Amid the global energy transition, offshore wind energy has been positioned as a pivotal technology,
utilizing both bottom-fixed (BOWT) and floating offshore wind turbine (FOWT) configurations. Offshore wind turbines face high operation and maintenance (O&M) costs, representing up to 35% of the levelized cost of energy (LCOE), with the drivetrain and especially the main bearing (MB) being among the most failure-prone components, leading to long downtime and reduced energy production. In floating wind turbines, main bearings experience additional challenges due to combined wind and wave loads and the platform motions.

This research investigates the differences in loading and fatigue damage of the upwind main bearing (MB1) in a monopile BOWT and semi-submersible FOWT, both based on the DTU 10 MW reference wind turbine (RWT). Using OpenFAST simulations under Design Load Case (DLC) 1.2, according to Standard IEC 61400-1: 2019, this study calculates the MB1 loads for both wind turbine configurations, at a North Sea location east of Scotland, with a water depth of 60 m. Simulations are conducted across the full operating wind speed range (4.5 - 24.5 m/s), and loads are calculated through an analytical formulation. The axial and radial loads of MB1 are post-processed according to Standard ISO 281:2007, to compute the dynamic equivalent load, which is used to evaluate the fatigue damage of the main bearings. The Load Duration Distribution (LDD) method, which defines the load cycles, and the site-specific Weibull distribution are used to estimate the hourly fatigue damage of MB1, which is then extrapolated to a 20-year design lifetime, yielding the time-dependent Remaining Useful Life (RUL).

A comparative analysis of MB1 load means and standard deviations reveals that, for the examined
drivetrain configuration, radial loads dominate the main bearing loading and fatigue contribution in both configurations. Specifically, for the FOWT, they represent 74 to 90% of the dynamic equivalent load and 39 to 72% of the fatigue damage across all operating wind speeds. For the BOWT configuration, the corresponding ranges are 75 to 90% and 42 to 72%, respectively. MB1 of the FOWT experiences higher axial and radial loads, mainly due to platform surge and pitch motions, which increase rotor thrust and amplify the axial loading, as well as platform sway, roll and yaw motions that mainly amplify the radial loads. The largest load differences between FOWT and BOWT are encountered at around the rated wind speed of 11.4 m/s, and they peak at 13.5 m/s, where the FOWT axial load is 13.17% higher than in the BOWT.

Over the 20-year lifetime, MB1 in the FOWT accumulates 5.03% more fatigue damage, failing at 11.98 years, compared to 12.58 years for the BOWT. BOWT MB1 exhibits higher fatigue damage in the below-rated wind speed region, especially for wind speeds below 8.5 m/s. For aligned wind-wave cases, the reduction in the MB1 damage for both FOWTs and BOWTs is only 0.6% compared to realistic (misaligned) cases, indicating that, the wind-wave misalignment for wind speeds in the above-rated region, has a slight influence on the cumulative damage. A parametric sensitivity analysis shows that turbulence intensity is the most influential environmental factor: a change from Class A to C results in up to 10% reduction in MB1 damage. Among system parameters, platform mass significantly affects MB1 fatigue in FOWTs, with a 20% increase in mass reducing damage by 5.6%, while a 20% decrease increases it by 4.4%.

Overall, the findings of this thesis prove that MB loads in floating wind turbines are subjected to greater complexity and amplification, due to platform motions and aerodynamic, hydrodynamic, structural and control coupling. This results in increased fatigue damage and indicates the importance of advanced fatigue-aware, system-integrated control strategies that consider the platform dynamics to ensure main bearing reliability in future floating wind developments. The study concludes with recommendations for future work, including the validation of the results with field data, the exploration of alternative drivetrain layouts and the implementation of advanced control schemes to mitigate the impact of the platform motion.

Europe’sambition to become the world’s first climate-neutral continent by 2050 presentsseveral challenges in the domain of variable renewable energy generation andthe development of sustainable energy carriers. In support of this mission, theNorth Sea is identified as a promising energy source, to be efficientlyharnessed through the deployment of system-integrated offshore energy hubs combining wind farms withoffshore electrolysis. The discussion around hydrogen’s role as a renewablefuel in a high variable renewable energy energy system and its contribution tostable, systemic decarbonisation is acknowledged and relevant literatureexamined.

