High Temperature Ceramic Fuel Cell Measurement and Diagnostics for Application to Solid Oxide Fuel Cell Systems

Abstract

SummaryThere is a growing need for high efficiency, portable and distributed electric power generation. One family of technologies to meet these needs consists of the various forms of fuel cells. This paper is focused on the assessment of sensors and measurement technologies needed to give improved control, diagnostics and data for prognostics for use with high temperature ceramic fuel cells, and for initial demonstration of solid oxide fuel cells (SOFC). This paper also highlights the many challenges and complexities involved with SOFC technology, such as the lack of continuity between research projects, making it difficult to advance the technology in a cooperative manner. Research programs are noted; particularly those that are starting to provide continuity across the wide variety of research projects underway, such as the International Energy Agency. This paper is the result of an extensive literature review and technology evaluation, performed to determine the status of sensors and measurement technologies. It became apparent that many researchers are trying to overcome the same fuel cell design challenges. All researchers have found it difficult to obtain sound data from measurements inside inaccessible designs and heavily insulated enclosures operating at high temperatures. Although some advancement has been made in materials, systems modeling, and innovative manufacturing techniques, few answers have been found in the measurement and diagnostics field.Understandably, most approaches to measurements and diagnostics in fuel cells have been to extend an existing practice to solid oxide fuel cells, such as adapting established aqueous electrochemistry techniques (i.e., impedance spectroscopy). Although this technique has manifested some key characteristics of the SOFC, and is arguably one of the most advanced techniques in this field, work is still needed to resolve disagreements on the application and interpretation methods.Realizing the many constraints involved in SOFC testing and resolved to the fact that simple approaches may not be the complete answer, several innovative techniques and geometries have been tried and included in this report. Many researchers are using a combination of in-situ and ex-situ tests, involving a variety of disciplines and multiple steps to compile a range of diagnostic tools, as well as data acquisition and analysis equipment, which can be adopted to the SOFC technology. This has merit, but requires extensive cooperation between all involved throughout all the stages of the product development. These measurement tools will enable analysis of degradation mechanics leading to development of prognostic tools that can be used to analyze fuel cells and balance of plant (BOP) systems during research and development, subsequently minimizing operating costs and enhancing overall system efficiency. v

Degradation in Solid Oxide Cells During High Temperature Electrolysis

“…Table 2 lists many failure modes in a SOFC, degradation mechanisms, degradation activation agents, and parameters to be measured to detect degradation as given by Koehler et al [2001]. Table 2.…”

“…Table 2. Causes of degradation, failure mode, and needed measurements [Koehler et al 2001 Another such summary of the main degradation mechanisms is given by Blum et al [2007] and is listed in Table 3. Table 3.…”

Experimental evaluation of the operating temperature impact on solid oxide anode-supported fuel cells

“…The cell performance is estimated in terms of the area specific resistance of the cell (ASR) rather then power density, which is more often employed as suitable index to represent overall cell performance. In fact, this description of cell performance is known to be much less dependent on the individual test conditions compared with power density [1,2,11]. This parameter is representative of total cell polarization.…”

“…In the paper results are presented concerning the characterization of anode-supported cells with LSM and LSCF cathodes. Experimental data analysis consisted in the definition and evaluation of performance indexes of cells such as maximum power density, current density at 0.7 volts, area specific resistance analysis and polarization analysis coupled with parameter estimation methods [1][2][3][4][5][6][7][8][9][10]. Lanthanum-strontium manganite (LSM) is known to be the most promising candidate for practical SOFC cathode, due to mechanical and chemical compatibility with zirconia electrolyte and good electrochemical performances at 1000 °C.…”

Influence of the Number of Dimensions in the Impedance Spectroscopy Simulation of a YSZ Electrolyte

“…The most used materials in the manufacture of electrolytes for SOFCs are ceramics with a fluorite-like structure, mainly yttria-stabilized zirconia (YSZ) 2,3 . To fulfill their function, the electrolytes must have a relative density above 95% to prevent mixing of fuel and oxidizing gases, high ionic conductivity (above 0.1 S.cm -1 ), low electronic conductivity (electronic transfer number less than 10 -3 ) and uniform thickness to reduce ohmic losses [4][5][6][7] .…”