Life Cycle Analysis of Ceramic Anode-Supported SOFC System Manufacturing Processes

Abstract

The environmental impact of manufacturing an yttrium-doped strontium titanate (SYT) anode-supported planar solid oxide fuel cell (SOFC) system has been examined. Key components of an SOFC system including anode substrate, PEN (Positive electrodeElectrolyte-Negative electrode) structure, interconnects, and balance of plant (BoP) have been evaluated in terms of energy consumption and key air emissions using the Life Cycle Analysis (LCA) approach. IntroductionCurrent state-of-art SOFC systems most frequently use Ni/YSZ cermet anode materials, which possess excellent conductivity and catalytic activity. However, Ni/YSZ has many disadvantages, including nickel coarsening, sulfur poisoning and carbon deposition which can hinder the direct utilize of practical hydrocarbon fuels. What is more, nickel and nickel oxide may lead to allergies or cancer, adding difficulties in handling the material during manufacture (1).Recently yttrium-doped strontium titanate (SYT) is considered to be a promising alternative SOFC anode material (1)(2)(3)(4)(5)(6). Several studies demonstrated that SrTiO 3 -based materials satisfied the anode requirements well, being thermodynamically stable in anodic conditions, electronically and ionically conductive, chemically compatible with the electrolyte and interconnect, and has similar thermal expansion coefficient as other cell components (7-10). One of the most attractive properties of SYT compared to the nickel-based anode is the intrinsic sulfur tolerance and coking resistance, which indicate that practical fuels could be directly utilized in SOFC without addition of steam and extra balance of plant (BoP). These properties further enable SOFC use in stationary power generation to utilize fuels that are currently used such as natural gas and coal syngas.For anode-supported SOFC manufacturing, tape casting is often perceived to be the most cost-effective process to manufacture the anode substrate. In this study, SYT based anode substrates were manufactured via solvent-based tape casting, non-toxic solventbased tape casting and water-based tape casting processes. The development of the tape casting industry clearly shown that solvent-based tape casting outweigh water-based tape casting in terms of tape performance, because of it has higher tolerance to variations in influencing parameters (11). And solvent-based tape casting generally requires less energy to dry to form the green tape. However, the environmental impact of some of the organic solvents should be considered and evaluated. Compared to solvent-based, waterbased tape casting is generally less expensive and more environmentally benign. Analyses of the manufacture of the SOFC anode support should be carried out to carefully evaluate the overall merits of water-based system and compare to the traditional organic solvent-based system. As it was identified in other's study, more energy was required in the drying process in aqueous tape casting, and in some cases, the emissions and environmental impact were equally balanced for both solvent...