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

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A 100 year review of electricity policy in Ireland (1916–2015)
(Elsevier Ltd., 2017-02-21) Gaffney, Fiac; Deane, John Paul; Ó Gallachóir, Brian P.; Bord Gáis Energy
Over the past century, Ireland's electricity sector has undergone a significant transformation. This paper documents the nation's struggle to build an electricity system, to improve security of electricity supply through portfolio diversification and to promote indigenous energy sources. This was a challenge for an (electrically) isolated island with little natural resources. The paper also identifies the ineffective policy decisions that left Ireland exposed to the 1970s energy crises. The crises did, however, provide a clear impetus for focusing Irish energy policy going forward. The successful deployment and integration of large-scale wind power was due to strong national and supranational policy decisions. In 2015, Ireland had the third highest wind energy share of national electricity demand (22.8%) of all IEA Wind Member Countries. The paper also traces Ireland's transition through market reform, regional fragmentation, and looks onwards to the EU internal market for electricity. In essence, this paper provides a holistic view of the implications of various policy decisions on the electricity sector along with the stresses of external factors on the electricity market and should be useful for policy makers elsewhere faced with similar decisions.
Acoustic activity across a seabird colony reflects patterns of within-colony flight rather than nest density
(Wiley, 2019-05-18) Arneill, Gavin E.; Critchley, Emma Jane; Wischnewski, Saskia; Jessopp, Mark J.; Quinn, John L.; Department of Culture, Heritage and the Gaeltacht; Petroleum Infrastructure Programme, PIP, Ireland
Passive acoustic monitoring is increasingly being used as a cost‐effective way to study wildlife populations, especially those that are difficult to census using conventional methods. Burrow‐nesting seabirds are among the most threatened birds globally, but they are also one of the most challenging taxa to census, making them prime candidates for research into such automated monitoring platforms. Passive acoustic monitoring has the potential to determine presence/absence or quantify burrow‐nesting populations, but its effectiveness remains unclear. We compared passive acoustic monitoring, tape‐playbacks and GPS tracking data to investigate the ability of passive acoustic monitoring to capture unbiased estimates of within‐colony variation in nest density for the Manx Shearwater Puffinus puffinus. Variation in acoustic activity across 12 study plots on an island colony was examined in relation to burrow density and environmental factors across 2 years. As predicted fewer calls were recorded when wind speed was high, and on moon‐lit nights, but there was no correlation between acoustic activity and the density of breeding birds within the plots as determined by tape‐playback surveys. Instead, acoustic indices correlated positively with spatial variation in the in‐colony flight activity of breeding individuals detected by GPS. Although passive acoustic monitoring has enormous potential in avian conservation, our results highlight the importance of understanding behaviour when using passive acoustic monitoring to estimate density and distribution.
Adaptation knowledge for New Zealand's primary industries: Known, not known and needed
(Elsevier, 2019) Cradock-Henry, Nicholas A.; Flood, Stephen; Buelow, Franca; Blackett, Paula; Wreford, Anita; Ministry for Primary Industries
Climate sensitive primary industries including pastoral farming, high-value horticulture and viticulture are central to Aotearoa-New Zealand’s economy. While advances have been made in understanding the impacts and implications of climate change critical knowledge gaps remain, particularly for adaptation. This study develops and applies a novel methodology to identify and characterise adaptation knowledge for primary industries. The basis for the review is ten years’ of research and action under the Sustainable Land Management and Climate Change (SLMACC) program, supplemented with a systematic review of the published literature. Reports (n = 32) and literature (n = 22) are reviewed and assessed using the Adaptation Knowledge Cycle to characterise analytical and empirical foci. The detailed assessment of knowledge for Impacts, Implications, Decisions or Actions enables a robust and rigorous assessment of existing knowledge, identifies critical research gaps and emerging needs. Results show research to date has focused almost exclusively on understanding the impact of climate variability and extremes on land management. There are significant empirical (e.g. location and sector) and methodological (e.g. integrated assessments, scenarios, and vulnerability assessment) gaps, for at risk regions and sectors, and limited understanding of the decisions and actions necessary to enable successful adaptation. To inform future adaptation planning, additional work is required to better understand the implications, decision-making processes and obstacles to action. More detailed understanding of location-, season-, time- and sector-specific responses to climate change is also necessary. Findings advance our understanding of adaptation knowledge and reflect on diversity of information necessary to enable and sustain resilient rural futures and provide a conceptual and methodological basis for similar assessments elsewhere.
