Centre for Marine and Renewable Energy (MaREI) - Conference Items

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Access to a floating wind turbine
(The Royal Institution of Naval Architects, 2017-03) Shanley, Matthew; Wright, Christopher S.; Otter, Aldert; Desmond, Cian J.; Murphy, Jimmy; The Royal Institution of Naval Architects; Lir National Ocean Test Facility, Ireland; Science Foundation Ireland
The offshore wind turbine service industry is now well established with a large number of turbines being successfully operated and maintained. A number of methods and technologies are available to allow the safe transfer of service crews to these primarily fixed monopile installations. The most common of these is the bow transfer method which uses a combination of a high friction fender and a large vessel thrust to minimise relative motion between the bow and the turbine foundation. An upcoming challenge for the offshore wind turbine service industry will be the increasing use of floating foundations in far offshore and deep water sites. A number of structures are currently being developed and the first commercial floating wind farm is expected to be commissioned in late 2017. The use of floating structures will make it more difficult to ensure crew safety and comfort during transfer operations as the interaction between two floating bodies needs to be considered. Thus, the bow transfer method used to access fixed foundations may not be suitable for accessing floating turbine platforms. This paper will use a combination of physical and numerical modelling to assess the ability of a wind farm service vessel to maintain contact with a floating offshore wind turbine structure by use of the bow transfer method.
Artificial neural network application in short-term prediction in an oscillating water column
(The International Society of Offshore and Polar Engineers (ISOPE), 2010-01) Sheng, Wanan; Lewis, Anthony; Science Foundation Ireland; Department of Communications, Energy and Natural Resources, Ireland
Oscillating Water Column (OWC) is one type of promising wave energy devices due to its obvious advantage over many other wave energy converters: no moving component in sea water. Two types of OWCs (bottom-fixed and floating) have been widely investigated, and the bottom-fixed OWCs have been very successful in several practical applications. Recently, the proposal of massive wave energy production and the availability of wave energy have pushed OWC applications from near-shore to deeper water regions where floating OWCs are a better choice. For an OWC under sea waves, the air flow driving air turbine to generate electricity is a random process. In such a working condition, single design/operation point is nonexistent. To improve energy extraction, and to optimise the performance of the device, a system capable of controlling the air turbine rotation speed is desirable. To achieve that, this paper presents a short-term prediction of the random, process by an artificial neural network (ANN), which can provide near-future information for the control system. In this research, ANN is explored and tuned for a better prediction of the airflow (as well as the device motions for a wide application). It is found that, by carefully constructing ANN platform and optimizing the relevant parameters, ANN is capable of predicting the random process a few steps ahead of the real, time with a good accuracy. More importantly, the tuned ANN works for a large range of different types of random, process.
The assessment of water surface elevation uncertainty in a hydraulics laboratory
(Seoul National University, 2019-05) Desmond, Cian; Buret, Benoit; Shanley, Matthew; Murphy, Jimmy; Pakrashi, Vikram
Physical model testing forms a critical part of the development process for offshore renewable energy (ORE) technologies. Devices and structures generally follow a Technology Readiness Level (TRL) development pathway which has nine steps ranging from the initial idea (TRL1) to commercialisation (TRL9). In ORE, technologies are tested extensively in laboratory environments up to TRL4 after which a decision is made as to whether a particular technology has sufficient potential to justify moving to open sea environments where the costs can be much higher. Therefore, physical model testing plays a critical role in the development process and in recent years increased emphasis has been placed on improving quality procedures and implementing best practice methodologies. The International Towing Tank Conference (ITTC) and the International Electrotechnical Commission (IEC) have been developing testing standards whilst European Union funded projects such as Equimar, MaRINET and MaRINET2 have been working with testing infrastructures in developing a more uniform approach to testing. However, a standardised approach to the assessment of uncertainty in physical testing has yet to emerge. This paper focuses on and estimates the variation associated with wave elevation measurements using conductive wave probes in a hydraulics laboratory, a key input in all physical testing analysis.
