The electrical energy output and the performance of a PEM fuel cell is dependent on the ion transfer in the fuel cell. The ion transport mechanism in the electrolyte cell membrane is dependent on the charge site in the membrane.
The charge sites increases with an increase in the hydration of the membrane, this shows that the water content of the membrane is important to facilitate the ion transfer in the electrolyte membrane, hence proper management of water is essential to the operation of the PEM fuel cell system, to achieve these a proper balance of the water transport within the PEM fuel cell is needed for the optimum operation of the PEM fuel cell membrane.
This work is based on an assessment of the humidity management effect on the performance of the PEM fuel cell. If the fuel cell membrane is over hydrated with water, it results in over flooding of cell membrane, which causes activation losses and H+ ion cross over losses in the fuel cell, and if the membrane is poorly hydrated it results in poor hydration of the membrane which causes concentration loss, and very low ion conductivity.
The water balance system of the fuel cell is such that water vapour is present in the air at the inlet, the water is also used for H+ ion transport from the anode to the cathode, the excess water in the cathode is back diffused in to the anode, at the cathode it is also produced from the chemical reaction of the fuel cell, at the exits water it is evaporated at both the anode and cathode of the cell, and finally with the use of water mass balance we determine the mass of the water which is injected into the fuel cell to meet up the water demand for the hydration of the membrane.
This work analyses how these parameters, the operating temperature, relative humidity of air, the inlet temperature, the pressure drop in the cell membrane, the operating temperature, the membrane thickness and the stoichiometry of air affects the water content of the cell membrane. The results from this work showed that a proper management of the PEM fuel cell is of central importance to control the membrane hydration and ensure proper performance of the fuel cell.
Source: KTH
Author: Osamudiamen Ose Micah, Ose Micah
