Performance analysis of solid oxide fuel cell based energy generation systems with alternative criteria

Solid oxide fuel cells are conjectured as 21th century?s energy generation systems due to high efficiency and environmental friendliness compared to conventional energy generation systems. Modeling and simulation studies of this new technology based energy generation systems are the easiest, cheapest and the most effective way to research and develop their performance characteristics. This study aims to develop the thermodynamic models providing the performance analysis, and giving the effects of design and operation parameters on the performance of solid oxide fuel cell based energy generation systems. The mathematical models of solid oxide fuel cell based energy generation systems are developed with combining each component models taking into account the electrochemical, chemical and thermodynamic processes. Initially, an electrochemical model of single tubular solid oxide fuel cell is presented which is consisted of ohmic, activation and concentration polarizations. Afterwards, solid oxide fuel cell module model that is able to convert methane fuel to hydrogen is developed. Different systems producing heat and electricity are designed with integration various components (recuperator, gas turbine, heat recovery steam generation) to the solid oxide fuel cell module, and these systems are modeled mathematically. Computer models of these system configurations are written in a computer software program, and simulations are carried out at the given certain conditions. Simulation results are compared to the experimental data in the literature, with this way; the developed models are validated. Net power output, first law efficiency, exergy output, exergy efficiency, exergy loss are used to evaluate performance of the systems. In addition, a new criterion, which is called the exergetic performance coefficient and defined as the ratio of total exergy output to the total exergy loss, is applied to assess the performance of the systems. As a conclusion, solid oxide fuel cell based energy generation systems can be evaluated on basis of alternative performance criteria, and also an informative expansion can be provided in the determination of the most convenient design and operation parameters based on energetic and exergetic approaches by means of this study. Keywords: Tubular solid oxide fuel cell, electrochemical model, polarizations, performance analysis, exergy, exergetic performance coefficient, gas turbine, cogeneration, hybrid systems