The transition to a decarbonised energy system requires a cost-effective, reliable and sustainable supply of renewable hydrogen, particularly for industrial hubs like the Port of Rotterdam. Multiple supply pathways could potentially contribute to such an energy system, with each pathway characterised by different advantages and disadvantages. Therefore, it is crucial to consider the system-wide implications of various supply pathways in order to make balanced trade-offs. This study functions as an exploratory investigation into the relations between various system designs and their characteristics. It examines techno-economic trade-offs between local hydrogen production using offshore wind-powered electrolysis and cracking of imported ammonia. Key performance indicators for system affordability, security of supply and sustainability are defined in order to facilitate a comparison of the two supply pathways. Employing a quantitative system model, these indicators are evaluated across different system configurations and demand scenarios for the Port of Rotterdam.
This research highlights the complexity of the energy transition and the absence of a universally optimal hydrogen supply pathway. Local electrolysis offers lower operational costs and import independence but requires high capital investment. In contrast, ammonia imports ensure a stable supply with lower local capital expenditure but depend on a resilient supply chain and are highly sensitive to ammonia costs. Local production demands more space but has a lower carbon footprint, while imports require less space at the import site but result in higher emissions. Additionally, electrolysis competes with power demand in Rotterdam’s harbour-industrial complex and hinterland, adding strain to their decarbonisation efforts. Local production also requires multiple salt caverns for storage due to constrained extraction rates, along with significant overcapacity in wind power and electrolysis to ensure supply continuity. Conversely, import-dependent systems rely on large ammonia shipments, and as hydrogen demand increases, local production reaches clear supply limits, leading to greater import reliance.
Future research should expand model applicability to different locations and supply chains, enhance key performance indicator scope, and incorporate stakeholder-driven decision-making frameworks. Ultimately, an effective hydrogen strategy must balance affordability, security of supply and sustainability, navigating the trade-offs between supply pathways and their broader implications for the energy transition.

Floating offshore wind farms enable wind energy deployment in deeper waters, where bottom-fixed turbines are not viable. However, integrating mooring systems and dynamic cables introduces additional challenges in cable routing, increasing design constraints and costs. While research on cable optimization for bottom-fixed wind farms is well-developed, studies focused on floating wind farms remain limited.
This thesis presents an optimization framework that minimizes inter-array cable length while ensuring compliance with mooring system constraints and loop topology requirements. A Mixed-Integer Linear Programming model is used to enforce spatial and technical constraints, structured into three phases: preprocessing, optimization, and postprocessing. Preprocessing defines feasible cable connections while preventing crossings with mooring lines. To manage complexity, turbines are grouped into clusters with defined boundaries to separate routing areas. The optimization phase determines the best cable layout while ensuring loop connectivity and balanced electrical loads. Postprocessing checks compliance with industry standards, identifying clearance violations and refining layouts for feasibility.
A case study of the London Array wind farm demonstrates the model’s effectiveness, achieving a 1.1% reduction in total cable length while maintaining the original layout structure. When adapted for floating wind, spatial constraints from mooring systems cause clearance conflicts, which are mostly resolved by scaling the layout. Minor turbine adjustments eliminate remaining issues. The study highlights that increasing the number of loops and reducing loop size creates more routing conflicts, particularly near the offshore substation and at cluster boundaries. It also finds that centrally positioned substations significantly reduce clearance violations compared to those at the field boundary.
This research provides practical insights into the spatial constraints of floating wind farms and offers a structured, computationally feasible approach to optimizing inter-array cable routing for large-scale farms.

Although the percentage share of renewable energy in the global energy landscape is increasing rapidly and consistently breaking records for annual installation, there is still a need for tripling up of renewable energy capacity by 2030.The costs and prices of renewable energy are declining year by year, this is one of the key reasons for the shrinking of profits for renewable power developers(RPDs). Different strategies can be adopted by the renewable developers to increase revenues like improving financing costs, making multiple revenue streams for individual renewable assets etc. This creates an opportunity for P2X technologies, which are becoming popular due to their ability to facilitate the integration of different energy sectors like electricity and hard-to-abate sectors.

