The global emission of harmful greenhouse gasses has to be reduced. Commercial shipping contributes to these emissions by using fossil fuel as the only energy source to provide propulsion and power auxiliary systems. In order to reduce fuel consumption, much research is focused on increasing the efficiency of the propulsion system and reducing the required power consumption. In recent years an increasing amount of research focuses on utilizing wind energy as an alternative energy source. This is a renewable source of energy which is plentiful at sea. This thesis focuses on the novel concept of using a Vertical Axis Wind Turbine (VAWT) as a means of ship propulsion and power generation. Existing Wind Assisted Ship Propulsion (WASP) systems can only be utilized in conditions when the ship is in transit and when the apparent wind conditions are favorable. The VAWT concept has the ability to generate power in wind conditions where conventional sailing systems are not functional, including when the ship is in port. This system can also be used as a thrusting device when the wind conditions are favorable for sailing systems. Therefore this system can be used more frequently which is beneficial for the overall power savings. The use of a VAWT for WASP in combined operation as a thruster and a power generator does currently not exist. Therefore the design of the rotor has to be investigated and optimized in order to evaluate effective designs for different conditions and to compare this device to existing sailing concepts. The aerodynamic performance of the VAWT will be evaluated using numeric simulation models. This model will be coupled to an optimization algorithm in order to find the optimal design parameters for different wind conditions and modes of operation. This project will result in a better understanding of the working principles of VAWT used for WASP and the potential energy saving of optimized designs for the operational modes as a generator, thruster and combined-operation. There is a large opportunity for capturing wind energy at sea. This project has the potential to add a new method of ship propulsion to reduce shipping emissions and reducing the cost of ship operation. When one or multiple of these systems can be applied on a large share of the worldwide shipping fleet, this research can contribute to the reduction of commercial shipping emissions.

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 idea behind Power-to-Gas (P2G) is to help provide flexibility to renewable energy sources such as wind farms with intermittent nature. Additionally, hydrogen shows a great potential to help decarbonize several industries and its demand is expected to rise massively. Several studies for the technical and economic feasibility of P2G show possibilities of positive business cases far offshore. Platforms, owing to their minimal construction time and lower environmental impact provide an interesting choice of hub structure to equip electrolyser systems. However, gaps exist in the understanding of the costs of such a P2G offshore platform, driving factors, equipment involved, capacity limit and the feasible substructures to support such a facility. The main goal of this thesis is to increase the knowledge of system integration of offshore wind and electrolysers, estimate the scale and size of such a platform involving stacks, balance of plant, power electronics, auxiliary systems and the substructure supporting the topsides. In line with this goal, the study details the system design and parameters, estimates costs of each of the components involved and finally builds a cost model to understand the driving factors for an economical design of such a facility offshore.

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 human eye has turned itself back to the sky with the commercialisation of the space industry, and a new goal has been set. Setting foot on the Red Planet is the next stage of the human exploration of the universe. The travel to Mars is very lengthy and costly, nonetheless the planet still shows great potential for sustaining human life. To make this a possibility, there is a need for locally sourced energy. The presence of (re-)usable resources on Mars could pave the way to further expand the exploration to an interplanetary scale, and successfully maintain a human presence outside the Earth's atmosphere. The availability of energy will be a key indicator for the success of the human race in the colonisation of Mars. To answer this call for the need to generate locally sourced energy, the design of a renewable energy system was started by a team of students and staff from the faculty of Aerospace Engineering at Delft University of Technology: The Arcadian Renewable Energy System (ARES). The energy system will power the construction and operations of a Mars habitat, to support the livability of humans. The system will use complementary renewable energy sources integrated into a microgrid, to sustainably harvest energy from local Martian environment and resources. To ensure the design will be able to fulfil its purpose, a mission need statement and a project objective statement are generated: Mission Need Statement: To provide renewable energy supply of 10 kW to a Mars habitat. Project Objective Statement: Design a renewable energy supply system, primarily focusing on wind energy, which provides 10kW to a Mars habitat, by 10 students in 10 weeks. Synthesis Exercise (DSE) will last a total of 10 weeks, beginning on the 20th of April, ending on the 2nd of July, with a poster session and symposium. The DSE is in collaboration with the Architectural faculty, where a separate team of students is working on a rhizomatic Mars habitat project as part of an ESA competition, which has an ESA-ESTEC feasibility study proposal incorporated. Due to the multi-disciplinary nature of this project, it is important that the DSE team produces a complete and verified design as the outcome. The Design The design the DSE has come up with consists of two energy production systems, namely the primary and secondary energy system providing wind and solar energy, respectively. In addition the system also consists of a power management and energy storage system.

