13. Energy Efficiency of PEM Fuel Cell Hybrid Power Source

The chapter deals with a single DC bus hybrid configuration of a power source required for an automotive application. Such system architecture is the best choice for interconnecting multiple energy sources in order to meet the load profile in the most efficient way. This work analyzes a new PEM Fuel Cell stack-Hybrid Power Source (PEMFCs-HPS) topology consisting of a 5 kW PEMFC stack (primary source of power) and a bank of ultracapacitors (130 F, 56 V, 57 Wh) (auxiliary power source) to fulfill the high energy and high power requirements of the vehicle applications, wherein the power demand is impulsive rather than constant. This topology uses three programmable unidirectional DC/DC converters which connects the PEMFCs, the UC and the programmable electronic load. The energy management strategy (EMS) for different power sources has great effect in decreasing the fuel consumption, increasing the performance and the lifetime of the fuel cells. The proposed EMS is based on the FC efficiency map and on the state of charge of the UC. The EMS is used to split the power between the PEMFCs and the UC in the hybrid arrangement to fulfil the power requirement, which depends on the operating conditions considering the optimum power of PEMFCs and UC. An algorithm the EMS is able to achieve the steady-state PEMFCs operating with minimum hydrogen consumption and the UC state of charge (SoC) maintaining at values higher than 20%. The system ability to efficiently follow the load variations under that EMS is also presented. The consumption of hydrogen was reduced by 11.8% in comparison with the system without UC. The experimental data acquisition system is monitored and controlled using the NI Labview® software with the NI Compact-RIO hardware.