The design of a Hybrid power plant(HPP) is a complex problem that combines different assets to maximize the value of the power plant. Researchers at the Technical University of Denmark(DTU) are in the process of developing an open-source tool called HyDesign. According to desktop research, it was understood before HyDesign that no other open-source HPP sizing tool in the market could size and optimize the P2X designs. The purpose of this thesis study is to analyze how can RPDs improve their economic value by coupling with green ammonia(GNH3) production using HyDesign. The quantitative data is collected through the literature research and qualitative data is collected through attending various conferences and industrial events.This study models the most prominent and proven technology, which existed for more than a century now called the Haber Bosch process. Around 30+ industrial professionals were interviewed to entrepreneurially validate TUDelft's patented methodology of the Green Haber Bosch process. These interviews also provided reliable qualitative data for this study.

Since there is no reference, open-source green ammonia model, modelling checks were developed in this study to verify the functioning of the model and increase confidence in the reliability of the results. Site selection hypothesis was also made for hybrid renewable power plants. Evaluation results depict that the revenue of HPP+GNH3 is more than the HPP. However, various financial metrics were more for the HPP than HPP+GNH3, this is due to the huge technology costs of the GNH3 plants and the lack of economies of scale of such new plants.

Sensitivity analysis is performed in this study to analyse value addition and its source for improving various financial metrics of HPP+GNH3.Increasing RE resource capacity will improve financial metrics. Increasing electrolyser capacity or battery capacity will also improve a few of the financial metrics but not to the extent of increasing solar and wind capacities .

The study finds that building a large-scale HPP+GNH3 system is beneficial for RPDs and to society, which yields better financial benefits and more green ammonia production, which can be used in many hard-to-abate sectors.

This thesis presents a thorough exploration of mid-term storage strategies aimed at enhancing flexibility in hybrid offshore power systems that integrate wind and solar energy. A multi-criteria analysis was employed to identify the most suitable storage technologies for medium-term applications, resulting in the selection of Compressed Air Energy Storage (CAES), Lithium-ion batteries, and Lead-acid batteries as the top three candidates.
A specific study area, already equipped with offshore wind turbines, was selected for this research. Weather data were obtained and analyzed to reduce power mismatches and their associated costs. A multi-objective optimization approach was applied, focusing on minimizing the hourly loss of load and total capital costs associated with the hybrid renewable energy system.
In the base case scenario examined, which comprised 100% wind power, CAES emerged as the storage technology with the lowest total capital cost. However, by varying the proportions of offshore wind and solar energy, it was found that adjusting the mix to 80% offshore wind and 20% solar led to a significant reduction in the annual loss of load, thus reducing the total capital cost of the renewable hybrid system.

This thesis investigates the feasibility of using concrete-filled double skin steel tubes (CFDST) as an innovative design for wind turbine towers, addressing the need for lighter, stronger, and more sustainable structures in the wind energy sector. The research is motivated by the challenges faced by the industry, including the limitations of traditional tubular steel towers, the increasing size of wind turbines, and the demand for cost-effective and environmentally friendly solutions.

The primary objective of this study is to explore whether CFDSTs could reduce steel usage while maintaining or enhancing the structural integrity of wind turbine towers, particularly in resisting local buckling under axial loads. To achieve this, both experimental and numerical investigations were conducted. The experimental phase focused on analyzing the local buckling behavior of S355 steel skins, both in single and double skin configurations, filled with high-strength concrete (C60/67). A finite element model (FEM) was developed to simulate these experiments, validate the results, and provide insights into the performance of CFDSTs under axial loading conditions.

Key findings from the study indicate that the inclusion of concrete infill significantly alters the buckling mode of the steel skins, increasing the resistance, and enhancing the post-buckling capacity. This effect was particularly pronounced in sections with higher cross-section slenderness, suggesting that CFDSTs could allow for the use of thinner steel sections without compromising structural performance, provided that optimal cross-sectional dimensions are selected. The numerical models show comparable resistance to the experimental results, though further fine-tuning of the models is necessary to enhance accuracy and better align the outcomes.

The research concludes that CFDSTs offer a promising alternative for wind turbine tower design, with the potential to achieve significant steel savings. Furthermore, suggestions for future research are presented, focusing on optimizing material selection, investigating the long-term durability of CFDSTs, and enhancing the numerical model.

The development of floating offshore wind farms (FOWF) represents a significant advancement in the renewable energy sector, offering a scalable solution to harness wind energy in deep-water locations. This thesis investigates the effectiveness of multiline anchor systems in improving the cost-efficiency, operation, and maintainability of FOWFs. Utilizing the modified Windfarm Operation and Cost-benefit Analysis Tool (WOMBAT), this research comprehensively analyzes multiple case studies, focusing on critical factors such as cost, profit, operational performance, and maintenance occurrences.

