Effects of substrate concentrations on performance of serially connected microbial fuel cells (MFCs) operated in a continuous mode

Stacking of microbial fuel cells (MFC) by connecting multiple small-sized units in a series is used for generating higher power from the MFCs. However, voltage reversal is a critical problem in a serially connected MFC unit. The voltage reversal often occurs when substrate concentration is relatively low in the anodic compartment. Two rectangular individual cells were stacked together in series: MFC1 was fed with 1?g?glucose?L^?1 throughout the experiment while MFC2 was fed with various concentrations of glucose (0.1, 0.2, 0.3, 0.5 and 0.8?g?L^?1). Voltage reversal occurred when the stack configuration was performed using (1?+?0.1)?g?glucose?L^?1. The stacked configurations with (1?+?0.2, 1?+?0.3, 1?+?0.5 and 1?+?0.8)?g?glucose?L^?1 were operated successfully without the voltage reversal. The maximum powers of 1.88, 2.04, 3.6, 2.5 and 2.18?mW were obtained with the stacked configurations of (1?+?0.2), (1?+?0.3), (1?+?0.5), (1?+?0.8) and (1?+?1)?g?glucose?L^?1, respectively. Except in the stacked configuration with (1?+?0.1)?g?glucose?L^?1, the stacked voltages obtained were similar.