Thermodynamics and operating conditions for proton exchange membrane fuel cells

In this chapter, we set up the thermodynamic framework to analyze proton exchange membrane (PEM) fuel cell performance. The study of thermodynamics is key to understanding energy conversion in this energy system and to make sure the laws of thermodynamics are obeyed. The chapter starts with the main electrochemical reaction occurring in the hydrogen fuel cell and a comparison of hydrogen with other fuels. Then, the fuel cell energy system is studied with regard to both the first and second laws of thermodynamics. Next, the concepts are extended to assist understanding of the impact of the most important operating parameters on fuel cell reversible voltage, namely, temperature, pressure and reactant concentration. Finally, we define cell efficiency in both ideal and real conditions and compare it with conventional technologies. The study overall defines the thermodynamic limits in which a hydrogen PEM fuel cell operates.