Shoreline and Bathymetry Approximation in Mesh Generation for Tidal Renewable Simulations

Due to the fractal nature of the domain geometry in geophysical flow simulations, a completely accurate description of the domain in terms of a computational mesh is frequently deemed infeasible. Shoreline and bathymetry simplification methods are used to remove small scale details in the geometry, particularly in areas away from the region of interest. To that end, a novel method for shoreline and bathymetry simplification is presented. Existing shoreline simplification methods typically remove points if the resultant geometry satisfies particular geometric criteria. Bathymetry is usually simplified using traditional filtering techniques, that remove unwanted Fourier modes. Principal Component Analysis (PCA) has been used in other fields to isolate small-scale structures from larger scale coherent features in a robust way, underpinned by a rigorous but simple mathematical framework. Here we present a method based on principal component analysis aimed towards simplification of shorelines and bathymetry. We present the algorithm in detail and show simplified shorelines and bathymetry in the wider region around the North Sea. Finally, the methods are used in the context of unstructured mesh generation aimed at tidal resource assessment simulations in the coastal regions around the UK

Efficient unstructured mesh generation for marine renewable energy applications

Renewable energy is the cornerstone of preventing dangerous climate change whilst maintaining a robust energy supply. Tidal energy will arguably play a critical role in the renewable energy portfolio as it is both predictable and reliable, and can be put in place across the globe. However, installation may impact the local and regional ecology via changes in tidal dynamics, sediment transport pathways or bathymetric changes. In order to mitigate these effects, tidal energy devices need to be modelled in order to predict hydrodynamic changes. Robust mesh generation is a fundamental component required for developing simulations with high accuracy. However, mesh generation for coastal domains can be an elaborate procedure. Here, we describe an approach combining mesh generators with Geographical Information Systems. We demonstrate robustness and efficiency by constructing a mesh with which to examine the potential environmental impact of a tidal turbine farm installation in the Orkney Islands. The mesh is then used with two well-validated ocean models, to compare their flow predictions with and without a turbine array. The results demonstrate that it is possible to create an easy-to-use tool to generate high-quality meshes for combined coastal engineering, here tidal turbines, and coastal ocean simulations

Integrating Research Data Management into Geographical Information Systems

Ocean modelling requires the production of high-fidelity computational meshes upon which to solve the equations of motion. The production of such meshes by hand is often infeasible, considering the complexity of the bathymetry and coastlines. The use of Geographical Information Systems (GIS) is therefore a key component to discretising the region of interest and producing a mesh appropriate to resolve the dynamics. However, all data associated with the production of a mesh must be provided in order to contribute to the overall recomputability of the subsequent simulation. This work presents the integration of research data management in QMesh, a tool for generating meshes using GIS. The tool uses the PyRDM library to provide a quick and easy way for scientists to publish meshes, and all data required to regenerate them, to persistent online repositories. These repositories are assigned unique identifiers to enable proper citation of the meshes in journal articles.Comment: Accepted, camera-ready version. To appear in the Proceedings of the 5th International Workshop on Semantic Digital Archives (http://sda2015.dke-research.de/), held in Pozna\'n, Poland on 18 September 2015 as part of the 19th International Conference on Theory and Practice of Digital Libraries (http://tpdl2015.info/

Methodology in Setting-Up a Three-Dimensional Flow Model for the Strait of Malacca, Malaysia

As a rapidly developing and expanding country, Malaysia is expected to see an increase in its electricity consumption in the near future. Although known for its abundance of natural resources, specifically petroleum and natural gas, Malaysia has pledged to reduce its dependency on conventional resources and aims to become a carbon-neutral nation by the year 2050. This can be achieved by unlocking sustainable alternatives from the ocean, such as waves and tidal current energy, which are known to be abundant, continuous, and clean. Although various studies had identified several locations along the Straits of Malacca with potential to be used as deployment sites for tidal stream turbines, most of them were focused only on theoretical resource assessment. Since detailed three-dimensional flow models for the Malacca Strait have yet to be thoroughly developed, examined, and discussed, this study aims to provide a preliminary methodology for setting up a three-dimensional numerical model for this region. The analysis of the study consists of three steps: pre-processing using Blue Kenue; processing with Telemac 3D; and post-processing, which visualizes the simulation outcome. The output from the simulation is validated against published measurement data to ensure the accuracy and robustness of the numerical model. The simulation outcome reveals that the southeast part of the Malacca Strait could be a promising area for deploying tidal stream turbines due to the high tidal current velocity in that area. Additionally, it is also observed that the kinetic energy flux increases towards the southeast part of the strait due to the strait's narrow size in that area. Overall, a detailed procedure for setting up a three-dimensional flow model for the Strait of Malacca is presented, and it is hoped that this work could highlight some of the complexity involved in developing an ocean-scale model for this region

