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2011-Sustainable Industrial Processing Summit
|Publisher:||Flogen Star OUTREACH|
|ISSN:||2291-1227 (Metals and Materials Processing in a Clean Environment Series)|
Regenerative energy systems (RES) are the answer to the grand challenge of this century to use sunlight and water to produce clean, environment-friendly energy for sustainable development on a massive scale. The individual RES subsystems are photovoltaic array, electrolyzer, storage for hydrogen and oxygen, and fuel cell. The efficiency of RES is low based on current proton exchange membrane (PEM) and solid oxide membrane (SOM) technologies for the electrolyzer and fuel cell. A partially regenerative system with significant improvement is efficiency can be designed by using carbon or hydrocarbon fuels in high-temperature solid oxide electrolyzers and fuel cells based on liquid metal electrodes. In this presentation results obtained with laboratory tubular cathode supported fuel cells based on stabilized zirconia electrolyte, and using carbon saturated liquid copper electrodes, will be presented. High current density of 2.3 A/cm2 and power density of 1.7 W/cm2 have been achieved. The power output is based on the oxidation of C to CO and external heat supply, in contrast to conventional SOFC which derives power from the oxidation of H2 and CO to H2O and CO2. The conceptual design of partial oxidation fuel cells surrounded by a combustion chamber will be presented. Such fuel cells can in principle be used to convert thermal energy from high-temperature nuclear reactors to electricity without the Carnot restriction.In a high-temperature electrolyzer based on cermet supported zirconia electrolyte tubes and carbon-saturated liquid copper electrode, spontaneous electrolysis is observed up to a current density of 0.75 A/cm2. A small voltage is required for electrolysis at higher current densities. The power required for electrolysis using this electrolyzer is less than the power generated by combining the products of electrolysis in a conventional SOFC operated at the same current density up to 2.2 A/cm2. The liquid metal offers a favorable medium for rapid reaction between carbon and oxygen.