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.

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.

The development of a wind farm is a highly sophisticated task, whereby many stakeholders are involved and several unique disciplines come together to form a whole. Commonly, the unique disciplines are optimized individually which leads to sub-optimal windfarm designs. Therefore, it is of great importance that an interdisciplinary approach is used to overcome sub-optimal designs and that they work together to accomplishing a common objective. To capture the interdisciplinary dynamics of the different disciplines, a Systems Engineering (SE) approach is used. This approach makes it possible to design the wind farm in an agile manner, whereby the in- and outputs, from the different disciplines, are coupled to accomplish a combined objective. The foundation of systems engineering in this report is the Multidisciplinary Design Analysis and Optimization (MDAO). The MDAO framework includes models for various disciplines in a wind farm, such as the wake aerodynamics, rotor nacelle assembly, support structure, cabling, etc. The MDAO framework facilitates system-level analysis by capturing interdisciplinary interactions - both implicit and explicit - to analyze the system for a particular objective. The research objective of this thesis is to determine the effect of up-scaling on the optimum design of an offshore wind farm for different drive train configurations. This is done by constructing engineering models and implementing these in the MDAO framework. The analysis will specifically focus on the three configurations: Doubly Fed Induction Generator with a 3-stage gearbox (DFIG - 3S), Permanent Magnet Synchronous Generator with direct drive (PMSG - DD), and Permanent Magnet Synchronous Generator with 1-stage gearbox (PMSG - 1S). The implementation of the updated models, will contribute to the dissemination of knowledge on the utility of the MDAO framework, whereby the process of selecting the optimal drive train configuration will become easier. Alongside, the updated models implemented in the framework will result in better cost predictions and therefore a wind turbine size closer to the optimum will emerge. At first, the missing links of the current drive train models are tackled by the implementation of the higher fidelity engineering models. This is done for the generator and gearbox of the three drive trains configurations. The updated engineering models assure better estimations of the Levelized Cost of Energy (LCOE) and therefore a better estimation of the optimum wind turbine size in offshore wind farms. Once the models were updated, the framework was run for two case studies: a far offshore wind farm and a nearshore wind farm. This leads to an optimum wind turbine size in the range of 4 to 6 MW. The optimal wind turbine sizes for the different configurations are very close to each other. The DFIG - 3S configuration is the most economical option, followed by the PMSG - 1S configuration, thereafter the PMSG - DD configuration. The sequences applied for both the wind farms that were analyzed and for all scales when upscaling the wind turbine. The PMSG - 1S is a promising configuration, whereby further cost reductions in the permanent magnets is expected and further optimization and integration of the power electronics is possible. The optimum power densities for both wind farms were similar, whereby the spreading in power density was large. The optimal wind turbine size when upscaling was found for power densities from 200 to 400 W/m2. In the far offshore wind farm, the optimal configuration was a 6MW DFIG - 3S wind turbine with a power density of 290 W/m2. The optimum power density in the nearshore wind farm was 209 W/m2 for a 4MW PMSG - DD wind turbine.

One of the main drawbacks of offshore wind energy is its high levelized cost of electricity (LCOE). One explanation for these high costs arises from the large amount of uncertainties that come with such complex projects. As a result of this complexity, it’s difficult to foresee the course of events in advance. Decisions made during the preliminary design phase are often based on limited data while having a great impact on project outcome. A tool is needed to assist engineers during these early stages of design. This tool should deliver good results using limited input data and require little computational time. An example of such a tool is TeamPlay; an engineering model that evaluates offshore wind farm design using automated optimization techniques. In its current state, only a monopile type foundation is analyzed within this process. Since the current trend in the industry is to build larger farms further from shore, this foundation type will become less popular in the future. A jacket type foundation is better suited for far-­‐shore application. In this thesis, a new stand-­‐alone engineering model is created which can be added to TeamPlay’s functionality to extend future use...

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.

