Hybrid backward bent duct buoy and point absorber wave energy converter for low wave height

Recently, most Wave Energy Converter (WEC) was designed to harvest energy from high wave height conditions, which had less efficiency for low wave height conditions. This weakness causes difficulties for countries with a high potential to utilise ocean energy, such as Malaysia. Furthermore, research on suitable designs to harness highly efficient energy from low wave heights is lacking. Therefore, this study aims to determine the optimum condition parameters for a WEC to provide the best performance in low wave height. Its main objective is to investigate the hydrodynamic characteristics of a hybrid WEC by applying a new form of hybrid Backward Bent Duct Buoy (BBDB) and Point Absorber (PA) at low wave height. To overcome the weakness of BBDB and PA as well as to solve precision methods for investigating the performance of the results, the effects of single BBDB, PA, and a new hybrid form of BBDB-PA on heave Response Amplitude Operator (RAO) and power absorption were examined within various ranges of wave periods under regular wave conditions using ANSYS Advanced Quantitative Wave Analysis (AQWA) is examined. The results revealed that the new hybrid form significantly influenced the hydrodynamic characteristics like excitation force, radiation damping coefficient, and added mass of the BBDB and PA. This form also has a peak of heave RAOs and power absorption occurring in T = 1.2 s, with a value around 1.5 - 3 and 6 kW -16 kW, respectively. Besides, this research also optimises the position of PA, gap length between BBDB and PA, and diameter of PA of hybrid WEC and performs an empirical model at low wave height. The optimisation process was applied based on the data collected over one year about sea characteristics for a nearshore region of Mantanani Island. Note that this research presents a methodology for optimising the hybrid BBDB-PA based on statistical analysis and hydrodynamics of the system in frequency and performing empirical model. The optimum parameter was selected for front position PA with a 5 m diameter and 7 m gap length with BBDB for the Mantanani Island wave characteristics. To validate the empirical model of response amplitude operator for hybrid WEC at low wave height using an experiment, it was verified with an experimental scale model of 1:30 in a 2D wave flume with a wave height of 0.5 m and a wave period of 1 s -1.5 s. The hybrid BBDB and PA yielded higher performance at T = 1.25 s, with a value of 4 and 8, respectively, compared to the single BBDB and PA. Despite the condition parameter, it was discovered that the WEC position and arrangement were responsible for the highest power value regardless of the PA position used in the experiment. The results offer recommendations for optimising the design of hybrid WECs and imply the possibility of synergy between BBDB and PA to fully utilise ocean space for energy.