Modeling and simulation of high temperature proton exchange membrane fuel cell based cogeneration systems

In this thesis, a HT-PEMFC system is investigated through modeling studies at cell and system levels. Firstly, a one-dimensional, semi-empirical, and steady-state model of a HT-PEMFC fed with a gas mixture consisting of hydrogen and carbon monoxide is developed. Some parameters of this model are adjusted using empirical data, which are obtained conducting experiments on a HT-PEMFC for different values of Pt loading and cell temperature. The effects of some important parameters such as operating cell temperature, Pt loadings, percentage of PA, and the amount of CO on the performance of the fuel cell are assessed. Secondly, a mathematical model of a simple cogeneration system, which includes a HT-PEMFC stack, a heat exchanger, and a pump, is developed. After validating this model using an in-house experimental data, the effect of anode stoichiometry ratio on the electrical and simple cogeneration efficiencies are examined. In addition, the average temperature of hot water is calculated for each month in a case study. Finally, the thermodynamic model for a cogeneration system including HT-PEMFC, SMR, WGS, and burner that converts natural gas into electricity and heat is developed and investigated through energy and exergy analyses. The effects of some key parameters, e.g. steam-to-carbon ratio (SCR), fuel cell operating temperature, and anode stoichiometric ratio on the system performance namely electrical efficiency, exergetic efficiency, and cogeneration efficiency are examined parametrically using energy and exergy analyses. The exergy destructions of each component in the cogeneration system are also examined according to these parameters.