Centre for Marine and Renewable Energy (MaREI) - Masters by Research Theses

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https://hdl.handle.net/10468/10082

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The development of a data-driven decision support tool to reduce the energy consumption of a manufacturing process
(University College Cork, 2022-10-07) Morris, Liam; Bruton, Ken; O'Sullivan, Dominic; Horizon 2020
With an ever-growing urgency to reduce energy consumption in the manufacturing industry, process stakeholders need more visibility and insights into how much energy they consume, or can expect to consume, for production. In industry today and with the use of Industry 4.0, the way data is utilised has evolved, with data collection and analysis performed digitally. With many long-established manufacturing processes, the jump from older empirical practices to digitalised practices can be difficult. Similarly, many process stakeholders use process data for different means such as production efficiency improvements. From this it can be difficult to ascertain what information is recorded on machines. And with various machines performing varying tasks in part production, this may drive high energy consumption. One such example is computer numerically controlled (CNC) machining tools. These tools are a common manufacturing apparatus and are known to consume energy inefficiently. This thesis describes the development of a hybrid methodology to identify and select key data features on a CNC machine in medical devices manufacturing. Subsequently, this data is used in an empirical energy consumption model of a CNC machine which enables the energy consumption to be determined from the number of parts processed by the machine. In using a calibrated approach, the data undergoes initial preparation followed by exploratory data analysis and subsequent model development via iteration. During this analysis, relationships between parameters are explored to identify which have the most significance on energy consumption. A training set of 191 data points yielded a linear correlation coefficient of 0.95 between the power consumption and total units produced. Root Mean Square Error, Mean Absolute Percentage Error and Mean Bias Error validation tests yielded results of 0.198, 6.4% and 2.66%, respectively.
Feasibility study of reusing concrete gravity-based foundations designed for tidal energy converters
(University College Cork, 2022) Dineen, Kate; Li, Zili; Ryan, Paraic; European Regional Development Fund
Tidal energy converter devices have been developed to capture the enormous energy potential of the tides. These devices rely on robust mooring and foundation systems to ensure efficient energy extraction in operational conditions, and stability in extreme environmental conditions. Gravity-based foundations (GBF) are currently the most commonly used foundation type within the tidal energy industry. While tidal turbines are typically supported using bespoke carbon-steel tripod structures, concrete gravity-based foundations have been put forward by a number of studies as an alternative support solution. Several novel concrete GBF concepts exist and the developers of such concrete structures state that these foundations may be reused or relocated following decommissioning. Reuse of these massive concrete structures would greatly reduce construction and demolition (C&D) waste, and the need for new concrete GBFs for future devices, thus contributing significantly to the sustainability of the tidal energy industry. However, the concept of reusing concrete gravity-based foundations following long periods of deployment underwater has not been tested in real-world scenarios due to the nascent nature of the industry and long commissioning time periods. As highlighted from a related concept in the oil and gas industry, several safety issues may arise from reusing and relocating concrete GBFs, including geotechnical hazards and concrete degradation due to corrosion. Therefore, this study assessed the practicalities of reusing concrete foundations following decommissioning by designing a concrete GBF from first principles to be used for further analysis. This representative GBF was then extensively tested using Plaxis geotechnical software to investigate soil subsidence and differential settlement, assessing their impact on GBF relocation feasibility. Subsequently, the risk of corrosion to the steel reinforcement in the GBF was examined by, firstly, modelling the chloride concentration profile of the concrete, and secondly, investigating the interrelationship between oxygen availability and water saturation level. Thorough investigation into these study considerations can significantly contribute to the determination of whether it is practicable to reuse or relocate concrete gravity-based foundations in the tidal industry. The findings from the geotechnical analysis supports the possibility of reusing and relocating concrete GBFs for tidal turbines as both the total settlement and the tilt were significantly less than the allowable total settlement and tilt tolerance in a deployment site for which the GBF was designed and a contrasting site for which it was not. However, the findings from the concrete degradation analysis does not support the feasibility of reusing concrete GBFs. A chloride ingress analysis encapsulating three datasets indicated that the critical chloride threshold would be surpassed during a GBFs deployment period, meaning that the protective passive layer on the steel would be compromised leaving it vulnerable to corrosion should sufficient oxygen and water be present.
Performance and hull pressure analysis of scaled physical testing of a wave energy converter
(University College Cork, 2022-06) Bevin, Anne; Murphy, Jimmy; O'Shea, Michael; European Regional Development Fund
