Centre for Marine and Renewable Energy (MaREI)http://hdl.handle.net/10468/48172019-12-07T04:42:38Z2019-12-07T04:42:38ZWave diffraction from multiple truncated cylinders of arbitrary cross sectionsZheng, SimingZhang, YongliangLiu, JiabinIglesias, Gregoriohttp://hdl.handle.net/10468/90182019-11-15T19:01:01Z2020-08-19T00:00:00ZWave diffraction from multiple truncated cylinders of arbitrary cross sections
Zheng, Siming; Zhang, Yongliang; Liu, Jiabin; Iglesias, Gregorio
Many marine structures are supported by piles or caissons which, from a mathematical point of view, can be assimilated to an array of truncated cylinders of arbitrary cross sections. The focus of this paper is such an array subjected to harmonic waves of small steepness. We develop an analytic method based on linear potential flow theory to solve the diffraction problem and evaluate the excitation forces and moments acting on each cylinder. The water domain is divided into the interior regions below each cylinder and an exterior region extending to infinity in the horizontal plane. A series of eigen-functions are applied to express the velocity potential in each region. The Fourier series method combined with the eigen-function expansion matching method is used to satisfy the wetted surface body conditions and continuity conditions between adjacent regions. The analytic model is validated by comparing its results with numerical modelling results and published data. It is then applied to two truncated cylinders with caisson cross sections, and results are given for the excitation forces and moments on each cylinder for different values of incident wave direction and spacing between the cylinders, and for different configurations.
2020-08-19T00:00:00ZSizing battery energy storage systems: using multi-objective optimisation to overcome the investment scale problem of annual worthKelly, Joseph J.Leahy, Paul G.http://hdl.handle.net/10468/91692019-11-21T12:00:56Z2019-11-20T00:00:00ZSizing battery energy storage systems: using multi-objective optimisation to overcome the investment scale problem of annual worth
Kelly, Joseph J.; Leahy, Paul G.
The financial objective, when sizing a Battery Energy Storage System (BESS) for installation in a microgrid, is to maximise the difference between discounted BESS benefits and discounted BESS costs. This may be described as maximising Annual Worth (AW). However, one drawback of sizing microgrid BESS using AW is that the scale of investment is not taken into consideration. This can lead to unrealistic BESS sizes. This paper presents two multi-objective optimisation (MOO) models to account for the scale of investment required in sizing BESS. The first model, Paired Comparison, utilises two objective functions: Daily Worth (DW), which maximises daily benefit cost differences a BESS installation provides a microgrid; and Daily Cost (DC), which minimises the daily cost of a BESS installation. The second model, called Rating Method, uses the objective functions DW and Daily Benefit-Cost Ratio (DBCR), the latter of which maximises the relative measure of BESS benefit and BESS cost. Both models are solved for a test microgrid system under three different scenarios using Compromise Programming (CP). For system designers who rank objective functions by importance, the Rating Method is the appropriate approach, whereas system designers who rank objective functions by absolute values should use Paired Comparison.
2019-11-20T00:00:00ZBiological hydrogen methanation systems–an overview of design and efficiencyRusmanis, DavisO’Shea, RichardWall, David M.Murphy, Jerry D.http://hdl.handle.net/10468/93312019-12-05T12:01:03Z2019-11-03T00:00:00ZBiological hydrogen methanation systems–an overview of design and efficiency
Rusmanis, Davis; O’Shea, Richard; Wall, David M.; Murphy, Jerry D.
The rise in intermittent renewable electricity production presents a global requirement for energy storage. Biological hydrogen methanation (BHM) facilitates wind and solar energy through the storage of otherwise curtailed or constrained electricity in the form of the gaseous energy vector biomethane. Biological methanation in the circular economy involves the reaction of hydrogen – produced during electrolysis – with carbon dioxide in biogas to produce methane (4H2 + CO2 = CH4 + 2H2), typically increasing the methane output of the biogas system by 70%. In this paper, several BHM systems were researched and a compilation of such systems was synthesized, facilitating comparison of key parameters such as methane evolution rate (MER) and retention time. Increased retention times were suggested to be related to less efficient systems with long travel paths for gases through reactors. A significant lack of information on gas-liquid transfer co-efficient was identified.
2019-11-03T00:00:00ZAssessing the effectiveness of foraging radius models for seabird distributions using biotelemetry and survey dataCritchley, Emma JaneGrecian, W. J.Bennison, AshleyKane, AdamWischnewski, SaskiaCañadas, A.Tierney, D.Quinn, John L.Jessopp, Mark J.http://hdl.handle.net/10468/93462019-12-05T19:01:06Z2019-11-01T00:00:00ZAssessing the effectiveness of foraging radius models for seabird distributions using biotelemetry and survey data
Critchley, Emma Jane; Grecian, W. J.; Bennison, Ashley; Kane, Adam; Wischnewski, Saskia; Cañadas, A.; Tierney, D.; Quinn, John L.; Jessopp, Mark J.
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.
2019-11-01T00:00:00Z