Distributed multi-heat-source hybrid heating system based on waste heat recovery for electric vehicles

Abstract

Air-conditioners usually consume the most electricity among all of the auxiliary components in an electric bus, over 30% of the battery power at maximum. A distributed multi-heat-source phased control method was developed to reduce the energy consumption of heating in electric vehicles (EVs). This method combines the application of multiple heat sources, including waste heat from battery cooling, motor and controller cooling, and positive temperature coefficient heating. Analyzed the internal thermal process and heat generation law of the power battery, and explored the thermal process of the driving motor and its controller. Apply the cooling waste heat from the power battery and the driving motor to the heating system of pure electric vehicles. The heat sources are distributed at different locations on the vehicle and provide heating in stages at various temperatures. Numerical analysis was conducted to calculate the heat output of each heat source, and a phased control strategy for the air conditioning system was designed according to the heat release characteristics and magnitudes of each component. Heating control functions for different stages were established at varying temperatures. The temperature rise patterns at different points on the vehicle were examined, and the positions of the heat sources were redesigned accordingly. The proposed method selects the appropriate heating mode according to factors such as the external temperature, the heat release sequence of the heating components, and passenger comfort requirements. Low-temperature experiments were performed at different temperature stages to compare the heating performance of this method with those of traditional heating methods and heat pump air conditioning for new energy vehicles. The experimental results show that the heating system has good heating effect. Compared with heat pump air conditioning and PTC heating, the proposed collaborative system saved 31.1% and 63.6% of energy, respectively, after operating at − 22℃ for 2 h. It demonstrates good energy-saving and heating performances at different temperature stages. The heating method is currently one of the best energy-saving solutions for EVs.