Energy, economic, and environmental (3 E) examinations of the indirect-expansion solar heat pump water heater system: A simulation-oriented performance optimization and multi-objective decision-making

In this paper, a simulation-oriented optimization integrated with the multi-objective decision-making (MODM) model for an indirect-expansion solar-assisted heat pump (IDX-SAHP) water heater is proposed and the energy, economic, and environmental (3 E) aspects of the system are examined. The developed model is verified and its performance is scrutinized in a humid continental climate region of China. Next, the sensitivity analysis is conducted via the one-way analysis of variance (ANOVA) approach. Then, the single-objective optimization (SOO) and multi-objective optimization (MOO) are conducted via the migrating birds optimization (MBO) method to maximize the coefficient of performance (COP) and the collector efficiency (CE), singly and concomitantly. The SOO results indicate the IDX-SAHP design as per the COP-oriented optimization causes the system to operate less for about 120 hours a year in contrast to the system design as per the CE-oriented optimization. Also, the results of MOO integrated with MODM indicate that MOO gives better performance in contrast to the SOOs so that although the CE of the maximized IDX-SAHP reduces a little from 51% to 46%, its COP increases greatly from 2.5 to 7. Therefore, the overall power consumption of the system decreases about 269 hours in contrast to the initial IDX-SAHP. Besides, the environmental examination illustrates the use of IDX-SAHP in Beijing buildings can prevent the burning of 2,877, 000, 000 cubic meters of natural gas per year in the fossil fuel power plants and prevent the release of 8,055,600 tons of CO₂ per year into the environment. Furthermore, the economical examination illustrates that Beijing residents may save approximately one billion USD per year on the purchase of electricity if they use the IDX-SAHP. Besides, the Chinese government can achieve about 109 billion USD per year if the equivalent electricity is exported instead of domestic consumption for Electric Water Heaters (EWHs). Moreover, the external costs decrease by 928 million USD per year if the IDX-SAHP is replaced with the EWHs. This paper discloses the significance of energy, economic, and environmental (3 E) examinations, optimization, and MODM during the IDX-SAHP design to increase the system efficiency and decrease the costs and environmental impacts by opting the most appropriate design parameters of the system.