TenneT,alongside other European TSOs, has proposed certain hub layouts as a part ofseveral studies and reports looking into the various aspects of ofshore enegryhubs. However, limited information exists on the financial attractiveness ofthese conceptual hubs for investors and developers. This study aims todetermine the optimal configuration of such energy hubs from the standpoint of economic viability.

A modularmathematical model is developed to represent offshore energy hubs, enabling thetesting of multiple configurations across various energy scenarios. Parameterssuch as electrolysis capacity, interconnection capacity, and ownershipstructures are varied, generating a range of configurations evaluated underdifferent price profiles for electricity and hydrogen. The model is applied to a case study based on the2x2 GW offshore hub configuration, aligned with the North Sea Wind Power Hubprogramme. Results point to a weak business case for electrolysers under thedatasets used. However, configurations featuring smaller electrolysers co-ownedwith relatively larger wind farms exhibit lower investment costs and greatereconomic benefit compared to those with larger electrolysers and smaller windfarms.

The thesisextends the analysis to consider implications for policy, tendering procedures,and broader socioeconomic dynamics. Strategies such as phased build-out andpublic ownership of power-to-gas infrastructure are explored as potentialenablers of hydrogen integration into offshore wind systems. Finally, concernsabout energy security, heightened by recent disruptions in global supplychains, particularly in the energy sector, are discussed. This shifts the focusbeyond pure economic considerations, toward the strategic value ofsystem-integrated offshore hubs and their supporting infrastructure.

Transitioning to renewable energy is essential for mitigating climate change and ensuring long-term energy security. Offshore wind farms offer a promising solution by harnessing strong and consistent wind resources at sea while minimizing land use conflicts. However, developing cost-effective offshore wind farm networks in the Baltic Sea—due to its unique geographical and environmental conditions—presents significant challenges.

This study addresses these challenges by developing a techno-economic optimization model to identify the most cost-effective offshore wind farm network configurations in the Baltic Sea Region. The model evaluates various configurations, including national (limited to domestic connections) and international networks (allowing cross-border connections), as well as single-stage (planning the entire network at once) and multi-stage (developing the network in phases) development plans. It optimizes the placement and capacities of wind farms, energy hubs, and export cables to minimize total system costs while adhering to technical and capacity constraints. Key geographical factors—such as water depth, ice cover, and proximity to ports—are integrated into the spatial data processing method to accurately assess infrastructure costs. The model also explores different network designs, including hub-and-spoke configurations that utilize energy hubs to consolidate and distribute power from multiple wind farms. The incorporation of single-stage and multi-stage optimization approaches allows for holistic and phased network developments, providing flexibility in planning and implementation.

The findings reveal that international networks are more cost-effective, totaling €28.5 billion, compared to national-only networks. This cost advantage is primarily due to enhanced flexibility in wind farm placement and power distribution. Specifically, national networks are 1.51% more expensive due to less optimized wind farm locations and localized grid overloading. Additionally, single-stage optimization outperforms multi-stage approaches by reducing costs by 1.71%, highlighting the benefits of a holistic planning strategy. While energy hubs can lower export cable costs by consolidating power transmission, they introduce higher overall expenses due to the additional costs associated with the hubs themselves. Specifically, the hub-and-spoke network is 1.15% more expensive than connecting wind farms directly to the onshore grid, suggesting a need for improved network optimization strategies. The study further identifies potential cost savings by positioning wind farms closer to shore in ice-covered areas when additional costs resulting from sea ice adaptation are minimized. This adjustment results in savings on export cables, as wind farms positioned closer to shore within these regions prove more economical due to their proximity and positioning in relatively shallow waters.

Ultimately, this research enhances the efficiency and economic viability of offshore wind infrastructure by optimizing design and cost estimation processes. The study provides actionable strategies for effective planning and investment in renewable energy infrastructure, offering valuable insights for policymakers and investors. By addressing the spatial, technical, and economic challenges associated with large-scale renewable energy deployment, the findings contribute significantly to academic knowledge and practical applications. The research emphasizes the importance of strategic long-term planning and international collaboration in developing sustainable and cost-efficient offshore wind energy infrastructures.

