Energy Engineering - Doctoral Theses

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    Combined wave, wind, and current simulation in laboratory basins with floating offshore wind turbines
    (University College Cork, 2022-09-16) Otter, Aldert; Murphy, Jimmy; Desmond, Cian; Pakrashi, Vikram; Science Foundation Ireland
    Testing scale models of Floating Offshore Wind Turbines (FOWT) under realistic offshore conditions at scale in wave basins is challenging. There exists a strong coupling between the turbine aerodynamics and platform hydrodynamics, and working in the two different fluid domains of air and water causes a scaling mismatch between Reynolds- and Froude scaling. Furthermore, not every test facility with wave basins has the equipment to generate wind and current to simulate combined environmental loadings. To overcome these challenges a hybrid test method to simulate wind and current was developed for this thesis. Hybrid testing is a combination of real-time numerical modelling and scale model testing. The aerodynamic loads of wind and hydrodynamic loads of currents are calculated in real-time and applied to the FOWT scale model via mechanical actuators. To emulate aerodynamic loads a Multi-Propeller Actuator (MPA) was developed using off-the shelve parts from recreational aerial drones on a custom-made frame. By using several propellers with different thrust directions, multiple aerodynamic loads can be emulated simultaneously, and emulating forces rather than viscous loads solves the scaling mismatch. Aerodynamic loads have been emulated by other researchers with propeller actuators, however, only very few examples of using multiple propellers were found in the literature. The study with the MPA adds to this knowledge gap. A winch actuator was developed to simulate sea currents. By emulating the drag force of a current on the platform of the FOWT, and approximating wave-current interactions by adjusting wave spectra, currents can reliably be simulated. No other examples of this method to simulate current were found, representing a clear knowledge gap. The study with the winch actuator fills this gap in the literature. Both actuators are controlled with a Software-in-the-Loop (SIL) application. This control method uses real-time feedback from a load cell and motion tracking system to update the loads calculation with the real-time numerical simulation for each time-step, improving the accuracy of the simulation. Simulating current with the winch actuator is referred to as SIL current. Experimental results throughout this body of work have been validated with offline numerical simulations using FAST and AQWA. Two validation metrics, developed for this study, have been applied to the results. Experiments with SIL current have also been validated by repeating the experiments with physical current, referred to as the full physical method, and comparing the results of both methods. Both actuators were applied to a 1/50 scale model of the INNWIND semisubmersible platform with the NREL 5 MW as the simulated wind turbine. The results have shown the winch actuator can reliably and accurately emulate the drag force of a current on the FOWT platform and the method to approximate wave-current interactions was found adequate. The results also showed that the MPA can reliably and accurately emulate thrust- and torque loads of the NREL 5 MW turbine. The SIL current and aerodynamics emulation with the MPA, in combination with physical waves, were found suitable to replicate realistic offshore conditions at scale in the wave basin.
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    Challenges in the design of tension moored floating wind turbines
    (University College Cork, 2022) Wright, Christopher S.; Murphy, Jimmy; Pakrashi, Vikram; Science Foundation Ireland
    In order to harness the extensive offshore wind resource, both in Ireland and in many parts of the world with deep offshore seas, the deployment of wind turbines on floating structures is required. Tension moored floating wind turbines are one type of platform with potential to be used for such deployments. These highly constrained platforms offer many benefits but also unique challenges compared against other platform stability types. This thesis investigated the use of such platforms through a combination of numerical simulations and experimental wave basin tank testing. Design improvements in an existing platform, HEXWIND, are identified, leading to the design of a novel platform, TWind. As tension moored platforms are highly constrained in heave, pitch and roll motions, a significant coupling and design complexity is introduced between the wind turbines flexible tower and the pitch/roll motions. The effect of this tower flexibility is parametrised in this work. As tension moored platforms rely on the tendon pretension for stability, operations such as installation and maintenance towing without tendons are statically unstable. Additional float for tow stability are designed and analysed in this work. These floats are designed to become wave energy converters once the platform is installed on site. The structural dynamic and hydrodynamic interaction effects of including these WEC are analysed in detail. Novel survival modes for the WEC floats are proposed. Design considerations related to potential tendon anchor misplacement are also analysed. A platform parameter study has led to a greater understanding of the design effects of modifying the floating concept dimensions. The addition of active WEC on the TMFWT is seen to significantly increase the platform forces and dynamics, with the tower root bending moment doubling compared to the standalone TMFWT. With 100's of GW's of proposed floating offshore wind capacity to be developed this century, the results from this thesis help improve the state of the art in tension moored floating wind design, installation and survivability.
