Scaling of a Prototype Tidal Stream Turbine using Non-Dimensional Parameters

The impact of local depth-wise velocity profiles on tidal turbine performance is important. Although the use of standard power laws for predicting velocity profiles is common, these laws may underestimate the magnitude of the depth-wise velocity shear and subsequent power attenuation. Where shipping restrictions exist, the position of the rotor tip must include the lowest negative storm surge to minimise the damage from local shipping lanes. In addition the lower portion of the rotor swept diameter should not be within the lower 25% of the water column. However, it may not be possible to avoid this as arrays expand into areas where large cargo shipping lanes occur, such as within the Severn Estuary. Predicting the performance of a tidal turbine in a high velocity shear is therefore crucial in terms of power extraction. This paper discusses the dimensional scaling of a turbine using CFD and experimental data. Key performance characteristics of torque and power coefficients were generated to estimate the turbine’s performance over a range of diameters and tidal velocities, providing a first order approximation for matching HATT performance characteristics to site conditions. The paper will also show that the turbine’s performance characteristics are independent of Reynolds number.