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.

Hydrogen is emerging as a promising energy carrier that can potentially solve the challenges like long-term storage and intermittent power supply associated with a 100%-renewable economy. Moreover, hydrogen can be used in industry sectors such as steel manufacturing and aviation, which struggle with carbon abatement. To increase the supply of green hydrogen, the European Union aims to have at least 40 GW of renewable energy sources connected to electrolysis by 2030. In light of this ambition, the Dutch government recently issued an offshore wind tender that should incorporate 500 MW of offshore electrolysis capacity. A hybrid farm with offshore electrolysis contains both a hydrogen pipeline and an electricity cable as the export connection to shore. Appropriately sizing these connections to ensure financial feasibility becomes a design challenge for wind farm developers as the technology is still maturing. This study considers a case study of an offshore hybrid wind farm situated in the European North Sea, connected to the Dutch energy infrastructure. A Python model was developed to simulate the sales and production of hydrogen and electricity on an hourly time scale. The simulation was executed by using historical data for electricity pricing and assuming a perfect forecast from a developer’s perspective. The objective function was to determine the optimal ratio between electrolyzer and electricity cable capacity (EC ratio) to maximize the net present value (NPV) of such a project. A sensitivity analysis on various system parameters was performed, and multiple scenarios reflecting potential future circumstances were simulated. The study revealed that both oversizing and downsizing the total export capacity was not beneficial. Instead, the optimal EC ratio followed a linear trend, where the sum of connection capacities equaled the total farm capacity. The hydrogen price, electricity price, and nominal efficiency of the electrolyzer were identified as key factors influencing the optimal EC ratio. This research establishes optimal EC ratios for a range of hydrogen prices spanning from €3/kg to €8/kg based on different scenarios. For each scenario, different electricity prices and electrolyzer specifications were defined. The findings indicate that including an electrolyzer in the design is not economically viable for hydrogen prices below €4.00/kg. Conversely, an electrolyzer-dominated system becomes favorable in each scenario when the hydrogen price exceeds €7.50/kg. For prices in between, optimal EC ratios resembling hybrid systems were identified depending on the other key parameters defined by the scenarios.

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.

Transonic buffet is an aerodynamic instability that appears on aerofoils and wings at certain combinations of Mach number and angle of attack, and which limits the aircraft flight envelope. This thesis project presents an experimental investigation of buffet employing stereoscopic PIV and Background Oriented Schlieren. By using four aerodynamic models, a 2D aerofoil and three 3D wings with sweep angles of 0o, 15o and 30o, the differences between the 2D buffet typical of aerofoils and the 3D buffet typical of swept wings is studied, scrutinising the influence of the sweep angle. The results confirm that for the same aerodynamic conditions the 2D buffet experiences larger shock oscillations than the 3D case. A frequency analysis reveals a clear peak at 160 Hz for the 2D case, which is also visible in the 3D case for low sweep angles. As the sweep angle increases, this peak is replaced by a bump at higher frequencies.

