Xia-Chang Zhang

Modelling of a microbial fuel cell process

SummaryAn electrochemical model for a microbial fuel cell process is proposed here. The model was set up on the basis of the experimental results and analysis of biochemical and electrochemical processes. Simulation of the process shows that the model describes the process reasonably well. The analysis of model simulation illustrates how the current output depends on the substrate concentration, mediator concentration and other main variables. The relationship between the current output and over-voltage is revealed from the modelling study.

Functional state modelling approach for bioprocesses: local models for aerobic yeast growth processes

Abstract The functional state of a process is a novel concept which helps in monitoring and control of complex processes such as bioprocesses. The concept was introduced originally by Halme. The main idea is to use a two-level hierarchy where on the top level the process is divided into macrostates, called functional states, according to behavioural equivalence. In a functional state, the process is described by a conventional type of model which is valid in this functional state — called the local model. To illustrate further the concept of functional state in fermentation processes, experimental data and simulations of an aerobic fed-batch bakers yeast fermentation are presented. It is shown how this process can be divided into functional states by considering the cell metabolism in more detail, how the local models can be obtained, and how the functional states of a fed-batch bakers yeast fermentation and recognized on-line. By simulation and comparing the results to experimental data, it is further shown how the concept works in practice. The results are also used to demonstrate an optimal substrate feed control policy.

Functional state modeling and fuzzy control of fed-batch aerobic baker's yeast process

Abstract A novel concept of functional state in combination of local modeling is presented as an aid in monitoring and control of complex bioprocesses. On the basis of this approach a fuzzy substrate feed rate control scheme for fed batch aerobic bakers yeast process is proposed. The control algorithm was modified to advantage by including a fuzzy term. The controlled variables were either respiratory quotient or specific growth rate estimated on-line. Effective and precise operation of the system was demonstrated by computer simulation.

Biofuel Cell Utilizing Saccharomyces cerevisiae - Modelling of the Process

Abstract Biofuel cell is a device generating electrical energy by using microorganism. The driving force of a biofuel cell is the redox reaction of substrate such as glucose by using microorganism as the catalyst In this paper a biofuel cell device is presented by using Saccharomyces cerevisiae baker’s yeast as microorganism. A fairly large power output (120 μW/cm3) was obtained by using nickel net packing with graphite particles as the anode electrode. The cell can be run in batch, fed-batch, or continuous mode. Experiments indicate that yeast fermentation broth includes large amount of electroactive substances which can be utilized in the anode without the aid of mediators. An electro-biological model is proposed from the results of theoretical and experimental analysis.

Monitoring and Control of a Bacteria Fuel Cell Process by Color Analysis

Abstract Monitoring and control of a bacterial fuel cell system is investigated by using color analysis of the biofilm reactor which converts substrate to electroactive substances in the system. A change of the color in the different parts of the biofilm reactor has been notified as a useful variable to monitor the state of the fuel cell process and furthermore to control it. In the fuel cell system, the biofilm reactor is made from a perspex tube with artificial sponge used as support structure for bacteria to form biofilm. There are three parts in the biofilm reactor: upper, middle and lower part. Biofilm bacteria exists in the middle part. The reducing broth (biofuel) is accumulated in the lower part. The upper part is the place for measurement of variables and for mixing of broth with both fed substrate and oxidized broth from the fuel cell. With a mediator (2-hydroxy-1, 4-naphthoquinone) used in the fuel cell system, the upper part of the biofilm reactor is normally red and the lower part is gray when the electron transfer in the anode corresponds biological production capacity. The results from the color analysis with the help of a computer indicate that the color changes in the biofilm reactor clearly determine the state of the fuel cell process. The state is affected by both the activity of the biological part and loading of the electrical part of the cell. Color changes give a direct method to control optimally the feed rate of the substrate to the fuel cell.