Performance comparison of electric vehicle air-conditioning system using R1234yf with various compressor lubricants

Electric vehicles (EVs) increasingly rely on electric-drive compressors (EDCs), where lubricant behaviour plays a decisive role in determining automotive air-conditioning (AAC) efficiency, cooling performance, and overall energy consumption. However, the compatibility and thermodynamic influence of different compressor lubricants on R1234yf-based EV-AAC systems remain insufficiently explored. This study experimentally evaluates the performance of an EDC-driven AAC system using R1234yf and three commercially available compressor lubricants (PAO, PVE and POE) across varied compressor speeds and refrigerant charges. The test rig consisted of an EDC unit, a condenser, an evaporator, an expansion valve, and a refrigerant–lubricant circulation loop. Results show that PAO consistently outperformed PVE and POE, exhibiting the lowest power consumption, highest cooling output, and strongest thermodynamic efficiency. At high speeds, PVE required up to 24 % more power than PAO, while POE consumed almost 14 % more. PAO also achieved the greatest heat-absorption capability (148 kJ/kg at 2000 rpm) and delivered the highest cooling capacity at peak load (826 W at 5000 rpm). In contrast, the POE cooling capacity was 34 % lower than that of PAO at 5000 rpm and 180 g charge. Correspondingly, the coefficient of performance (COP) of PVE and POE decreased by 15 % and 12 %, respectively, compared with PAO under identical conditions. These findings demonstrate that lubricant selection has a substantial and quantifiable impact on EV-AAC efficiency, and PAO emerges as the most suitable candidate for R1234yf-based electric-driven systems. Therefore, lubricant formulation should be treated as a critical design parameter in the development of future EV thermal-management and AAC systems.