Adaptive and interactive climate futures: systematic review of 'serious games' for engagement and decision-making
(IOP Publishing, 2018) Flood, Stephen; Cradock-Henry, Nicholas A.; Blackett, Paula; Edwards, Peter; Resilience to Nature's Challenges; Ministry for Business Innovation and Employment; Strategic Science Investment Fund; Manaaki Whenua Landcare Research; Natural Hazards Research Platform
Climate change is already having adverse impacts on ecosystems, communities and economic activities through higher temperatures, prolonged droughts, and more frequent extremes. However, a gap remains between public understanding, scientific knowledge about climate change, and changes in behaviour to effect adaptation. 'Serious games' - games used for purposes other than entertainment - are one way to reduce this adaptation deficit by enhancing opportunities for social learning and enabling positive action. Games can provide communities with the opportunity to interactively explore different climate futures, build capability and capacity for dealing with complex challenges, and socialise adaptation priorities with diverse publics. Using systematic review methods, this paper identifies, reviews, synthesises and assesses the literature on serious games for climate change adaptation. To determine where and how impact is achieved, we draw on an evaluation framework grounded in social learning, to assess which combinations of cognitive (knowledge and thinking), normative (norms and approaches) and relational (how people connect and network building) learning are achieved. Results show that factors influencing the overall success in influencing behaviour and catalysing learning for adaptation include generating high levels of inter- and intra- level trust between researchers, practitioners and community participants; strong debriefing and evaluation practices; and the use of experienced and knowledgeable facilitators. These results can help inform future game design, and research methodologies to develop robust ways for engaging with stakeholders and end users, and enhance learning effects for resilient climate futures.
Adaptive V2G peak shaving and smart charging control for grid integration of PEVs
(Taylor & Francis, 2019) Erden, Faith; Kisacikoglu, Mithat C.; Erdogan, Nuh
The stochastic nature of plug-in electric vehicle (PEV) driving behavior and distribution grid load profile make it challenging to control vehicle-grid integration in a mutually beneficial way. This study proposes a new adaptive control strategy that manages PEV charging/discharging for peak shaving and load leveling in a distribution grid. For accurate and high fidelity transportation mobility modeling, real vehicle driving test data are collected from the field. Considering the estimated total required PEV battery charging energy, the vehicle-to-grid capabilities of PEVs, and the forecasted non-PEV base load, a reference operating point for the grid is estimated. This reference operating point is updated once at the end of peak hours to guarantee a full final state-of-charge to each PEV. Proposed method provides cost-efficient operation for the utility grid, utmost user convenience free from range anxiety, and ease of implementation at the charging station nodes. It is tested on a real residential transformer, which serves approximately one thousand customers, under various PEV penetration levels and charging scenarios. Performance is assessed in terms of meansquare-error and peak shaving index. Results are compared with those of various reference operating point choices and shown to be superior.
Advanced biohydrogen production using pretreated industrial waste: outlook and prospects
(Elsevier Ltd., 2018-08-16) Prabakar, Desika; Manimudi, Varshini T.; Subha, Suvetha K.; Sampath, Swetha; Mahapatra, Durga Madhab; Rajendran, Karthik; Pugazhendhi, Arivalagan
In order to address existing environmental concerns as a result of non-renewable energy sources and to meet future energy demands, biohydrogen offers a suitable alternative energy reserve. Discrete as well as integrative methods of biohydrogen production have been analyzed over time, optimized for achieving high yields. In addition, key process parameters such as temperature, pH, hydraulic retention time, substrate concentration etc., which influence the rate of production have been clarified. Several studies have exploited industrial waste as feed sources for the production of biohydrogen; however, lower yields from these add an additional requirement for suitable pretreatment methods. The present communication examines various pretreatment methods used to increase the accessibility of industrial wastewater/waste for biohydrogen production. Furthermore, a brief overview addresses challenges and constraints in creating a biohydrogen economy. The impacts of pretreating wastes on biohydrogen generation and the latest trends are also supplied. This study helps in the critical understanding of agro-industrial wastes for biohydrogen production, thereby encouraging future outcomes for a sustainable biohydrogen economy.