Case Study 3 compares the performance of multiline anchor systems against traditional single-line configurations in the Morro Bay scenario. The results indicate that multiline systems significantly enhance availability, reduce operational expenditure, and improve overall profit. Case Study 4 extends this analysis to the Gulf of Maine, confirming that multiline systems maintain their advantages under varied environmental conditions and extended operational lifespans. This study underscores the robustness and adaptability of multiline anchors in diverse offshore environments.

Case Study 5 provides a sensitivity analysis to evaluate the reliability of the simulation inputs. It demonstrates that the fundamental benefits of multiline systems remain consistent despite variations in mooring line failure rates. However, it also underscored the importance and need for available data and how the model and its outputs are only as credible as the inputted values.

The findings contribute to the offshore wind industry by providing actionable insights into the deployment of multiline mooring systems and offering recommendations for enhancing the cost-effectiveness and reliability of FOWFs. The research also highlights opportunities for further development of the WOMBAT tool, particularly in incorporating proactive maintenance strategies and environmental factors such as wind and wave directions.

This thesis supports the broader adoption of multiline anchor systems in floating offshore wind farms. With a demonstrated lower cost in operation and maintenance, it advocates for their strategic deployment in various environmental conditions to drive the transition to a sustainable energy future.

In this thesis, the integration of mooring design with the layout optimisation of floating offshore wind farms is investigated. The objective of the research is to devise a method to unite the two design processes and then evaluate the benefits of this approach. Further, it will be investigated how to model mooring systems in an optimisation problem, the stage of the wind farm design process at which mooring design can be integrated, the couplings between mooring design, turbine placement and cable routing that exist and must be used to arrive at an improved design, and to what extent the approach improves the design of the floating wind farm.
Floating wind farms are still in a developmental phase, but will be key to meet the energy goals of the future. However, floating wind farm design brings with it challenges that do not exist for bottom-fixed offshore wind farms. Chief among these challenges is the mooring system, which not only has a significant impact on the performance of the turbine, but also due to its potentially large footprint can force alterations to the layout of the inter-array electrical cables with which turbines are connected to each other and the substations. Particular focus in this regard is on catenary mooring systems, given they are common in existing demonstrator projects and have a large footprint.
In this thesis, mooring design will be performed through a multi-objective optimisation using the NSGA-II algorithm, where the objectives will be to minimise the anchor radius as well as the system cost, with constraints to ensure adequate performance in terms of handling motions and loads. The mooring system will be described by 5 design variables, the line length ratio, synthetic fraction, anchor radius, synthetic line diameter, and chain line diameter. The Pareto-optimal solutions from this optimization will then be used to optimize the layout and cable routing using an algorithm based on the work of Cazzaro and property of Vattenfall AB.
It is found that the Pareto-optimal designs have anchor radii ranging from 394 to 494 m, with system costs ranging from \$3.352 million to \$6.441 million. However, with current layout design methods, the turbine placement is done independently of mooring system parameters, and the cable routing is not affected by a change in mooring system. Thus, using the cheapest mooring system regardless of footprint is optimal on a farm level, using current layout design methods.

The demand for hydrogen is expected to increase significantly in the coming years due to its critical role in decarbonizing industrial processes. Offshore wind presents a viable energy source for powering electrolyzers, though it leads to intermittent production. While underground salt caverns are acknowledged as a promising solution for large-scale hydrogen storage, the technology still faces challenges regarding integration with fluctuating renewable energy sources.

This research, conducted in collaboration with Vattenfall, introduces a framework for modeling hydrogen storage in salt caverns, linked to hydrogen production from offshore wind farms. The framework features a technical model that addresses the thermodynamic changes within the cavern during hydrogen injection and withdrawal.

This new framework was expanded with an economic model and used to evaluate the optimal configuration for a standalone green hydrogen production and storage system. The analysis demonstrates that, up to a high security of supply threshold, increasing the storage capacity is the most effective strategy. Beyond this threshold, optimizing the configuration by increasing the number of stack changes or slightly enhancing the overall production capacity proves more beneficial than merely expanding storage. Additionally, the study explores two case study variations to assess the impacts of integrating flexible demand and line packing into the system.

The study concludes that the thermodynamic modeling of caverns significantly improves the accuracy of storage capacity estimations. It also highlights that optimal system design extends beyond adjusting storage capacity, necessitating comprehensive component optimization to strike a cost-effective balance for required supply securities. Furthermore, integrating demand flexibility enhances security of supply, enabling systems with high flexibility to achieve 100% security of supply with smaller storage capacities. However, the inclusion of line-packing does not improve economic performance. The insights underscore the need for strategic system design in hydrogen production and storage systems.

