlex, including the vessel, crane, rigging, and a 125 m monopile. Hydrodynamic forces, including wave excitation, added mass, and damping, were applied based on site-specific sea states from a U.S. offshore wind location.

A central contribution is the development of a continuous upending simulation, capturing the full 0° through 90° upending motion in one simulation. This allows for dynamic updating of hydrodynamic properties and monopile orientation throughout the operation. Compared to quasi static analysis, the continuous approach avoids oscillation build up and tends to produce less conservative operability estimates.

The developed model offers a practical foundation for design optimisation and for assessing whether a continuous or quasi static simulation is more appropriate for a given analysis.

The increasing presence of electric vehicles onshore has also sparked a growing interest in offshore electrification. Simultaneously, the past decade has seen a significant increase in offshore renewable energy sources, a trend projected to accelerate in the future. Based on this growth and improving battery technology, the market potential of offshore charging solutions is highlighted. To address this emerging opportunity, this report presents a technical feasibility study of the novel KONGSBERG floating offshore charging station (OCS). The primary focus of the system is the offshore wind sector, particularly the support of operations for crew transfer vessels (CTVs) and service operation vessels (SOVs). As the majority of offshore wind farms are currently located in shallow water, this is where the largest market potential is expected. However, shallow water presents greater design challenges, as wave non-linearity increases and wave height becomes more significant relative to the water depth.

In this report, it is studied how the water depth affects the technical feasibility of the KONGSBERG OCS in shallow water. To do so, the KONGSBERG OCS is modeled in OrcaFlex for water depths ranging from 60 to 30 meters, analyzing key system components such as the buoy, the mooring system and the dynamic power cable (DPC). A surface-based charging concept was found to be unfeasible due to excessive pitch motion, leading to a focus on submerged designs. The analysis shows that the OCS is technically feasible at 40 m and 60 m depths, fulfilling both ultimate and fatigue limit state requirements. At 30 m depth, the system remains technically possible, but it exhibits several limitations, including a significantly reduced cable fatigue life of about 7.5 years, occasional buoy emergence above the sea surface, and increased interference with the seabed and mooring lines. The dominant driver of fatigue was identified as cable motion and the most critical load cases were those with aligned wave and current directions. Polyester was confirmed to be the most suitable mooring material, maintaining acceptable cable curvature in all feasible configurations.

To further improve the system and expand its applicability, several areas of future research are proposed. These include: evaluating the system’s behavior during charging mode with vessel interaction; developing a plug retrieval mechanism for emergency release scenarios; conducting fatigue enhancement studies for operation in shallower depths; incorporating rotational flow and vortex shedding effects using CFD to improve added mass and damping accuracy; and performing an economic assessment comparing the submerged system to a monopile-mounted alternative in very shallow waters. These directions aim to refine the design and expand its deployment potential within the growing offshore wind and electrification landscape.

The global concern over climate change has accelerated the shift towards renewable energy sources, in which floating offshore wind energy is expected to play an important role. A floating wind turbine could be installed in a harbour using a quayside crane. Various types of floating foundations are available, where a semi-submersible floater has the advantage of versatility in different water depths due to its small draft. However, the continuous upscaling of wind turbine sizes introduces new challenges for the installation process. Installing these larger turbines requires the use of the world’s largest cranes and large quaysides. The operability of the wind turbine generator (WTG) installation has a significant impact on the planning and feasibility of a floating wind farm project. Therefore, this research is aimed at studying and understanding the factors that influence the operability of the WTG blade installation on a semi-submersible floating wind foundation using a quayside crane.
To investigate how the dynamics of the floater and blade are affected by wind and wind conditions, a numerical model is developed. This is done in frequency domain which allows for fast calculations to gain insight into a variety of parameters. The floater model includes a 3D wave diffraction-radiation analysis, as well as a procedure for including viscous damping. Moreover, a response-based approach is applied to obtain the characteristic displacement and velocity of the turbine hub, which correspond to specific sea states. The blade is modelled as a pendulum with two degrees of freedom in axial and radial directions. Taglines are modelled as spring dampers that reduce the blade motions. A similar response-based method is used to obtain the characteristic motions that correspond to specific wind speeds and directions. During the critical alignment and mating phases, the relative displacement and velocity between the blade root and turbine hub are the limiting factors for installation. These relative motions, that follow from the floater and blade model, are then used to calculate the allowable environmental conditions for the wind turbine blade installation. There after, these allowable conditions are combined with metocean data to obtain the operability.
The model is used to study the sensitivities of parameters for the blade and floater motions. Aligning the blade with the wind is the most effective way to reduce blade motions because the motions in the axial direction are significantly lower compared to the radial direction. The influence of the distance between the quayside and the floater is also studied. For specific sea states, there are beneficial distances. However, when considering a large range of sea states, there is no significant advantage for certain distances. An important parameter affecting the relative motions between the blade and hub is the nacelle and blade heading. Optimising this orientation significantly increases the allowable environmental conditions. For low wind speeds, the optimal relative nacelle heading with respect to the wind and wave directions is dependent on these directions. For high wind speeds, above approximately 6.5 m/s, the blade should be aligned with the wind. Additionally, the lowest motions occur when the nacelle is rotated inward, closer to the floater’s centre of gravity.
Five different blade installation strategies are studied to identify one that yields the highest operability. A method where the nacelle and blade heading is adjusted to the optimal position for each change in environmental conditions yields the highest theoretical operability. However, in practice, a better solution is to select a single nacelle heading that is optimised for high wind speeds from a dominating wind direction. Utilising this strategy, it was found that a yearly operability of approximately 65% and 45% could be achieved for installing the turbine blade in a sheltered and exposed harbour, respectively. During the summer months, this operability increases to approximately 80% and 58%, respectively. The operability is mainly driven by wind-induced motions, so a location where wind speeds are low is favourable for achieving high operability.
In conclusion, this research contributes to the understanding of the critical factors that influence the op- erability of wind turbine blade installation on floating foundations, which is a crucial step in the upscaling of floating offshore wind technology.