This study investigates on the hydrodynamic efficiency of a wave energy converting device using multiple floats. The floats have the same size and mass, arranged along the wave propagation direction and close to each other. A scale model was built in the laboratory at Hohai University and then employed to study the device's performance in wave controlling and wave energy conversion. During the physical tests, the water surface fluctuation around the structures, the motion of floats, and the voltage output of the dynamos are simultaneously measured. Results show that the incoming wave energy is effectively dissipated by the interactions between waves and structures for the waves with an intermediate wave period. The energy conversion is also helpful for the wave controlling as electricity generation modules absorb part of incident wave energy. Meanwhile, the advantage of the present device in extracting wave energy efficiently at a wide range of wave frequency is confirmed. When the wave period is 1.2~1.6 s, the device's performance is optimal, and the energy conversion efficiency is about 15%.
Wave energy has the limitless foreground as a kind of newly arisen and renewable energy due to numbers of advantages, such as wide distribution and pollution-free. In previous studies, the global gross wave energy resource is estimated to be about 3.7 TW (Mørk et al. 2010). However, the development of wave energy industry is still limited due to a few factors when compared with fossil energy, including conversion efficiency and economic feasibility. Therefore, it is essential to improve the wave energy conversion efficiency and reduce the construction and maintenance cost of wave energy converters (WECs). In recent years, hundreds of patents have been issued to harness the wave energy or improve WECs' performance (Falcão, 2010; Bahaj, 2011; Vicinanza, 2019; Qiu, 2019). Among them, one category is combining WECs with other coastal structures, to save costs and avoid extra sea area fees.