AbstractMost of our energy supply nowadays relies on converting thermal energy to mechanical energy. Mechanical energy is then either used directly to drive vehicles or electric generators that supply the global needs of electricity. The main source of thermal energy is combustion of fossil fuels, which are limited, and have many detrimental effects on polluting the environment and adding to the greenhouse effect. Fuel cells offer the best alternative to replace existing energy conversion processes, as they convert the chemical energy of hydrogen fuel directly into electricity, bypassing fuel combustion. In addition, the only by-products in fuel cells are water and low temperature heat, and both are benign to the environment. Being a single step energy converting devices, fuel cells have high efficiencies. However, the fuel cell outputs unregulated voltage that depends on the operating conditions of the fuel cell and the load connected across its terminals.
A dynamic fuel cell model was developed in Simulink and integrated with the load in what is believed to be a new approach to reproduce and analyse the actual fuel cell-load interactions. Upon this, a control strategy was developed to match the power demand and regulate the output voltage for varying power demand. The strategy is based on using DC-to-DC converters and regulating the flow of the reactants. The control strategies are believed to be the first to deal with system’s nonlinearities and covering the entire operational range. A novel solution was proposed to deal with the problem of irrecoverable control observed when the fuel cell was overdriven to the concentration losses region, which if untreated, would short-circuit the fuel cell and permanently damage it.
The overall fuel cell power generation system was simulated under varying load conditions observed in automotive driving schedules and domestic applications. Results showed promising performance of power regulation that meets the requirements of modern electrical voltage standards. An energy storage device could be used to improve the efficiency and performance of the system by absorbing the excess energy generated and using it during sudden increases in demand.
|Date of Award||2010|
|Supervisor||Fateh Bhinder (Supervisor) & William Hall (Supervisor)|