Research on Deep-Sea Electric Power Generation Technique From Seawater Pressure

Abstract

A novel seawater pressure energy conversion system that utilizes seawater pressure to generate electric energy has been studied in this paper. The energy conversion system utilizes the pressure difference between the pressurized seawater and the empty pressure container to drive hydraulic motor and the coaxially coupled generator to generate electric energy. The output electric energy has been recorded by the data logger throughout the process. However, the actual conversion efficiency from seawater pressure energy to electric energy reaches only 63.8%. Moreover, the electric power supply time of the conversion system has mainly been limited by the holding capacity of the empty pressure container. The low conversion efficiency and the short electric power supply time have limited its application in the long-term in-situ observatory stations. Therefore, a new hydraulic driving system consisting of high-speed on/off valves will be applied to the system not only to improve the conversion efficiency but also to extend the electric power supply time. In the new hydraulic driving system, the input flow rate of the system has been largely reduced due to the recycle of the flow through the hydraulic motor. Thus the conversion efficiency has been improved and the electric power supply time has been extended. In the current study, the analysis is conducted at various duty ratios of PWM (Pulse Width Modulation) signal which is provided to highspeed on/off valves so as to obtain maximum conversion efficiency. Research shows the optimum duty ratio and the maximum conversion efficiency at the optimum duty ratio can be theoretically calculated when the properties of the system are known. Simulation results have demonstrated the influence of duty ratio on conversion efficiency. Although the conversion efficiency of the system with the new hydraulic driving system has not increased significantly, the reduction of the input flow rate has largely extended the electric power supply time which is very useful for long-term in-situ observatory stations.