Experimental investigation of fuel cell-battery hybrid power system performance

Many efforts have been made in recent years to determine issues surrounding the use of fossil fuels for energy. However, it must be admitted that we can not finish our dependence on fossil fuels in a short time. Actually it is possible by a relatively slow migration of technologies over several years. During this transition period the world will need establishing connections between technologies to support in the transition to alternate energy sources. The first stage of this support is the acceptance of hybrid power systems which shows much promise in boosting energy efficiency while reducing emissions and costs. A proton exchange membrane (PEM) fuel cell–battery power system using hydrogen as fuel has a higher energy and power density than conventional batteries, and it is one of the most up-and-coming environmentally friendly alternative energy sources. A general methodology of building of a PEM fuel cell–battery system is introduced in this thesis. A PEM fuel cell that operates in low temperature conditions is suitable for the portable power applications. However, PEM fuel cells have some problems about working independently as a power system. A rapid voltage drop and a slow response to the load demand are the primary critical problems, as most electronic devices require stabilized power and fast transient response. Thus, energy storage devices, such as fast charge and discharge battery and power regulation devices are required to work with the PEM fuel cell to form a power system to provide regulated, fast-response power to a variable load. Such a system consisting a battery, a hybrid battery charger and a PEM fuel cell is designed and its performance is investigated in this thesis. Battery is used as an auxiliary power source addition to fuel cell for a fast response to the load demand and it also stores surplus energy in case of load power is lower than nominal fuel cell power. Coordination between fuel cell, battery and load is provided by hybrid battery charger and it also regulates voltages. Thus, designed system eliminates all disadvantages of fuel cell and battery while saving advantages of both.