Earticle

This study considers the effect of anode capacitance as a mechanism to affect power and power quality from an MFC. A tubular MFC with a mixed culture biofilm on carbon veil electrode with a relatively high surface area was implemented. The influence of external loads (100, 500, 1k, 3k Ω) and switched open and closed circuit cycles on charge and energy were compared to the steady state load conditions. Furthermore, automated periodic discontinuous operation with short open and closed circuit cycles was applied (R = 100 Ω) and resulted in an increase in average power and current with prolonged open circuit and decreasing closed circuit periods. The capacitance effect was investigated by Electrochemical Impedance Spectroscopy (EIS) which resulted in a more than 10-fold higher double layer capacitance of the Helmholtz layer compared to the biofilm, as well as by dynamic step response of the anode and cathode potentials and their interaction during discontinuous operation. The results indicate that the capacitive behavior can be utilized to increase the power-quality, i.e. its availability/applicability with respect to the operation of low power consuming devices, however only at the expense of energy efficiency.