Modelling the Eddy Pattern in the harbour of Zeebrugge

Hydrodynamic

Characterizing the Great Lakes hydrokinetic renewable energy resource:Lake Erie wave, surge and seiche characteristics

Lake Erie is the fourth largest, in surface area, of the Great Lakes. Seiching events in the lake have in the past led to breaches of the flood wall in Buffalo (at the eastern end of the lake), causing loss of life, and significant loss to properties. Here, we analyze the potential of Lake Erie for generating electricity from its storm surge, seiching, and wave energy resources. We find that there is significant potential energy in the lake that may be suitable for generating meaningful levels of electricity from seiches and storm surge; for instance, by developing an artificial ‘lagoon’. It is shown that an extreme surge event similar to that of January 30, 2008 which generated a surge of approximately +3 m at the eastern end and a corresponding set-down of nearly −2.7 m at the western end of Lake Erie, could contain a total theoretical potential energy of approximately 5 × 107 kWh. If such energy could, practically, be harnessed using a surge lagoon with a surface area of 2 km2 near Buffalo, the potential energy would be 2.3 × 104 kWh, enough energy to power the equivalent of 40 homes for an entire month. The cost of such a lagoon could be partially offset by the potential of such a structure, and the operation of such a lagoon, to help alleviate flooding during extreme events. Furthermore, as an example, the analysis of the lake-wide wave data for 2011 shows that the monthly mean wave power is greater in the central and eastern basins of Lake Erie. Wave power was highest in October and November when the monthly mean wave power reached 10 kW/m. In contrast to most oceanographic environments, the wave power resource is reduced in winter, mostly due to the presence of surface ice in the lake. The surface ice appears to significantly reduce wave height and power during winter months, resulting in a relatively low annual mean wave power. However, the monthly mean wave power was the lowest in late spring and during summer when the monthly mean wave power was around 2.5 kW/m. Although this study represents the first attempt to assess the marine renewable energy of Lake Erie, further research is necessary to examine the feasibility of energy extraction in the lake

Tidal Energy and Coastal Models: Improved Turbine Simulation

Marine renewable energy is a continually growing topic of both commercial and academic research sectors. While not as developed as other renewable technologies such as those deployed within the wind sector, there is substantial technological crossover coupled with the inherent high energy density of water, that has helped push marine renewables into the wider renewable agenda. Thus, an ever expanding range of projects are in various stages of development.As with all technological developments, there are a range of factors that can con-tribute to the rate of development or eventual success. One of the main difficulties, when looking at marine renewable technologies in a comparative view to other en-ergy generation technologies, is that the operational environment is physically more complex: Energy must be supplied in diverse physical conditions, that temporally fluctuate with a range of time scales. The constant questions to the iteration to the local ecology. The increased operational fatigue of deployed devices. The financial risk associated within a recent sector.This work presents the continual research related to the computational research development of different marine renewable technologies that were under develop-ment of several institutional bodies at the time of writing this document.The scope has a wide envelopment as the nature of novel projects means that the project failure rate is high. Thus, forced through a combination of reasons related to financial, useful purpose and intellectual property, the research covers distinct projects

Hybrid global-local optimisation algorithms for the layout design of tidal turbine arrays

Tidal stream power generation represents a promising source of renewable energy. In order to extract an economically useful amount of power, tens to hundreds of tidal turbines need to be placed within an array. The layout of these turbines can have a significant impact on the power extracted and hence on the viability of the site. Funke et al. formulated the question of the best turbine layout as an optimisation problem constrained by the shallow water equations and solved it using a local, gradient-based optimisation algorithm. Given the local nature of this approach, the question arises of how optimal the layouts actually are. This becomes particularly important for scenarios with complex bathymetry and layout constraints, both of which typically introduce locally optimal layouts. Optimisation algorithms which find the global optima generally require orders of magnitude more iterations than local optimisation algorithms and are thus infeasible in combination with an expensive flow model. This paper presents an analytical wake model to act as an efficient proxy to the shallow water model. Based upon this, a hybrid global-local two-stage optimisation approach is presented in which turbine layouts are first optimised with the analytical wake model via a global optimisation algorithm, and further optimised with the shallow water model via a local gradient-based optimisation algorithm. This procedure is applied to a number of idealised cases and a more realistic case with complex bathymetry in the Pentland Firth, Scotland. It is shown that in cases where bathymetry is considered, the two-stage optimisation procedure is able to improve the power extracted from the array by as much as 25% compared to local optimisation for idealised scenarios and by as much as 12% for the more realistic Pentland Firth scenario whilst in many cases reducing the overall computation time by approximately 35%