In order to decarbonize the industry, green hydrogen production will need to be increased. An option for green hydrogen production is to use electrolysers and wind energy in an offshore location. This thesis aims to improve the design of offshore wind based hydrogen production by optimizing the design with the use of Multidisciplinary Design Optimization. The question is answered with the use of a modular design including desalination, hydrogen production, hydrogen compression and transportation with a hydrogen pipeline. The main conclusion from this thesis is that the design problem included non-linearities. The complex optimization problem could be solved by using a sequential differential evolution algorithm. The resulting optimized design showed that optimizing the pressure of the electrolyser could result in lower work requirements for the compressor and desalination and increasing hydrogen production.

Wake losses in wind farms, caused by closely spaced turbines, reduce downstream power production and overall efficiency. These losses can be mitigated through wind farm flow control strategies, specifically wake steering, which involves yaw control to misalign turbines with incoming wind, and redirecting wakes to enhance overall power output. This thesis aims to develop a real-time, model-based controller that addresses operational and environmental challenges in large-scale wind farms. The controller adapts to off-design conditions such as changing atmospheric factors and offline turbines, making it more effective than traditional controllers based on pre-optimized lookup tables. The research modifies engineering wake models to account for heterogeneous wind conditions, improves the computational efficiency of the Serial-Refine optimization strategy for real-time use, and incorporates tuning of wake model parameters to ensure adaptability. Additionally, the impact of offline turbines on optimal yaw misalignment angles is examined. Results indicate that adapting wake models using sensor data improves power predictions in non-uniform wind environments, while the distributed optimization framework for real-time yaw adjustments performs comparably to centralized methods. Incorporating offline turbines into the control strategy further boosts power output, leading to increased revenue for the wind farm. This research advances wind farm flow control by developing control policies that are tailored to dynamic, real-world site conditions.

The increasing demand for renewable energy and the need to achieve global decarbonization goals have led the energy sector to explore remote areas where Floating Offshore Wind Turbines (FOWTs) are expected to play a significant role. These far from shore located turbines harness strong and consistent winds, but their deployment in deeper waters poses challenges. In addition, the intermittent nature of wind energy, grid congestion, and transmission losses further complicate meeting the energy demands. Combining FOWTs with offshore hydrogen production offers a promising solution by reducing reliance on electrical infrastructure. Green hydrogen, produced from renewable sources, provides a versatile and proven option for decarbonizing hard-to-abate sectors. The integration of hydrogen production directly from a FOWT presents a compelling alternative, but the transportation of hydrogen from Hang-Off Point (HOP) at the FOWT to the Termination Point (TP) at the seabed through flexible pipes requires ensuring the structural integrity under static and environmental loading.
This research evaluates the impact of various parameters in lazy wave configurations on the tension and curvature behavior of flexible pipes used for hydrogen transport in offshore wind-to-hydrogen systems, utilizing simulations performed in OrcaFlex (OF). The research shows that failure modes, tension, overbending, and compression, are only exceeded in non-optimal wave configurations, with the Minimum Bend Radius (MBR) being a more critical constraint than the Minimum Breaking Load (MBL). However, both limits are breached when compression, looping at the Touch Down Point (TDP), or collapse has already occurred, suggesting that the pipe may be overdesigned or that the lazy wave configuration represents a conservative design approach. Furthermore, research also finds that environmental factors have minimal impact on tension and curvature, with static effects contributing for 86\% of total tension and 78\% of total curvature. This indicates that static analysis can provide an initial configuration without the need for computationally demanding dynamic simulations, as the design limits of MBL and MBR are exceeded in similar static and dynamic scenarios. Lastly, the design of a lazy wave configuration can be simplified to three configurational parameters: a buoyant section parameter (the outer diameter of the Buoyancy Modules (BM), pitch between BMs, or the buoyant section length), the first section catenary length, and a total configuration parameter (total length or horizontal distance between the HOP and TP), since the parameters within each group exhibit similar behavior in terms of tension and curvature responses when varied individually.

Dutch offshore wind farms are primarily located near the coast and connected to the grid, but as offshore wind farms continue to expand and occupy more space, developers are turning to deeper waters. However, installing traditional monopile or jacket structures in these deeper waters can be expensive. One potential solution is the Dogger Bank, a shallow sand bank located 275 km from the Dutch coast, which allows for inexpensive wind turbine installation and high capacity factors. For far offshore locations like the Dogger Bank, electricity transport can be costly, making hydrogen transport via the existing gas infrastructure a more efficient solution. This could enable hydrogen production far offshore and its use in the decarbonisation of hard-to-abate sectors.

