Relevance and Validation of Test Procedures for PEMFC Stack Performance Analysis

Kurzfassung

The harmonization of procedures for polymer electrolyte membrane fuel cells (PEMFCs) analysis is of significant interest for industry and academia. Up to the present date, PEMFC performance analysis has not been standardized leading to non-comparable results. This incomparability is clearly recognizable in single cells, but has an even higher effect on the stack level. The preparation of required protocols was realized in a two-step process. The crucial parameters have been identified in the first step. Subsequently, the procedure for the respective parameter variation has been specified. For example, the direction of parameter adjustment, the sensor position and the parameter control are defined in the protocols to achieve reproducible results. Furthermore, the feedback from a broad range of industrial institutions, from OEMs to stack manufacturers, and academia has been considered to improve the procedures. For the present work, these protocols were applied to a 10 cell stack. The operating parameters - reactant humidity, pressure and stoichiometry as well as stack temperature and electric load - have been varied according to the protocols. Thereby, the impact of the protocols to the test results was examined with respect to performance, cell voltage deviation, and behavior in continuous operation under constant load. Regarding the use of testing procedures in industry, the test duration is a further crucial parameter and should be minimized without endanger the result accuracy and reproducibility. This aspect will be demonstrated and presented on polarization curve studies, the most frequently used tool for PEMFC assessment. Our results show that comparability and constancy of the test results in different facilities across Europe are greatly influenced by the applied testing protocols. In this work, we will present the validation results, identify and highlight critical parameters and sequence of examination steps. Our work clearly demonstrates the great need for harmonized performance analysis protocols and their case dependent choice. All procedures and validation results are part of the Stack-Test project funded by the European Union Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant n° 303445. We gratefully acknowledge the members of the Stack-Test consortium who prepared, improved and validated the test procedures. All presented test procedures are acquirable at stacktest.zsw-bw.de.