An analysis of the potential benefits of centralised predictive control for optimal electrical power generation from wave energy arrays
(IEEE, 2018) O'Sullivan, Adrian C. M.; Sheng, Wanan; Lightbody, Gordon; Science Foundation Ireland
This work focuses on an array of point absorbers, with linear permanent magnet generators (LPMG) connected to the grid via back to back voltage source converters, controlled using economic model predictive control (MPC) that produces optimal electrical power generation. The main contribution of this paper is the comparison of the performance provided by using either a centralised or decentralised MPC scheme. In this study, it is shown how the inclusion of viscosity and system constraints limits the benefits to be obtained by the use of a centralised control scheme. Indeed, it was shown that a decentralised MPC scheme was sufficient for the provision of close to optimum electrical power extraction from the array when there was a reasonable separation between WEC devices. It was shown that the introduction of power constraints, either locally at each device or globally for the entire array, improved the quality of the power exported to the grid. Importantly, it was shown that from the viewpoint of power quality, that global predictive control of the wave energy array offered significant benefits over local decentralised control in increasing the average to peak power ratio of power exported to the grid.
Application of Marine Spatial Planning tools for tidal stream farm micro-siting
(Elsevier, 2022-02-11) Álvarez, M.; Ramos, V.; Carballo, R.; López, I.; Fouz, D. M.; Iglesias, Gregorio; Xunta de Galicia; Ministerio de Educación, Cultura y Deporte; Fundação para a Ciência e a Tecnologia
The operation of tidal stream energy farms may interfere with other uses of the marine space, especially in depth-limited areas (estuaries, rivers, etc.) which are typically subject to multiple demands of use. The Marine Spatial Planning Directive (MSP) was passed by the European Commission in 2014 to ensure a harmonic coexistence between different maritime activities and to protect the marine environment. In this context, the objective of this work is to present a methodology based on MSP tools for tidal-farm siting in depth-limited areas. The methodology is illustrated through a case study: Ria de Ribadeo, a shallow-water estuary in NW Spain. Having considered a number of uses (archaeological, biodiversity, fishing, aquaculture, recreational and navigation), two exploitable tidal farm sites (Areas A and C) with annual energy densities of 1 were found. The estuary is periodically dredged to maintain navigation. Dredging-related risks were analysed using a novel indicator, the Dredging Associated Risk (DAR), based on which Area C was discarded and Area A had its exploitable surface area reduced by 25%. In sum, the methodology proposed was proven to be effective for tidal stream farm planning.
Applying international power quality standards for current harmonic distortion to wave energy converters and verified device emulators
(MDPI AG, 2019-09-24) Kelly, James; Aldaiturriaga, Endika; Ruiz-Minguela, Pablo; Horizon 2020
The push for carbon-free energy sources has helped encourage the development of the ocean renewable energy sector. As ocean renewable energy approaches commercial maturity, the industry must be able to prove it can provide clean electrical power of good quality for consumers. As part of the EU funded Open Sea Operating Experience to Reduce Wave Energy Cost (OPERA) project that is tasked with developing the wave energy sector, the International Electrotechnical Commission (IEC) developed electrical power quality standards for marine energy converters, which were applied to an oscillating water column (OWC). This was done both in the laboratory and in the real world. Precise electrical monitoring equipment was installed in the Mutriku Wave Power Plant in Spain and to an OWC emulator in the Lir National Ocean Test Facility at University College Cork in Ireland to monitor the electrical power of both. The electrical power generated was analysed for harmonic current distortion and the results were compared. The observations from sea trials and laboratory trials demonstrate that laboratory emulators can be used in early stage development to identify the harmonic characteristics of a wave energy converter.
