UNS: Collaborative Research: Systematical Modeling and Control of Microbial Electrochemical Activities towards Efficient Electrical Energy Harvesting

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PI: Park, Jae-Do / Ren, ZhiyongProposal Number: 1511568 / 1510682 A microbial fuel cell contains special strains of bacteria that consume organic matter in waste water to generate electricity and clean up the water. These systems have been touted as a promising route for sustainable and "energy positive" waste water treatment. However, microbial fuel cell systems have many obstacles to overcome before widespread use is possible. Two of the major problems are low power output and reliability. The goal of this project is to adapt the principles of process control theory to microbial fuel cell systems to address these two problems. The research plan will focus on developing a scientific understanding of the interactions of the bacteria with electrical power control systems, and from this understanding, develop models to control the power output of a microbial fuel cell, improving reliability. It is also hoped that tuning the process to peak power output using these models will enrich the device with the bacterial strains that produce the most electric current to further improve power output. As part of the educational activities of this project, undergraduate students will participate in the research through University of Colorado Undergraduate Research Opportunities Program. The project will also work with University of Colorado Tech Transfer Office to help energy companies who are interested in commercializing the research for specialized waste water treatment applications.Microbial fuel cells generate electricity though metabolism of dissolved organic matter. The typical microbial fuel cell is two-compartment electrochemical cell which contains a biofilm of electrochemically-active microorganisms in the anode compartment that metabolizes dissolved organic materials to generate electrochemical potential and transfer electrons to the anode surface, which is harvested as current. Protons (H+) generated by this process transfer across an ion-exchange membrane to the cathode compartment, where they are reduced to water by dissolved oxygen on the cathode surface. The electrochemically active microorganisms have the capacity to transport charge to the outer surface of the cell through specialized membrane structures. The overall goal of this proposed research is to develop a fundamental understanding of the interactions between microbial electrochemical activities and externally-controlled electrical energy harvesting systems designed for microbial fuel cells using process control and systems theory. The central hypothesis of the proposed research is that if microbial fuel cell operation can be put into a process control scheme and tuned to maximum power input, then this process will put a selection pressure on the microbial community growing within the anode biofilm to enrich the consortium for the most electrochemically active microorganisms and ultimately improve current generation and biofilm stability. Within this context, the research plan has three objectives. The first objective is to develop an energy systems model in terms of measurable and controllable variables to quantify the relationships between inputs and electrical output for a single microbial fuel cell. Based on this single cell model, the energy harvesting and control system model for a multi-cell device stack will be developed. The second objective to understand how the selective pressure created by the new pulse-type power extraction stimulates bioelectrochemical activities within the microbial community, including cell electron transfer metabolism shifts and dynamic microbial community evolution. The third objective is to utilize electrical engineering techniques such as resonant impedance matching, time- and frequency-domain analysis, and transfer functions to analyze and improve the system performance and controllability. If successful, the proposed research will culminate in scalable and flexible real-time control scheme to capture and maintain the maximum usable energy output from multiple microbial fuel cell devices under different conditions to help enable system reliability and scale-up. Research outcomes will also be integrated into several renewable energy and water treatment course offerings at the University of Colorado Boulder and Denver campuses.