Capacitive Bioanodes Enable Renewable Energy Storage in Microbial Fuel Cells

We developed an integrated system for storage of renewable electricity in a microbial fuel cell (MFC). The system contained a capacitive electrode that was inserted into the anodic compartment of an MFC to form a capacitive bioanode. This capacitive bioanode was compared with a noncapacitive bioanode on the basis of performance and storage capacity. The performance and storage capacity were investigated during polarization curves and charge–discharge experiments. During polarization curves the capacitive electrode reached a maximum current density of 1.02 ± 0.04 A/m², whereas the noncapacitive electrode reached a current density output of only 0.79 ± 0.03 A/m². During the charge–discharge experiment with 5 min of charging and 20 min of discharging, the capacitive electrode was able to store a total of 22 831 C/m², whereas the noncapacitive electrode was only able to store 12 195 C/m². Regarding the charge recovery of each electrode, the capacitive electrode was able to recover 52.9% more charge during each charge–discharge experiment compared with the noncapacitive electrode. The capacitive electrode outperformed the noncapacitive electrode throughout each charge–discharge experiment. With a capacitive electrode it is possible to use the MFC simultaneously for production and storage of renewable electricity

Extraction of Energy from Small Thermal Differences near Room Temperature Using Capacitive Membrane Technology

Extracting electric energy from small temperature differences is an emerging field in response to the transition toward sustainable energy generation. We introduce a novel concept for producing electricity from small temperature differences by the use of an assembly combining ion exchange membranes and porous carbon electrodes immersed in aqueous electrolytes. Via the temperature differences, we generate a thermal membrane potential that acts as a driving force for ion adsorption/desorption cycles within an electrostatic double layer, thus converting heat into electric work. We report for a temperature difference of 30 °C a maximal energy harvest of ∼2 mJ/m², normalized to the surface area of all the membranes