Thermoeconomic analysis of two solid oxide fuel cell based cogeneration plants integrated with simple or modified supercritical CO2 Brayton cycles: A comparative study

Two supercritical CO2 (sCO2) Brayton cycles for waste heat recovery in a solid oxide fuel cell (SOFC)-based plant are assessed and compared from thermodynamic and economic perspectives. One cycle considered is a simple sCO2 cycle with recuperation, while the other is the supercritical recompression CO2 (srCO2) cycle. To provide a fair comparison between the performances of the SOFC-sCO2 integrated plants, the flue gas is considered to exit at the same temperature in both cases, through a heating unit to generate hot air. The findings indicate that designing an efficient SOFC-sCO2 integrated plant for cogenerating electricity and a by-product, e.g., heat, is not solely a question of selecting the most efficient sCO2 layout as the bottoming power cycle. Rather, it is a tradeoff between the exergetic performance of the sCO2 layout and its potential to absorb heat from upper SOFC system. It is shown that, at the optimized condition, the capability of a simple sCO2 cycle for recovering heat from the SOFC is 30.86% higher than a srCO2 layout. However, the exergy efficiency of the SOFC-srCO2 integrated cogeneration plant is 0.64% higher than that of the SOFC-sCO2, with a corresponding increase in the average unit cost of products of 3.06%. •Simple and modified supercritical CO2 Brayton cycles are compared for WHR of SOFC.•Thermodynamic and thermoeconomic analyses are implemented for cogeneration plants.•Using efficient SCO2 layout does not guarantee high waste heat to power conversion.•Employing a simple SCO2 cycle instead of a SRCO2 layout raises power production.•The SOFC-SRCO2 integrated cogeneration plant has a 0.64% higher exergy efficiency.