Centre for Marine and Renewable Energy (MaREI) - Journal Articles

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    Electrofuels in a circular economy: A systems approach towards net zero
    (Elsevier Ltd., 2023-07-05) Rusmanis, Davis; Yang, Yan; Long, Aoife; Gray, Nathan; Martins, Kelvin C.; Ó Loideáin, Seán Óg; Lin, Richen; Kang, Xihui; Cusack, Donal Óg; Carton, James G.; Monaghan, Rory; Murphy, Jerry D.; Wall, David M.; Science Foundation Ireland
    Decarbonising the hard-to-abate sectors will be necessary in realising a future net-zero economy. Electrofuels store electricity as low carbon energy vectors such as hydrogen or methane which can be used in areas where electrification is not ideal, and as such can facilitate decarbonisation of sectors such as transport, agriculture, and wastewater treatment. In this study, the production of electrofuels was analysed at an industrial site by storing renewable electricity as green hydrogen produced using electrolysis. The analysis highlighted the need for scale in hydrogen production. The cost of hydrogen was calculated at €8.92/kg when a 122 kW electrolyser operated solely on curtailed electricity generated from the industry site was situated at a 65,000 person equivalent municipal wastewater treatment plant. A subsequent integrated and circular approach to electrofuels production was investigated. The oxygen by-product from electrolysis could be utilised for wastewater aeration and reduce the annual electricity usage at the wastewater treatment plant by 3.6%. Furthermore, the carbon dioxide in biogas generated from sewage sludge could be converted to methane through a Sabatier reaction (4H2 + CO2 → CH4 + 2H2O) as a means of carbon capture and utilisation. The hydrogen produced from the 122 kW electrolyser could convert only 40% of the total carbon dioxide (within the biogas) in a biomethanation process, again supporting the argument for larger electrolyser systems with increased hydrogen production. Pyrolysis of digestate to produce biochar was investigated as a negative emissions technology. If pyrolysis is coupled with anaerobic digestion of feedstocks within 10 km of the industry site savings of 42.7 kt CO2/a could be achieved. In essence, a circular economy approach to electrofuel production could integrate existing electrical, gas and water infrastructure, whilst treating waste, improving the environment, decarbonising agriculture, and storing energy in the form of new low carbon energy vectors for use in heavy transport. Such an approach is vital to progressing future net-zero strategies, however future emissions accountancy processes must adapt to facilitate the benefits of a circular economy.
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    Scenario analysis of cost-effectiveness of maintenance strategies for fixed tidal stream turbines in the Atlantic Ocean
    (MDPI, 2023-05-13) Kamidelivand, Mitra; Deeney, Peter; Devoy McAuliffe, Fiona; Leyne, Kevin; Togneri, Michael; Murphy, Jimmy; European Regional Development Fund
    This paper has developed an operation and maintenance (O&M) model for projected 20 MW tidal stream farm case studies at two sites in the northeast Atlantic in France and at EMEC’s Fall of Warness site in the UK. The annual energy production, number of incidents, and downtimes of the farms for corrective and planned (preventive) maintenance strategies are estimated using Monte Carlo simulations that vary weather windows, repair vessel availabilities, and mean annual failure rates modelled by Weibull distributions. The trade-offs between the mean annual failure rates, time availability, O&M costs, and energy income minus the variable O&M costs were analysed. For all scenarios, a 5-year planned maintenance strategy could considerably decrease the mean annual failure rates by 37% at both sites and increase the net energy income. Based on a detailed sensitivity analysis, the study has suggested a simple decision-making method that examines how the variation in the mean annual failure rate and changes in spare-part costs would reduce the effectiveness of a preventive maintenance strategy. This work provides insights into the most important parameters that affect the O&M cost of tidal stream turbines and their effect on tidal energy management. The output of the study will contribute to decision-making concerning maintenance strategies.