The potential gain in energy production and profit by improving the placements of turbines within a wind farm is driving interest. However, finding the optimal placements provides a complex problem. A large number of inter-dependent design variables create a design space that is difficult to solve. Therefore there is much attention for offshore wind farm layout optimisation (OWFLO) in practice and literature. Most of the research is done in selecting and creating the best optimisation algorithms, wake models and cost models. This is not yet another study into better modelling or optimiser selection for OWFLO. Instead, this study aims to provide insight into what performance can be expected from OWFLO and to know when further optimising is not justifiable anymore. The study consists of three parts. All three parts make use of a referent. A referent can be considered a close representation of reality, obtained by a best-practice implementation of the optimisation problem and its associated models. It is assumed that the referent has the same characteristics as reality and that deviations of other implementations of OWFLO from the referent are representative of their deviations from the true optimisation problem.\ In this study, the referent is defined by, amongst others, the use of the Bastankhah and Porté-Agel Gaussian wake model, a 12 sector wind rose with a Weibull distribution per sector and the gradient-free covariance matrix adaptation evolution strategy. The referent is used to maximise annual energy production (AEP). The first part uses the referent to find and understand the characteristics of the OWFLO problem. Wind farms with 9, 25 and 64 turbines have been optimised 100 times with the referent. The results show a small spread in the performance of the found optimised layouts, indicating that many local optima exist with similar performances in an OWFLO problem. The spread between the highest and lowest found performance decreases with increasing numbers of turbines. A special form of the response surface is used to visualise the response surface. The visualised response surfaces, with only two design variables, showed that the wakes of the turbines created multiple local optima. The second part compares performances from optimised layouts with 25 turbines resulting from optimisations with alternative implementation choices, evaluated by the referent model. The performances are represented in boxplots for 100 optima each. The boxplots show that the influence of alternative implementation choices depends on the slightly different locations of the local optima in the design space and the roughness of the response surface they create. The influence of the shifts in locations of the local optima on the performance turned out to be minimal. An increase in the roughness of the response surface meant an increase in the spread of the performances. The difference in performance resulting from the alternative optimisers indicates that improvement of a state-of-the-art optimiser is not expected to lead to much better results. The third part explores the need for improvement of the analysis by adding a phenomena currently not considered in OWFLO. The influence of neighbouring wind farms on layout optimisation without including atmospheric stability is explored. Three cases have been defined to show the influence of neighbouring wind farms on layout optimisation. It is concluded that adding neighbouring wind farms for accurate energy yield assessments is necessary. However, for layout optimisation, the benefit of including neighbouring wind farms is not evident.

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.

With an increased demand for renewable energy wind farms, their efficiency receives growing attention from both the industry and academics. Mitigating wake interaction effects in wind farms is one of the ways wind farms could increase their efficiency. Control techniques to increase wake reenergizing are currently under development, however, are being held back by a lack of available medium-fidelity wake modeling methods. To sufficiently support developments in the wind industry, the wake model should yield an axial wind profile that can be used for load calculations for the downstream wind turbine and assess its energy production. Moreover, for the model to be useful in the research effort the method must either show an increase in accuracy or a decrease in time-cost. Finally, the model is desired to include the effects of wake control techniques in later iterations outside the scope of this research. This thesis investigates medium-fidelity models for wind turbine wake control techniques, with an exploratory study into applying a semi-infinite spectral method with an adjusted Laguerre basis to wind turbine wake modeling. The wake model used in this research is an altered version of the Ainslie wake model. To model the wake model a spectral method with Laguerre functions for the basis is employed in the radial direction and a marching scheme with a piecewise linear basis for the basis in the downstream direction. The potential benefits of spectral methods are lower rank systems and spectral convergence. The adjusted Laguerre functions used for this research naturally fit the boundary conditions for the wake model. At the start of the domain, a Dirichlet boundary condition is applied with fitted Laguerre functions to the result of a blade element simulation. The results did not account for wake expansion and diffused the wake much sooner than physical. The implementation of the explicit formulation for the triple product integral hindered higher-order simulations, disabling research into simulations for domains much higher than 11 radial modes. The errors for the different conservated quantities are significantly higher than they should be. From the verification efforts, a relation can be observed between the number of radial modes in the domain with respect to the number of radial modes used for the inflow, which suggests that the model should use much higher numbers of radial modes than this implementation allowed. i

