Thermodynamic Study of Operation Properties Effect on Polymer Electrolyte Membrane Fuel Cells (PEM)

Abstract

The thermodynamic analysis of PEM fuel cell energy production depends on the entropy and enthalpy of reaction with the changing of the operating temperatures that ranges between 50 and 100ºC, the electrical work done will be equal to the Gibbs free energy released. This paper presents a mathematical model of PEM fuel cells, based on physical-chemical procedures of the phenomena occurring inside the fuel cell, and it was theoretically studied the performance at different operation variables and conditions. The C++ program is designed to calculate all thermo-chemical parameters, i.e. enthalpy of formation, Gibbs free energy, work and efficiency for any type of fuel cells. The results are plotted as a function of fuel cell operating temperature. The results shows that the highest value of Gibbs energy is at the lowest operating temperature, and decreases gradually with increasing the temperature, the output voltage is determined by cell’s reversible voltage that arises from potential difference produced by chemical reaction and several voltage losses that occur inside a cell. In addition the results showed that the efficiency of this type of the fuel cells is much higher than the ideal Carnot’s efficiency, it changes between 82% to 85% depends on temperature operation. The heat output (required heat) from the fuel cell increases with increasing the operating temperature, this heat is used for many thermal applications such as buildings space heating.