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    Digitisation of industrial data with a view to improving decision making leading to increased efficiency
    (University College Cork, 2022-05) Clancy, Rose; Bruton, Ken
    Industry 4.0 is the fourth stage of the industrial revolution which involves the interconnectedness of products and services, brought about by their digitisation. Industry 4.0 has been criticised regarding its definition and steps for implementation. This research proposes that digitalisation initiatives are conducted to pave the way for organisations in their transition to Industry 4.0. The DMAIC and CRISP-DM methodologies were integrated together in a case study with the purpose of digitising a manufacturing process to enable data-driven decision making leading to process improvement. However, upon implementation of these existing methodologies, there was a lack of tools focused on digitisation specifically. Therefore, the HyDAPI framework was developed, integrating CRISP-DM and DMAIC along with specific tools focused on digitisation, to help managers embark on their digital transformation journey. In line with this, quality management practitioners have yet to reach the potential of digitalisation. One of the objectives of this research was to provide a framework to guide quality practitioners with the implementation of digitalisation in their existing practices. Therefore, the Hybrid Digitalisation Approach to Process Improvement (HyDAPI) framework was proposed to address the emergent need for a digital strategy framework providing a versatile, practical approach for practitioners to follow in implementing digitalisation. The implementation of the proposed HyDAPI framework in an industrial case study was shown to increase efficiency, reduce waste, standardise work and enable the root causation of non-conforming products. The case studies as part of this research focused on the foundry value stream which had a scrap rate of approximately 20% across the year 2020. Analysis was conducted to determine if a relationship existed between manufacturing process parameters and the number of defective parts. The findings from this analysis highlighted that the level of metal ingress scrap was reduced from an average of 0.12 units per batch when SiO2 was at the higher level (average 28.63%) in comparison to the mean of 0.03 units of metal ingress scrap per batch when the SiO2 was at the lower level (average 26.28%). Implementing the HyDAPI framework to digitalise a quality review process resulted in the elimination of 1.9 hours to 3.7 hours per week spent manually gathering data. This research also highlights the requirements for digitalisation found in literature, including advanced skills, organisation structure and organisation agility along with the major barriers to the implementation of digitalisation. The HyDAPI framework was demonstrated to aid organisations in overcoming the barriers to digitalisation. This research also demonstrated how Lean Six Sigma practices can effectively be incorporated to aid the successful implementation of digitalisation and adoption of digital technologies as organisations migrate towards Industry 4.0.
