4E optimization comparison of different bottoming systems for waste heat recovery of gas turbine cycles, internal combustion engines, and solid oxide fuel cells in power-hydrogen production systems

Gas turbine cycles (GTC), internal combustion engines (ICE), and solid oxide fuel cells (SOFC) are three important sources of waste energy, and although some studies have been done about their waste heat recovery (WHR) systems individually, there is a lack of a study comparing them to select the best solution. In the present research, the steam Rankine cycle, CO2 supercritical Brayton cycle (SBC), inverse Brayton cycle (IBC), and air bottoming cycle are used for WHR of high-temperature exhausted gas of 500 kW natural gas-fueled GTC and ICE. Furthermore, the organic Rankine cycle (ORC), trilateral cycle, organic flash cycle, Kalina cycle, and CO2 SBC are utilized for the WHR of the SOFC-gas turbine (GT). The performance of 13 proposed configurations is compared through 4E (energy, exergy, exergy-economic, and environmental) three-objective optimizations. Considering exergy efficiency, total cost rate, and unit cost of products as target functions, the SOFC-GT-ORC system has the best performance with exergy efficiency, total cost rate, and unit cost of 64.74%, 92.51 $/h, and 19.03 $/GJ. Furthermore, GTC-IBC and ICE-IBC have the best performance in their respective categories.

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