Microenergy Harvester for Remote Ocean Buoys Using Piezoelectric Sensors Coupled with Superballs

Wave energy is a renewable resource with high energy potential. This research work proposes a low power piezoelectric energy harvesting system based on the heave motion of ocean buoys. This Piezoelectric Energy Harvester (PEH) is composed of piezoelectric diaphragms coupled with superballs to enhance the output of the piezoelectric sensor. The PEH setup is designed within a floating buoy and tested in a wave flume by varying the frequency of regular waves. The heaving of the buoy causes the superball to oscillate and impact upon the piezo diaphragms thereby producing power. This output is then processed using appropriate AC to DC converter and booster circuits. The single-axis sensor-diaphragm responses under regular wave conditions with varying wave heights were analyzed. A rms voltage of about 2.56 V was generated for a wave height of 0.21 m and wave period of 1.2 s. The wave flume experimental results show that the maximum harvested power was about 80 mW by the entire piezo sensor diaphragm setup for the wave height range of 0.06 m to 0.21 m and wave period of 1.22 s to 2.13 s. Using the same technique in the ocean buoys of diameter 0.9 m in the swell wave conditions between 0.5 to 3.5 m significant wave height, the system can generate maximum voltage of up to 16 V using 28 numbers of superballs with sensors arranged in parallel/series combinational power circuits. This harvesting technique will be very much useful for coastal & offshore buoys to harvest power in a hybrid approach during the failure in solar battery charging during monsoon and unfavorable weathers.