Voltage balancing strategies for serial connection of microbial fuel cells^*

¹ Université de Lyon, INSA de Lyon, Laboratoire Ampère, 21 avenue Jean Capelle, 69100 Villeurbanne, France
² Université de Lyon, Université Claude Bernard Lyon, 1, Laboratoire Ampère, 43 bd. du 11 novembre 1918, 69622 Villeurbanne Cedex, France
³ Université de Lyon, école Centrale de Lyon, Laboratoire Ampère, 36 avenue Guy de Collongue, 69134 écully, France

^a e-mail: firas.khaled@insa-lyon.fr

Received: 26 January 2015
Revised: 22 April 2015
Accepted: 8 July 2015
Published online: 31 July 2015

Abstract

The microbial fuel cell (MFC) converts electrochemically organic matter into electricity by means of metabolisms of bacteria. The MFC power output is limited by low voltage and low current characteristics in the range of microwatts or milliwatts per litre. In order to produce a sufficient voltage level (>1.5 V) and sufficient power to supply real applications such as autonomous sensors, it is necessary to either scale-up one single unit or to connect multiple units together. Many topologies of connection are possible as the serial association to improve the output voltage, or the parallel connection to improve the output current or the series/parallel connection to step-up both voltage and current. The association of MFCs in series is a solution to increase the voltage to an acceptable value and to mutualize the unit’s output power. The serial association of a large number of MFCs presents several issues. The first one is the hydraulic coupling among MFCs when they share the same substrate. The second one is the dispersion between generators that lead to a non-optimal stack efficiency because the maximum power point (MPP) operation of all MFCs is not permitted. Voltage balancing is a solution to compensate non-uniformities towards MPP. This paper presents solutions to improve the efficiency of a stack of serially connected MFCs through a voltage-balancing circuit.