The effect of internal capacitance on power quality and energy efficiency in a tubular microbial fuel cell

a b s t r a c t The pseudo-capacitive behaviour of a high surface area carbon veil electrode in a tubular microbial fuel cell (MFC) was investigated as a mechanism to enhance power quality and energy efficiency. Accumu- lated charge and energy from the anodic biofilm after prolonged open circuit times (1-120 min) were compared against equivalent periods of steady state loading (R = 100-3000 � ). A significant difference in the amount of accumulated charge with different loads was observed, resulting in 1.051 C (R = 100 � ) compared to 0.006 C (R = 3 k� ). The automated application of short open and closed circuit (0.5-10 s) cycles resulted in an increase of power/current production (closed circuit alone), but presented lower efficiency considering entire open and closed period. The cumulative charge on the carbon veil electrode with biofilm was 39,807 C m −2 at 100 � . Electrochemical Impedance Spectroscopy (EIS) showed that the Helmholtz layer presented a double layer capacitance of more than ten times the biofilm on electrode. The results indicate that the capacitive behaviour could be utilized to increase the power quality, i.e. its availability/applicability with respect to the operation of low power consuming devices. © 2014 Elsevier Ltd. All rights reserved.