Beyond car efficiency and electrification: Examining the role of demand reduction, public transit, and active travel measures to reduce GHG emissions in transport
(2021) O'Riordan, Vera; Daly, Hannah; Mac Uidhir, Tomás; Ó Gallachóir, Brian P.; Rogan, Fionn; Climate and Energy Modelling Services
This paper applies a data set of passenger kilometre transport demand by trip-purpose, mode type and tripdistance based on the outcomes of a National Travel Survey. The Irish Passenger Transport Emissions and Mobility (IPTEM) model enables a system-wide perspective on various measures which could be introduced to reduce passenger transport emissions. Combined with the LEAP Ireland 2050 energy systems simulation model, the carbon abatement potential of trip-purpose based policies, modal shift policies and technology improvements in public transport can be assessed. The results indicate that significant savings can be achieved from modal shift in Ireland, and that trip-purpose based targets and policies have a relevance in the effort to reduce Ireland’s energy related transport CO2 emissions. The active mode scenarios, which focus on increased walking and cycling achieve a 0.2 – 1 MTCO2 reduction in annual passenger transport emissions in 2030. The range of public transport scenarios, inspired by targets set out by the Irish Government’s Climate Action Plan achieve a between 0.001 – 0.3 MTCO2 reduction in annual passenger transport emissions in 2030. In addition, traffic camera data is used to model the impact of COVID-19 travel restrictions on transport CO2 emissions. The calculated reduction in transport CO2 emissions is 3.9 MTCO2 for 2020 and 2021. This study highlights the importance of factoring modal shift, trip distance and trip purpose into scenario analysis for transport emissions reduction, as it provides a framework for looking beyond only improving technologies in private vehicle transport.
Combined current and wind simulation for floating offshore wind turbines
(IOP Publishing, 2022) Otter, Aldert; Desmond, C.; Flannery, Brian; Murphy, Jimmy; Science Foundation Ireland
This paper describes the validation of a novel method to simulate current loading on a floating offshore wind turbine model. A dynamic winch actuator is used to emulate the drag force of current on the platform of the model with a Software in the Loop application. Current loads are combined with wave- and wind loads. The results of experiments with physical current are validated against the results of experiments with simulated current. A method to simulate wave-current interactions is also described. The results show that the winch actuator can reliably emulate current induced drag forces in comparison with physical current under various combinations of environmental loads. Experimental repeatability of the response of the platform is shown to be superior when using simulated- rather than physical current.
Comparative realistic objectives oriented optimization framework for EV charging scheduling in a distribution system
(Institute of Electrical and Electronics Engineers (IEEE), 2022-05-18) Güldorum, Hilmi Cihan; Erenoğlu, Ayşe Kübra; Erdinç, Ozan; Şengör, İbrahim; Türkiye Bilimsel ve Teknolojik Araştirma Kurumu; Türkiye Bilimler Akademisi
The integration of large-scale electric vehicles (EVs) into the distribution system has emerged as a critical topic of research with the proliferation of EVs over the years. To mitigate the negative effects of EVs on the distribution system (DS), in this study, the optimal operation of an EVPL is investigated with a model in the form of mixed-integer quadratic constrained programming (MIQCP) that aims to minimize a variety of realistic objectives including active power losses, charging cost or voltage deviations while taking DS constraints into account. Also, uncertain behavior of the EVPL has been considered via machine-learning based forecasting by using historic data. The effectiveness of the proposed model has been evaluated using a 33-bus test system with 15-minute time granularity and compared to models that had various objective functions.
Development and operation of a power take off rig for ocean energy research and testing
(2011-01) Rea, Judith A.; Kelly, James F.; Alcorn, Raymond; O'Sullivan, Dara
Distributed hierarchical droop control of boost converters in DC microgrids
(Institute of Electrical and Electronics Engineers (IEEE), 2017-07-20) O'Keefe, Daniel; Riverso, Stefano; Albiol-Tendillo, Laura; Lightbody, Gordon; Irish Research Council; University College Cork
Voltage stability and accurate current-sharing are primary features of an efficiently operating power distribution network, such as a dc islanded-microgrid. This paper presents the development of a distributed hierarchical droop control architecture for dc-dc boost converters within a dc islanded-microgrid. Decentralised controllers are conventionally designed for local voltage and current control without accounting for coupling to other converters. However, due to the non-minimum phase action of boost converters, global knowledge of coupling is required to inform stable local controller tuning over a range of load disturbances. Consensus-based distributed secondary controllers, utilising low-bandwidth communications, are designed to coordinate voltage levels and improve current-sharing accuracy. The control architecture is tested in response to communication faults, non-linear loads, and plug-and-play operations.
