Thermo-economic evaluation of supercritical CO₂ Brayton cycle integrated with absorption refrigeration system and organic Rankine cycle for waste heat recovery

Energy efficiency of the power generating system can be enhanced by utilizing low-grade waste heat from the system. Absorption refrigeration system (ARS) and organic Rankine cycle (ORC) are considered famous technologies for waste heat recovery applications. In this work, novel optimized trigeneration system comprising waste heat recovery of internal combustion engine, has been proposed and analysed with respect to energy, exergy and economic considerations. Three systems have been proposed by utilizing the engine's waste heat at 470 °C in producing power and refrigeration simultaneously using integration of supercritical carbon dioxide Brayton cycle, ORC, and ARS. Energy analysis, exergy analysis, and economic analysis have been carried out to examine the performance of these integrated systems. A parametric study has been performed over gas turbine inlet temperature, compressor inlet temperature, Brayton cycle pressure ratio, ORC boiler pressure, and ARS evaporator and absorber temperatures. The most efficient and economical configuration was the one, in which the flue gas from the internal combustion engine gives thermal energy to the Brayton cycle and ORC in a cascaded manner, while ARS was operated using the under-utilized thermal energy of working fluid from ORC turbine. It was concluded that the aforementioned most efficient and economical configuration when optimized using genetic algorithm (GA), produced exergy efficiency and levelized cost of electricity of 59.21% and 0.063 $/kWh for two separate optimization problem formulations, respectively.