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. ... Read more

Renewable energy sources have become a cost-competitive and green option for supplying power to the grid in recent years. Nonetheless, their variable nature poses a problem to the regular operation of the electrical grid by introducing severe fluctuations of large magnitudes and/or short-duration known as ramps. There is a lack of research in the literature on characterizing ramp events induced by wind-based hybrid power plants. The main research question of this study is how to characterize the ramping behaviour of wind-based hybrid power plants and what impact they have on the system. The application of the different methods to detect and assess the implications of ramps were presented in this thesis using wind and solar power based on the reference location.

Due to dependence on threshold values that vary across the literature and the limitations associated with calculating thresholds as a percentage of installed capacity, it was demonstrated that binary ramp definitions are not ideal and result in under-reporting. On the other hand, the wavelet approach extracts ramp events from the generation using statistically determined threshold values. As a result, the problem of under-detection of ramp events is mitigated. The proposed approach of "significant ramps" allows the evaluation of which ramp events are important and which are far less disruptive and may be ignored.

It was demonstrated that anti-correlation between wind and solar resources alone is not adequate to promise a smoother output as it does not provide sufficient information about ramp events. Anti-correlations at shorter time resolutions, such as 15 minutes or an hour, could be preferable. While seasonal anti-correlation may benefit national system adequacy, it does not benefit daily ramping events.

The optimal wind-PV capacity size for decreasing the total number of ramps was such that wind turbines filled the grid capacity, as solar power would result in extra ramps. It was observed that solar over-planting leads to a significantly increased number of ramp events, whereas wind over-planting results in a minimal change in ramp events. A penalty price was proposed to internalize the severity of ramp events, which could influence the choice between wind and solar over-planting. A solution was presented to mitigate ramp incidents in a hybrid power plant using a battery which was found to be more effective and/or more economical in minimizing ramps compared to over-planting.

The proposed "significant wavelet ramp approach" is shown to be a useful metric for characterizing wind-based hybrid power plant ramp occurrences. For a future in which variable renewable energy sources account for a substantial portion of the energy mix, it is proposed that demand information be considered when defining ramp events. More attention must be paid to power ramp occurrences, either by penalizing ramps or enforcing tougher grid codes. The ramp events must be considered at the sizing and development stage, with the possibility of including a ramp-mitigating battery strategy. A thorough examination of ramp events in hybrid power plants demonstrates the importance of minimizing and managing ramp events for both the system operator and the producer.
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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. ... Read more

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. ... Read more

The largescale installation of wind energy will provide challenges, such as maintaining a stable grid, security of supply, and profitability of renewables. The unpredictable nature of wind energy will cause more imbalances between generation and consumption to occur, consequently increasing the demand for the balancing energy reserves that ensure the grid’s stability. The intermittent nature of wind energy necessitates the ability to time shift energy production from high to low periods of wind energy availability to retain the security of supply. Furthermore, generators can face imbalance costs due to errors in wind energy generation forecasts. They are already being confronted with the declining value of wind energy in energy systems with a high share of renewables. Storage capacity is widely perceived as a technologically possible solution to alleviate these issues. Additionally, storage capacity can be a carbon neutral alternative to the traditional power plants that currently provide the required flexible generation and balancing energy. However, the lack of economic benefits is the missing link between the technical benefits and mass implementation of storage capacity.

This study explores whether operating storage, collocated with a utility scale wind power plant, can solve these challenges while improving the bottom line for operators. Spot market arbitrage, providing balancing energy through the automatic frequency restoration reserve, and generator imbalance cost reduction are identified as possible strategies for operating storage that can add value whilst also alleviating the identified issues. Furthermore, this study explores if arguments for co locating storage with wind energy to form hybrid wind and storage power plants exist or if the business case for operating storage is independent of being collocated.

It was found that an 8-hour battery performs best when undertaking spot market arbitrage. Still, even with a perfect market forecast and no storage degradation costs, it will need at least a 65% decrease from current Li-ion storage costs to become profitable. The 8-hour battery outperforms the higher power batteries because the low volatility of the spot market doesn’t warrant the higher costs of 1 and 4-hour batteries. Additionally, it was found that providing non-contracted balancing energy to the grid with a 1-hour battery provides a potential 5-fold increase in profitability compared to having no co-located storage. However, the sensitivity analysis to storage degradation costs ultimately makes the case less profitable compared to having no co-located storage. The lower sensitivity to degradation costs of the 8-hour battery cause it to outperform the 1 and 4-hour batteries. Providing contracted balancing energy showed less potential than non-contracted balancing energy before the sensitivity analysis. However, the contracted balancing energy scenario is less sensitive to storage degradation costs. It was found that a 4-hour battery providing contracted balancing energy performed best. However, this strategy was ultimately 20% less profitable compared to not operating co-located storage. Furthermore, the results of the proposed strategies turned out to be independent of the storage being co-located. Therefore, no strong arguments for collocating storage could be made here.

The business case for storage, as put forth in this project, might not exist today. However, strong clues exist that it will in the future. The predicted drop in costs of storage and the increased volatility in electricity markets will provide opportunities for the profitable operation of storage systems. When that time comes WPP operators should also be interested to operate these storage systems to further their goal of competing with traditional fossil-fuel-fired power plants.
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