Power electronic converters for microbial fuel cell energy extraction: Effects of inductance, duty ratio, and switching frequency

Power converter based microbial fuel cell (MFC) energy harvesting has been recently researched to replace the external resistors that have been utilized to show MFC output in many studies. The electronic circuit can operate as an equivalent external resistor, but the energy generated from MFC can be harvested in storage instead of being dissipated. However, there is limited information in the literature about the effects of operating configuration of power electronic circuits on MFC energy harvesting. In this study, a boost-converter based energy harvester circuit was examined in terms of inductance, duty ratio, and switching frequency. The results showed that all of these factors play important roles for the performance of MFC and energy harvesting, and their effects can be cross-linked. Current and voltage is generally proportional and inversely proportional to the inductance, respectively. The total harvested energy and efficiency vary significantly by combinations of duty ratio and switching frequency. For the MFC reactor tested in the study, the highest energy harvested was 3.48 J which was under the combination of 14 mH inductance, 75% duty ratio and 5000 Hz frequency, comparing to the highest efficiency of 67.7% happened at 130 mH inductance, 25% duty ratio and 4000 Hz frequency. When using the smallest inductance of 0.45 mH, the highest energy and efficiency were only 1.38 J (50% duty ratio and 5000 Hz frequency) and 19.9% (25% duty ratio and 5000 Hz frequency), respectively. Regardless of the voltages and currents produced in various operating configurations, anode potentials were stable, suggesting that there were enough electrons available to be utilized for current generation. An optimal operating configuration that provides ideal system performance can be found for different reactors and applications.