In the past, the vertical axis wind turbine (VAWT) lost the competition to its horizontal axis counterpart, having (wrongfully) presumed disadvantages like increased fatigue and low efficiency. Little research and development into the VAWT led to a large gap between the maturity of technology of both turbine types. Now that due to modern techniques the VAWT experiences renewed interest, topics like airfoil design are reinvestigated. One phenomenon particularly, plays an important role in VAWT aerodynamics: flow curvature. Due to the VAWT airfoil’s rotation about an offset centre, there exists a chordwise angle of attack variation. Also, the added rotational velocities will alter the pressure distribution and boundary layer of the airfoil, leading to a change in force distribution and turbine efficiency. This research sets out to chart these flow curvature effects and implement suggested models to cope with them. Furthermore, using a pitching airfoil model, an implementation in the airfoil analysis code XFOIL will provide the possibility to investigate inviscid and viscous flow curvature effects. What effect these have on airfoil design shall be found using an airfoil optimiser, generating optimal airfoils for various levels of flow curvature. This thesis has applied six models authors suggested to investigate flow curvature. By applying transformations to virtual airfoils, leading to added camber and incidence angle, the researchers thought to mimic rotating VAWT airfoils in straight flow. Comparison with each other and a solution of a verified panel method showed that their approximation is reasonable within bounds. When the pitch rate and location is kept to practical values, also the difference between the methods is very little. Therefore the methods can be used interchangeably. A pitching model has been devised, showing that the chord-to-radius ratio an be simulated by the pitch rate of a pitching airfoil. As the chord-to-radius ratio determines the amount of variation of angle of attack over the chord due to flow curvature, this model can be used to investigate flow curvature effects. The model has been applied in XFOIL and the results show a good comparison to the benchmark panel code. There still exists a discrepancy between the solutions, inherent to the difference calculation methods and dependent on the pitch location. The latter determines the arm to the surface and therefore the magnitude of rotational velocity, which increases the error with respect to the benchmark. Cambered airfoils and airfoils at a larger pitch setting showed less susceptibility to flow curvature. The modified version of XFOIL is used in an optimisation campaign to investigate the impact of increasing chord-to-radius ratio. The method proved to be slightly unstable and therefore little data is obtained. Of the dataset the following trends can be obtained, using the least-squares method. With increasing chord-to-radius ratio, the camber tends to become more negative and shift forward. This is the optimiser trying to maintain optimal power, by choosing airfoils which will stall later to avoid power loss. Also, this results in thinner profiles with their maximum thickness more aft. Finally, the optimal airfoils have been applied in a two-dimensional VAWT analysis model. This showed that there is very little power gain, and possible power loss when applying the pitch optimised airfoils.

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.

The rapid growth in world population and increasing demands have led to the lack of fresh water, taking a toll on several of earths reserves, mainly the fresh water supply reserves. Water stress deters economic growth, leads to conflicts and has a direct impact on the health of humans. Studies show the trends in the increase of water consumption per capita due to increase in higher standards of living over the last years, resulting in the decrease of usable high purity water. 97% of the world’s water supply is locked in the salted, often unusable oceans. In recent times, water stressed countries are using the saline water from the oceans and desalinating it to produce fresh water for domestic, industrial or agricultural use. The state-of-the art method for desalinating saltwater is by Reverse Osmosis (RO). The biggest drawback of this technology is its high energy consumption mostly provided by conventional sources like fossil fuels. Therefore, for a sustainable future, a renewable energy source must be integrated to power the RO system. Delft Offshore Turbine (DOT) is currently developing and testing a new hydraulic drive train solution for fluid power transmission in offshore wind turbines using seawater as the medium. A hydraulic positive displacement pump is driven by the DOT wind turbine creating a flow of sea water under high pressure. This high-pressure flow can be either directed to a RO unit to desalinate seawater or converted into electricity using a spear valve and pelton turbine generator. A major challenge while using wind as an energy source is its intermittency. Reverse osmosis plants are designed to operate at a fixed flow and pressure while due to the uncontrolled, varying nature of the wind, the pump output experiences fluctuations in both pressures and flows. The aim of this thesis is to analyze the steady-state behavior of the integrated system for wind speeds up to the turbine rated wind speed under different operating conditions. This is achieved by simulating the behavior of the DOT500 hydraulic drive train wind turbine coupled to a RO system with pressure exchanger energy recovery device and a nozzle with a pelton turbine generator. The main objective of this research is to build a numerical model in Python using algorithms to solve the system of steady-state equations and optimize the integrated system for maximum water and maximum electricity production at specified locations. The numerical model is simulated for all combinations of wind speeds and nozzle positions and the behavior of the high-pressure pump, RO system, pelton turbine and various system parameters are shown. A sensitivity study is performed for important desalination parameters and their effect on system performance is analyzed. This research has yielded three main conclusions / deliverables: 1. Behavior of the wind powered integrated system to produce freshwater and electricity at different operating conditions. 2. Steady state control of DOT500 turbine and behavior of the pelton turbine to produce either maximum electricity or maximum water. 3. Sensitivity of important desalination system parameters on overall system behavior for future optimization of RO membranes.

