Abstract
The InWave wave energy converter (WEC), which is three-tether WEC type, absorbs wave energy via moored cylindrical buoys with three ropes connected to a terrestrial power take-off (PTO) through a subsea pulley. In this study, a simulation study was conducted to select a suitable PTO when designing a three-tether WEC. The mechanical PTO transfers energy from the buoy to the generator using a gearbox, whereas the hydraulic PTO uses a hydraulic pump, an accumulator, and a hydraulic motor to convert mechanical energy into electrical energy. The hydraulic PTO has a lower energy conversion efficiency than that of the mechanical PTO owing to losses resulting from pipe friction and the individual efficiencies of the hydraulic pumps and motors. However, the efficiencies mentioned above are not the efficiency of the whole system. The efficiency of the whole system should be analyzed considering the tension of the rope and the efficiency of the generator. In this study, the energy conversion efficiencies of the InWave WEC installed the mechanical and hydraulic PTO devices are compared, and their behaviors are analyzed through numerical simulations. The mechanics of mechanical and hydraulic PTO applied to InWave are mathematically expressed, and the issues of the elements constituting the PTO are explained. Finally, factors to consider for PTO selection are presented.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The simulation model developed in this study provides information on the behavior of the buoy, generator, rope drums, and ropes
In order to compare the efficiency of the wave energy converter (WEC) system, it is necessary to analyze the energy obtained from the buoy (=rope tension) and the behavior of the generator that converts it into electrical energy
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Renewable energy is an energy resource that is naturally replenished over time, such as sunlight, wind, rain, waves, and geothermal heat. Developed countries are increasing their renewable power output to reduce dependence on fossil fuels. Higher energy conversion efficiencies have been achieved for solar and wind power generators through continued development. Solar and wind energy are the dominant forms of renewable energy resources owing to the abundant scope for harnessing them. Wave energy has been drawing considerable research interest as it involves a higher energy density than that of the aforementioned two resources
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