In the twenty-first century, the need of the hour is power generation with environmental protection, a need that has prompted extensive research on energy conversion technologies such as fuel cells. Research efforts directed toward the widespread commercialization of fuel cells have accelerated in light of on going efforts to develop a hydrogen-based energy economy to reduce dependence on foreign oil and decrease pollution. This book presents development of different types of fuel cells, which with high efficiency and high environmental performance have shown excellent potential as a future source of energy for vehicles and homes.