The reduction of the Levelised Cost of Electricity (LCoE) in wind energy, and offshore in particular, is among the main objectives of research in the academia nowadays, and a demanding task as well. Offshore wind farms are capital intensive investments and lowering uncertainties and costs throughout design, planning, installation and operational phases will offer cheaper electricity production and a more competitive nature against fossil fuel powered energy. Of course, a big part of the total cost of a wind farm is the wind turbines themselves. Innovations in the design and manufacturing processes are always welcome in order to further advance within the learning curve of the technology and achieve efficient economies of scale. Furthermore, the blades of the wind turbine rotor are its most important component because they express the most basic operation of the turbine, aerodynamics and energy capture. Yet they pose structural challenges. There are efforts to maximise energy output while keeping their mass low, which should subsequently drive down secondary costs. Additionally, another important factor is the increase of energy output in the farm level that can lead to a larger cost reduction. This thesis aims to investigate the performance and feasibility of lightweight, low power density rotors. This investigation is made by acquiring a performance baseline with the reference rotor of the 10 MW INNWIND machine and comparing it with the proposed alternative rotor designs by means of parametrical modifications. The reference machine rotor radius is 89.166 m, with a blade mass of 41.7 tn and a rated power output of 10 MW operating at an optimal lambda of 7.5. All the new designs include an increase in rotor radius to 103 m. They also include differences in operational parameters such as rated rotational speed, blade slenderness and tip speed, while rated power stays the same. These designs result in different blade masses and allocation of energy production...

The global issue on global warming leads nations to reduce their carbon emission, and one way to do it is by decarbonising the power system and employing higher penetration of renewable energy technology. However, due to the variable nature of renewable energy, their integration to the power system poses challenges to the utilities and system operators. Hybrid power system, due to its feature of complementary generations, serves as one of the option to answer the integration issues. This research studies the optimisation of a hybrid power system, consisting of a wind turbine and solar PV, by designing the wind turbine that operates in such systems. The design approach of the wind turbine design emphasises the complementary generation feature of the hybrid power system, which is conducted by optimising the wind generation for times when the output power from the solar PV are low. Thus, the wind turbine design considers the diurnal and seasonal variation. The diurnal turbine design is optimised for the night-time, and the seasonal turbine design is optimised for the low solar irradiance season. The wind turbine design is focused on the conceptual design phase with the objective of rotor diameter optimisation that generates electricity with the lowest cost. The cost function employed is taken from the NREL mass and cost model with additional adjustment, due to the different scaling approach. The data for the design process is obtained from a case study to represent real generation data, and the chosen location is Muppandal, India. The research aims to identify the impact of the specific operational conditions on the design parameters and the design result. Subsequently, the impact on the system performance is observed by modelling the hybrid power system in different topologies that include zero-curtailment, grid-constrained and demand load-supplying topology. The result on the site condition indicates that the affected important design parameters include wind speed distribution, wind shear profile and turbulence intensity. The research limits the analysis only on the wind speed distribution and the wind shear profile. The site condition analysis of the case study indicates that the diurnal variation of the wind speed distribution is similar to the full-year wind speed distribution and the seasonal variation that consider the season with low solar irradiance coincide with the low wind speed season. In zero-curtailment topology, higher wind speed distribution leads to smaller optimum rotor diameter and vice versa. In the grid-constrained and demand load supplying topology, larger rotor diameter suffers from curtailment due to the limited grid capacity and low demand load level. This condition leads to the shifts of optimum rotor diameter to the smaller rotor. The level of curtailment is higher in the demand load-supplying topology due to the overall lower evacuation capacity. When the night-time design and low-wind speed period design is fully operated in a year, the wind turbines are not operating at its optimum, and higher cost of electricity is expected. This result implies the higher cost for designs that correspond to the diurnal and seasonal variation. The storage system is applied to save the curtailment of wind energy. The result of this analysis suggests that the relationship between the amount of saved curtailment and the capacity of the storage is linear for higher storage capacity (<10%) and non-linear at lower storage capacity. It is found that the first few additions of storage yield the most cost-efficient of curtailment saving. The cost and benefit analysis of the storage system also indicates that the current cost of the storage technology is not compensated by the benefit of evacuating the curtailment.

