Development History of Thermal Management
System of Electric Vehicles (1)
Phase I: Cooling only + electric heating
Phase characteristics: In the initial stage of electric vehicle industrialization, passenger compartment air conditioning and battery motor temperature control systems are modified based on traditional fuel vehicles, and each subsystem independently meets the thermal management requirements.
Traditional fuel vehicle air conditioning uses vapor compression cycle refrigeration, and the air conditioning compressor is indirectly driven by the engine through a belt, using the engine waste heat for heating.
Electric vehicle air conditioning uses vapor compression cycle refrigeration but uses an electric drive compressor instead. Since the motor waste heat cannot meet the winter heating demand, the PTC electric heater is used for heating.
In early electric vehicles, air cooling was widely used to dissipate heat and cool the battery. Coolant circulation and a radiator dissipated heat and cooled the electric drive system.
Phase II: Heat pump + electric auxiliary heating
Phase characteristics: To improve heating energy efficiency, heat pump technology is applied to electric vehicles, and the passenger compartment thermal management system and battery thermal management system are simply integrated.
Heat pump technology can realize the utilization of low-grade air sources, which can improve the heating COP compared with traditional electric heating. However, in low-temperature environments, the heating performance of the heat pump system is attenuated, and PTC electric heater is required for auxiliary heating.
By controlling the refrigerant flow path through the valve, the switching of cooling, heating, dehumidification, and defrosting modes can be realized.
As the battery capacity and power continue to increase, the traditional air cooling solution cannot meet the temperature control requirements of the power battery, and liquid cooling has gradually become the main way of battery temperature control. The cooling requirements of the passenger compartment and the power battery are met respectively by connecting the evaporator in parallel to the heat pump system.
Phase Ⅲ: wide temperature range heat pump + vehicle thermal management integration
Stage characteristics: the subsystems are coupled with each other, the components are integrated, the comprehensive energy efficiency of the system is improved, the low-temperature adaptability of the heat pump is improved, and the integration of the vehicle thermal management system is improved.
Given the problem of attenuation of the low-temperature heating performance of traditional heat pumps, low-temperature heat pump technologies such as motor battery waste heat recovery and refrigerant injection air replenishment are gradually applied, and the temperature range of heat pump adaptation is widened.
The degree of coupling of each thermal management subsystem is deepened, and valves, water tanks, coolant pumps, and other components are integrated.
The refrigerant and coolant loops are modularized, and the vehicle thermal management system is integrated and lightweight.
The development goal of the thermal management system is to develop a safer, energy-saving, environmentally friendly, and comfortable thermal management system to ensure the charging and driving safety of electric vehicles, improve the endurance performance of electric vehicles, and improve user comfort.
