Hydro-environmental Impact Assessment of the Significance of the Shape of Arrays of Tidal Stream Turbines

This study focuses on far-field hydro-environmental impacts of turbine arrays, with different shapes located in the Severn Estuary and Bristol Channel, UK, using a dynamically linked 1-D/2-D hydroenvironmental model. The estuary, including the Bristol Channel, is approximately 200 km long and has the third highest rise and fall of tide in the world, with typical spring tidal range of over 14 m, whilst the spring tidal currents in the estuary are well in excess of 2 m/s. There are a number of tidal renewable energy options being considered around the Severn Estuary, including but not limited to: tidal stream turbines, offshore tidal impoundments and a barrage at various locations. The model was used to predict the hydrodynamic, sediment transport and water quality processes as well as power output predictions. In order to simulate the impact of the tidal stream turbines, the model was refined and the turbines were included as momentum sinks in the momentum equation. This study shows that the impact of the arrays on the water levels was negligible. However, the impact on velocities was more significant and the flow was retarded both upstream and downstream of the arrays, whilst it was faster on the side of the arrays. It was found that changes in the suspended sediment concentrations did not follow a simple pattern and that more detailed model studies are required to achieve a better understanding of this process. Finally, it was found that the power generated was dependent on the array layouts with the power output of different arrays used in this study varied by up to 20%.