Hybrid Energy Harvesting from Natural Wind and Traffic-Induced Bridge Vibrations

This paper describes the development and validation of a hybrid electromagnetic energy harvester capable of simultaneously scavenging energy from two different energy sources: low-speed natural wind and traffic-induced bridge vibrations. The harvester employs a cantilever structure designed to exhibit significant vibrations due to aeroelastic instability even at low wind speeds and dynamic excitation from traffic-induced bridge vibrations through an electromagnetic transduction mechanism. It is noted from the laboratory tests using a shaker and wind tunnel that the electrical load resistance significantly influences vibration amplitude, generated power, and the onset velocity of galloping in the harvester. Wind tunnel test results also reveal the necessity of adjusting load resistance according to wind speed for optimal power output. This study provides approximate analytical solutions for the optimal external load resistance and corresponding maximum power under wind and base excitation separately. These solutions are validated through comparisons with numerical simulations and wind tunnel tests. Additionally, under hybrid excitations, particularly at low wind speeds and accelerations, a notable enhancement in average power output is observed. Combining wind with vibration-only or base excitation with galloping-only harvesting significantly improves power output, ensuring enhanced energy availability even if one source is interrupted. Field tests on the bridge confirm the effectiveness of the present harvester in generating electricity from both wind-induced galloping and bridge vibrations, demonstrating its capability to harness energy from two complementary sources. Overall, this hybrid harvester presents a promising solution for maximizing energy capture from ambient natural sources, contributing to advancements in sustainable energy generation.