Abstract
Ocean energy is a kind of renewable energy contained in seawater, which has the characteristics of large total reserves, sustainable use, and its being green and clean. Influenced by rising oil prices and global climate change, an increasing number of countries are attaching great importance to the strategic position of ocean energy in the future energy sector, and are formulating national ocean energy development roadmaps and conducting research and development on ocean energy technologies. Ocean current energy is a widely existing kind of ocean energy with abundant reserves. However, due to the low current velocity in most of the deep sea, low current energy has not been effectively exploited. In this paper, the Blade element momentum (BEM) theory based on Vortex column theory is used to design a special airfoil for low current energy applications, and a prototype turbine with rotor diameter of 4.46 m and tip speed ratio (TSR) of 6 is fabricated. In order to achieve stable electric power output, this paper designs a hydraulic conversion power generation control system with flexible control, and the hydraulic system working pressure designed to 21 MPa. In this paper, we conducted towing experiments on the prototype of an ocean current energy turbine, with hydraulic transmission and a control power generation system applied to the low flow rate, and achieved the target of hydraulic motor speed in the range of 14.7~15.9 r/min and steady-state speed accuracy in the range of ±1%. The research conducted in this paper can provide a research basis for the efficient exploitation of low-flow ocean current energy.
Highlights
Current energy is an important aspect of marine renewable energy, including offshore tidal energy, offshore current energy, deep-sea circulation energy, etc
Lee used the Blade element momentum (BEM) to optimize blade chord length and and the built-in twist angle of the blade, which are important design variables for the the built-in twist angle of the blade, which are important design variables for the optimal optimal design of the ocean current turbine blade, and his research showed that the blade design of the ocean current turbine blade, and his research showed that the blade effiefficiency increases by 8.7%, with an annual energy production increase of approximately ciency increases by 8.7%, with an annual energy production increase of approximately 7%
Borkowski showed that the control complexity in small hydropower plants is mainly caused by special steady-state features of the ocean current turbine, the longterm constants of the hydraulic system and/or aging-related degradation in the system performance, and proposed a simple formula verified on a real small hydropower plants, with 150 kW as the optimal operating curve [23]
Summary
Current energy is an important aspect of marine renewable energy, including offshore tidal energy, offshore current energy, deep-sea circulation energy, etc. The selected of energy turbines has been a focus and hotspot of current research. Katsutoshi Shirasawa proposed a novel submerged horizontal axis izontal axis ocean-current turbine, to kites [4]. The discactuator is described a region swept by the ocean current energy. At the tip of blade, spiral vortex intensity occurs inoccurs the downstream zone and attachment rings. To research the aerodynamic performance characteristics of acteristics of turbine, Wu utilized the multi-relaxation time lattice Boltzmann (MRT-LBM).
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