This study focuses on the development of a stand-alone offshore hydrogen production system, incorporating battolyser technology, on the Dogger Bank. The battolyser, which combines a Ni-Fe battery and an alkaline electrolyser, is able to store energy and produce hydrogen efficiently and flexibly. However, as the battolyser is not yet commercially available, the proposed systems are analysed for the years 2030 and 2050. The study examines three system configurations: an electrolyser-battolyser, battolyser-only, and electrolyser-battery configuration. For the electrolysers, alkaline and PEM electrolysis is considered. For the battery a vanadium redox flow battery (VRFB).

To ensure autonomous operation, the battolyser serves as a backup power source for supplying
the system’s auxiliary energy demand. This demand is used to determine the system’s sizing, and a MATLAB/Simulink model is developed to calculate the hydrogen production based on future estimates of technical parameters. The hourly wind data from offshore platforms near the Dogger Bank is used as input for the model. To project future capital expenditures (CAPEX) for the model components, a learning curve method is employed, which assumes a specific cost reduction rate with every doubling of cumulative installed capacity.

This study demonstrates the feasibility of an offshore wind-hydrogen system with battolyser
technology, both technically and economically. Battolyser CAPEX are used as an input variable to estimate a range of possible levelized cost of hydrogen (LCOH) values for different systems. The study findings indicate that LCOH values of less than 1.55 C/kg could be achieved by 2030, and by 2050, these values could drop to less than 1.18 C/kg.

As part of the Dutch government’s ambitions to realise significant offshore wind energy capacity (70 gigawatts (GW) by 2050), the Port of Rotterdam is to become a hydrogen hub for North-Western Europe. To achieve this, it is expected that around 20 megatonnes (Mt) of hydrogen could be throughput in the Port of Rotterdam, out of which 2 Mt will be produced locally from offshore wind farms. Current offshore wind farms use high voltage electricity cables to transport energy to shore, but could, in the future, also transport energy in the form of hydrogen to shore via a transport infrastructure.
The objective of this thesis is to investigate the techno-economical feasibility of an offshore hydrogen production value chain connected to the Port of Rotterdam. The technical analysis gives insights into the possible technologies that can be used for the offshore value chain. It will also look at the technical feasibility of system integration in the Noth Sea's energy system. The economic analysis gives insights into the economic feasibility of the offshore hydrogen production value chain. The total costs are of importance, as well as the levelised cost of hydrogen.
In this thesis, a qualitative literature study maps the different possibilities per component of the value chain. A decision framework is then used to discuss the best possibility per component and to build three promising designs. These designs are then modelled in MATLAB to size their components. With the model’s output, a cost analysis can be done to determine whether such a value chain would be feasible compared to other ongoing projects. A special focus will be put on the Port of Rotterdam, to which the value chain will be connected.
The offshore decentral configuration is found to be the best-performing design based on assessments through a multi-criteria decision analysis, a technical model and a financial model. It is, therefore, the most promising design.

In the conceptual design phase, OEMs perform technology assessment to identify feasible solutions for their new aircraft. When the OEM is unable to assess a certain technology themselves, they consult Tier-1 suppliers to involve
them in the design process. The suppliers have higher fidelity analysis tools that can help the OEM with their assessment, but the characteristics of such tools (e.g. high detail of input, computational time to execute) prevent an in-depth exploration of the design space. This thesis proposes a framework that enables a closer collaboration between the OEM and their supplier. The collaboration is streamlined through a web-based collaborative environment. Front-loading principles are applied to capitalise on existing data, reducing the efforts required by the supplier to service the OEM. The framework was successfully applied to an internally developed test case, and a use case within the ongoing collaborative research project DEFAINE, concerning the design of an aileron.

The offshore wind market is rapidly growing, resulting in increasing wind turbine sizes, increasing distances to port, and a shift to deeper waters. A literature study in this thesis shows that existing wind turbine installation vessels, vessels under construction, and innovative concepts will not be able to install next-generation turbines or that they would have installation bottlenecks, making them cost-inefficient. This goes against the goal of decreasing the Levelized Cost of Energy (LCOE) of wind energy, to ensure that offshore wind stays competitive with other energy sources, enabling the energy transition. There is thus a gap between future demand of offshore wind installation vessels and current and near-term solutions. The research proposes a new floating monohull vessel concept, called Moonshot, to fill this gap. Moonshot will thus be different than traditional jack-up or semi-submersible installation vessel options.

In this research, various design strategies were analyzed. Based on the findings, a design strategy is developed to design and analyze Moonshot. A combination of Ulstein Design and Solution B.V.’s Controlled Innovation process and Blended Design were used and extended to develop this new concept. First, the important functions and design aspects of the design were established using Controlled Innovation. Blended Design was then used to create a design space of the design configurations and to explore multiple market scenarios to establish optimal ship parameters for further development. As part of the research, the existing design process and model were modularized and new features were developed to suit wind turbines, assess seakeeping behavior, and explore the design space of the future wind turbine installation vessel.

The results of this research aim to elucidate optimal design parameters across certain market scenarios. Results show how optimizing the design for financial performance, seakeeping behavior, or a combination of the two, influences the optimal design point. With the optimal design ranges, the initial design parameters for the next stage in the design of Moonshot are established. Finally, Blended Design is used to benchmark Moonshot against existing wind turbine installation solutions to assess its performance. A version of Moonshot is developed as a direct competitor for the largest jack-up design available, the NG-20000X. Benchmarking with the jack-up, an SSCV, and Huisman’s WIV concept showed that Moonshot would be a more efficient solution, capable of installing a larger number of turbines per year at a considerably lower cost per megawatt compared to the other solutions.

In summary, this research concludes Moonshot as an innovative concept to address the evolving challenges of offshore wind turbine installation. By combining innovative design strategies, extensive assessment, and optimization, Moonshot emerges as a promising contender in the quest for effective and cost-efficient installation solutions for offshore wind.

Implementing green alternatives in the heavy­-duty mobility market is required to reach the set climate goals of 2050 and decrease greenhouse gas emissions. Refuelling infrastructures based on alternative fuels such as hydrogen are not sufficiently available. This poses a barrier to large scale implementation and investment in new emission­ free heavy-­duty fuel cell vehicles.

Early market value chain configurations and low refuelling station demand levels are researched and evaluated to determine the optimal future strategy decision based on operational decision-making results. A Mixed Integer Linear Programming (MILP) optimisation model is adopted to simulate a small scale hydrogen value chain dominated by hydrogen production directly from wind energy at the wind turbine location. Additionally, a method is proposed to define future demand for two separate end-­user categories at a hydrogen refuelling station. The spatial configuration of the researched infrastructure is based on a ”Hub” and ”Satellite” concept with distributed production locations and demand locations.

With the current market pricing of all value chain components, cost parity with diesel fuel is reached if the total production capacity of the value chain is utilised. Future cost development will result in a lower total cost for hydrogen per kg than the diesel fuel equivalent. The hydrogen refuelling infrastructure based on wind energy is resilient against increased energy price fluctuations by an expected increase in the installed capacity of renewable energy sources. The operational decision ­making process regarding the hydrogen production process is generally independent of the distribution system size, spatial configuration, and type of non­-stationary storage container, taking into account similar demand within a specified time frame. The hydrogen infrastructure project of DUWAAL by HYGRO is used as a basis for the research.

New offshore wind farms are moving farther away from the shore; to locations characterised by adverse weather conditions. This challenges current maintenance strategies because, besides being further from shore, far-offshore wind turbines need more frequent maintenance and must be accessed in rougher weather conditions. Service Operation Vessels provide high accessibility to far-offshore wind turbines, but they lack multitasking capabilities. Its daughter craft is a valuable asset for unplanned maintenance in the summer when it can operate safely, but it is often not deployable during the winter due to the rougher weather conditions. The main research question is: What are the deficiencies of current DCs, and how can these access vessels be modified to operate year-round at far-offshore wind farms? The results show that the current DC’s deficiencies lie in its current operational requirements. Also, performance in oblique waves is currently riskiest since that is when there are higher vertical accelerations or a combination of vertical and lateral accelerations. Furthermore, wave steepness has significantly more effect on accelerations that wave height. Lastly, future DC designs should be focussed on stable seakeeping performance during transfers rather than high-speed transit. An analysis into the seakeeping performance of four prototypes showed that it is feasible to increase the transfer requirement from Hs ≤ 1.5 m to 2.0 m ≤ Hs ≤ 2.5 m. The catamaran type DCs have a high potential to realise year-round accessibility to far-offshore wind farms due to their resulting performance in oblique waves.

The offshore wind industry in Europe has experienced significant growth in the past decade, with wind farm development mostly focusing on the shallow area's in the North Sea. Naturally, the market is driven to reduce the Levelised Cost of Electricity (LCoE) to become more competitive with fossil fuels and less dependent on government subsidies. A transition in wind farm development towards deeper waters is expected and already observed in the market, driven by decreasing availability of shallow area's and higher wind resource at far offshore locations. The majority of the northern part of the North Sea is between 60 - 120 meter deep, currently the jacket foundation is deemed as the foundation of choice for this water depth range. Despite several technological advantages of the jacket, the main downsides are the large engineering effort and welds required to produce such a foundation resulting in difficult series production and high costs. This does not align with the industry's ambition to lower the LCoE. As such, the need for a technologically viable and economically attractive foundation concept for waters between 60 - 120 meter deep arises.

The goal of this research can be divided in to two parts. The first part is to determine the potential of conventional monopiles in this water range and identify the main limiting factors. To do so, a monopile is dimensioned at a selected reference location for three turbines representing the current, near future and future outlook of the market. The designed monopiles are tested for manufacturabiliy, Ultimate Limit State (ULS) and Fatigue Limit State (FLS) to identify the technical showstoppers. Next, in the second part, a novel monopile design is introduced and analysed to work around the identified limits.

To dimension the monopiles for the three reference turbines a parametric dimensioning script is developed. The monopile geometry is dimensioned to have a selected first natural frequency of 0.20 Hz, based on the relevant frequency diagrams. Next, these geometries are tested against mudline ULS failure for the power production and parked condition load cases. Hereafter, an FLS check for the B1, C1 and D S-N curves is conducted based on the obtained scatter tables for site conditions. It was found that D-curve fatigue damage for non grinded butt welds is the main limiting factor for all dimensioned monopiles in deep water. However, industry experts believe that all welds can be grinded in the production process, eradicating the need to assess the D-curve. When assuming this statement to be true the newly obtained limits become ULS failure during parked conditions for the 15 MW reference turbine and manufacturability constraints for the 20 MW reference turbine. The Haliade X showed no limits within the specified water depth range when neglecting the D curve fatigue damage.

A perforated monopile concept with reduced available area for wave loading is introduced. A Computational Fluid Dynamics (CFD) model based on the 2003 Menter Shear Stress Transport turbulence model is constructed for a perforated monopile to gain insights into how waves propagate through the structure and the forces associated with this. The CFD model is verified against experimental wave flume data before being used for further analysis showing a root mean square error of 0.0192 between model results and experiments. The CFD model is used to assess three geometries with different perforations and levels of porosity. No increased drag around the first natural frequency caused by the perforations, hinting to favourable dynamics, was found in any of the test cases. As such, the dynamic response of the three perforated monopiles was found to be unchanged when compared to a reference pile without perforations. Despite this, a significant reduction of lifetime fatigue damage was observed caused by the reduced forces acting on the structure resulting from the smaller frontal surface. Next, the mudline stresses are recalculated and a structural finite element model to assess the stress concentrations around the perforations is set up to verify the maximum allowable stress level threshold is not exceeded. A geometry was found which shows a 35.5% reduction of lifetime fatigue damage whilst stresses remain below the maximum threshold, hereby showing the potential of the perforated monopile. Implementing this perforation allows the use of monopiles up to 87 meter deep, limited by D curve fatigue. Reference piles without perforations were found to be infeasible for all assessed water depths, also limited by D curve fatigue. It is shown that the perforation concept can either be implemented to push the monopile foundation to deeper waters, or can be used to realise steel reduction at current water depths.

A gap in the understanding of offshore wind submarine power cables is responsible for 70-80 % of failures in recent times. The failures originate from the phases of design, manufacturing, installation and operations. Joint industry collaborations such as the Cable Lifetime Monitoring project that form the background for this thesis, are aimed at developing knowledge of these failures. The origination of failures from the installation phase of power cables is of particular interest. In order to do so, a model has to be developed first to understand the processes involved in an installation plan, as well as their time and resource costs. Logistics and planning tools such as ECN Install are utilized for this purpose and provide the medium for capturing the installation processes for submarine power cables. This thesis aims to describe the installation of power cables using a discrete event simulation based logistics model such as ECN Install. The first part of the thesis focuses on a literature review to categorize all aspects of power cable installation. Here the stages of a project, the installation processes, assets, methods and influencing weather parameters are identified. From this literature review it is found that the most important stage of a power cable installation project is the Marine Installation Program. The decisions leading to the development of a Marine Installation plan are mapped for modelling. The second part of the thesis deals with applying the knowledge acquired into the logistics model. Here, the model assumptions are set in order to create an accurate depiction of the installation processes. The third part of the thesis investigates the influence of input uncertainties on the model as a means to understand the relationship between the different aspects of a power cable installation project to its Marine Installation Program. A sensitivity study is performed to quantify the impact of different uncertainties on a Marine Installation Program. The final part of the thesis has the
analysis of a historical case study. Here the Marine Installation Program of the Gemini export cable is constructed.

This thesis describes the identification and cost calculation of WACC1 stabilizing support mechanisms for new Dutch offshore wind parks, which are funded with PPA2 based project financing facilities, in a non-SDE+3 and electricity price volatile market.

Since the ratification of and commitments made under the COP 21 summit, we have witnessed an increase towards implementing and utilizing renewable technologies in our energy mix. The global cumulative installed wind energy capacity in 2017 surpassed 540 GW, which is an increase of over 173% compared to 2010 levels. At the same time, Solar PV technology has also experienced a significant cost reduction, and the global installed capacity was 500 GW in 2018. Despite rapid development and growth, the overall contribution on the global energy scene is still limited. Fossil fuels still dominates the global energy supply, and are likely to do so in the coming years. This thesis explores the potential upside of considering synergies in the offshore domain, in order to further expand the diffusion of renewable technologies.

With Multidisciplinary Design Analysis and Optimization (MDAO) a fully automated aircraft design analysis is set up and optimization algorithms are used to obtain better designs by balancing the synergy between components. In the EU project AGILE, a new methodology and framework were developed to make the MDAO approach more accessible to industry. A key component of this framework is the KADMOS package. KADMOS is used to formulate large, heterogeneous MDAO problems and their execution process before they are implemented as executable workflows. This thesis focuses on the automation of a key step in the problem formulation for MDAO systems: the execution process definition, i.e. the order and grouping of the disciplines. Several sequencing and decomposition algorithms are developed to optimize the execution order of the disciplines and their division over multiple processors for parallel execution. The algorithms are verified and validated on thousands of MDAO systems using a scalable mathematical test case. Furthermore, the conceptual design of a conventional aircraft is performed using a novel implementation of the Initiator toolbox in KADMOS to test the algorithms in a realistic aircraft design problem. This showed that the algorithms resulted in a setup time reduction due to the automation of the execution process formulation and a reduced convergence time thanks to the improved usage of computational resources.

