Heating performance characteristics of a dual source heat pump using air and waste heat in electric vehicles

•An R134a heat pump with the dual heat source was investigated.•Performance characteristics were analyzed by varying heat source condition.•Performance of the dual source system was higher than that of the single source.•Optimum operation methods were suggested to improve the heating performance. A heat pump has been considered as an alternative to an electric heater to increase the efficiency of the heating unit in electric vehicles. However, the heating performance of a single source heat pump has yet to be improved at low outdoor temperatures. This study investigates the feasibility of a dual source heat pump using both air and waste heat in electric vehicles. The performance of the dual source heat pump was measured at various operation modes: air source-only, waste heat-only and dual heat source. The heating performance of the dual source heat pump was higher than those of the single source heat pumps. In addition, an alternating single mode operation of air source-only and waste heat-only modes was proposed to improve performance at low outdoor air temperatures.