Currently, the design approach in the wind industry is to perform sequential optimization of different disciplines like wake aerodynamics, turbine, support structure, etc., which might fail to capture the interactions between these disciplines, leading to a sub-optimal design. Literature suggests that a Multi-disciplinary Design Analysis and Optimization (MDAO) tool that integrates all the different disciplines of a wind farm results in a lower LCOE value compared to the conventional approach. However, of all the existing tools, some of them lack user agility (do not cater to all the stakeholders of a wind farm), demand high computational resources, or use low fidelity models. This thesis deals with the wind turbine discipline, with a focus on rotor optimization. The existing framework of WINDOW (the tool being developed at TU Delft) uses a low fidelity static model for the rotor, with a safety factor of 1.5 to account for the missing dynamic effects of loading. To study the implications of the same, a high fidelity dynamic model with an aero-servo-elastic coupling, is integrated into WINDOW, and the differences resulting in the optimized design, from the two models, are evaluated.

Wind energy is the most promising renewable energy source for the Netherlands in the energy transition period. However, the investment costs of the offshore wind are huge. Until now, the government was supporting the investments in wind farms with subsidy schemes irrespective of the electricity market dynamics. The latest large-scale offshore wind projects in Germany and the Netherlands (Hollandse Kust Zuid 1 and 2) have been awarded zero-subsidy. However, in the Netherlands, the transmission costs of the offshore wind electricity are socialized. This would force the un-subsidized wind-farms to feed their electricity into the public grid exposing them directly to the whole sale electricity market. With large shares of wind penetration in the market, the value of the electricity is declining. At the same time, the intermittent nature of the renewable energy sources generates large demand for flexibility in the electricity system. These pros and cons of renewable energy sources create new opportunities for electrification of other sectors to support achieving Paris climate agreement goals of the country. Heat and hydrogen sectors are identified as potential flexibility options to facilitate the de-carbonization of the energy system by 2050. European electricity market simulation model COMPETES is identified as potential tool to assess the integrated systems at national level. However, the flexibility provided by heat and hydrogen demands with thermal and hydrogen storage technologies is not part of the model directly. Therefore, an optimization model is developed to determine the size of power to heat and power to hydrogen systems with least cost. The results of this problem determine the outlook for investments in power to heat and power to hydrogen technologies. The problem also determines the operational strategy of these units in response to the hourly power prices. Consequently, the coupled implications of the emerging electricity load from heat, hydrogen markets on the national power system is studied. Industrial heat, domestic district heat networks currently provided by combined heat and power gas plants in the Netherlands and the developments in hydrogen consumption market are taken as study cases for assessment. This work provided insights about the opportunities, threats and solutions for the involved stakeholders.

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.

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.

The models with different fidelities for the siloed application of niche wind farm disciplines - rotor aerodynamics, aeroelasticity or wake aerodynamics - are prevalent in literature. These models are often used sequentially while designing a wind farm that may lead to a sub-optimal design due to their agnosticism towards the inter-disciplinary influences. This paper demonstrates the multi-disciplinary optimization of rotor nacelle assemblies for offshore wind farms. The designs of three aspects of rotor nacelle assembly are addressed - rotor blade, power density and drive train configuration - that support the development of an open-source agile systems engineering framework and allow flexibility in their utility to various stakeholders of offshore wind farms.

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.

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.

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.

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.

In order to assist project developers in efficient offshore wind farm installation planning a decision-support tool has been developed. The tool combines Discrete Event Simulation and Black-box Optimization. The focus of the development was on providing the flexibility allowing a user to compare various installation strategies and impact on the total installation cost and vessel workability. Synthetic weather generation with Markov Chains was implemented in order to account for weather effects. Recomendations have been given for weather modelling (for the purpose of installation planning) and for applying different families of black-box optimization algorithms.