The increase of energy consumption as well as the need to reduce green-house emissions trigger the shift from a fossil-fuel based society towards a sustainable society. With a constant increase in the installed power capacity, wind plays a key role in the global energy framework. The improvement of the technology opens up new targets for the wind development [28]. In particular, the installation of small wind turbines in the urban environment represents a promising solution to supply residential power. Whilst, some of the problems faced by large-scale wind farms, like losses in the electrical distribution and transportation system, can be reduced. However, the immaturity of the technology leads to elevated capital costs and technical challenges [41]. Among these disadvantages, the siting near human activities is limited by the sound emitted by small wind turbines [65].
The current work focuses on the aerodynamic noise produced by horizontal-axis small wind turbines. For this purpose, the rotational beamforming algorithm, ROSI (i.e. ROtating Source Identifier), together with microphone array measurements, have been used. The ability of the method to follow the movement of the sound source is essential to correctly localize and quantify the rotating sound source. ROSI is applied in the time domain: first, for every source position a time history reconstruction of the signal recorded at each microphone is performed. Then, the microphone signals are sampled for every emission time, leading to the de-Dopplerisation of the signals. Last step is to sum all de-Dopplerised signals and to repeat this procedure for each scan point [33].
In order to validate the technique, the ROSI performance has been investigated with an increasing degree of uncertainty: initially, under ideal and know conditions with simulated datasets and, then, applying ROSI to experimental data. The results of the simulations show that ROSI is not influenced neither by the rotational speed of the source or by the selected time snapshot. Furthermore, the differences in the beamformed results always agree with the differences in the source level, proving that ROSI can be used to compare different blade or turbine geometries. Additionally, the ROSI performance is in agreement with the Rayleigh limit. In fact, if the spacing between the sound source is below the Rayleigh limit, the sources are not distinguished as separated and their SPLs are not correctly estimated. As regards the experimental approach, a small-scale prototype simulating the acoustic of a small wind turbine was tested in the Anechoic Tunnel facility while an upwind turbine was measured in the Open Jet Facility, varying both the wind speeds of the tunnel and the rotational speed of the blades. The two facilities are located at the TU Delft University. During the first experiment, the measurement geometry is verified and the resulting outcomes are compared with the simulations. It is confirmed both that the rotational speed does not limit the ROSI performance and that the source localization and quantification are affected by the Rayleigh limit. As regards the last experiment, the ROSI uncertainty is investigated in a non-anechoic environment. In the range of frequencies where the wind turbine noise is expected (i.e. 500 Hz - 2000 Hz [60]), the high levels of background noise do not allow to localize and to quantify the main noise sources in the small wind turbine. Thus, the wind turbine noise is not assessed and the experimental data are not compared with the analytical noise models, provided in literature.

In the case of unsteady loading conditions at a rotor, the induced velocity response lags the thrust coefficient at the rotor. The two parameters that are responsible for unsteady loading conditions are rotor thrust (due to blade pitch, or rotational speed) and incoming wind speed. The induced velocity response to these two sources of unsteadiness have been compared in a free wake vortex ring model. It was found that a varying wind speed has a non-negligible dynamic inflow effect, and the effect is different from varying rotor thrust. Additionally, current engineering models are incapable of capturing this difference. Recently a new engineering model was proposed at the TU Delft by Wei Yu, and this model is extended such that it is able to distinguish between the response to dynamic wind and to dynamic thrust.

The pioneers in the early 21th century who built the first big offshore wind farms now have to compete with the quickly improving renewable energy technologies and see their farm being out-dated (See also: Dvorak, 2013 & Wind Energy Update, 2013). At present, wind farm owners face difficult decisions when finding the right O&M contract for their offshore wind farm after the warranty period with the original equipment manufacturer (OEM) has ended. Because of a lack of experience in this new O&M phase, decision-making processes are not yet structured or standardized. During the warranty period of approximately 5-10 years, traditional performance-based contracts based on availability guarantees are offered by the turbine manufacturer. To stimulate innovation and increase the energy output, some O&M activities may be better off outside the scope of the performance contract and need a different sourcing scenario. This leads to the aim of this research to compose a decision-making flowchart that can be used when finding a new sourcing strategy for the O&M of offshore wind farms in the post-warranty future. It was concluded that these O&M activities can be segmented in three main items: the offshore turbine maintenance activities, offshore logistics and the onshore back-office maintenance operations. Increasing the maintenance efforts will improve the overall availability of the wind farm but will also increase the required resources to be devoted to O&M. For this reason, it is important to know the cost-drivers for the main O&M activities (Milborrow, 2010). Insights in these costs-drivers and performance shapers were combined and used as input for the decision-making tool. Next, three decision-making variables were derived from the Transaction cost theory and Agency theory that structures the outsourcing decision including the type of contract. First, the owners’ techniques and processes that are needed to transfer or take in-house a good or service were identified as the ‘proprietary nature’ which is an important decision variable when choosing between the O&M in-house or outsource option. Secondly, when outsourcing with a performance-based contract, a relatively high level of knowability of the performance is required compared to behaviour-based contracts. Thirdly, it was found that the type of contract is influenced by the dynamics of the environment because if the performance requirements change due to new innovations, the performance outcome becomes difficult to measure. The three decision-making options altogether lead to four scenarios that could offer a possible sourcing strategy after the warranty period: The Broker scenario, The Incubator scenario, The Coordinator scenario and The Controller scenario. The decision-making flowchart and the four post-warranty sourcing scenarios contribute to a more efficient scoping of the current performance-based maintenance contract in the post warranty future, so that O&M costs can be minimized while keeping the performance high.