Effects of tidal range on mooring systems of wave energy converters
(EWTEC, 2015-09) Murphy, Stephen; Bhinder, Majid A.; Casaubieilh, Pierre; Sheng, Wanan
Wave energy converters are currently proposed to be deployed near coastal area for the closeness to the infrastructure and for ease of maintenance in order to reduce operational costs. The motivation behind this work is the fact that the deployment depths during the highest and lowest tides will have a significant effect on the mooring system of WECs. In this paper, the issue will be investigated by numerical modelling (using ANSYS AQWA) for both catenary and taut moorings to examine the performance of the mooring system in varying tides. The case study being considered is the ¼- scale wave energy test site in Galway Bay off the west coast of Ireland where some marine renewable energy devices can be tested. In this test site, the tidal range is macro-tidal with a range of approximately 6 m which is a large value relative to the water depth. In the numerical analysis, ANSYS AQWA suite has been used to simulate moored devices under wave excitation at varying tidal ranges. Results show that the highest tide will give rise to larger forces. While at lower depths, slackening of the mooring occurs. Therefore, the mooring lines must be designed to accommodate both situations.
EV specific time-of-use rates analysis for workplace charging
(Institute of Electrical and Electronics Engineers (IEEE), 2021-08-02) Kucuksari, Sadik; Erdogan, Nuh; Sustainable Energy Authority of Ireland
EV specific time-of-use rate plans have been recently introduced by several utilities to overcome the demand charge issue that is the main barrier impeding EV growth in the commercial and industrial sector. This study analyses two EV specific TOU rates in place from a customer and the grid perspectives. The analysis relies on a developed optimal cost model with coordinated charging strategies that minimizes the total cost of a workplace charging station over its lifetime. From a customer perspective, it is shown that the cost benefits are not always achievable and depends on the rates provided. From the grid perspective, the peak demand is found to be increased. Thus, the EV specific rates may not always provide an efficient use of the grid assets.
Experimental study on the wave measurements of wave buoys
(International Conference on Ocean Energy, 2014-11) Liu, Qiulin; Lewis, Anthony; Zhang, Yongliang; Sheng, Wanan; National Natural Science Foundation of China; National High Technology Research and Development Program, China; State Key Laboratory of Hydroscience and Engineering, China
Wave measurement is of vital importance for assessing the wave power resources and for developing wave energy devices, especially for the wave energy production and the survivability of the wave energy device. Wave buoys are one of the most popular measuring technologies developed and used for long-term wave measurements. In order to figure out whether the wave characteristics can be recorded by using the wave buoys accurately, an experimental study was carried out on the performance of three wave buoy models, viz two WaveScan buoys and one ODAS buoy, in a wave tank using the European FP7 MARINET facilities. This paper presents the test results in both time and frequency domains and the comparison between the wave buoys and wave gauge measurements. The analysis results reveal that for both regular and irregular waves, the WaveScan buoys have better performances than the ODAS buoy in terms of accuracy and the WaveScan buoys measurements have a very good correlation with those from the wave gauges.
