Power management systems for use with microbial fuel cells

Abstract

The Navy has the need to power underwater sensor packages. Powering these systems with batteries requires constant upkeep that involve diving teams. This is a hazardous and expensive process so they want to explore alternate methods of powering these sensor packages. Microbial fuel cells (MFCs) are a potential energy source that could power devices placed underwater. MFCs are able to harvest energy from naturally occurring bacteria in open water environments. However, MFCs produce very little voltage and current. Traditional methods of power conversion are not able to allow an MFC to operate as a power source because of these limitations. This paper describes two power management systems have been designed for use with a microbial fuel cell (MFC). These systems create a power source suitable for powering electronic devices requiring higher voltage and power than what the MFC is able to supply on its own. Though the two systems use different methods they share a similar operating concept. The systems oscillate between two modes: (1) a period when energy from the MFC is accumulated in a supercapacitor and (2) when energy accumulated in the supercapacitor(s) is used to power external electronic devices. The power management system controls the operation of the integrated system, making decision about switching the modes of operation. The power supplies are entirely autonomous and the load and power management system require no external power besides the MFC. These power management systems were designed, built, and tested in the laboratory. In our application the power management systems increased the input potential from MFCs, which were as low as 300mV, to 3.3V and the input power from microwatts to milliwatts.