Lars Rose

Characterization of Porous Stainless Steel 430 for Low- and Intermediate-Temperature Solid Oxide Fuel Cell (SOFC) Substrates

One approach to lower the cost of solid oxide fuel cells (SOFCs) is to lower the operating temperatures below 1073 K to allow the use of robust and comparatively inexpensive stainless steels not only for interconnects but also for SOFC support structures. The metal supports must be sufficiently porous to facilitate gas flow toward the reactive sites in the electrodes. Gas flow and electrical conductivity must remain adequate during any oxidation that occurs during operation. In order to identify microstructures most suitable for use as SOFC supports, a series of gas permeation and surface profilometry experiments was conducted to determine the permeability and surface roughness of porous steels (AISI 430) having different pore structures. The materials were also characterized by a variety of porosity measurement methods, each yielding complementary information on the three-dimensional structures. A combination of moderately low surface roughness and high gas permeability was found to represent a good combination of properties for metal-supported SOFC application.

Processing of Ce1-xGdxO2-δ (GDC) Thin Films from Precursors for Application in Solid Oxide Fuel Cells

Extensive interfacial reactions are known to occur between Fe-Co based perovskite cathode materials and the standard solid oxide fuel cell (SOFC) yttria stabilized zirconia (YSZ) electrolyte. Thin films of gadolinia doped ceria (GDC) could be used as a diffusion barrier between the cathode and the electrolyte. The present work investigates spin coating thin diffusion reaction inhibiting films onto SOFC electrolytes. The chemical and structural evolution of ethylene glycol based precursor solution is studied by means of rheology, x-ray diffraction (XRD), high temperature XRD (HT-XRD), Fourier-transformed infrared spectroscopy (FTIR) and differential thermal analysis (DTA). The studies show that cerium formate is formed as an intermediate resin. Thin films, up to 500 nm thick, of gadolinia doped ceria (GDC) are successfully produced by multiple spin coating of polymerized ethylene glycol derived solutions on 200 1m thick YSZ tapes. The GDC and YSZ interfacial surface morphology and film thickness are studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). These films are shown to successfully prevent the creation of non-conducting reaction phases at the cathode-electrolyte interface by blocking interdiffusion.

A Comparative Life Cycle Assessment of Compressed Natural Gas and Diesel Powered Refuse Collection Vehicles

Consumers and organizations worldwide are searching for low-carbon alternatives to conventional gasoline and diesel vehicles to reduce greenhouse gas (GHG) emissions and their impact on the environment. A comprehensive technique used to estimate overall cost and environmental impact of vehicles is known as life cycle assessment (LCA). In this article, a comparative LCA of diesel and compressed natural gas (CNG) powered heavy duty refuse collection vehicles (RCVs) is conducted. The analysis utilizes real-time operational data obtained from the City of Surrey in British Columbia, Canada. The impact of the two alternative vehicles is assessed from various points in their life. No net gain in energy use is found when a diesel powered RCV is replaced by a CNG powered RCV. However, significant reductions (about 24 % CO2-equivalent) in GHG emissions are obtained. Moreover, fuel cost estimations based on 2011 price levels and a 5 year lifetime for both RCVs reveal that considerable cost savings may be achieved by switching to CNG vehicles. Thus, CNG RCVs are not only favorable in terms of reduced climate change impact but also cost effective compared to conventional diesel RCVs, and provide a viable and realistic near-term strategy for cities and municipalities to reduce GHG emissions.