Experimental analysis of hydrodynamic loadings on stationary tidal turbines under wave conditions

Abstract Tidal energy has gained increased attention in recent years as the global energy sector pursues net-zero CO 2 by 2050. As tidal turbines are designed to operate for long periods of over 20 years, they must withstand harsh ocean conditions, placing high demands on long-term durability. Many existing studies have revealed that tidal turbines are subject to frequent and large-scale hydrodynamic loading fluctuations after installation, particularly for floating turbines or turbines operating in shallow waters where wave action has influence. These unsteady loads could lead to fatigue damage of the blades. Consequently, the fatigue loading on tidal turbines should be accurately evaluated during the design stage to ensure their longevity, with little need for expensive offshore repairs. Therefore, this study uses a 3D printed tidal turbine model, installed in a physical wave tank, to conduct a series of hydrodynamic tests under wave loads. The hydrodynamic loads due to waves on stationary tidal turbines and blockage effects at different submergence depths under various wave conditions have been systematically investigated, and the fatigue-inducing damage equivalent loads have been calculated. The results show that the damage equivalent load on the model turbine decreases with increasing submergence depth, while being significantly affected by the tested wave conditions. The study is then expanded to a twin turbine, from which the results reveal that the twin turbine can experience 1.25 to 2 times the hydrodynamic loads on a single turbine, and the load can be increased by increasing the orientation angle due to the turbine array interactions. This research provides important details that assist with the fatigue design of tidal turbines, advancing turbine reliability and efficiency and, in the long run, contributing to society's transition to sustainable energy consumption.