The decommissioning of offshore wind farms (OWFs) presents a significant challenge due to the environmental impact associated with the process, particularly in terms of greenhouse gas (GHG) emissions. This research aims to develop a model for quantifying and analysing the GHG emissions associated with large-scale OWF decommissioning. It examines key variables, including vessel types, decommissioning activities, transport strategies, and weather conditions, to assess their impact on total emissions.

Using a GHG inventory-based approach, the research applies both deterministic and probabilistic methods to assess emissions across various decommissioning scenarios. The model integrates operational logistics with emission factors, providing a flexible framework that adapts to different OWF projects. The research specifically examines the decommissioning of OWF Lincs Limited.

The results of this study highlight the potential for emissions reduction through optimised vessel strategies, transport methods, and campaign scheduling. While operational activities dominate emissions, the research underscores the importance of addressing external factors, such as weather and campaign timing, to minimise environmental impact. The developed model offers valuable insights to stakeholders aiming to implement effective GHG emission reduction strategies in future OWF decommissioning projects.

This research evaluates the economic feasibility of adding offshore solar farms (OSFs) to planned offshore wind farms (OWFs) in Europe, identifying feasible ranges of OSF and subsidy levels to reach economic feasible projects. Ultimately, this leads to conditions to reach economically feasible projects for adding OSFs to OWFs. Using shared infrastructure, such as the power export infrastructure (PEI), it reduces the need for offshore grid expansion and lowers initial OSF investment costs. This study addresses a gap by examining the economic feasibility of this integration, specifically through an economic added value (EAV) analysis, combined with various OSF cost scenarios through a net present value (NPV) assessment.

First, a literature review explores the economic and technical benefits, focusing on shared OWF infrastructure and identifying relevant stakeholders, when adding an OSF. A techno-economic model is developed to calculate the economic added value based on increased OSF revenues and the added value subsidy (AVS), which reflects cost savings from using shared infrastructure. Subsequently, the model is applied to two OWF case studies, a wind farm site in the Netherlands and wind farm site in Italy, where economic feasibility is evaluated.

This study concludes that the addition of an OSF to an OWF at the Italian site is economically feasible, when an optimistic OSF cost scenario is used. With less optimistic OSF cost scenarios, the the addition of an OSF to an OWF would require higher AVS from increasing shared infrastructure costs to become feasible. The integration of OSFs shows greater economic potential in southern Europe, particularly in regions such as Italy, where abundant solar resources and a lower wind potential contribute to a higher EAV per unit of OSF capacity because of substantial growth of the PEI capacity factor. Locations with lower initial OWF capacity factors, greater increases in additional OSF capacity factors, and high shared infrastructure costs lead to faster NPV improvement and reduced dependence on subsidies, representing economically favourable conditions for adding OSFs to OWFs.

The escalating demand for green hydrogen as a sustainable energy carrier has sparked significant interest in offshore wind-to-hydrogen systems, which hold the promise of expediting the transition towards renewable energy sources. The objective of this research is to provide insight in the techno-economic feasibility of semi-centralised electrolysis in an offshore wind farm. The semi-centralised offshore wind-to-hydrogen configuration will be compared with centralised and decentralised offshore wind-to-hydrogen to potentially reduce the levelised cost of hydrogen (LCOH) in future wind-to-hydrogen production designs.

This research was conducted in collaboration with Vattenfall, a leading player in offshore wind energy within Europe, who recognizes the potential of green hydrogen as a key driver in the ongoing energy transition. Vattenfall provided access to an in-house wind farm layout optimisation model to create optimised wind farm layouts as well as site specific data for the case study. This model and data allowed a narrowed focus on the hydrogen aspects of the wind-to-hydrogen configurations.

The technical examination explores crucial elements such as the conversion of wind energy into hydrogen through electrolysis, hydrogen transmission and variances in offshore substations and hydrogen wind turbines, to understand the technical differences between the different offshore wind-to-hydrogen configurations. Additionally, by analysing the hydrogen production process and comparing the scale of hydrogen production in offshore substations or hydrogen wind turbines, the study exhibits the technical feasibility of a wind-to-hydrogen farm with numerous semi-centralised monopile hydrogen substations in comparison with wind-to-hydrogen farms consisting of a single centralised jacket hydrogen substation or decentralised hydrogen wind turbines.

