Harvesting energy from microbes

One activity within HE4T been to assist in power extraction from Microbial Fuel Cells (MFC) which is one research area within Biochemical Process Engineering at LTU. The fuel cells generate electricity by the oxidation of sulfide using bacteria. The long term goal with the use of multiple MFCs is to use the output power to energize bioelectrochemical systems (BES) which are used to treat sulfate rich waste waters, with sulfide as one resulting output. The sulfide will then in turn be used to continue to energize the MFCs, closing the energy loop. The cells as shown below are at an early experimental stage, and yield at this time very low voltages and power, typically a few tens of microwatts at an output voltage of a few tenths of Volts.

The MFCs have in HE4T been characterized in a test setup as shown on the top of the page with results showing the output power as function of loaded voltage seen below. As an additional experiment, a low power dedicated DC-DC boost converter was designed to extract power from the MFC to give usable voltage level. The boost converter was built to be able to operate at input voltages as low as 100 mV, and uses an MPPT algorithm to extract maximum power. A demonstration was performed where the boost converter was operated from solely two series connected MFCs, operating a blinking LED from the MFC power alone (Blinker_circuit.MOV). The work now continues with investigations of integrated circuit solutions for boost converter designs, as well as with continued characterization of more MFCs.