Are electrofuels a sustainable transport fuel? Analysis of the effect of controls on carbon, curtailment, and cost of hydrogen
(Elsevier Ltd., 2019-04-30) McDonagh, Shane; Deane, Paul; Rajendran, Karthik; Murphy, Jerry D.; Science Foundation Ireland; Gas Networks Ireland; Ervia, Ireland
Variable renewable electricity (VRE) decarbonises the electricity grid, but its intermittency leads to variations in price, carbon intensity, and curtailment over time. This has led to interest in utilising difficult to manage electricity to produce electrofuels (such as hydrogen via water electrolysis) for transport. The vast majority of the environmental impact of electrofuels is contained in the electricity they consume however, only consuming otherwise curtailed electricity (produced when supply exceeds demand) leads to prohibitively expensive hydrogen due to low run hours. Using a model which bids for wholesale electricity, two operational strategies (controls) aimed at increasing sustainability without requiring policy changes were tested in electricity system models of 40–60% renewable electricity penetration. (1) Bid price control set a maximum price the plant will pay for electricity. (2) Wind forecast control dictated that the plant may only run when a minimum forecast VRE production is met. It was shown that sourcing electricity at times of low cost or high forecast wind power can lead to more decarbonised hydrogen production (up to 56% more) at a lower cost (up to 57% less). When economically optimised (minimising levelised costs) the bid price control reduced the carbon intensity of the electrofuel produced by 5–25%, and the wind forecast control by 14–38%, compared to the grid average. Both controls demonstrated a high proclivity to utilising otherwise curtailed electricity and can be said to aid grid balancing. The bid price control also greatly reduced the average cost of electricity to the plant. The positive impacts increased with renewables penetration, and significant synergies between economic and environmentally conscious operation of the plants were noted. The operational strategies tested in this paper allow for transport fuels to be produced from grid electricity, without exacerbating the mismatch of supply and demand. Future decentralised quasi-storage using these operating strategies may economically produce transport fuel, and aid grid balancing.
Artificial neural network–genetic algorithm-based optimization of biodiesel production from Simarouba glauca
(Taylor & Francis, 2018-02-13) Sivamani, Selvaraju; Selvakumar, Selvaraj; Rajendran, Karthik; Muthusamy, Shanmugaprakash
A transesterification reaction was carried out employing an oil of paradise kernel (Simarouba glauca), a non-edible source for producing Simarouba glauca methyl ester (SGME) or biodiesel. In this study, the effects of three variables – reaction temperature, oil-to-alcohol ratio and reaction time – were studied and optimized using response surface methodology (RSM) and an artificial neural network (ANN) on the free fatty acid (FFA) level. Formation of methyl esters due to a reduction in FFA was observed in gas chromatography–mass spectroscopy (GC–MS) analysis. It was inferred that optimum conditions such as an oil-to-alcohol ratio of 1:6.22, temperature of 67.25 and duration of 20 h produce a better yield of biodiesel with FFA of 0.765 ± 0.92%. The fuel properties of paradise oil meet the requirements for biodiesel, by Indian standards. The results indicate that the model is in substantial agreement with current research, and simarouba oil can be considered a potential oil source for biodiesel production.
Assessing the effectiveness of foraging radius models for seabird distributions using biotelemetry and survey data
(Blackwell Publishing Ltd, 2019-11-01) Critchley, Emma Jane; Grecian, W. J.; Bennison, Ashley; Kane, Adam; Wischnewski, Saskia; Cañadas, A.; Tierney, D.; Quinn, John L.; Jessopp, Mark J.; Department of Communication, Climate Action and Environment; Dept of Culture, Heritage and the Gaeltacht; Petroleum Infrastructure Program; Zoological Society of London; Irish Research Council; Dept of Agriculture, Fisheries and the Marine
Relatively simple foraging radius models have the potential to generate predictive distributions for a large number of species rapidly, thus providing a cost‐effective alternative to large‐scale surveys or complex modelling approaches. Their effectiveness, however, remains largely untested. Here we compare foraging radius distribution models for all breeding seabirds in Ireland, to distributions of empirical data collected from tracking studies and aerial surveys. At the local/colony level, we compared foraging radius distributions to GPS tracking data from seabirds with short (Atlantic puffin Fratercula arctica, and razorbill Alca torda) and long (Manx shearwater Puffinus puffinus, and European storm‐petrel Hydrobates pelagicus) foraging ranges. At the regional/national level, we compared foraging radius distributions to extensive aerial surveys conducted over a two‐year period. Foraging radius distributions were significantly positively correlated with tracking data for all species except Manx shearwater. Correlations between foraging radius distributions and aerial survey data were also significant, but generally weaker than those for tracking data. Correlations between foraging radius distributions and aerial survey data were benchmarked against generalised additive models (GAMs) of the aerial survey data that included a range of environmental covariates. While GAM distributions had slightly higher correlations with aerial survey data, the results highlight that the foraging radius approach can be a useful and pragmatic approach for assessing breeding distributions for many seabird species. The approach is likely to have acceptable utility in complex, temporally variable ecosystems and when logistic and financial resources are limited.
