Low Power Control Systems for Microbial Fuel Cell Batteries

摘要

The URI Ocean Engineering Department has been working with the US Naval Research Laboratory to develop and test microbial fuel cell battery systems for low power seafloor applications of extended duration. These low power fuel cells utilize graphite electrodes in anoxic sediment coupled to bottle brush graphite electrodes in the water column to make up a battery system. These battery systems typically produce power on the order of 10-50 milliwatts per square meter of electrode area, or as much as ten times more if sediment electrode pore water can be exchanged by means of a pump. As part of this program, testing of these microbial fuel cell batteries has been conducted in the Potomac River Washington D.C., Narragansett Bay Rhode Island, Tuckerton New Jersey, and Monterey Bay California. For these tests it has been necessary to develop long term, low power control and monitoring systems to manage the batteries operation and to record their performance without consuming a significant portion of the meager power produced. This paper details the development and testing of these low power monitoring systems and their results. For this project we have developed several related systems. All of the systems utilize Oopic microcontrollers as the core low power computer. The Oopic consumes about 20mA at 5 volts when on and none when off. Its programs are stored on EEPROM, and they start from the beginning each time the Oopic is powered up. Notes from the previous time awake can be stored in the EEPROM below the program. The microcontrollers are turned on by an electronic alarm from an I2C real time alarm clock chip with its own multi year lithium battery. The microcontrollers command the shut off of power as part of their program. The real time clock maintains crystal controlled date and time without using any system power. The clock can be programmed to wake up the system at a specific date and time, or at any of numerous intervals.