Overcoming Thermal Management Challenges In The Electric Vehicle Industry: Comprehensive Guide
Understanding the thermal management challenges of automotive thermal management
1-The importance of thermal management
New energy vehicles are complex industrial products with a large number of components and assemblies, of which the power battery is the core of the new energy vehicle, so thermal management of the power battery is a prerequisite to ensure the safe, efficient and stable operation of the vehicle.
The optimum working temperature for power batteries is 20°C-35°C. If the temperature is too low, the charging and discharging capacity of the battery will drop sharply, while if the temperature is too high, the consistency of the battery cells will be affected and even thermal runaway will occur.
Battery thermal management can heat the battery when it is at low temperature and dissipate heat when the temperature is too high, so as to control the temperature of the battery pack within a reasonable range and ensure the consistency of the battery pack temperature, making the power battery in a reliable and efficient state.
2-Factors affecting thermal management in automotive batteries
The difficulties of battery thermal management are mainly the following three issues:
1. Constant temperature control of the battery: the energy density of the power battery of new energy vehicles is getting higher and higher with the development of the industry, but at the same time the high power density of the battery will also generate a lot of heat with the charging and discharging process, the high temperature will have a negative impact on the performance of the power battery, how to carry out efficient heat dissipation is one of the major problems
2. Uneven distribution of cell temperature: Due to the production capacity, cell material and space limitations of the battery pack, there will be uneven distribution of the modules inside the pack, resulting in overheating of some modules.
3. Heat dissipation restrictions: The heat transfer of the battery module is restricted by the heat dissipation method, pack design, pack material and heat dissipation layout, which makes heat dissipation more difficult.
Identifying common thermal management problems
1-Hazards of overheating problems
Power batteries in an overheated environment can have serious negative impacts, with the following five main hazards:
- Decay of battery capacity: In an overheated operating environment, the electrochemical reactions of lithium-ion batteries will intensify rapidly, and the electron transfer rate inside the battery is faster than the diffusion rate of lithium ions, resulting in less and less lithium ions being accommodated in the positive electrode, thus reducing the capacity of the battery.
- Reduced battery performance: Excessive temperatures inside the pack can damage the structure of the cells, such as the electrode materials and electrolyte, which is the root cause of reduced battery performance and power output capability.
- Reduced cycle times: Charging and discharging operations in high temperature environments can accelerate the ageing of lithium cells, thereby reducing their use.
- Risk of thermal runaway: Excessive temperatures can reduce the safety of the battery and increase the risk of thermal runaway. This can lead to serious accidents such as a battery catching fire or exploding.High temperatures increase the risk of thermal runaway of the battery, which can lead to serious accidents such as a battery pack fire or even an explosion.
- Uneven temperature distribution: Uneven temperature distribution inside the pack can lead to uneven chemical reaction rates in the cells, which can affect the performance of the battery.
2-Problems facing effective heat dissipation
In the thermal management of power batteries, effective heat dissipation is subject to various constraints and limitations. Take for example the heat transfer mechanism: conduction is by direct transfer through solid matter, whereas the cell module of a power cell is usually separated by an insulating material, limiting the conduction of heat. Convection is a way of transferring heat through the movement of the fluid receiving it, in the case of power packs, space constraints and complex irregular shapes restrict the flow, resulting in reduced thermal performance. Radiation heat dissipation is a form of heat transfer from the body to cooler objects in the outside world by means of radiation, and is not the main heat transfer mechanism in power packs, where heat dissipation efficiency is influenced by differences in temperature and surface characteristics. Optimising the design of the heat dissipation system and choosing the right materials for the battery pack is an effective solution to these limitations.
- rational design shapes to ensure contact between the cold plate and the heat sink components in order to minimise the interface resistance between all contact surfaces;
- carrying out a rational runner design to improve the efficiency of heat transfer, the balanced temperature distribution of the core and the efficiency of space utilisation;
- the selection of thermally conductive interface materials with high thermal conductivity and heat dissipation properties for application at cold plate joints to facilitate the provision of gap-free thermal interfaces and enhance heat transfer performance
- the selection of appropriate coolants and consideration of fluid dynamics and heat transfer properties to optimise the design and flow distribution of the cooling system;
- the use of an intelligent thermal management system and the incorporation of sensors, data algorithms and analysis to achieve an optimal thermal management strategy.
Effective solutions for thermal management
1-Cooling technology options
Cold plate liquid cooling: This technology uses coolant as the heat transfer medium, which is in contact with the heat dissipation components through the cold plate, where the coolant flows inside the liquid cooling plate to effectively remove heat. This method is characterised by high thermal conductivity, adjustability and efficiency, but it is complex in composition, requires a cooling system and risks leakage.
Phase change heat dissipation: This is a technology that uses changes in the phase state of a substance to exert latent heat. This type of heat dissipation has the advantages of high heat storage density, high reliability and reliability and no external energy required, but is difficult to control and slow to dissipate, and cannot meet the heat dissipation needs of power batteries.
Heat pipe cooling: Heat pipe cooling is the process of transferring heat from a heat source to a heat sink component by using the principle of circulating the heat transfer medium internally. The advantages are high flexibility and reliability and space saving, but the disadvantage is that the cooling effect is limited.
Thermoelectric technology: Thermoelectric cooling is a cooling method based on the thermoelectric effect, a cooling technology generated on the basis of the Seebeck effect, the Palatinate effect and the Thomson effect. Its stability and reliability are high and the temperature control is precise, but the energy efficiency ratio is relatively low.
2-System layout optimisation
A reasonable system layout plays an important role in the thermal management of new energy vehicles, in four main areas:
Optimisation of the heat dissipation path: The layout must optimise the design of the heat dissipation runners or paths to ensure that the cooling liquid can effectively conduct heat from the heat dissipation components to the cooling plate/radiator, maximising heat dissipation efficiency.
Space utilisation of the battery pack: A good system layout should make full use of the available space and minimise the gap between contact surfaces so that heat transfer is not compromised.
Position and size of heat sink: it should be placed around the heat sink components and have sufficient area to absorb heat and reduce heat build-up.
System safety systems: The materials used for insulation, the construction of the battery pack and the location of the thermally sensitive electronic components should be carefully selected to ensure the safety performance of the power cell.
3- Thermal simulation and analysis
Thermal simulation and analysis has a very key role in new energy thermal management solutions. Most of the power battery thermal management design work and testing work can be done on the software, which greatly reduces the design, manufacturing, testing and other tedious work, reducing development costs.
During system design, thermal field simulation analysis of the Pack, module or battery can be carried out to select the cooling and heating methods based on the data; during the design of the cooling subsystem, the conclusions of the simulation can be used to determine the cooling channel design, cooling medium, cooling During the design of the cooling subsystem, important components and parameters such as cooling channel design, cooling medium, cooling inlet temperature and flow rate can be determined with the help of simulation findings.
Common simulation software includes STARCCM+, FLUENT, Flotherm, etc.
The following is an example of a simulation done by Trumonytechs: