Energy Engineering - Journal Articles

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    Wave power extraction from a hybrid oscillating water column-oscillating buoy wave energy converter
    (Elsevier B.V., 2020-08-23) Cui, Lin; Zheng, Siming; Zhang, Yongliang; Miles, Jon; Iglesias, Gregorio; European Regional Development Fund; National Natural Science Foundation of China
    Oscillating water column (OWC) devices and oscillating buoys (OBs) are two of the main types of wave energy converters (WECs). In this paper a hybrid oscillating water column-oscillating buoy wave energy converter is proposed, which we have named OWCOB. The oscillating buoy is hinged at the outer wall of the oscillating water column. As waves propagate through the OWCOB, the water column within the OWC chamber moves up and down, producing air flow to propel a turbine. Meanwhile, the oscillation of the OB drives a separate hydraulic system. To solve the wave diffraction and radiation problems of the OWCOB and investigate its energy capture performance, an analytical model is developed based on linear potential flow theory and the eigenfunction matching method. Assuming that the PTOs of the OWC and OB are both linear, the wave power extraction of the OWCOB is evaluated in the frequency domain. Of the two configurations considered, the OWCOB with the OWC opening waveward and the OB hinged leeward is found to have a broader primary frequency band of wave power capture compared to the OWCOB with the OWC opening and the OB on the same side. Further, a thorough sensitivity analysis of power capture is carried out considering the main design parameters (size and submergence of the OWC opening, distance between the OWC and the OB, OB hinge elevation, OB radius), which can form the basis of an optimization study for a particular wave climate. Importantly, we find that the OWCOB performs generally better than stand-alone OWCs and OBs, not least in terms of frequency bandwidth.
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    Least cost energy system pathways towards 100% renewable energy in Ireland by 2050
    (Elsevier B.V., 2020-07-03) Yue, Xiufeng; Patankar, Neha; Decarolis, Joseph; Chiodi, Alessandro; Rogan, Fionn; Deane, J. P.; Ó Gallachóir, Brian P.; Science Foundation Ireland; National Science Foundation; Engineering and Physical Sciences Research Council; NTR Foundation, Ireland; National Natural Science Foundation of China
    Studies focusing on 100% renewable energy systems have emerged in recent years; however, existing studies tend to focus only on the power sector using exploratory approaches. This paper therefore undertakes a whole-system approach and explores optimal pathways towards 100% renewable energy by 2050. The analysis is carried out for Ireland, which currently has the highest share of variable renewable electricity on a synchronous power system. Large numbers of scenarios are developed using the Irish TIMES model to address uncertainties. Results show that compared to decarbonization targets, focusing on renewable penetration without considering carbon capture options is significantly less cost effective in carbon mitigation. Alternative assumptions on bioenergy imports and maximum variability in power generation lead to very different energy mixes in bioenergy and electrification levels. All pathways suggest that indigenous bioenergy needs to be fully exploited and the current annual deployment rate of renewable electricity needs a boost. Pathways relying on international bioenergy imports are slightly cheaper and faces less economic and technical challenges. However, given the large future uncertainties, it is recommended that further policy considerations be given to pathways with high electrification levels as they are more robust towards uncertainties.
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    A perspective on novel cascading algal biomethane biorefinery systems
    (Elsevier Ltd., 2020-02-15) Bose, Archishman; O'Shea, Richard; Lin, Richen; Murphy, Jerry D.; Science Foundation Ireland; Horizon 2020; Environmental Protection Agency; Gas Networks Ireland; Ervia, Ireland
    Synergistic opportunities to combine biomethane production via anaerobic digestion whilst cultivating microalgae have been previously suggested in literature. While biomethane is a promising and flexible renewable energy vector, microalgae are increasingly gaining importance as an alternate source of food and/or feed, chemicals and energy for advanced biofuels. However, simultaneously achieving, grid quality biomethane, effective microalgal digestate treatment, high microalgae growth rate, and the most sustainable use of the algal biomass is a major challenge. In this regard, the present paper proposes multiple configurations of an innovative Cascading Algal Biomethane-Biorefinery System (CABBS) using a novel two-step bubble column-photobioreactor photosynthetic biogas upgrading technology. To overcome the limitations in choice of microalgae for optimal system operation, a microalgae composition based biorefinery decision tree has also been conceptualised to maximise profitability. Techno-economic, environmental and practical aspects have been discussed to provide a comprehensive perspective of the proposed systems.
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    Capturing the distributional impacts of long-term low-carbon transitions
    (Elsevier B.V., 2019-01-31) Fell, Michael J.; Pye, Steve; Hamilton, Ian; Energy Technologies Institute; Research Councils UK; UK Research and Innovation
    Major policy proposals often require a distributional impact assessment, focusing on differential financial and other impacts across population segments. Such assessments are rare, however, at the multi-decadal scale addressed in long-term (e.g. to 2050) low carbon transition modelling. There is therefore a risk of socially inequitable outcomes, which in turn presents a socio-political risk for decision-makers driving transitions. This paper uses a literature review and expert interviews to identify mechanisms by which low carbon transitions could differentially impact population sub-groups. As well as impacts of policy costs on bills, this includes factors such as ability to connect to heat networks or install onsite generation or storage. An approach to exploring distributional impacts across a range of long term scenarios from a United Kingdom energy model (ESME), is proposed. This sets out how bill changes and other costs associated with low carbon transition could impact different income quintiles in the UK.
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    A numerical and experimental investigation of the effect of side walls on hydrodynamic model testing in a wave flume
    (Elsevier Ltd, 2019-08-15) Xie, N.; Hann, M.; Pemberton, R.; Iglesias, Gregorio; Greaves, D.; Engineering and Physical Sciences Research Council
    The side wall effect was normally tackled by potential flow based numerical methods. It is well known that, due to the existence of the resonance frequency in the wave tank, the numerical methods over-predict the hydrodynamic forces when comparing with model experiments. Furthermore, in most of the previous studies on the effects of the side walls, the model was located at the centre of the tank, the disturbances on both sides of the model are symmetric, and the resonances of some of the responses such as wave surface elevation and motions may not be excited at the tank natural frequencies. In the present study, a Rankine source panel method is used to tackle the effects of the side walls and artificial damping is introduced in the free surface boundary condition to account for the viscous damping effect. Model experiments are carried out for a lifeboat model located at various positions in a wave flume. Numerical results of the wave forces, free surface elevations and motions of the model are compared with the model test measurements, and good agreement is found. It is shown that the inclusion of the artificial damping in the free surface boundary condition is effective, in particular for the model at off-centre position of the tank.