New floating MFCs for Energy harvesting : a cell design overview

Microbial Fuel Cells are a very promising technology for energy harvesting in remote sensing devices. Several attempts were conducted in the past with sedimentary MFCs, with promising results. The challenge is now to scale up cells and operate them in remote real environments where there is the necessity of monitoring water parameters. Here, a simple design of floating MFCs was studied, suitable for energy harvesting in both aerobic and anaerobic waters. Several sets of cells were tested, using cheap materials, like plastic fruit boxes or panels, using a polystyrene frame or wood as floater. Untreated carbon cloth was used in both electrodes. The electrodes were insulated by felt and clay. In case of anoxic water, the anode faced the water and the cathode faced the air, while in case of aerated water the cathode faced the water and the anode was buried in a box of soil, arranged as a “floating garden” fluctuating on the surface of the water body (Fig. 1). To test this new architecture of energy harvesters, some cells were connected with electronic devices, such as LED lights (500Ω) and buzzers (1000Ω), with power management system. Difference of potential measure and Power curves were performed to evaluate the productivity of these cells. Stacks of MFCs were also tested in Milano Nosedo aerated wastewater. The cells with dimensions 50 x 30 cm were the most effective among other tested dimensions (with average power and current densities around 15 mW/m2 and 750 mA/m2, respectively), in experiment conducted in anoxic wastewater [Martinucci et al. 2015). The experimentation in natural water bodies (OD>3 mgO2/l) was conducted in city lakes of Milan from February to October 2015, for dissemination events at the International EXPO2015 in Milan (average power and current densities of around 5 mW/m2 and 100 mA/m2, respectively).