Assessment of continuous fermentative hydrogen and methane co-production using macro- and micro-algae with increasing organic loading rate
(Elsevier, 2018-03-20) Ding, Lingkan; Chan Gutierrez, Enrique; Cheng, Jun; Xia, Ao; O'Shea, Richard; Guneratnam, Amita Jacob; Murphy, Jerry D.; Science Foundation Ireland; Chongqing University; Consejo Nacional de Ciencia y Tecnología; Science and Technology Department of Zhejiang Province; National Natural Science Foundation of China; Consejo De Ciencia, Innovación Y Tecnología Del Estado De Yucatán; Gas Networks Ireland
A two-stage continuous fermentative hydrogen and methane co-production using macro-algae (Laminaria digitata) and micro-algae (Arthrospira platensis) at a C/N ratio of 20 was established. The hydraulic retention time (HRT) of first-stage H2 reactor was 4 days. The highest specific hydrogen yield of 55.3 mL/g volatile solids (VS) was obtained at an organic loading rate (OLR) of 6.0 gVS/L/d. In the second-stage CH4 reactor at a short HRT of 12 days, a specific methane yield of 245.0 mL/gVS was achieved at a corresponding OLR of 2.0 gVS/L/d. At these loading rates, the two-stage continuous system offered process stability and effected an energy yield of 9.4 kJ/gVS, equivalent to 77.7% of that in an idealised batch system. However, further increases in OLR led to reduced hydrogen and methane yields in both reactors. The process was compared to a one-stage anaerobic co-digestion of algal mixtures at an HRT of 16 days. A remarkably high salinity level of 13.3 g/kg was recorded and volatile fatty acid accumulations were encountered in the one-stage CH4 reactor. The two-stage system offered better performances in both energy return and process stability. The gross energy potential of the advanced gaseous biofuels from this algal mixture may reach 213 GJ/ha/yr.
An assessment of near-to-mid-term economic impacts and energy transitions under “2 °C” and “1.5 °C” scenarios for India
(MDPI, 2018-08-24) Mittal, Shivika; Liu, Jing-Yu; Fujimori, Shinichiro; Shukla, Priyadarshi Ramprasad; Environmental Restoration and Conservation Agency; Japan Society for the Promotion of Science
The goal of limiting global temperature rise to “well below” 2 °C has been reaffirmed in the Paris Agreement on climate change at the 21st Conference of the Parties (COP21). Almost all countries submitted their decarbonization targets in their Intended Nationally Determined Contributions (INDC) to the United Nations Framework Convention on Climate Change (UNFCCC) and India did as well. India’s nationally determined contribution (NDC) aims to reduce greenhouse gas (GHG) emissions intensity of national GDP in 2030 by 33–35% compared to 2005. This paper analyzes how India’s NDC commitments compare with emission trajectories consistent with well below 2 °C and 1.5 °C global temperature stabilization goals. A top-down computable general equilibrium model is used for the analysis. Our analysis shows that there are significant emission gaps between NDC and global climate stabilization targets in 2030. The energy system requires significant changes, mostly relying on renewable energy and carbon capture and storage (CCS) technology. The mitigation costs would increase if India delays its abatement efforts and is locked into NDC pathways till 2030. India’s GHG emissions would peak 10 years earlier under 1.5 °C global temperature stabilization compared to the 2 °C goal. The results imply that India would need financial and technological support from developed countries to achieve emissions reductions aligned with the global long-term goal.
