Hybrid multi-objective optimization and thermo-economic analysis of a multi-effect desalination unit integrated with a fuel cell-based trigeneration system

Abstract

Due to fossil fuel depletion and global warming, biomass plays a significant role in supplying the required energy in the industrial and residential sectors. In order to develop clean and efficient conversion technology, an innovative combined cooling, heating and power (CCHP) system based on biomass is introduced in this paper. The proposed system comprises a gasification process, solid oxide fuel cell, gas turbine cycle, Rankine and organic Rankine cycles, absorption chiller, and multi-effect desalination unit simulated in ASPEN. In this system, a new configuration is proposed in order to regenerate the waste heat efficiently at every level of temperature and increase energy and exergy efficiencies. Also, thermodynamics, economic, and sensitivity analyses are performed in order to investigate the energy and exergy efficiencies, the overall cost of the system, and effective parameters. The novel optimization approach (RSM-GA-TOPSIS) is introduced by combining the response surface methodology, genetic algorithm, and Shannon entropy and TOPSIS in order to model and optimize the objective functions in DESIGN EXPERT and MATLAB software, respectively. The objectives of the optimization are maximizing energy and exergy efficiencies and minimizing the overall cost of the system. As a result, based on the initial conditions, the electricity production, overall energy and exergy efficiencies, overall cost of the system, and overall exergy destruction can be acquired at 25.235 MW, 76.69%, 57.07%, 6.1063 × 106 $, and 26.03 MW, respectively. After performing the optimization method, the optimum solution (point 3) is obtained through the TOPSIS approach. In terms of thermodynamics analysis, the electricity production, energy and exergy efficiencies are acquired at 31 MW, 88.15%, and 67.30%, which are increased by 22.85%, 14.94%, and 17.93%, respectively, compared with the initial conditions of the proposed system. In terms of economic analysis of the optimum solution, the annualized total cost, COE, and COTP can be obtained at 6.594 × 106 $, 7.3857 $/GJ, and 6.7624 $/GJ, respectively. By comparing this point to the initial conditions, although the annualized total cost at this point is increased by 7.99%, the COE and COTP are decreased by 12.1% and 10.4% due to a further increase in electricity production. Therefore, for producing energy with high efficiency and low COE, the system should be operated according to the working conditions of this point (point 3).