Wave energy conversion is an emerging field with the potential to capture a significant amount of a globally abundant energy resource to lower reliance on fossil fuels. At present, many designs for wave energy converters are being developed which show great promise for efficiently capturing wave energy. One of the most common barriers to the commercial development and deployment of these devices, however, is the high cost of manufacturing and design validation. The ocean is a harsh environment in which to place infrastructure, and there is a high risk of a wave energy converter being critically damaged at sea after going through a long and costly development process. For this reason, small-scale tank tests and computer modelling of concepts are vital to develop wave energy converter technologies to the highest possible degree before being put into an open-water operational environment. This study describes a physical tank testing campaign of one such model, the Ocean Energy (OE) Buoy, a floating oscillating water column wave energy converter. The walls of the OE Buoy are open to allow water to freely flow through it, and this study seeks to determine whether this might allow for the device to be made with a thinner hull than “closed-container” marine devices. If the water pressure that the hull walls will experience during operation is overestimated in the OE Buoy’s current design, this could have the potential to significantly lower costs of materials and production. This testing was conducted at University College Cork’s Lir NOTF tank facility in November and December of 2021, and the OE Buoy model used is designed at 1:15 scale.
GEOBIM, BIM integrated geohazard monitoring of at risk slopes and historical retaining structures
(University College Cork, 2022-06-30) Pantoja Porro, Roberto; O'Shea, Michael; Murphy, Jimmy; Geological Survey of Ireland
Over time, structures such as slopes and retaining walls are increasingly deteriorating, resulting in a risk of collapse. Factors such as climate change, human activities, societal development, rapid growth of cities, increasing population and economy make geological disasters occur more frequently than usual. Geological hazards of nature, slope collapse, slope fractures or slope movements have become a problem to be solved by civil engineering. With the advent of low-cost sensors, optical topographic surveying and BIM (Building Information Modelling), such risk could be mitigated and, in some cases, eliminated. The main aim of this research was to use wireless sensors to monitor slopes that are potentially at risk and to incorporate all the information obtained in BIM (Building Information Modelling), in order to make a digitalized vision of the structures in real time. High precision and innovative tools, such as drone flights and slope scanners were utilized for a detailed analysis of the risk of change in the geohazards including soil slopes and historic retaining walls. Through the combination of data from sensors with point clouds generated from drone flights, an early warning system was developed. This early warning system was clearly able to display when there was surface changes therefore highlighting the areas of high risk of collapse. This thesis shows how continuous real-time surveillance of soil slopes and retaining walls can be achieved clearly and concisely, in a cost-effective manner.
An experimental investigation into the most prominent sources of uncertainty in wave tank testing of floating offshore wind turbines
(University College Cork, 2022-08-30) Lyden, Eoin; Murphy, Jimmy; Judge, Frances
There is an urgent need to replace carbon-based energy sources with renewable energy sources, and floating offshore wind is seen as a critical component in the drive towards energy diversification. Floating offshore wind facilitates accessing a far vaster wind resource that exists in deeper waters, further offshore. Floating offshore wind platforms must undergo wave tank testing in the early stages of development to assess model responses to different wave and wind conditions. Wave tank testing, while highly beneficial, is liable to errors arising throughout the testing campaign. Errors can arise during wave tank setup, testing, and analysis of results. Some of the primary sources of error include errors in the model location within the tank, errors in model parameters like mass, inertia and CoG, and errors due to incorrect replication of mooring forces and aerodynamic forces from the turbine. Scaling wind turbine blade properties can be challenging; this is because aerodynamic forces are scaled using Reynolds scaling, but all hydrodynamic forces are scaled using Froude scaling. For this reason, wind emulation systems are used to replicate the aerodynamic forces from the turbine only. Testing was completed using two very different floating offshore wind concepts. A sensitivity analysis was completed by conducting variations to the wind emulation system used, the model inertia and centre of gravity, and the mooring stiffness of the model. The magnitudes of the variations to the inertia, centre of gravity and mooring stiffness were based on the uncertainty in the values of each of the parameters. Three wind emulation systems of varying complexity were used for this comparison, a simple weighted pulley system, a constant thruster and the software in the loop system developed by CENER. The comparison was conducted to assess the influence of wind emulation systems on the uncertainty of platform response It was found that the effects of each variation conducted were magnified at resonance, and the magnitude of platform response was affected to a greater extent than the period of resonance response. Of all the variations to the model properties conducted, the inertia about the y-axis and location of the centre of gravity along the x-axis affected pitch response to the greatest extent. A 7% change in the inertia about the y-axis coupled with an 8.57% resulted in a 10% change in the period of resonance response for pitch, Tr, and 52% decrease in the magnitude of resonance respsonse for pitch, Tr, mag. Changes in the wind emulation system affected the pitch response most significantly, while the period of resonance response Tr, was mostly unaffected , the magnitude of resonance response Tr, mag, was reduced by nearly 90% when a pulley system was used in lieu of a conventional thruster for a semi-submersible model. Changes in mooring stiffness did not influence the period of resonance response but did affect the magnitude of resonance response, particularly in surge. For a linear horizontal mooring system applied to a semi-submersible model, a 1% decrease in the spring stiffness resulted in a 9% decrease in the magnitude of resonance response for surge, Tr, mag.

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