Shape geometry of floating oscillating water column for wave energy converter at low wave height condition

The Oscillating Water Column (OWC) is one of the most promising Wave Energy Converter (WEC) concepts in terms of practicality, survivability, and efficiency. This study was done to design and investigate the performance of floating OWC for WEC in low wave height condition. In the past few decades, different ideas, designs and devices have been put forward to extract energy from high heave wave condition, therefore this research addresses to extract energy from low heave wave condition. Pugh Matrix method was used to select the type of WEC to be study. The Backward Bent Duct Buoy (BBDB) was selected and three different back bottom
corner shapes of BBDB were developed. The experiment was conducted in a 3D wave basin at National Hydraulic Research Institute of Malaysia (NAHRIM). Wave heights of 0.05 m to 0.15 m with a wave period of 1 s to 5 s were used in regular
wave condition. Results showed that water column characteristics of the BBDB for different bottom corners were quite similar in terms of pressure, water elevation and
airflow rate at the nozzle outlet. In addition, it was found that the optimum wave height and wave period for all BBDB models were 0.15 m and 1.6 s, respectively.
The highest performance of the BBDB was produced by the BBDB with a curve bottom corner shape with an efficiency of 1.50 followed by BBDB with square bottom corner shape with an efficiency of 1.20 and BBDB with 45o bottom corner shape with an efficiency of 0.9. Overall, the obtained results provided important insights in selecting the BBDB as a best design for WEC. It can be proposed that the curve bottom corner shape is the most efficient BBDB performance in low wave height conditions. This is due to the minimising energy losses around corners compared to the sharp edges. Moreover, it is also found that the resonance frequency help to increase the performance of the BBDB regardless the back bottom corner shapes. Thus, the observation was attributed to the suitability of floating OWC WEC in low wave height condition.