Efifciency Analysis Of Oscillating Water Column Wave Energy Converter And The Modified Design

Ocean waves are a significant resource of inexhaustible, non-polluting energy. Wave energy converters provide a means of transforming wave energy into usable electrical energy. The development of these devices is undergoing rapid change. The oscillating water column (OWC) wave energy converter is one of the most widely used facilities all over the world, whose hydrodynamic characteristics was studied by numerical method. And a novel OWC wave energy converter was presented in this paper.Based on the potential flow theory, a two-dimension mathematical model of OWC was obtained. The fully nonlinear wave was simulated by desigularized boundary integral equation method (DBIEM), which was based on a mixed-Eulerian-Lagrangian formulation. The oscillating air pressure inside the OWC air-chamber was modeled by assuming that the air is incompressible and the air-turbine mass-flow rate is proportional to the pressure difference (a linear turbine). For shallow draughts of the front wall, the numerical results agreed well with the available analytical results. The effects of the dimensionless air-chamber width, immersed depth of the front wall,water depth, wave height and the turbine constant on wave energy extraction efficiency were discussed.Moreover, hydrodynamic characteristics of the OWC were studied under the anti-reflection condition. The anti-reflection condition was achieved by adjusting the amplitude and phase of the oscillating air pressure in the air-chamber. The relationship of the wave energy extraction efficiency with the amplitude and phase of the oscillating air pressure in the air-chamber was investigated. The numerical results showed that the wave energy extraction efficiency of the OWC under anti-reflection condition was much higher than that of the traditional OWC. Under the condition of anti-reflection, the amplitudes of the oscillating air pressure in the air-chamber and the flow rate through the turbine were much higher and the phase differences between them were observed.A novel design of the OWC wave energy converter was also presented, in which the phase differences between the oscillating air pressure and the flow rate can be adjusted. By this way, it is possible to achieve higher wave energy extraction efficiency under different wave conditions.