To enable a quantitative comparison of the different offshore wind-to-hydrogen setups in the economic analysis, the LCOH for each configuration was modelled. This process involved creating wind farm layouts and calculating the associated cost for a variety of offshore substations using Vattenfall's optimisation model. Moreover, aspects such as hydrogen production, the dimensions and cost of hydrogen pipelines, and the weight and expense of offshore hydrogen facilities were modelled to estimate the costs associated with hydrogen production and transmission for each configuration.

In the economic analysis, a detailed case study is conducted. The research investigates cost drivers, including wind farm expenses, hydrogen substation investments, and energy transmission infrastructure costs. The results reveal the economic viability of the semi-centralised configuration. The findings highlight the importance of considering monopile load capacity and substructure costs in determining the optimal number of hydrogen substations for semi-centralised configurations. However, the decentralised configuration exhibits a 5\% lower LCOH compared to the centralised and semi-centralised configurations due to the lack of additional substructures and high voltage electrical equipment.

In conclusion, this research contributes comprehensive insights into the techno-economic feasibility of semi-centralised offshore wind-to-hydrogen configurations. The findings highlight the potential of semi-centralised configurations and call for further research and optimisations. Unlocking the potential of semi-centralised offshore wind-to-hydrogen configurations can drive the transition toward sustainable and renewable energy sources.

The replacement of conventional generation units with variable renewable energy sources could have a negative impact on the balance of supply and demand of electricity. Moreover, since the variable renewable energy sources are inverter based and therefore decoupled from the grid, the overall grid inertia will decrease. To solve this problem, the traditional mechanical frequency response can be re- placed by synthetic inertial response and fast frequency response (FFR) alternatives from wind turbines. However, there is uncertainty about the order of magnitude of these ancillary services and how these ancillary services will affect the ultimate and fatigue loads on the wind turbine. The aim of the study is to gain an understanding of the extent to which an offshore wind turbine can provide synthetic inertia and fast frequency response and how this affects the fatigue and ultimate loads on the wind turbine.

Simulations were performed in FASTTool to study the response of the IEA 15MW offshore wind turbine using the baseline controller, synthetic inertia controller and FFR controller. The moments at the blade roots and tower base were used to perform a fatigue and ultimate load analysis. Three different grid frequency data sets were used for the grid frequency inputs of the synthetic inertia controller and FFR controller. In addition, the response of the wind turbine was studied at two different response sizes for both the synthetic inertia controller and the FFR controller.

This study showed a significant increase in fatigue damage equivalent load and maximum stresses due to an increase in the response size of the synthetic inertia and FFR controller. The results therefore showed that the extent to which an offshore wind turbine can provide synthetic inertia and FFR depends mainly on the magnitude of the controller response and not on the size of the wind turbine.

Floating wind turbines despite the the potential to harness energy from deep offshore areas where higher average wind speeds face challenges in terms of competitiveness. One approach to raising the competitiveness of a wind farm is to mitigate efficiency losses resulting from the wake effect. This report focuses on the combination of three notable wake effect mitigation strategies: layout optimization, yaw-based wake redirection, and turbine repositioning.

A preliminary analysis of the combined effect of wind turbine repositioning and yaw-based wake redirection on power performance for the case of two turbines only is performed. Above rated wind speeds, upstream turbine yawing reduces downstream turbine movement, with reductions of around 1 to 4 rotor diameters longitudinally and 0.2 to 0.5 times the rotor diameter laterally, keeping the same level of power efficiency.

Nextly, an optimization problem that integrate layout optimization with yaw-based wake steering and turbine repositioning for power maximization across an extended wind farm is formulated. The optimization frame followed a sequential approach. The results on a case study confirmed that the effect of adding yaw-based wake redirection to turbine repositioning remains significant for multiple turbines, with several percent-point efficiency improvements for small movable ranges. For larger ranges, the contribution of yaw control diminishes rapidly to one percent-point or less. Yaw control enables movable range reductions of 10% to 50%, preserving wind farm efficiency. Yet, reductions are more pronounced in smaller, less effective movable ranges. Below rated conditions, the effectiveness of yaw control diminishes swiftly.

Furthermore, the study delves into the implications of integrating position mooring for turbine repositioning and yaw-based wake mitigation strategies on mooring system performance. This examination employs a proposed methodology aimed at minimizing the position error across most points within the movable range Both the tension of the mooring lines and the static stiffness of the floater showed to be sensitive to the position of floater, the direction of the wind load and the yaw of the wind turbine, with percentual changes ranging from 0.5% up to 50%. It results that the orientation of the mooring lines with correspondence of the prevailing wind direction, as well as that restrictive constraints on the tension and stiffness may be taken should be taken into account when designing a mooring system for turbine repositioning.

