(Drs. William Wepfer and Comas Haynes, co-advisors)

"Enhancing the Thermal Design and Optimization of SOFC Technology"

Abstract

Solid Oxide Fuel Cells (SOFC) are promising energy converters that have fewer emissions and higher efficiencies than conventional power plants (e.g., the gas turbine). Despite numerous advantages, however, SOFC systems are presently too expensive and bulky for significant market penetration. Additionally, the cells’ reliability is still an area of needed research and development. These difficulties are largely due to the challenge of effective thermal management. This study is concerned with enhancing the thermal design of SOFC technology by optimizing isothermal cell conditions and analyzing an alternative stacking arrangement for improved thermal management.

One of the most important thermal management issues is realizing cell temperature uniformity. SOFCs require the inlet air to be preheated; otherwise, thermal stresses may threaten cell integrity. A focus of the research was to determine optimal geometries and process conditions for the fuel cell stack that minimized axial temperature gradients in an effective measure.

In addition, an analysis of cell stack “thermal multistaging” was conducted. SOFCs require the air stream, used as both the oxidant source and heat sink, to be preheated to prevent excessive cooling at the leading edges of the cells. Air pre-heaters, however, reduce overall system efficiency and power density; and they add significant cost to the entire system. The conventional method of stacking involves having all air preheated before entering the stack. Cell thermal multistaging instead allots cells in flow path series with air injection in between cells to take advantage of regenerative heating so that external preheating is mitigated. A computational model of an SOFC was created to investigate the alternative arrangement of stacking, and the results were compared to the conventional stacking arrangements.