Assessment of pretreatment and digestion temperature on anaerobic digestion of whiskey byproducts and microbial taxonomy
(Elsevier, 2021-09) Kang, Xihui; Lin, Richen; Li, Lianhua; Wu, Benteng; Deng, Chen; O'Shea, Richard; Sun, Yongming; Murphy, Jerry D.; China Scholarship Council; Science Foundation Ireland; Environmental Protection Agency; Strategic Priority Research Program of the Chinese Academy of Sciences; European Regional Development Fund; Pernod Ricard; Gas Networks Ireland
The effects of steam and sulfuric acid pretreatment on anaerobic digestion (AD) of whiskey byproducts (including draff, thin and thick stillage) were investigated in order to improve the digestion performance under both mesophilic and thermophilic temperatures. The results of biomethane potential assays suggested that thermophilic AD facilitated the release of free ammonia (ca. 1200 mg/L) from byproducts, resulting in strong ammonia inhibition and volatile fatty acid accumulation. In contrast, no free ammonia inhibition (ca. 700 mg/L) was observed under mesophilic AD; the methane yield from mesophilic AD was between 375.3 +/- 13.6 mL/g volatile solid (VS; acid-treated sample) and 389.1 +/- 8.5 mL/g VS (untreated sample). Although acid pretreatment (2% acid under 135 degrees C for 15 min) did not improve the methane yield from mesophilic AD, it reduced the digestion time by 14.3% compared to that of the untreated sample. Microbial community analysis showed that irrelevant of pretreatment, hydrogenotrophic methanogens of Methanobrevibacter (28.9%-49.8% in abundance) and Methanoculleus (26.0%-55.9% in abundance) were the dominant archaeal genus under mesophilic AD. In comparison, hydrogenotrophic Methanothermobacter (over 97% in abundance) were dominant in thermophilic AD. This study could be exploited to aid in decarbonizing the whiskey industry by optimizing the biogas process in a circular economy system.
Assessment of primary energy conversion of a closed-circuit OWC wave energy converter
(MDPI AG, 2019-05-22) Benreguig, Pierre; Pakrashi, Vikram; Murphy, Jimmy; Horizon 2020
Tupperwave is a wave energy device based on the Oscillating-Water-Column (OWC) concept. Unlike a conventional OWC, which creates a bidirectional air flow across the self-rectifying turbine, the Tupperwave device uses rectifying valves to create a smooth unidirectional air flow, which is harnessed by a unidirectional turbine. This paper deals with the development and validation of time-domain numerical models from wave to pneumatic power for the Tupperwave device and the conventional OWC device using the same floating spar buoy structure. The numerical models are built using coupled hydrodynamic and thermodynamic equations. The isentropic assumption is used to describe the thermodynamic processes. A tank testing campaign of the two devices at 1/24th scale is described, and the results are used to validate the numerical models. The capacity of the innovative Tupperwave OWC concept to convert wave energy into useful pneumatic energy to the turbine is assessed and compared to the corresponding conventional OWC.
Assessment of primary energy conversions of oscillating water columns. I. Hydrodynamic analysis
(American Institute of Physics, 2014-09-29) Sheng, Wanan; Alcorn, Raymond; Lewis, Anthony; Science Foundation Ireland
This is an investigation on the development of a numerical assessment method for the hydrodynamic performance of an oscillating water column (OWC) wave energy converter. In the research work, a systematic study has been carried out on how the hydrodynamic problem can be solved and represented reliably, focusing on the phenomena of the interactions of the wave-structure and the wave-internal water surface. These phenomena are extensively examined numerically to show how the hydrodynamic parameters can be reliably obtained and used for the OWC performance assessment. In studying the dynamic system, a two-body system is used for the OWC wave energy converter. The first body is the device itself, and the second body is an imaginary “piston,” which replaces part of the water at the internal water surface in the water column. One advantage of the two-body system for an OWC wave energy converter is its physical representations, and therefore, the relevant mathematical expressions and the numerical simulation can be straightforward. That is, the main hydrodynamic parameters can be assessed using the boundary element method of the potential flow in frequency domain, and the relevant parameters are transformed directly from frequency domain to time domain for the two-body system. However, as it is shown in the research, an appropriate representation of the “imaginary” piston is very important, especially when the relevant parameters have to be transformed from frequency-domain to time domain for a further analysis. The examples given in the research have shown that the correct parameters transformed from frequency domain to time domain can be a vital factor for a successful numerical simulation.
