PERFORMANCE STUDY OF 200W PEM FUEL CELL STACK WITH AN EVAPORATIVE COOLER HUMIDIFIER

Abstract

Many fuel cells are currently under fast development to compete for their next role as a substitute for the future energy system. The proton exchange membrane fuel cell gains a wide recognition as a growing and a good substitute during this transition from the traditional fossil fuel powered system to the hydrogen economy with its numerous advantages such as: quick start ability, modularity, least environmental pollution and simplicity in design. With the advent of increasing energy prices, more focus has been placed on alternative fuels and power generating systems. One possible source of alternative power generation is the fuel cell. Over the past several decades fuel cell research has intensified because of the system's efficiencies. Since the 1960's, research into the Proton Exchange Membrane Fuel Cell (PEMFC) has been exponentially conducted, as PEMFC is viewed as a strong substitute candidate for power generation especially in the automotive sector. It is found that approximately a quantity of heat equal to the power output of the cell is given out from the cell. Hence, cooling is highly essential in order to keep the temperature of the membrane at the rated temperature; otherwise the membrane may be damaged due to hot spots. Generally distilled water is used as a cooling medium to take out this heat by circulating through the cell. Different external humidifiers are used for humidification of inlet gasses such as bubble humidifier which uses heating element in it, membrane humidifier which uses water produced at the cathode side of the fuel cell. In the present work an evaporative-cooler humidifier is proposed for humidification of hydrogen and oxygen as well as for cooling the fuel cell in a 200 W PEM fuel cell stack. An evaporative cooler humidifier is preferred technology for external humidification of fuel cell reactant gasses in mobile applications because no extra power supply is required and there are no moving parts. Each humidifier is designed to operate as a wet cooling tower using the cooling water and the respective gas stream as working fluids. When the cooling distilled water is being cooled by evaporation, hydrogen and oxygen gas streams are humidified. Experimental test runs are carried out to study the efficiency of the proposed humidifier and different readings are taken to study the effect of variation of cell performance at different temperatures, step loading, variation in hydrogen flow rate, decrease in mass flow rate of water, humidification analysis and it is found that the proposed humidifier is capable of achieving cooling of water by 4°C and effective humidification. The results are reported in the form of V-I characteristic curves of the cell.