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    Understanding future power system challenges with higher renewables and electrification
    (University College Cork, 2022-01) Mehigan, Laura; Deane, Paul; O'Gallachoir, Brian; Bertsch, Valentin; Science Foundation Ireland
    Urgent action to reduce global greenhouse gas emissions is needed to prevent irreversible damage to the world’s climates. An opportunity exists to decarbonise electricity systems and to aid decarbonisation of heat and transport through electrification. This can only be achieved if electricity systems incorporate significantly higher levels of renewables and can cope with higher electrification. However, achieving this is not without its challenges particularly in the decade to 2030. Failure to make meaningful progress in this crucial decade will reduce the likelihood of meeting the commitments under the Paris Climate Agreement. To solve these challenges, they must first be understood. The central focus of this thesis is to improve the understanding of the challenges faced by future electricity systems with higher Renewable Energy Sources (RES) and higher electrification with an emphasis on the European power sector for the year 2030. The thesis investigates the role of Distributed Generation (DG) in future electricity systems and acknowledges that while the role of DG is important it is not the key determinant of the challenges faced in future electricity systems. The challenge of declining rotational inertia from synchronous generators is investigated and the impact of managing rather than solving this challenge is quantified for every synchronous area in the pan European power system. An exploration of how carbon price influences the role of flexibility providers (batteries and interconnection) in decarbonisation of the European power system for a policy relevant scenario reveals new insights. These insights include the importance of a high carbon price to ensure that flexibility providers reduce emissions while fossil fuels remain in the generation mix, batteries reduce solar curtailment more than interconnection, and interconnection reduces wind curtailment more than batteries. The main contributions of the thesis are the methodological contributions and insights gained into the future challenges from both a synchronous area level and a broader European perspective. The work undertaken as part of this thesis has accelerated discussions on the challenges that will be faced to achieve renewable ambitions in 2030. In particular, this research has contributed to a recent policy decision in Ireland on the need for backup generation in 2030 and during the transition to a decarbonised system.
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    Wind energy perspectives: climate change and economic viability of floating offshore wind
    (University College Cork, 2022-04-01) Martinez Diaz, Abel; Iglesias Rodriguez, Jose Gregorio; Leahy, Paul; Science Foundation Ireland; European Commission; Interreg
    The increasing demand for clean energy is boosting the wind energy industry. Combatting the sources of climate change has become a priority in developed countries, and wind energy is poised to occupy a central role thanks to its technological maturity. However, several drawbacks are arising, e.g., the variability of the wind resource or the lack of onshore available areas. It follows that the further expansion of the industry relies on a deeper knowledge of the resource and the development of new technologies for wind energy harvesting. This thesis is devoted to the advancement of wind energy by investigating two fundamental aspects of its future: the evolution of the wind energy resource under the effects of climate change and the economic viability of floating offshore wind projects. It has been demonstrated that global warming is affecting atmospheric circulation. Hence, there is value in evaluating future changes in the wind energy resource as a result of climate change – regions with a well-developed wind industry may see their wind resource endangered, while areas not yet explored may become attractive for the industry. In this thesis, the evolution of the future wind energy resource under the effects of climate change in the 21st century is studied in Europe and North America (two of the biggest markets for wind energy) using wind climate projections coming from 18 different global climate models (GCMs). These data on the future wind climate are produced following the novel narratives of socioeconomic development and land use, i.e., the Shared Socioeconomic Pathways (SSPs), and therefore represent the most-up-to-date climate change scenarios, leading to different radiative forcing. Two climate change scenarios are considered: a business-as-usual scenario (SSP2-4.5), in which policies regarding climate change do not vary significantly; and a scenario of intensive energy consumption coming from fossil fuels (SSP5-8.5). General and regional trends of the future wind energy resource are assessed – mean value, overall variability and intra-annual variability of wind power density are evaluated. Drastic changes in the available wind resource are anticipated and therefore must be taken into consideration provided that future policies are similar to those in the scenarios considered. Recently, the wind energy industry has found new areas for development in offshore regions, which present a stronger and steadier resource. With wind turbines mounted on jacket structures and monopiles, offshore wind farms are being installed in growing numbers. However, the majority of the offshore available areas have great water depths, precluding the installation of bottom-fixed turbines; hence, floating technologies represent a much more promising option. This thesis introduces a method to evaluate the economic viability of floating offshore wind projects by means of the levelised cost of energy (LCOE), which includes a breakdown of all the costs incurred in the lifetime of a project. By employing site-specific variables, the LCOE is computed and mapped in the European Atlantic and the Mediterranean Sea to identify regions with the most potential for the deployment of floating offshore wind turbines. The contents of this thesis investigate two aspects that will be of great relevance for the development of wind energy in the 21st century and thus can be of great use for the industry. Both the method introduced, in the case of the LCOE of floating wind, and the results can be employed in future policy-making processes and the planning of new wind energy projects.