Experimental investigation of voltage variation of purge cells at dead-end mode in a ۲kw cascade-type PEM fuel cell stack

PEM fuel cells (PEMFC) are most widely used types of fuel cells for power generation purposes. Increasing fuel efficiency and proper water management are important challenges in a fuel cell system, especially in the dead-end mode. The voltage stability of the purge cells in the dead-end mode strongly depends on the control parameters of the purge valve, such as the valve opening, purge interval, and purge time. In this study, the performance of a ۲ kW cascade type PEMFC in the dead-end mode was investigated and the effect of purge parameters on cells voltage variation and overall stack performance was investigated. The results showed that not only efficiency of fuel and oxidant consumption increased with the dead-end operation, but also the cells voltage stability was acceptable. Also during the test, acceptable reproducibility was observed in the amount of exhaust gas as well as the voltage fluctuation of the purge cells.PEM fuel cell has received a lot of attention in recent years due to its advantages such as high efficiency, low noise, and zero-emission. Increasing fuel and oxidant consumption efficiency and managing water properly are of particular importance [۱]. One way to increase efficiency is to operate the PEMFC in dead-end mode. Operation of the fuel cell in the dead-end requires careful management of gas and water to achieve the best performance [۲]. In this research, the effect of the dead-end mode on a cascade type PEMFC performance was investigated. The effect of the purge valve control parameters, such as the percentage of valve opening, purge interval, and purge time, on the cells' voltage variation was investigated.The fuel cell examined was a ۲ kW cascade type stack with ۱۵ cells. This fuel cell worked with pure hydrogen and oxygen, so the dead-end mode for both anode and cathode sides has been investigated. The number of Purge cells on each side was ۲.At the beginning of the test, the purge valves were adjusted so that the anode and cathode gas flowrates in the flow-through mode are ۲-۳ SLPM higher than the gas consumption at ۲ kW. Then the purge valves on both sides opened for ۱ second in a ۱۰ seconds interval for dead-end operation. The pressure variation at the anode and cathode side with the opening and closing of the purge valves are ۰.۰۲ and ۰.۰۶ bar, respectively. The purge flow rate for the anode and cathode side was ۰.۴۲ and ۰.۵۱ SLPM, respectively, which is equivalent to the stoichiometry of ۱.۰۲ for the anode side and ۱.۰۵ for the cathode side. In this case, the fuel cell efficiency reaches ۵۳%. Figure ۲ shows the voltage of the anode and cathode purge cells in the ۲ kW power output. The voltage variation of anode purge cells is from ۷۱۱ mV to ۷۶۵ mV (۵۴ mV difference). On the cathode side, the purge cells voltage ranges from ۷۱۸ mV to ۷۶۰ mV (۴۲ mV difference). Despite these high fluctuations in the voltage of the purge cells, the average voltage of the stack cells did not change much during the test and its fluctuation was approximately ±۵ mV. In Figure ۳, the time-averaged voltage of purge cells and the total cells average are shown In this study, the performance of a ۲ kW fuel cell in the dead-end mode on both the anode and cathode sides was investigated. It was observed that with proper management of the purge parameters, the efficiency of fuel and oxidant consumption increases and it is possible to achieve proper stability cells voltage and fuel cell performance. This stability is a sign of proper water management in the fuel cell. In this case, anode and cathode stoichiometry were reduced to ۱.۰۲ and ۱.۰۵, respectively, while the mean voltage variations of the cells were about ±۵ mV during the test