Polygeneration systems based on high temperature fuel cell (MCFC and SOFC) technology: System design, fuel types, modeling and analysis approaches

No one can disagree the growing attention to developing and utilizing high temperature fuel cells partly due to their potential for multi-service applications. Recently, much focus can be observed on examination of the integration of solid oxide fuel cell (SOFC) or molten carbonate fuel cell (MCFC) systems with other subsystems to propose polygeneration plants. Literature review prove that, to propose a polygeneration concept based on SOFC and MCFC systems, there is not a typical way commonly used by researchers. So it is tried to categorize and survey the current challenges of the high temperature fuel cell polygeneration plants. In this regard, the most common concepts and some unique system designs are reviewed and investigated in terms of fuel type, plant scale, electrical efficiency, overall efficiency and other performance indicators. It is figured out that similar to the typical CCHP system, the most common polygeneration designs are those utilizing the potential of exhaust gases from the natural gas fed fuel cell system in a heat recovery unit and a refrigeration system. A notable observed trend in recent years is the coupling of biofuels with polygeneration concepts. We found that there are still great challenges regarding how to predict the fuel cell actual cell voltage influencing the overall efficiency of polygeneration plants. It is also observed that attendance of researchers to analyze the polygeneration systems from the viewpoints of economic and environmental is less in comparison with the investigation of the systems from the thermodynamics point of view.