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    Dedicated large-scale floating offshore wind to hydrogen: Assessing design variables in proposed typologies
    (Elsevier B.V., 2022-03-01) Ibrahim, Omar S.; Singlitico, Alessandro; Proskovics, Roberts; McDonagh, Shane; Desmond, Cian; Murphy, Jerry D.; Horizon 2020; Science Foundation Ireland
    To achieve the Net-Zero Emissions goal by 2050, a major upscale in green hydrogen needs to be achieved; this will also facilitate use of renewable electricity as a source of decarbonised fuel in hard-to-abate sectors such as industry and transport. Nearly 80% of the world's offshore wind resource is in waters deeper than 60 m, where bottom-fixed wind turbines are not feasible. This creates a significant opportunity to couple the high capacity factor floating offshore wind and green hydrogen. In this paper we consider dedicated large-scale floating offshore wind farms for hydrogen production with three coupling typologies; (i) centralised onshore electrolysis, (ii) decentralised offshore electrolysis, and (iii) centralised offshore electrolysis. The typology design is based on variables including for: electrolyser technology; floating wind platform; and energy transmission vector (electrical power or offshore hydrogen pipelines). Offshore hydrogen pipelines are assessed as economical for large and distant farms. The decentralised offshore typology, employing a semi-submersible platform could accommodate a proton exchange membrane electrolyser on deck; this would negate the need for an additional separate structure or hydrogen export compression and enhance dynamic operational ability. It is flexible; if one electrolyser (or turbine) fails, hydrogen production can easily continue on the other turbines. It also facilities flexibility in further expansion as it is very much a modular system. Alternatively, less complexity is associated with the centralised offshore typology, which may employ the electrolysis facility on a separate offshore platform and be associated with a farm of spar-buoy platforms in significant water depth locations.
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    Participatory methods in energy system modelling and planning – a review
    (Elsevier, 2021) McGookin, Connor; Ó Gallachóir, Brian P.; Byrne, Edmond P.; Science Foundation Ireland; ESB Networks; National Science Foundation
    This paper presents a systematic review of participatory methods used in energy system modelling and planning. It draws on a compiled database of fifty-nine studies at a local, regional, and national level detailing analysis on full energy systems down to sectors, modes, and single technologies. The initial aim of the paper is to consolidate and present this growing body of literature, providing a clear understanding of which stakeholder groups have been engaged and what methods have been used to link stakeholder engagement with quantitative analysis. On from this, the progress to date in democratising key decision-making processes is discussed, reflecting on the benefits and challenges of a participatory approach, as well as highlighting gaps within the current body of literature. During the review, two differing spatial levels at subnational (cities, municipalities, or regions) and national scale emerged as separate groups for analysis. A clear distinction between the two groups was the motivation for involving stakeholders. At a subnational level, researchers hoping to build local capacity to bring about real-world change engaged with community representatives, whereas national level studies concerned with generating more impactful energy policy measures involved industry, policymaking, and academic experts. One key finding from the review was that only ten out of the fifty-nine studies reviewed noted some form of collaboration with non-academic stakeholders, and moreover 36% of studies involved just a single interaction with participants. This indicates a lack of progress to date in process democratisation within energy system modelling and planning research.
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    Doing things differently: bridging community concerns and energy system modelling with a transdisciplinary approach in rural Ireland
    (Elsevier, 2022-07) McGookin, Connor; Mac Uidhir, Tomás; Ó Gallachóir, Brian P.; Byrne, Edmond P.; Science Foundation Ireland; ESB Networks; National Science Foundation
    This paper reflects on the experience of co-producing energy strategies on the Dingle peninsula, a rural peripheral region in Ireland's South West. For the past three years, researchers from sociology, community development, and energy engineering have worked in partnership with Ireland's electricity distribution system operator and local non-profit organisations supporting enterprise and community development in the region. This involved coordinating the research with the transdisciplinary partnership established and widespread community consultation (including fifteen community meetings that received roughly 400 attendees) to understand the concerns and priorities of residents. The initial research focus was to incorporate stakeholder preferences into energy scenarios using a simulation modelling tool (Low Emissions Analysis Platform, LEAP). This was revised in favour of support for local development effort to prepare a strategic plan for the area across social, economic, and environmental domains. Widening the scope in this manner posed a serious methodological challenge but was necessary to respond to local needs and foster local impact. The results highlight the imperative of understanding the messy reality within which energy systems operate, and the need to align rural development with climate action policies via authentic engagement. A key contribution from this novel approach is to shine a critical light on the limitations of energy system models. This research serves to highlight the need for co-production/action research efforts that can support real-world transition processes and provide a better understanding of local contexts as an alternative to efforts that would seek to simply improve societal representations within energy system models.