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Page 6 of 14 Li et al. Carbon Footprints 2024;3:6 https://dx.doi.org/10.20517/cf.2023.54

throughout the system’s lifecycle, as outlined in Equation 3.

where OpEx is the annual operating cost of EV air conditioning, the discount rate r is assumed to be 5%,
A
and n denotes the number of years the system operates.

To demonstrate the cost-benefit of substituting low-GWP refrigerants, the ROI (Return on Investment) is
defined as in Equation 4, where CapEx represents the acquisition cost of the low-GWP refrigerant system,
α
CapEx is the acquisition cost of the R134a system. OpEx and OpEx are the annual operating costs of
β
β,A
α,A
the low-GWP refrigerant system and the R134a refrigerant system, respectively.

Moreover, the IRR (Internal Rate of Return) for refrigerant replacement technology is further calculated
using the IRR function in Microsoft Excel 2021. The additional cost of the low-GWP refrigerant system is
defined as the initial investment, and the annual energy cost savings during the operational stage are defined
as annual benefits. The discount rate at which the Net Present Value of cash flows over the life cycle equals
zero represents the internal rate of return.

RESULTS
Firstly, the carbon emission reduction potential of various refrigerant replacement alternatives is calculated.
Utilizing data from CSWD for 31 major cities in China and incorporating them into the LCA model, the
[24]
average calculated results are employed to represent the nationwide average carbon emission level for
electric vehicle air conditioning. According to the literature review, the adoption of heat pump air
conditioning as a replacement for PTC heating has emerged as an industry trend [20,21] . Figure 2 depicts the
life cycle carbon emissions proportions of electric vehicle heat pumps employing different refrigerants. It is
evident that, in the R134a refrigerant heat pump, the proportion of direct emissions caused by the
refrigerant is notably high at 24.54% in the LCA. Conversely, the use of environment-friendly refrigerants
such as R1234yf, R744, and R290 in heat pumps results in a significant reduction in direct emissions, with
proportions all below 1%.

The selection of different refrigerants not only significantly affects the direct carbon emissions resulting
from refrigerant leakage but also indirectly influences the operational carbon emissions generated during
the operation of automotive air conditioning due to variations in system efficiency. Together, these two
factors contribute to substantial variations in the life cycle carbon emissions of electric vehicle air
conditioning products using different refrigerants, as depicted in Figure 3A. To highlight the emission
reduction effect of utilizing heat pump technology, a comparison is made with air conditioning plus PTC
heating technologies. As observed in Figure 3A, the product life cycle carbon emissions of AC + PTC
technology are the comparatively highest, exceeding those of R134a heat pumps by 1,646.3 kg CO -eq. In
2
contrast to electric heating technology, heat pump technology can achieve a carbon reduction of between
23% and 45%. Among the three heat pump air conditioners using low-GWP refrigerants R1234yf, R744, and
R290, the R290 heat pump exhibits the lowest life cycle carbon emissions, approximately 3,939.7 kg CO -eq.
2
The nationwide LCA ranking of electric vehicle air conditioning products is R290 < R1234yf < R744 < R134a
< AC + PTC. Figure 3B illustrates the local life cycle carbon emissions of electric vehicle air conditioning