Review of tidal characteristics of Uldolmok Strait and optimal design of blade shape for horizontal axis tidal current turbines

Ocean energy is a promising renewable energy resource. In particular, South Korea is a country with a large amount of tidal current energy needed for the economically and technically feasible development of a tidal current power plant. In this study, the environmental conditions including the bathymetry and tidal conditions for Uldolmok Strait and previous studies carried out in Uldolmok Strait are first briefly reviewed, and the optimal design of the blade shape and performance of an optimally designed horizontal axis rotor for a 200-kW class tidal current turbine are discussed. For the optimal blade shape design, the design code, the Horizontal Axis Rotor Performance Optimizer developed by the National Renewable Energy Laboratory in the United States, is utilized, and the performance is investigated with respect to the number of blades (two or three) and the pitch control algorithms (variable or fixed). The results indicate that a variable speed fixed pitch turbine with three blades showed the best performance. However, the performances of four alternative cases did not show significant differences. Considering the advantages in terms of maintenance, we also conducted an analysis under various rotor and cut-in speed conditions. Hence, to select the final design, it is necessary to consider the structural integrity related to fatigue, as well as the economic feasibility in manufacturing the blades.