Energy autonomy in robots through Microbial Fuel Cells

The ability of robots to operate with minimum human intervention, independent of the energy supply, is often enough to term an agent autonomous. However, there is a clear distinction between computational ability and energy obtainment. These have already been identified as computational autonomy and energetic autonomy [1]. Battery-operated robots, for example, demonstrate computational autonomy but not energetic, whereas solar-powered robots demonstrate both provided that sufficient energy is available. Energetic autonomy is particularly important as robots will be required to extract energy from the environment. In many ways robots will face the same problems as animals. A robot powered by live microorganisms can utilise as fuel a wide range of organic substrates of the types found in agriculture or food wastes. This implies that robots can be designed to operate in a range of habitats where they can exploit various forms of energy sources and hence illustrate a different (perhaps higher) level of autonomy. We believe this is the first step towards a truly energetically autonomous robot. Microbial Fuel Cell (MFC) technology offers the potential of exploiting microbial metabolism to produce electrical energy. This is a good way forward, as the robot will incorporate in its behavioural repertoire actions that involve search and get hold of food and also remain inactive until energy is sufficient to do the next task. This will be a paradigm shift in the way action selection mechanisms have been designed so far. A MFC is a bio-electrochemical transducer that converts biochemical energy to electrical energy, in roughly the same manner as a normal fuel cell. Microbial fuel cells fall under the proton exchange membrane (PEM) fuel cell category, since that is the solid electrolyte used in the system. The MFCs used for this line of experiments were of identical design and structure to the ones previously used for EcoBot I. The difference in these fuel cells was the biocatalyst employed, i.e. the culture of microorganisms. In this case it was decided to employ sewage sludge obtained from anaerobic activated samples (Wessex Water Scientific Laboratory). The choice of this microcosm proved to be advantageous for a number of reasons some of which are ease of preparation, growth media and substrate diversity, and unmodified physicochemical conditions. Furthermore, MFCs incorporating sewage sludge are producing as much as 10 times more power than that produced by the MFCs using E. coli and mediator. Figure 1 below shows a picture of …