This paper presents a multi-objective optimization model for estimating the cooling capacity of refriger- ation in a trigeneration system for both grid on and offoperating modes. In trigeneration systems, the cooling demand can be provided by single effect absorption and compression chillers (as the refrigeration system). Genetic Algorithm and LINMAP selection procedure are used for obtaining the final optimum point considering four-E analysis (energy, exergy, economy and emission) with the help of net future worth benefit difference (NFWBD) and global exergy efficiency objective functions. It was found that the NFWBD and exergy efficiency with cooling capacity of 1800 and 5600 kW for absorption and compres- sion chillers, respectively, are 330 ×10 6 $ and 41.9% for grid on mode, while they reduce to 232 ×10 6 $ and 32.7% for grid offmode. Sensitivity analysis in grid on mode shows that the increase in the num- ber of equipment (gas engine and chillers) leads to the decrease in both NFWBD and exergy efficiency, while selecting two similar absorption chillers (with cooling capacity of 900 kW), has payback period of 5.1 years, and provides the maximum NFWBD (321 ×10 6 $) and exergy efficiency (40.02%).

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