Overall, combining , yaw-based wake redirection, and turbine repositioning allows for greater wind farm AEP, with gains contingent on turbine movable range and upcoming wind speeds. Designing position mooring systems must factor in the influence of yaw-based wake redirection and turbine repositioning on mooring system tension and stiffness. More advanced analyses, including dynamic assessments, are essential for comprehending the mooring lines system's response to position mooring for turbine repositioning, and yaw-based wake redirection.

Green hydrogen is expected to play a crucial role in the energy transition as it can be utilised for both storage purposes and as fuel for hard-to-abate sectors. One of the possible configurations for producing green hydrogen is by means of a central offshore hydrogen production platform powered by offshore wind energy. Producing hydrogen offshore facilitates the possibility to eliminate parts of the expensive electrical infrastructure present in conventional offshore wind farms and could result in lower losses.

In collaboration with Vattenfall, this study provides a thorough examination of centralised offshore hydrogen production. The study addresses both the techno-economic feasibility of the centralised configuration and the effects of aggregating the power supplied by individual offshore wind turbines.

In Part 2, the study presents a comprehensive techno-economic analysis of different electrolysis technologies, the optimal hydrogen production unit capacity, and compressor output pressure. The outcomes reveal that an optimal levelised cost of hydrogen can be achieved by reducing the hydrogen production unit capacity compared to the offshore wind farm capacity. Moreover, increasing the hydrogen pressure above the minimum pressure required to overcome the pipeline pressure drop, reduces the levelised cost of hydrogen further. The study reveals a small preference for hydrogen production based on proton exchange membrane electrolysis, in comparison to hydrogen production based on alkaline electrolysis.

In Part 2, the focus is shifted towards hydrogen production solely, influenced by power fluctuations. By using historical offshore wind turbine power output data, it was found that aggregating the power output significantly reduces the normalised power output fluctuations, compared to a decentralised offshore configuration. However, the reduced power fluctuations did not result in a higher hydrogen yield, attributed to the inter-array cable losses of the centralised configuration. Nevertheless, a significant reduction in the number of switches of operational mode and the number of turn-offs of the stacks was observed. Reducing the number of switches and turn-offs will reduce the process of stack degradation.

The study concludes that centralised offshore hydrogen production facilitates the possibility to produce hydrogen at a competitive levelised cost of hydrogen. Furthermore, the reduction of the power fluctuations will benefit this configuration due to the deceleration of the stack's degradation process.

Solar and wind will displace fossil fuels as the main source of energy in a net-zero world. However, renewable energy sources provide intermittent power, hence an energy carrier that enables the balancing of demand and supply is needed. Here green hydrogen comes in place.
In addition, the demand for green hydrogen is expected to rise in the coming decades.
Given the geographical wind resource availability combined with supportive policy, the supply of green hydrogen can be delivered through offshore electrolysis. Moreover, in addition to higher yield, going further offshore creates a stronger case for hydrogen export as power export would become impracticable.
The energy industry is investigating what kind of typology and system configuration is most suitable for offshore green hydrogen production. This report provides insight into the performance of a single wind turbine integrated electrolysis system. For which the effect of different control strategies, electrolyser dimensioning and electrolyser capacities are analysed.

The study comprehends the requirements for transforming a single wind turbine into decentralised hydrogen producing wind turbine. This configuration is designed for an offshore application, but is not restricted to an offshore location. This novel system is equipped with a power conversion system, to power the electrolyser and auxiliaries. Seawater lift with water treatment for desalination and demineralisation. And ultimately, the electrolyser with accompanying balance of system.
This study selects a PEM electrolyser with three parallel modules of 5 MW capacity each. The individual components are separately modelled and combined to complete the system into a mathematical model. Furthermore, a power management strategy is included. The power management strategy determines which, how much and how many modules are powered. The enhanced results are measured by key performance indicators, which are total annual yield, number of start-stop events and power fluctuation within a module. These KPI's are inspired by the drivers of Shell to get the lowest levelised cost of hydrogen. More hydrogen production drives down the costs and the two other KPI's ensures less degradation on the modules, therefore extending the longevity.

