## 3 Results and Discussion  
When replacing a refrigerant in a refrigeration system, it is important to investigate the system's energy performance. In Figures 3 and 4, the COP, heating capacity and compressor discharge temperature when using the alternative refrigerants to R134a and R245 fa are shown and compared. The \(x\)-axis represents the difference between condensation and evaporation temperatures (DT). The condensation temperatures are assumed to be fixed at 40 and 100 \({}^{\circ}\)C in MTHP and HTHP applications, respectively, while the evaporation temperature varies to provide the desired DT. In the MTHP application, R134a has the highest COP among the DT range of 50-70 \({}^{\circ}\)C, while the COP values of R1234 ze(E), R290 and R450A are close to the COP of R134a. Among tested refrigerants, R1234 vf has the lowest COP, which is on average 4% lower than R134a. The comparison between the heating capacity of the refrigerants revealed that the utilization of R290 could provide greater heating capacity than other refrigerants at a given DT. The heating capacity of R290 and R513A is larger than that of R134a, while the heating capacity of R1234 ze(E) is lower than that of other refrigerants. The discharge temperature analysis of the refrigerants in the MTHP application revealed that all the alternative refrigerants have lower discharge temperatures than R134a. The lowest discharge temperature belongs to R1234 vf, which is 15 \({}^{\circ}\)C, on average, lower than that of R134a. Figure 2: Electricity generation by sources in (**a**) Brazil, (**b**) Sweden, (**c**) Canada and (**d**) Poland [29]. In the HTTP application, the COP of the R1336 mzz(Z) is higher than that of other refrigerants. The COP of R1336 mzz(Z) is 24%, on average, higher than that of R245 fa. It was also found that R1233 zd(E) and R1234 ze(Z) have higher COP than R245 fa, but R600 exhibits the lowest COP among all the tested refrigerants. Although R600 shows the lowest COP value, this refrigerant provides the highest heating capacity, which is 27%, on average, higher than that of R245 fa. The lowest heating capacity is observed when using R1336 mzz(Z) and maintains a heating capacity value of less than 40 kW over the operating range. Among alternative refrigerants, R1336 mzz(Z), R1234 ze(Z) and R1233 zd(E) have higher discharge temperatures than R245 fa, while the highest discharge temperature belongs to R1336 mzz(Z). The discharge temperature of R1336 mzz(Z) is on average 19 \({}^{\circ}\)C higher than that of R245 fa. The discharge temperatures of R1224 yd(Z) and R600 are very close to that of R245 fa, mostly below 104 \({}^{\circ}\)C.  
The direct and indirect emissions of a heat pump system are shown in Figure 5. The contour of the direct emissions for each kilogram of refrigerant charge confirms that the increment of the leakage rate, and GWP of the refrigerant, increase the direct CO\({}_{2}\)-eq. emissions remarkably. It is also revealed that for the refrigerants such as R290, R1234 yf, R1234 ze(E), R1336 mzz(Z), R1233 zd(E), R1224 yd(Z), and R1234 ze(Z) with very low GWP values, the increase in the leakage rate does not have a noticeable influence on direct emissions. However, for the refrigerants such as R134a and R245 fa with much higher GWP values, the direct CO\({}_{2}\)-eq. emissions increase significantly with an increase in the  
Figure 3: R134a and its alternative refrigerants: (**a**) COP, (**b**) heating capacity and (**c**) discharge temperature. leakage rate. This result indicates that the direct CO\({}_{2}\)-eq. emissions can be negligible by the utilization of refrigerants with very low GWP values in RACHP systems. Figure 4: R245 fa and its alternative refrigerants: (**a**) COP, (**b**) heating capacity and (**c**) discharge temperature. Figure 5: CO\({}_{2}\)-eq. emissions as a function of their inputs: (**a**) direct and (**b**) indirect components. The analysis of the indirect CO\({}_{2}\)-eq.