New generation thermal management system: Add a heat pump system. The overall thermal management system is more efficient and more complex.
The refrigerant side and water medium side are integrated, and the overall development is towards integration.The working principle of a heat pump air conditioning system is based on the “reverse Carnot cycle,” which involves the following main processes:
- Evaporation Stage: The low-pressure liquid refrigerant absorbs heat in the evaporator, turning into gas. During this stage, heat from the surrounding environment is transferred to the refrigerant.
- Compression Stage: The gas refrigerant is compressed by the compressor, raising its temperature and pressure, and placing it in a high-pressure state.
- Condensation Stage: The high-pressure gas releases heat in the condenser, condensing into a liquid. The heat released can be used to warm indoor air or water.
- Expansion Stage: The liquid refrigerant passes through the expansion valve, dropping in pressure and temperature, and returns to the evaporator, completing the cycle.
We can see that the overall efficiency of the system is defined as (heat absorbed by the refrigerant from the air + work done on the refrigerant by the compressor) / power consumption of the compressor. This efficiency can easily exceed 100%. However, in extremely low external temperatures, the evaporation temperature of the refrigerant and the temperature difference with the environment become too small, resulting in less heat being absorbed. Therefore, in low-temperature conditions, the efficiency of the heat pump decreases significantly. This is why many control strategies avoid using the heat pump when the ambient temperature drops below -10°C, opting instead for direct high-pressure PTC heating.
Taking Tesla model Y as the represent. On the refrigerant side, an indoor condenser and a refrigerant three-way valve are added to meet the heat pump heating needs, replacing the original high-pressure PTC heating. Two new low-pressure PTC heaters are added to realize the functions of defrosting, defogging and auxiliary heating. Generally speaking, after replacing it with a heat pump system, the power consumption per 100 kilometers will be saved by 2-3kwh, and the overall battery life will be improved by 10%-15%.
The Tesla Model Y employs an advanced waste heat recovery and integrated heat pump system that enhances the efficiency of its thermal management. Central to this system is an eight-way valve connecting four main circuits, enabling 12 operational modes for heating, defogging, frost management, and dehumidification. This setup allows for electronic control of waste heat circulation from the motor to heat the battery while also facilitating indirect heat transfer to the cockpit.
Additionally, the system integrates the motor electronic control system, water-cooled condenser, and low-temperature radiator into a single loop, allowing them to share a radiator for improved efficiency. The battery thermal management circuit can be linked with the chiller circuit, providing effective cooling for the battery while the heat pump function can warm the cockpit. By utilizing the eight-way valve, the overall operational status of the thermal management system—including the battery, motor electronic control, chiller cooling, and water-cooled condenser heating circuits—can be flexibly managed to maximize efficiency in new energy vehicles.
Through its heat pump system, Tesla appears to be building a sophisticated “thermal generation and collection system.” This system has evolved from initially relying solely on battery energy for heating (battery-level only) to combining battery heat with waste heat from the electric motor (whole vehicle level). It has now expanded to utilize heat generated from various components within the vehicle and the surrounding environment (both car and environment). In extremely low temperatures, techniques like using motor stall to heat the battery rely on precise software control.
The innovations in Tesla’s thermal management are evident, from the eight-way valve to the automated control of twelve operational modes and the thermal management of motor stall. These advancements showcase Tesla’s leadership in thermal management technology, becoming standard features for the brand. The Model Y’s influence could accelerate the adoption of heat pump air conditioning and motor stall technologies in electric vehicles, driving the industry toward greater efficiency.
