How optimal thermal management for electric vehicles works
Thermal management entails regulating heat flows inside the vehicle. After all, components must be operated in their respective optimal temperature range while also generating pleasant temperatures for passengers in the vehicle interior. Thermal management systems in electric vehicles are generally more complex than in conventional vehicles featuring combustion engines. The eAxle, for example, must be cooled at all times while the battery needs to be cooled or heated depending on the respective situation. Furthermore, no waste heat is available from a combustion engine to heat the vehicle interior requiring the use of energy-efficient measures here, e.g. by using a heat pump.
The refrigerant circuit and the cooling circuit must be optimally coordinated to transport heat inside the vehicle and to provide the requisite temperatures. Interconnection of these two circuits changes depending on the heating or cooling requirements. This gives rise to various operating modes.
Coolant is circulated by a pump in the cooling circuit. The coolant transports heat from where it is produced to wherever it is required inside the vehicle. The high specific thermal capacity enables coolant to absorb a lot of heat in a very small space, which is necessary for effectively cooling the eAxle or battery, for example. Coolant can also be used to distribute heat very flexibly within the vehicle. When coolant absorbs heat, its temperature rises and needs to be cooled in a heat exchanger.
A refrigerant circulates in the refrigerant circuit which can be both liquid and gaseous. By means of evaporation (transition from liquid to gaseous) of the refrigerant, a refrigerating capacity is generated which facilitates cooling even below the ambient temperature. This well-known principle for air conditioning the vehicle interior in the summer is also used to cool the battery at very high outdoor temperatures. The heat released during condensation (transition from gaseous to liquid) can also be used to heat the vehicle interior in winter. The refrigerant circuit is powered by an electric air conditioning compressor which compresses the refrigerant to the requisite pressure, enabling evaporation and condensation at the chosen temperature levels.