Research status and future development of thermal management system for new energy vehicles under the background of carbon neutrality

Abstract

Since the signing and implementation of the Kigali Amendment to the Montreal Protocol, reducing equivalent carbon emissions and effectively slowing down global warming have become the most appealing topic in various industries worldwide. The total carbon emissions of the transportation industry, which is one of the most important sources of carbon emissions, account for approximately 30% of the total value of the economy and society. As a result, the rapid development of new energy vehicles (including passenger cars, commercial vehicles, and rail vehicles) also represents the great change of energy structure of the transportation sector. However, the abovementioned new energy vehicles still have some technical flaws, such as safety risks, range anxiety, and the greenhouse effect caused by the thermal management working fluids, which should be noted. Nowadays, it can be assumed that more advanced and precise requirements for the vehicle thermal management industry are being put forward from two perspectives: "Energy-saving" and "environmental protection". From the perspective of "energy savings", this paper summarizes the system architecture transformation and realization by upgrading the heat management system from conventional single cooling air conditioning technology to heat pump air conditioning (HP&AC) technology. The purpose of saving a lot of energy consumption of positive temperature coefficient (PTC) electric heating in winter heating conditions can be achieved using the abovementioned HP&AC operation mode. Furthermore, the combination of the new concept of integrated thermal management and various intelligent optimal control algorithms (proportional-integral-derivative, model predictive control, and extremum seeking control included) is clearly demonstrated in this paper, so that the integrated thermal management of the crew cabin, battery, motor, and electric control continues to evolve toward better performance and less energy consumption. Based on the record of this article, the evolution process of vehicle thermal management technology from single cooling air conditioning + PTC mode, then to the bi-directional HP&AC mode, and finally to the concept of integrated thermal management of the whole vehicle can be briefly shown. Hydrofluorocarbons (HFCs), which are classified as strong greenhouse gases (such as R134a and R407C) and will be gradually phased out, are still widely used as refrigerants in the thermal management systems of new energy vehicles in recent years. From the perspective of environmental protection, this paper briefly introduces several popular environmentally friendly refrigerant alternatives, such as CO2, R290, and R1234yf. Based on a large number of studies on the fourth generation of the abovementioned environmentally friendly refrigerants, the substitution of the refrigerant HFCs in the vehicle thermal management industry will be rapidly carried out worldwide. With the development of the automobile industry, electrification, intelligentization, network connection, and sharing have become four important development directions of the future automobile, which also indicates the development directions of the vehicle thermal management technology to some extent. Finally, it is stated that the new energy vehicle thermal management technology will continue to advance in the direction of "green and efficient", "functional integration", "structural modularization", and "intelligent control", and will contribute significantly to China's carbon peak and carbon neutrality goals.