Effects of blockage, arrangement and channel-dynamics on performance of turbines in tidal array.
How to increase the power per turbine is crucial for the development of tidal energy as this decides the performance and economics of the turbine in tidal array. In this work we combine the two-scale partial array model and one-dimensional channel model to investigate the effects of blockage, arrangement and channel-dynamics on tidal turbine together and individually. The power per turbine is deduced as the product of two parameters, the power coefficient measuring the power acquired from instantaneous flow and the environment coefficient showing the response of channel to added drag. The results suggest that the channel-dynamics decrease the predicted power and the optimal induction factor compared with situations of constant velocity amplitude. The model also shows that depending on two characteristic parameters of the channel, $\alpha$ and $\lambda_0$, the power per turbine may monotonously increase, decrease or get the maxima at certain global blockage when we increase the number of turbines in a row. Furthermore, we find that besides density (blockage), the arrangement should also be considered to obtain an efficient array. Although the beneficial effects would be partly offset by reduced velocity, when channel-dynamics are considered, appropriate arrangements can still enhance the performance of turbine, increasing the power while decreasing the force and environment influence. The arrangement also changes the global blockage to get maximum power. As the increase rate of power per turbine from array across the whole width to optimal partial array diminishes with the adding of the blockage, arranging optimally would reduce the global blockage where power gets maximum value.
Publisher URL: http://arxiv.org/abs/1711.00364