Exergy, exergoeconomic, and exergoenvironmental analyses of a combined cooling, heating, power, and freshwater poly-generation system driven by methane-fueled solid oxide fuel cell

Exergy-based analysis has been widely applied in performance evaluation of different kinds of energy systems, and the degree of irreversibility in the specific energy conversion process can be determined. It is regrettable that the most of the related researches cannot explain the classification and real source of irreversibility. This study aims to present exergy-based evaluations of a poly-generation system driven by a methane-fueled solid oxide fuel cell for investigating the source of thermodynamic, economic, and environmental irreversibility in fuel cell-based energy systems. After performing the traditional exergy-based analysis of the proposed system, the advanced exergy, exergoeconomic, and exergoenvironmental analyses are further conducted by splitting the economic and environmental items associated with exergy destruction and system component into avoidable, unavoidable, endogenous, and exogenous parts. The real source of irreversibility and potential for improving the system performance could be explicitly revealed by the advanced exergy-based evaluation. The evaluation results demonstrate that most parts of exergy destructions, investment costs, and environmental impact in the fuel cell, combustion chamber, Preheaters 1 and 3 are the unavoidable-endogenous. It is also indicated that air compressor owns the greatest avoidable-endogenous part of investment cost rate with the value of 0.4377 $/h, and gas turbine possesses the largest avoidable-endogenous part of environmental impact rate that is found to be 108.2820 mPts/h. Finally, sensitive analysis of core design parameters on system performance are presented, and the results indicate that increasing fuel utilization factor and inlet temperature of fuel cell are beneficial for decreasing system nonreversible cost and environmental impact.