Energy loss analysis of horizontal axis tidal turbine based on entropy production theory

In the study of horizontal axis tidal turbines (HATTs), extensive research has been conducted on wake flow fields, yet the relationship between vortices and energy loss has not been thoroughly elucidated. To better investigate the mechanism of wake energy loss and enhance the efficiency of tidal current turbines, this study is based on entropy generation theory, exploring the relationship between energy loss and vortex structures in HATTs, as well as the spatial distribution of wake energy loss under different tip speed ratio (TSR) conditions. Furthermore, a quantitative analysis of the variation in wake energy loss is conducted. The results indicate that the total energy loss initially decreases and then increases with the increase in TSR, which is consistent with the interval where the power coefficient first increases and then decreases with TSR. Tip vortices are the primary factors affecting the distribution of energy loss in the wake region. The entropy production rate (EPR) curve in the wake region exhibits three peaks, with EPR in the wake region showing a centrally symmetric distribution along the x axis. Hub vortices and separation vortices only cause energy loss in a small section behind the blades and do not spread to the main wake region, thus having minimal impact on the primary wake region. Near the optimal operating condition, the maximum peak and major area of the EPR curve occur in the middle section of the wake region, while at lower and higher TSRs, the maximum peak and major area of the EPR curve appear in the front section of the wake region.