Multi-objective optimization of combined cooling, heating, and power (CCHP) system based on CNG engine

In this paper, the technical and economic optimization of a combined cooling, heating, and power (CCHP) system based on a compressed natural gas (CNG) engine is presented. The innovations are optimization of CNG engine operating parameters (including ignition time, ignition duration and engine speed) to improve the technical and economic performance of the CCHP system, which has not been focused much in previous studies. The engine speed, combustion duration, and spark advance are used to optimizing the CCHP system with using the genetic algorithm method, and the LINMAP, TOPSIS, and Shannon methods have been used as decision-making methods. The results showed that for goal of minimizing the overall specific fuel consumption (OSFC) and maximizing fuel cost reduction (CR), the LINMAP and TOPSIS methods suggest the engine speed, combustion duration, and spark advance 1920.65 rpm, 35.17°, and −16.74°, respectively. Also, these values are evaluated based on Shannon's method. Also, the optimum values of OSFC and CR are evaluated and three-objective optimization approach to achieve maximum technical and economic efficiencies of CCHP system is used. The investment payback period, CR, and power under these conditions are evaluated with LINMAP method equal with 4.23 years, 81.1 %, and 68.62 kW, respectively.