Novel compound waste heat-solar driven ejector-compression heat pump for simultaneous cooling and heating using environmentally friendly refrigerants

This work investigates the theoretical performance of a novel compound waste heat-solar driven ejector-solar assisted heat pump for simultaneous heating and cooling purposes. The system utilizes waste heat from three different sources, PV/T (photovoltaic thermal) with flat plate collector, milk pasteurization process, and condenser exchange heat. Real weather data is employed to determine the hourly performance of the system in three European cities, Valencia (Spain), Berlin (Germany), and Stockholm (Sweden) representing warm, middle and cold climates, respectively. Moreover, R450A and R513A alternative refrigerants are compared to the greenhouse gas R134a. The results show that the proposed system improves cooling COP by 7% using R450A in comparison with a conventional R134a vapor compression system. Furthermore, the utilization of waste heat recovery enhances the system COP from 3.7 to 4 in the absence of solar intensity. On the other hand, the results of the heating mode show that the system with PV/T and using R450A has a COP increase over the adopted solar time, ranging from 2 to 5% in Valencia; 2 to 2.5% in Berlin, andl to 1.5% in Stockholm. However, R513A shows a COP reduction of about 5% in comparison to R134a. Regarding the heating mode with waste heat utilization from milk pasteurization, the system based on R450A results in the highest system COP, increasing COP up to 75% compared to the R134a baseline scenario. Overall, the proposed R450A systems show the highest equivalent carbon dioxide emission reduction and, therefore, it is recommended from an environmental point of view.