Author(s): Samuel Bray; Reza Ahmadian; Roger A. Falconer
Keywords: Severn Barrage; EFDC_B; Hydrodynamics; Mathematical Modelling; Turbine Representation
Abstract: There is a growing requirement for renewable energy production globally, and one area with considerable scope to increase energy generation, particularly in the UK, is the tidal power sector. The Severn Estuary, located in South-West of Britain, is a site that offers a uniquely excellent opportunity for tidal power extraction, with a very large tidal range and shape that allows for a large impounded area of water. More accurate modelling of proposed renewable energy projects, including more realistic representation of turbines and structure operation, would enable a better evaluation of hydroenvironmental impacts which could assist in improving the design and operation of the scheme. In this study, the numerical model EFDC was used to predict the hydrodynamic processes, both with and without the inclusion of a Severn Barrage. To eliminate any impact of the simulated structures on the model boundary, the domain was extended to beyond the continental shelf, covering an area of 846, 000km 2. The model uses a curvilinear grid where the resolution is much coarser in the open sea West of Ireland, and becomes much finer in the specific area of interest around the barrage, down to a grid size of under 2500m 2 (i. e. 50m x50m). In this paper, details are given of refinements to the representation of sluices and turbines, and to the treatment and operation of the barrage itself, with the aim of improving the prediction of velocity and discharge across the structure. The enhancements to the turbine representations were then applied to the Severn Tidal Power Group Cardiff-Weston Barrage, using the EFDC Continental Shelf Model, and the hydro-environmental impacts reassessed. The modifications were found not only to improve the simulation of water levels, velocity and discharge in the immediate vicinity of the hydraulic structure, but also affected water levels upstream of the barrage, reducing the maximum water elevations to levels that are in better agreement with values reported elsewhere in the literature.