From M&V to M&T: An artificial intelligence-based framework for real-time performance verification of demand-side energy savings
(Institute of Electrical and Electronics Engineers (IEEE), 2018-09) Gallagher, Colm V.; O'Donovan, Peter; Leahy, Kevin; Bruton, Ken; O'Sullivan, Dominic T. J.; Science Foundation Ireland
The European Union's Energy Efficiency Directive is placing an increased focus on the measurement and verification (M&V) of demand side energy savings. The objective of M&V is to quantify energy savings with minimum uncertainty. M&V is currently undergoing a transition to practices, known as M&V 2.0, that employ automated advanced analytics to verify performance. This offers the opportunity to effectively manage the transition from short-term M&V to long-term monitoring and targeting (M&T) in industrial facilities. The original contribution of this paper consists of a novel, robust and technology agnostic framework that not only satisfies the requirements of M&V 2.0, but also bridges the gap between M&V and M&T by ensuring persistence of savings. The approach features a unique machine learning-based energy modelling methodology, model deployment and an exception reporting system that ensures early identification of performance degradation. A case study demonstrates the effectiveness of the approach. Savings from a real-world project are found to be 177,962 +/- 12,334 kWh with a 90% confidence interval. The uncertainty associated with the savings is 8.6% of the allowable uncertainty, thus highlighting the viability of the framework as a reliable and effective tool.
Greenway pedestrian and cycle bridges from repurposed wind turbine blades
(Irish Transport Research Network (ITRN), 2021) Leahy, Paul G.; Zhang, Zoe; Nagle, Angela J.; Ruane, Kieran; Delaney, Emma; McKinley, Jennifer; Bank, Lawrence; Gentry, T. Russell; Department for the Economy; Science Foundation Ireland; National Science Foundation; Munster Technological University
Greenways are long-distance walking and cycling routes, often developed along the routes of disused railways. Greenways therefore are a means of repurposing underused infrastructure to provide sustainable transport. They also offer benefits for leisure activities, rural development and tourism. The network of greenways in the Republic of Ireland is projected to grow to 240 km by 2022, and a further 800 km of long-distance pathways has been proposed. The Irish government announced â ¬64m in funding for greenway projects in 2020, with further commitments to sustainable transport spending in the 2020 Programme for Government. In Northern Ireland there is 1,000 km of abandoned former transport routes with the potential for development as greenways. Many of the proposed greenway routes will need extensive works. In many cases, bridges and overpasses are in poor condition and will require complete reconstruction. Alongside the repurposing of disused railways as sustainable transport routes, there is an opportunity to reuse another type of repurposed infrastructure to create functional and attractive new bridges on greenways: end-of-life decommissioned wind turbine blades. Wind turbine blades are made of durable, lightweight and strong fibre-reinforced polymer (FRP) materials. They are difficult to recycle by conventional methods, but are ideally suited to repurposing. A US-Ireland-Northern Ireland initiative, the Re-Wind network, has created designs for several new artefacts from repurposed wind turbine blades, including a pedestrian bridge. In this paper we will show the advantages of the blade bridge design for deployment on greenways, show details of the testing and design of the worldâ s first repurposed greenway blade bridge, scheduled for installation on the Midleton-Youghal Greenway in Co. Cork in 2021, and outline the environmental and social advantages of using repurposed FRP blades in new infrastructure such as bridges. The paper also discusses the future expected flow of end-of-life blades from decommissioned wind turbines in Ireland and how this can be aligned with repurposing opportunities.
Guiding stakeholders to participate in Marine Strategy Framework implementation
(MARMONI project, 2012-11) Twomey, Sarah; Baltic Environmental Forum and the MARMONI project.
Large marine areas and regional seas present a challenge in terms of management. They are often bordered by numerous maritime jurisdictions; with multi-use and multi-sector environments; involving varying governance arrangements; and generation of sufficient levels of data to best inform decision-makers. Marine management at the regional scale involves a range of mechanisms and approaches to ensure all relevant stakeholders have an opportunity to engage in the process; and these approaches can differ in their legal and regulatory conditions. At present, no such comparable structures exist at the transnational level for the ecosystem-based management of the Celtic Sea. Against this backdrop, a participative process, involving representatives from differing sectors of activity in the Celtic Sea spanning four Member States, was established for the purpose of identifying realistic and meaningful management principles in line with the goals of the Marine Strategy Framework Directive.
