P. Aguiar

Operational Experience of an IT-SOFC / Battery Hybrid System for Automotive Applications

Testing of a 300 W stack, supplied by Versa Power Systems Ltd., and a sodium - metal chloride (ZEBRA) battery has been performed with a view to assessing the feasibility of combining an intermediate temperature solid oxide fuel cell with a high temperature battery for automotive traction applications. Field testing of a self-compressed stack is demonstrated including consideration of the mechanical robustness of the technology. The battery system, comprising novel cell technology, is tested under pulse discharge and standard driving cycle conditions. Based on modeling studies previously performed, the performance results obtained and the reliability of the respective technologies, development of a full-scale prototype is considered viable and ultimately commercially relevant.

Application of Infrared Thermal Imaging to Map Stress Distributions in a Solid Oxide Fuel Cell

The application of infrared thermal imaging to the study of solid oxide fuel cell components with applied thermal gradients is demonstrated. Thermal imaging of a technologically relevant SOFC sample was carried out while a temperature gradient was induced by heating the sample in a furnace and blowing cold nitrogen at its centre. Subsequently the stress field in the sample was determined by a novel method of converting the thermal image into nodal temperatures for a finite element analysis. Asymmetry in the temperature distribution across the samples was marked, whereas previous versions of the thermal gradient experiment had assumed axisymmetry.

Response of a planar intermediate-temperature anode-supported direct internal reforming solid oxide fuel cell to load changes

Abstract In operation, solid oxide fuel cells (SOFCs) can be subjected to frequent load changes due to variable power demand. Knowledge of their dynamic behaviour is thus important when looking for suitable process control strategies. The present work investigates the dynamic response of a planar intermediate-temperature anode-supported direct internal reforming SOFC when a load step-change is imposed. A previously developed SOFC model, which consists of mass and energy balances and an electrochemical model that relates the fuel and air gas composition and temperature to voltage, current density, and other relevant fuel cell variables, is used. Dynamic simulations have shown that, after a positive current density step-change, the overall SOFC temperature increases and the intermediate period between the disturbance imposed and the new steady-state is characterised by an undershooting of the cell potential. In these simulations, the fuel and air flowrates follow at first any variation in load when a disturbance is imposed, keeping both the fuel utilisation and air ratio constant. A control strategy, where a typical PI feed-back controller varies the air flowrate to keep the fuel channel exit temperature within certain specified limits, has been implemented. Results have demonstrated that the fuel exit temperature can be successfully controlled although new control strategies, that consider the various failure conditions in a ceramic SOFC, need to be investigated.