EFFECT OF. EXTERNAL HUMIDIFICATION ON MEMBRANE WATER BALANCE OF A PEM FUEL CELL

Abstract

The fossil fuels will get depleted by the end of this century. Hence it is necessary to pay attention towards alternative energy resources due to increase in power demand. Some of the alternative energy resources are nuclear energy, fuel cells, solar cells, wind power, tidal power and so on, out of which fuel cells are the most promising alternative energy resources since it is highly environment friendly. Membrane is a critical component of a PEM fuel cell. The water content of the membrane directly controls the power output of the cell. Humidification of fuel cell membrane can be controlled by the relative humidity of inlet gases fed into the fuel cell. Water balance in the membrane is required for proper understanding of humidification process inside the membrane. Since membrane is only of few microns thickness, it is very difficult to find membrane condition by using direct instruments. It may cause damage to the membrane which in turn leads to failure of cell. Presence of more water in a membrane will lead to flooding and Iess water content causes hot spots across the membrane. Therefore optimum hydration is required to operate the cell with optimum performance under normal conditions. Based on theoretical model using MATLAB, the water balance analysis is computed. Experiments were also conducted by using H2-02 gas humidification system. The performance of the cell increased by the use of H2-02 gas humidification system, and the results are closely matching with the simulation values. H2-02 gas humidification system shows about 6 to 8% improvement in the performance compared to the porous matrix humidifier and 10 to 12% compared to Bubble humidifier. The performance of fuel cell is 13.62% higher when H2 gas is allowed for humidification instead of 02 gas is allowed for humidification. H2-02 gas humidification system is able to meet the sudden rise in the humidification levels when the cell was suddenly loaded to a higher load with a very short duration of time compared to porous matrix humidifier, The H2-02 gas humidification system is found to operate efficiently especially at higher load conditions for any given cell parameter variation