Long-Term Testing in Dynamic Mode of HT-PEMFC H3PO4/PBI Celtec-P Based Membrane Electrode Assemblies for Micro-CHP Applications

High temperature proton exchange membrane fuel cells (HT-PEMFC) have a promising market in micro-combined heat and power (mu-CHP) applications. Operating above 150 degrees C, they would better cope with return temperatures of typical heating systems than conventional PEMFCs and would allow simplification of system regulations dedicated to failure prevention. Single cell and 500 W-e HT-PEMFC stack integrating Celtec P 1000 MEAs were fed with synthetic reformate and air and successfully operated at 160 degrees C under accelerated typical annual mu-CHP profile. The single cell was unaffected by 500 h of current cycling while stop/start cycles induced some voltage loss. After 658 h of cumulated operation, stack performance loss was limited at 7.6%: its electrical efficiency (LHV) decreased from 30.6 to 28.3%. Moreover, four initial stop/start cycles weakly impacted its performance, indicating that selected shutdown/restart protocol is convenient for field application. Conversely, after additional start/stop cycles, degradation rate was increased by stop/start cycling and some specific cells (mostly associated with lower initial OCV) exhibited significantly higher degradation rates. Finally, voltage transient evolution during current step exhibits undershoot which magnitude is strongly depends on cell location in the stack: it increased at stack dead-end and for cells exhibiting highest degradation rates.