The energy transition towards carbon neutrality requires a rapid electrification of all energy sectors by 2050. In the EU-27, the REPowerEU strategy, initiated in March 2022, is pursuing this target even more ambitiously. However, in order to achieve the aforementioned goals, the increasing demand for green hydrogen will cause an increase of the renewable energy needs as early as 2030. In this way, offshore wind can be a solid supplier of the renewable energy for green hydrogen production. However, since nearly 80% of the worldwide wind energy potential is situated in deep waters, floating offshore wind turbines (FOWT) can be used to cover those energy needs. In addition, the literature review showed that when green hydrogen production via FOWT is considered, the most economically and energy efficient layout is the in situ topology, where hydrogen is locally produced on the FOWT. Although FOWT and green hydrogen production via FOWT have been lately examined in literature, a literature gap was found. More specifically, no attention was given on the performance change of a turbine when it is adapted from a bottom fixed (BF) application to a FOWT. Also, the effect of the in situ hydrogen plant to the FOWT performance was not considered. Thus, the aim of this project is to highlight if FOWT for in situ hydrogen production should be aerodynamically redesigned to improve their performance or to tackle possible energy losses. In this direction, several sub-questions should be answered, including the selection of turbine, floater type and site to be investigated, the effect of the floater design on the FOWT performance, the performance change of a turbine due to its adaptation as FOWT and the effect of the added mass of the hydrogen plant on the FOWT performance. Lastly, in case of a proven FOWT performance deterioration, solutions should be provided so as to regain performance.  Aligned with the previous goals, the IEA 15MW reference wind turbine on top on the UMaine Volturn US-S semi-submersible floater is simulated in OpenFAST under steady and turbulent wind fields, according to wind & wave conditions of a typical US East Coast site. In addition, the in situ hydrogen plant is incorporated in the model using a simplified approach. The results suggest that in the whole partial load region, the FOWT experiences power losses due to the static floater pitch angle, which reduces the inflow wind speed seen by the rotor. However, between 9 and 12 m/s, a peak shaving routine is incorporated in the FOWT controller, which results in early power shedding and contributes, together with the static floater pitch, to considerable power losses. Furthermore, the simulations conducted using the OpenFAST FOWT model, which incorporated the hydrogen plant, suggest that it has a negligible effect on the FOWT performance and can be omitted from the model.  Finally, the comparison of the FOWT and of the BF turbine under turbulence, highlights the fact that the FOWT exhibits a spanwise aerodynamic torque reduction and a spanwise airfoil aerodynamic inefficiency in terms of angle of attack, that can be solved via an aerodynamic redesign. As a result, a variety of blade twist angle and airfoil chord length profiles are developed, tested and evaluated using the FOWT annual energy production (AEP) as an indicator. The results point out that all solutions result in a slight FOWT AEP gain, compared to the original FOWT design, at the expense of increased rotor loading, which effectively increases the static floater pitch. Thus, the aerodynamic redesign approach requires a more cautious approach.

In order to decarbonize the electricity grid, renewable energy sources must be utilised in con- junction with energy storage to provide ancillary services, which maintain electricity supply quality, reliability and restorability, whilst remaining aordable. Due to a lack of knowledge about the potential of stacking UK ancillary services and electricity markets to improve service aordability, this study of a wind farm with a co-located battery system compares the UK Black Start service, Firm Frequency Response static low frequency secondary and dynamic high frequency services, alongside the day-ahead market as sources of revenue, both provided individually and stacked, with all mismatches handled in the balancing market, to identify the most protable method of operation. A model of the wind farm - battery system power and energy ows is used to assess availability of Black Start and two Firm Frequency Response services, as well as operation in the day-ahead and balancing market, for a one-year period. Internal rate of return and levelized cost of electricity are used to measure nancial perfor- mance, with a weighted average cost of capital (WACC) of 7.75%. Is is found that no service or market provision is protable compared to the WACC, and the most protable method of operating the system is to sell all wind energy forecast on the day-ahead market, not using storage and not stacking services. The most protable method of providing the BS service is when stacked with the FFR static low frequency secondary service. The most protable method of providing either the FFR static low frequency secondary service or FFR dynamic high frequency service is alone, not stacked. The protability of stacks are most sensitive to the changing of BS requirements, although the protability rank order of stacks doesn't change. A single bad wind year has a very small eect on BS availability, and the eect of increased frequency deviations doesn't aect the stacks of FFR services due to limited income from FFR service energy provision compared to the balancing market or from FFR service availability.

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%.