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Heat pumps a promising way to extend electric vehicles' range

Two articles recently published in the International Journal of Refrigeration highlight heat pumps – especially with integrated desiccant – as a promising way to extend the range of electric vehicles.

According to OECD/IEA, the global stock of electric vehicles (EV) is booming: it surpassed 2 million in 2016 after crossing the 1 million threshold in 2015. Models show that by 2050, a decarbonised grid combined with an EV fleet could reduce greenhouse gas emissions by 48–70% in the electricity and transportation sectors combined, compared to 2015. 


EV development is limited to some extent, however, due to various bottlenecks, such as the short cruising range compared to that of traditional internal combustion engine vehicles. Due to their relatively low heating efficiency, the range of EVs may decrease by more than 50% in cold climates due to the energy consumption of the heating/air-conditioning (AC) system. AC systems for vehicles are generally operated under three modes: cooling, heating and dehumidification-reheating.


Two articles [1 - 2] that were recently published in the International Journal of Refrigeration stress the importance of reducing climate control loads – especially the heat demand – and highlight heat pumps as a promising way of extending EVs' range.


In particular, Li Zhang et al [1] propose a heat pump system with integrated desiccant where desiccant dehumidifies the cabin interior, reducing the amount of incoming fresh air needed and the cabin's demand for heat. They calculate that, at an ambient air temperature of -20°C, compared to a 228 km cruising range when the AC system is off, the cruising range falls to 105 km with a traditional heater, but drops to only 155 km with a conventional heat pump and 172 km with the proposed heat pump system due to the decreased cabin heat load and the energy saved by the compressor.


1 Li Zhang, Katsumi Hashimoto , Hiromi Hasegawa , Michiyuki Saikawa. Performance analysis of a heat pump system with integrated desiccant for electric vehicles. International Journal of Refrigeration [online]. 2018-02, vol. 86, 8 p. Available free of charge for IIR members.

2 Ziqi Zhang, Dandong Wang, Chengquan Zhang, Jiangping Chen. Electric vehicle range extension strategies based on improved AC system in cold climate – A review. International Journal of Refrigeration [online]. 2018-04, vol. 88, 10 p. Available free of charge for IIR members. (fiche 23327)