Performance Investigation of Hydraulic Wave Energy Capture System

A hydraulic wave energy capture system with irregular wave forces is established to simulate the system performance. Energy conversion characteristics of the hydraulic wave energy capture system are obtained while the significant wave height is in the range of 1 m to 4 m, and the energy period is in the range from 4 s to 11 s. Influences of significant wave height and energy period on the system are also investigated. The results show that the mean hydraulic cylinder displacement increases linearly with the increase of significant wave height. When the energy period changes from 4 s to 7 s the mean hydraulic cylinder displacement increases obviously and gradually trend to be stable as the energy period increases from 7 s to 11 s. The mean cylinder force, mean cylinder captured power, mean high-pressure accumulator pressure, mean motor speed and mean motor output power also increase with the increasing of significant wave height. When the energy period increases, those values rapidly increase and then gradually decrease. The maximal values occur when the energy period is between 5 s and 6 s. The cylinder captured power matrix, the motor output power matrix and the hydraulic system conversion efficiency matrix are also calculated. Under the significant wave height of 4m and energy period of 5.5 s, the mean hydraulic cylinder captured power is 62.44 kW, the mean motor output power is 47.52 kW and the hydraulic system conversion efficiency is 76%. The hydraulic system conversion efficiency in different sea states is in the range of 74% to 80%. With the sea state data of 15 typical points in the South China Sea, the annual captured energy of the hydraulic wave energy system year can be calculated. The annual captured energy of a single buoy is 106.82 MW•h at point P11. Those results provide a theoretical basis for the design and location selection of wave energy capture systems. © 2020 Journal of Mechanical Engineering.