| Experimental Study on Heat Pump Application in a Hybrid Electric Vehicle Under Cold Conditions for Fuel Economy and Waste Heat Utilization |
| Ahyun Ko1, Youngjin Shin1, Yongjin Jung1, Min Wook Kim2, Dae Woong Lee2, Yong Kil Cha2, Chongpyo Cho1 |
1Energy Convergence System Research Department, Korea Institute of Energy Research, Daejeon 34129, Korea
2Advanced System Team, Hanon Systems, Daejeon 34325, Korea |
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Received: April 15, 2025; Revised: May 28, 2025 Accepted: May 30, 2025. Published online: July 8, 2025. |
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| ABSTRACT |
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The causes of winter fuel economy deterioration varied depending on the type of vehicle. In internal combustion engine vehicles, the primary causes were reduced combustion performance and increased cooling losses, whereas in electric vehicles (EVs), the predominant factor was the increased internal resistance of the battery. To mitigate the reduced driving range of EVs during winter, heat pump technology and thermal management systems have recently gained attention and significantly alleviated this issue. However, research aimed at improving the winter fuel economy of hybrid electric vehicles (HEVs) remained limited, and effective solutions had yet to be fully developed. In this study, the application of a heat pump in HEVs for enhancing winter fuel economy was experimentally investigated. Moreover, potential waste heat sources—including coolant, power electronics, and exhaust gases—were examined, and the heating energy requirements were analyzed under various operating conditions. Finally, to evaluate the potential improvement in winter fuel economy through the application of current heat pump technology, a heat pump system capable of recovering waste heat from engine coolant and power electronics (PE) was designed and installed in a test vehicle. The experimental investigations confirmed that the winter fuel economy of HEVs improved by more than 10%. |
| Key Words:
Hybrid electric vehicle (HEV) · Cold conditions · Heat pump · Waste heat utilization · Integrated thermal energy management |
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Corresponding Author.
Chongpyo Cho , Email. 
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