An efficiency-boosting design for backward bent duct buoy wave energy converter: Scaled prototype study in wave tank

This study proposes a novel efficiency-enhancing design for the backward bent duct buoy (EB-BBDB) wave energy converter. “Duck-wing” and “duck-bill” accessory structures are integrated into the buoyancy body to improve its energy harvesting efficiency. Physical experiments are conducted in a large-scale wave tank on three scaled prototypes to investigate the effects of the accessory structures on the hydrodynamic and energy-harvesting performance of the EB-BBDB model. Both the “duck-wing” and “duck-bill” accessory structures positively contribute to a larger amplitude of water column oscillation in the bent duct and a greater relative air pressure inside the air chamber. With the “duck-wing” accessory structures and further “duck-bill” accessory structure, the maximum capture width ratio (CWR) of BBDB is subsequently increased by 49.0% and 55.8%, respectively. Overall, these accessory structures amplify the maximum CWR by 5.7 times, reaching 128.1%. The effects of the single-point mooring and double-point mooring configurations on the hydrodynamic performance of the EB-BBDB model are also compared. The maximum CWR for the single-point mooring case further reaches 141.9%. This study presents the early-stage wave-tank model tests for the 10kW EB-BBDB named “WaveEast-1” which was manufactured in 2024 and successfully completed sea trials in 2025.