Hydrodynamics of oscillating water column wave energy converters
(2014-11) Sheng, Wanan; Alcorn, Raymond; Lewis, Anthony; Science Foundation Ireland
This work deals with the numerical studies on hydrodynamics of oscillating water column (OWC) wave energy converters and its damping optimization on maximizing wave energy conversion by the OWC device. As a fundamental step, the hydrodynamic problems have been systematically studied by considering the interactions of the wave-structure and of the wave-internal water surface. Our first attention is on how the hydrodynamic performance can be reliably assessed, especially when it comes to the time-domain analysis, and what the physics behind the considerations is. Further on, a damping optimization for the OWC wave energy converter is also present based on the dynamics of the linear system, and a study on how we can optimize the damping for the given sea states so that the power conversion from irregular waves from irregular waves can be maximized.
An innovative hull design for an offshore wind farm support vessel
(The Royal Institution of Naval Architects, 2016-03) Shanley, Matthew; Balke, Sebastian; Murphy, Jimmy; The Royal Institution of Naval Architects; University College Cork
Latching control theory for wave energy conversion
(2014-03) Sheng, Wanan; Alcorn, Raymond; Lewis, Anthony; Science Foundation Ireland
Looking for a simplified approach for the propagation of systematic uncertainty in the motion response of a floater
(IOP Publishing, 2022-11) Gueydon, S.; Lyden, Eoin; Judge, Frances M.; O'Shea, Michael; Murphy, Jimmy; Horizon 2020
This new research considers the 3 main motions of the moored floater (surge, heave and pitch) in head waves and it explores ways to estimate the systematic uncertainties on the RAOs, and 2 other metrics for these signals. Based on linear hydrostatics and the linear potential flow theory, simple relations can be found that bind the main characteristics of a floater. These relations are transformed using linear algebra to express how uncertainty bias on the main characteristics of the tested system can be propagated to the motion responses of the floater. Thanks to this approach, variations of the mooring stiffness, position of the centre of mass, radia of gyration can be represented through simple formulations that allow to very effectively assess their impact of the motion RAOs and other metrics. This approach is verified by comparing simulation and test results of the semisubmersible of the MARINET2 floating wind round robin campaign to approximations deduced from these theoretical relations.
Model scale testing of the Tupperwave device with comparison to a conventional OWC
(American Society of Mechanical Engineers (ASME), 2018-09-25) Benreguig, Pierre; Murphy, Jimmy; Sheng, Wanan; Horizon 2020
A model testing campaign of the Tupperwave device was carried out to prove the working principal and validate a numerical modelling that had previously been developed. An appropriate and challenging scaling method was applied to the floating device to correctly model the air compressibility in the Tupperwave PTO. In parallel, a model scale conventional OWC was also built using the same axisymmetric structure geometry and both devices were tested and compared. The testing showed that the Tupperwave device produced less average useful pneumatic power than the conventional OWC. The primary losses were attributed to pneumatic power dissipation through the valves. The pneumatic power delivered by the Tupperwave device was however significantly smoother. The paper describes the experimental set-up and the methods used to assess the devices performance. The results provide a direct comparison between the two physical models pneumatic power performances and an in-depth analysis of the valves behaviour is shown.
A new latching control technology for improving wave energy conversion
(2014-11) Sheng, Wanan; Alcorn, Raymond; Lewis, Anthony; Science Foundation Ireland
Extracting wave energy from seas has been proven to be very difficult although various technologies have been developed since 1970s. Among the proposed technologies, only few of them have been actually progressed to the advanced stages such as sea trials or pre-commercial sea trial and engineering. One critical question may be how we can design an efficient wave energy converter or how the efficiency of a wave energy converter can be improved using optimal and control technologies, because higher energy conversion efficiency for a wave energy converter is always pursued and it mainly decides the cost of the wave energy production. In this first part of the investigation, some conventional optimal and control technologies for improving wave energy conversion are examined in a form of more physical meanings, rather than the purely complex mathematical expressions, in which it is hoped to clarify some confusions in the development and the terminologies of the technologies and to help to understand the physics behind the optimal and control technologies. As a result of the understanding of the physics and the principles of the optima, a new latching technology is proposed, in which the latching duration is simply calculated from the wave period, rather than based on the future information/prediction, hence the technology could remove one of the technical barriers in implementing this control technology. From the examples given in the context, this new latching control technology can achieve a phase optimum in regular waves, and hence significantly improve wave energy conversion. Further development on this latching control technologies can be found in the second part of the investigation.

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