Design and optimization of a CCHDP system integrated with NZEB from energy, exergy and exergoeconomic perspectives

Abstract

Cogeneration systems are one of the most effective, practical and economical systems in the net-zero energy building (NZEB) field. In this research, analysis and optimization of a combined cooling, heating, desalination and power (CCHDP) system is performed based on solar energy and the geothermal source in four seasons with the aim of addressing the NZEB from energy, exergy and exergoeconomic perspectives. The CCHDP system is equipped with a geothermal well and photovoltaic/thermal panels (PVT) as supplier sources. Moreover, cooling (absorption chiller) and heating (stratified storage tank 1) units, domestic hot water supply unit (heat exchanger), potable water production unit (multi-effect desalination) and power production units (organic ranking cycle 1 (ORC 1), organic ranking cycle 2 (ORC 2)) are as consumers. Combination of steady-state and dynamic methods carried out by Engineering Equation Solver (EES) and TRNSYS packages for calculate the cooling, heating and electrical demands of the building and the system for four seasons. In addition, considering the net output power, total cost rate and exergy efficiency of the system as objective functions, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is used for optimization. Results showed maximum exergy efficiency and minimum total cost rate of the system were 81.2 % and 21.15 $/h in spring, respectively. Also, the minimum amount of state of charge was 0.15 in summer, which exhibits appropriate use of battery capacity. Electrical analysis has highlighted that the maximum power sold to the grid is related to spring and the present system never needs the grid power. Optimization is carried out to improve the performance of the proposed system. Optimization results have expressed maximum exergy efficiency and minimum total cost rate belong to the optimal PVT area in spring (165m2) and are 75.3 % and 20.92 $/h, respectively.