Modular multilevel converter-based energy harvester for microbial fuel cells stacked in series

Ever since Microbial Fuel Cells (MFCs) were introduced as a promising energy technology for simultaneously generating electricity and treating wastewater, scaling them up has become a critical focus for researchers. Large-scale MFCs hold the potential to make wastewater treatment plants energy-neutral by recovering bio-electricity from organic waste streams, offering both environmental and economic benefits. However, achieving effective scalability is challenging due to several factors, including increased internal resistance in large reactors, imbalances in multi-cell stacks, voltage reversal and voltage overshoot phenomena. Due to the low output voltage and power levels of individual MFC cells, scaling up, especially increased voltage by series stacking is essential to unlock the potential of MFCs at a commercial scale. In this paper, a novel technique to effectively increase the output voltage by stacking reactors in series using a modular multilevel converter-based harvester. The proposed approach enables independent control of individual reactors to avoid voltage reversal and overshoot while sustaining operation at the maximum power point at a higher stack voltage. The proposed scheme was experimentally validated.