I. Introduction
The search of alternative energy sources for power generation has resulted in photovoltaic (PV), wind, hydropower, biomass, and fuel cell (FC) and so on [1]. Among these resources fuel cell is one of the choices which is free from environmental effects. Also FC systems are capable of operating at higher efficiency (around 60%) than the other traditional energy sources [2]. Thus, the research of fuel cell power generation has been dramatically increased in recent years. FC is an electrochemical device which transforms the chemical energy of hydrogen and oxygen into electricity by producing water and heat as output [3]. For small scale power generation, proton exchange membrane fuel cell (PEMFC) or solid oxide fuel cell (SOFC) are appropriate [4]. Among these two types, PEMFC works at low temperature (60°C -100°C) and SOFC works at high temperature (500°C-650°C) [5]. Thus for small scale power generation PEMFC is more appropriate.