Investigation and control of high-temperature proton exchange membrane fuel cell operation
Date of Issue2016-03-22
School of Mechanical and Aerospace Engineering
The high-temperature proton exchange membrane fuel cell (HT-PEMFC) is considered as a new generation of power generating device evident from its superior performance over the traditional low-temperature proton exchange membrane fuel cell (LT-PEMFC). The key advantage of the HT-PEMFC is the significantly higher tolerance of carbon monoxide (CO) poisoning at elevated temperatures comparing with LT-PEMFC. However, an advisable operating temperature range should be determined by trading off the performance, CO tolerance and the degradation rate because an increase in operating temperature would improve the HT-PEMFC performance but accelerate the degradation of cell components. On the other hand, the produced water can be transported from cathode to anode and accumulated in anode flow field due to the water gradient across the membrane and its chemical interaction with phosphoric acid (PA) in the electrolyte. The accumulated water vapour exhibits significant effect on performance and stability under the dead-end mode of operation, because the crossover water vapour can hinder the hydrogen diffusion and reduce the hydrogen concentration in the anode. Thus, it is unlikely that one can fully block the anode outlet to improve the fuel utilization, which implicitly means that water management by periodic purging process to remove the accumulated water vapour is also needed in HT-PEMFC. The operating parameters of purging process, such as pressure, purging duration and purging interval, have been experimentally investigated in this study. It is suggested that a pertinent selection of H2 pressure, purging duration and purging interval can improve the performance as well as the fuel utilisation. A dynamic model of HT-PEMFC is thus developed and a fuzzy controller to schedule the purging process is designed. This obtained model fully described the dynamic behaviour of HT-PEMFC and it is capable to predict the dynamic responses of the HT-PEMFC operating at random current loads and purging intervals under flow-through and dead-end mode. The simulation results indicate that the fuzzy logic controller is effective and intelligent in the scheduling of purging process.