This report shows that the use of a power management strategy improves the annual yield, but is also capable of minimising the effect of degradation caused by start-stop events and power fluctuation. The equal power division strategy increases the annual yield by at least 2%. The total number of power fluctuations can be significantly reduced by using the segmented start strategy. Finally, a strategy is developed to enhance the longevity of the system and diminish the degradation of the modules.
Moreover, independent of the strategy, a higher annual yield is achieved by decreasing the size of the modules with the same total electrolyser capacity. However, only when it is operated on the right setpoint.
Furthermore, over-sizing of the electrolyser capacity results in under-utilisation of the electrolyser. While under-sizing the electrolysis capacity leads to an increase in performance as the system is utilised more efficiently. The results are tested and strengthened in a sensitivity study, where other wind conditions and design parameters are applied to the system.

Recently, there has been an increase in interest in floating wind turbines that are located offshore. These turbines allow for the harvesting of the power of the wind far offshore, where wind speeds are often higher.

Compared to their fixed counterparts, floating wind turbines allow for a certain mobility after the installation. This allows wind farm developers to consider layouts that change throughout the wind farm’s operational phase. The change in layout can increase the energy yield of the wind farm, which may reduce the cost of floating wind energy.

This Master’s Thesis presents a new method for wind farm layout optimization with movable floating offshore wind turbines. The objective function that is maximized is the annual energy production (AEP). The proposed method first finds the optimal installation locations of the turbines, then searches for the optimal wind farm layout for each wind direction while considering the movable range of the turbines. Different movable range sizes are considered in the analysis. These sizes range from small (there is almost no mobility allowed) to large (the turbine is allowed to move anywhere in the wind farm). The results show that the steepest gains are achieved for a movable range size of up to two rotor diameters (i.e., the turbine is allowed to move two rotor diameters in each direction, evaluated from the installation position). Above this range, a large additional movement is required for a minor increase in AEP. Moreover, for this movable range size, repositioning turbines is so effective that their installation positions almost do not affect the AEP.

In addition to the previous method, this Master’s Thesis also presents a novel method to assess the movable range of floating offshore wind turbines. In this method, it is assumed that the mobility is achieved by adjusting the mooring line lengths through a winch system on board of the floater. The proposed method optimizes the line lengths such that an equilibrium is obtained in the relocated position. Various locations are selected for the analysis that cover most of the mooring system footprint on the seabed. The results show that the assumed movable range shape is not the same as the actual movable range shape.
For a 15MW floating offshore reference turbine, the movable range size with the steepest gains in terms of AEP (two rotor diameters) and the actual movable range are compared. The results show that the actual shape covers large parts of the circular shape.

In conclusion, large gains are expected in terms of AEP for movable floating offshore wind turbines. This brings us one step closer to reducing the cost of floating wind energy, which in turn increases its competitiveness with other energy resources.

Producing hydrogen from renewable energy sources will play a pivotal role in the energy transition. It can reduce emissions in hard-to-abate sectors and be used for grid balancing services. The energy industry is looking into multiple different system configurations to produce green hydrogen. One such system is an offshore stand-alone wind turbine with the sole purpose of producing hydrogen. The reason for this interest is due to decreasing offshore wind costs, electrolyzer capital expenditure requirements are dropping, and such a system will have high electrolyzer operating hours. Further cost reductions can be achieved by substituting the electrical infrastructure in offshore wind farms as well as on the wind turbine, for hydrogen infrastructure.

When directly connecting an electrolyzer to a non-grid connected fluctuating power source, it will be hard to prevent frequently turning the electrolyzers on and off. That has been found to accelerate component degradation, thereby reducing the system lifetime.

This report aims to address how the system design and the advisory control strategy can increase hydrogen production while decreasing the number of electrolyzer turn-offs. The investigated system comprises a 20 MW wind turbine directly connected to PEM electrolyzers, a desalination system, a
water tank, and a battery. Two PEM electrolyzer configurations were compared, namely 4x5 MW and 2x10 MW. Furthermore, two interesting system additions were analyzed. Firstly, the inclusion of a weather forecast to aid the advisory control with making decisions on when to turn electrolyzers on.
Secondly, an additional storage element that could keep the last electrolyzer idling during a period of low wind speeds.

The individual components of the system were firstly modeled and then connected to get a representative system model. Two different advisory control strategies, which operate the components, were then designed to simulate the system behavior with regard to hydrogen production and the number of
turn-offs, among other key performance indicators.

This thesis project was done in collaboration with Vattenfall, who provided access to 5-second resolution power output data from a single offshore wind turbine. Using that data, different system designs and versions of the two advisory control strategies were simulated with the aim of selecting the best system design and advisory control strategy.