Assessment of primary energy conversions of oscillating water columns. II. Power take-off and validations
(American Institute of Physics, 2014-09-29) Sheng, Wanan; Alcorn, Raymond; Lewis, Anthony
This is the second part of the assessment of primary energy conversions of oscillating water columns (OWCs) wave energy converters. In the first part of the research work, the hydrodynamic performance of OWC wave energy converter has been extensively examined, targeting on a reliable numerical assessment method. In this part of the research work, the application of the air turbine power take-off (PTO) to the OWC device leads to a coupled model of the hydrodynamics and thermodynamics of the OWC wave energy converters, in a manner that under the wave excitation, the varying air volume due to the internal water surface motion creates a reciprocating chamber pressure (alternative positive and negative chamber pressure), whilst the chamber pressure, in turn, modifies the motions of the device and the internal water surface. To do this, the thermodynamics of the air chamber is first examined and applied by including the air compressibility in the oscillating water columns for different types of the air turbine PTOs. The developed thermodynamics is then coupled with the hydrodynamics of the OWC wave energy converters. This proposed assessment method is then applied to two generic OWC wave energy converters (one bottom fixed and another floating), and the numerical results are compared to the experimental results. From the comparison to the model test data, it can be seen that this numerical method is capable of assessing the primary energy conversion for the oscillating water column wave energy converters.
Associations between ambient particle radioactivity and lung function
(Elsevier Ltd, 2019-06-11) Nyhan, Marguerite M.; Rice, Mary; Blomberg, Annelise; Coull, Brent A.; Garshick, Eric; Vokonas, Pantel; Schwartz, Joel; Gold, Diane R.; Koutrakis, Petros; U.S. Environmental Protection Agency; NIH (US); National Institute of Environmental Health Sciences; U.S. Department of Veterans Affairs; Epidemiology Research and Information Center (ERIC); Epidemiology Research and Information Center (MAVERIC); VA Boston Healthcare System
Previous studies have suggested increased risk of respiratory diseases and mortality following short-term exposures to ionizing radiation. However, the short-term respiratory effects of low-level environmental radiation associated with air pollution particles have not been considered. Although ambient particulate matter (PM) has been reproducibly linked to decreased lung function and to increased respiratory related morbidity, the properties of PM promoting its toxicity are uncertain. As such, we evaluated whether lung function was associated with exposures to radioactive components of ambient PM, referred to as particle radioactivity (PR). For this, we performed a repeated-measures analysis of 839 men to examine associations between PR exposure and lung function using mixed-effects regression models, adjusting for potential confounders. We examined whether PR-lung function associations changed after adjusting for PM2.5 (particulate matter≤2.5 μm) or black carbon, and vice versa. PR was measured by the USEPA's radiation monitoring network. We found that higher PR exposure was associated with a lower forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1). An IQR increase in 28-day PR exposure was associated with a 2.4% lower FVC [95% confidence interval (CI): 1.4, 3.4% p < 0.001] and a 2.4% lower FEV1 (95% CI: 1.3, 3.5%, p < 0.001). The PR-lung function associations were partially attenuated with adjustment for PM2.5 and black carbon. This is the first study to demonstrate associations between PR and lung function, which were independent of and similar in magnitude to those of PM2.5 and black carbon. If confirmed, future research should account for PR exposure in estimating respiratory health effects of ambient particles. Because of widespread exposure to low levels of ionizing radiation, our findings may have important implications for research, and environmental health policies worldwide.
Automatically identifying and predicting unplanned wind turbine stoppages using SCADA and alarms system data: case study and results
(IOP Publishing, 2017) Leahy, Kevin; Gallagher, Colm V.; Bruton, Ken; O'Donovan, Peter; O'Sullivan, Dominic T. J.; Science Foundation Ireland
Using 10-minute wind turbine SCADA data for fault prediction offers an attractive way of gaining additional prognostic capabilities without needing to invest in extra hardware. To use these data-driven methods effectively, the historical SCADA data must be labelled with the periods when the turbine was in faulty operation as well the sub-system the fault was attributed to. Manually identifying faults using maintenance logs can be effective, but is also highly time consuming and tedious due to the disparate nature of these logs across manufacturers, operators and even individual maintenance events. Turbine alarm systems can help to identify these periods, but the sheer volume of alarms and false positives generated makes analysing them on an individual basis ineffective. In this work, we present a new method for automatically identifying historical stoppages on the turbine using SCADA and alarms data. Each stoppage is associated with either a fault in one of the turbine's sub-systems, a routine maintenance activity, a grid-related event or a number of other categories. This is then checked against maintenance logs for accuracy and the labelled data fed into a classifier for predicting when these stoppages will occur. Results show that the automated labelling process correctly identifies each type of stoppage, and can be effectively used for SCADA-based prediction of turbine faults

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