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Small scale Microbial Fuel Cell Stacks as a means of scaling up and implementation in low power and robotic applications
A Microbial Fuel Cell (MFC) is a bio-electrochemical system (BES), capable of generating electricity from organic matter. As a technology, it is receiving increased attention from the international community as a viable alternative energy source. It offers attractive benefits, such as waste, food-waste and wastewater treatment, pure water generation (from the cathode) and the potential to sense the environment in terms of Bilingual Oxygen Demand (BOD) and levels of water contaminants. MFCs employ bacteria, held in contact or in the vicinity of an electrode in the anode, to convert organic matter (the fuel) into electrical power. Hence they can also be used to remove (oxidising) contaminants from water supplies with the advantage that the electrical power that is simultaneously produced offsets the energy costs for remediation.
As knowledge about this technology advances, the system limitations become more evident. A key limitation is the maximum bio-electrochemical potential difference (open circuit voltage) that can be produced. This is governed by the bacterial internal metabolic (most negative) redox couple (NADH/NAD+) and the standard redox potential associated with the catholyte employed, which has been calculated to be 1.14V (for an oxygen-diffusion based cathode). This value, albeit the theoretical maximum, is insufficient to energise practical applications. Therefore there is a genuine need to use multiple MFCs connected as stacks (or networks) for powering real world applications. Over the last few years it has been shown that MFCs can work as the sole power supply for small robots (see EcoBots I, II and III; EcoBot-III is shown below). Designing MFCs with a practical application in mind (e.g. remote sensors, wireless transmitters, small dc motors, small dc pumps, small robots) is perhaps one of the most pragmatic ways that the technology can be driven forward.
News items have recently been published in both Chemical Science Magazine and Chemistry World Magazine (Royal Society of Chemistry) that highlight work reported by Fraser Armstrong"s group (Department of Chemistry, University of Oxford) in a recent Hot Article [Chem. Commun., 2006, 5033, DOI: 10.1039/b614272a].
This work details the development of micro enzyme fuel cells (see below) containing both oxygen-tolerant hydrogenase enzymes for hydrogen oxidation and laccase enzymes for oxygen reduction.
منبع:
http://www.tutorvista.com/content/physics/physics-iv/thermal-chemical-currents/electrochemical-cells.php
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