The results showed that the system design and advisory control could significantly reduce the number of electrolyzer turn-offs while producing close to the highest potential of hydrogen. The weather forecast and additional storage element brought substantial benefits regarding the electrolyzer turn-offs but did
not largely impact the hydrogen production.

Offshore wind farms designed solely for hydrogen production are promising solutions for maximizing wind energy conversion, decarbonizing industries that cannot directly utilize electricity, and reducing the need for additional grid reinforcements. Furthermore, floating offshore wind turbines enable the capture of wind resources in deeper waters. This has created the possibility of locating wind farms far offshore. This study looks into the technological and economic feasibility of in-turbine hydrogen production, storage, and transport via vessels from far offshore floating wind farms. Transport of hydrogen via pipelines and transport of hydrogen via a large vessel connected to the entire wind farm are also studied for comparison and bench marking purposes. To investigate the performance of various transport methods, a wind farm model is built that includes the components required for hydrogen production at the wind turbine as well as the components required for hydrogen transport. The model simulates wind farm operation, vessel operations with regard to onsite storage, and vessel operations when connected to the entire wind farm. Based on the levelized cost of hydrogen(LCOH), the performance of the three different farms has been compared. The study was conducted over distances ranging from 100 to 700 km. Throughout the range of distances studied, on-site hydrogen storage and periodic removal via vessel proves to be the least cost effective solution. Weather conditions are seen to be a significant factor in the operation of the vessel fleet servicing the farm with on-site storage. When combined with a four-vessel fleet servicing the entire wind farm, the optimum storage size in the farm type with onsite storage is found to be equal to the wind turbine average weekly production. A key distinction is seen in the cost trends, a steady increase is seen in hydrogen transport via pipelines with increase in distance, while, the LCOH of hydrogen remains nearly identical for the transport of hydrogen via vessels over the range of distances studied. The farm produces the most hydrogen with pipeline transport of hydrogen followed by transport of hydrogen via a large vessel, and the least hydrogen with in platform hydrogen storage and periodic emptying of the storage by vessels. The study indicates that the pipeline transport of hydrogen is the most cost effective transport option.

The objective of the thesis was to evaluate the cost reductions and tower design when production costs are included in the design process of an offshore wind turbine tower. First, a tower cost model had to be developed. Then, based on the findings, a cost optimization model was built with the tower design software from Siemens Gamesa Renewable Energy (SGRE). Three scenarios were developed
to mimic different supply chains. The results show that the production costs can be reduced by [0.2, 2%]. Moreover, in each scenario, a different optimum tower design was found. Another study into the optimum number of shells per section showed wind turbine manufacturers could reduce production costs up to 20%.

One of the major challenges that the world currently faces is the energy transition. The aim of most countries worldwide is to reduce their carbon footprint, in order to slow climate change. Fossil fuel powered energy generation is replaced with an increasing share of variable renewable energy sources such as wind and solar energy. Because of the inherent uncertainty and intermittency of these renewable power sources, large scale energy storage is considered inevitable in order to mitigate the mismatch between supply and demand. However, storage comes at a cost and uses precious materials, of which there might not be sufficient. Therefore, a whole range of solutions is being researched and implemented. Currently, it is not well-known what mix of which solutions will be the most technologically and economically effective. The Low-Wind turbine is a new turbine concept, specifically designed for low wind speed conditions, combined with a low rated and cut-out wind speed. The reduced normative loads on the blades enable a re-design of several components, which ultimately results in lower costs. This new turbine concept aims to be a system-friendly turbine, by decreasing the mismatch between production and demand and thereby reducing the total amount of storage or overplanting required in the system. This research assesses the effectiveness of the Low-Wind turbine in the Dutch energy grid, when it is predominantly powered by renewable energy sources. A power model, specifically developed for this research, simulates the power flows and optimises the seasonal storage required in order to meet the constraints. The power model is simulated for a range of installed turbines, consisting of combinations of conventional and Low-Wind turbines. This research also carries out a preliminary design off a Low-Wind turbine, based of a reference turbine, in order to determine its costs. The result of this study show that, if the cost of the installed wind farms dominate the costs, Low-Wind turbines does not provide a cost-effective solution to minimising system costs. However, the results also show that, in a situation where total costs are dominated by storage cost, the Low-Wind turbine can provide a cost-effective alternative to conventional turbines. The results also show that, for high overplanting factors, Low-Wind turbines and conventional turbines provide a similar effect on the reduction of system costs, but at lower costs.