Techno-economic and techno-environmental assessment and multi-objective optimization of a new CCHP system based on waste heat recovery from regenerative Brayton cycle

This investigation aims to present thermo-environmental and thermo-economic parametric studies for a new hybrid tri-generation energy system. In system, a regenerative gas turbine cycle (RGTC) is the runner system, while Kalina cycle (KC) and ejector refrigeration cycle (ERC) are considered as companion elements. The parametric study is done through validated computational program developed in EES software. Two new functions of levelized total annual emissions and costs (LTAE and LTAC), with two conventional indices of energetic and exergetic efficiencies (eta(en) and eta(ex)) are defined for system evaluation. Thermodynamics modeling revealed that almost 75 % of total exergy destruction is related to the RGTC. The outputs of parametric study prove that pressure ratio of compressor and pinch-point temperature of heat exchanger 2 are the most and least effective parameters, respectively. Also, for the bottoming cycles, changes in KC design parameters resulted in creation of peak points in all the evaluation criteria; but changes in the ERC design parameters resulted in uniform (ascending or descending) behavior in the evaluation criteria. The NSGA-II optimization procedure (using MATLAB software) results in eta(en,opt) = 77.17 %, eta(ex,opt) = 38.94 %, LTAE(opt) = 9.36 kg/kW.yr, and LTAC(opt) = 106.04 (sic)/kW.yr. The payback period and net present value of the tri-generation system are found as 3.74 yr and 1184525.43 (sic). (C) 2021 Elsevier Ltd. All rights reserved.