Dynamic polarisation reveals differential steady-state stabilisation and capacitive-like behaviour in microbial fuel cells

In this paper we present several preliminary results produced with a purposely-designed external-resistor (Rext) sweeping tool for microbial fuel cells (MFCs). Fast sampling rates show that MFCs exhibit differential steady-state stabilisation behaviours depending on Rext, with consequences for time constant (tc) selection. At high Rext (35 kΩ), it is demonstrated that a tc ⩾ 10 min avoids underestimation not overestimation, whilst at low Rext (100 Ω) 5 min are sufficient, suggesting that sweeps with variable tc are possible. However, within the maximum power transfer range (2.5 kΩ), steady-states are only observed at 20 min tc but with a smaller confidence interval, questioning whether the polarisation technique is suitable to estimate maximum power transfer. Finally, a strategy towards the exploitation of a capacitive-like behaviour in MFCs is proposed, tapping into ⩾10 min periods with up to 50% higher current and energy transfer that could prove important for MFC-powered applications.