This project developed an autonomous and self-sustained sensing system for in-situ monitoring of environmental parameters in water bodies near highways. The system uses a novel microbial fuel cell (MFC), a device that generates electricity through electrochemical reactions and maintains those reactions using a safe type of bacteria from the environment (L. discophora). Work in the initial phase included selecting water quality sensors, communication devices, and a microcontroller for the sensing system and analyzing the voltage, current, and power requirements for all of the selected components. Design guidelines for the fuel cells were developed and a DC-DC converter was designed specifically for the system. Finally, a microbial fuel cell (MFC) was designed. Anode and cathode materials were selected and tested to maximize MFC performance. Work in the second phase involved fabrication and testing of the MFCs. The performance of a single MFC under various conditions was tested. Subsequently, an array of MFCs was built for preliminary testing and, based on test results, improvements to the design of both the single MFC and the array of MFCs were made. The scalability of the current MFC design was tested to maximize the sustainable power output of MFCs and minimize their internal resistance. The sustainability of the MFC array as a power supply was also tested. The performance of the MFC array was evaluated under various simulated field conditions (varying temperature, pH, and cell density of L. discophora). Water quality sensors were purchased and tested. A low power microcontroller, a 900 MHz RF transceiver, and signal conditioning circuitry were built or purchased and tested. Firmware for the microcontroller was developed t allow reading data from the signal conditioning circuitry and transmitting to a remote PC. All sub-systems were constructed, tested, and assembled into an integrated system. The system’s power supplies were also tested and fine-tuned. In Stage 3, the entire system was tested over the span of several weeks in a local stream during varied weather conditions. The MFC array was found capable of providing enough power to sustain the function of the circuitry over a test period that included both temperature and sunlight fluctuations. The microcontroller successfully executed the proper system functions based upon the measured output power of the MFC array. The RF transmitter was tested to a maximum range of 250 meters with suboptimal antenna alignment due to the local terrain. Data was transmitted on a 60 second interval over a period of several hours and proved to be within acceptable tolerances for the chosen sensors. A patent for the developed technology was filed by the Montana State University.
The contractor's final report is available.