New Energy Vehicle Thermal Management
Thermal management sounds like coordinating the cold and heat requirements within the vehicle system, and it doesn't seem to make any difference, but in fact there are significant differences in thermal management systems for different new energy vehicle types, and the following will introduce the special features of their thermal management systems for each of the two types of new energy vehicles.
Fuel Cell Vehicle
The thermal management system for fuel cells is characterized by three main points:
Heat dissipation requirement of fuel cell reactor
The reactor is the site of hydrogen-oxygen reaction, which generates heat while producing electricity. The increase in temperature helps to increase the discharge power of the reactor, but the heat cannot be gathered, so the reaction product water and the reactor coolant need to flow together to dissipate the heat. And maintaining the temperature of the reactor can effectively control the output power to meet the driver's dynamic needs for the drive system. The heat generated by the power electronics of the reactor and motor inverter can be used as part of the heat for cockpit heating in winter.
The problem of cold start of the reactor
The fuel cell reactor cannot provide electricity directly at low temperature, so it needs to be warmed up by external heat before it can enter normal operation mode. At this point, the heat dissipation circuit mentioned above needs to be reversed to a heating circuit, and the switching here may require a circuit control valve similar to a three-way two-way valve. Heating can be done by an external electric heater, electric heating power from the battery to provide. It seems that there is also technology mentioned that the reactor can be self-heating, so that the energy generated by the reaction more in the form of heat to the body of the reactor heating.
Pressurized cooling
This part is a bit like the one mentioned by the hybrid side, in order to meet the power demand of the reactor, the amount of reactant oxygen is also in demand, so the air intake needs to be pressurized to increase the density and thus the oxygen mass flow rate. For this reason brings the post-boost cooling, which can be connected in series in the same cooling circuit since the temperature range is relatively close to the other components.
Pure Electric Vehicles
The last pure electric vehicle is the most popular player in the market today. Research and development in thermal management of electric vehicles has been done in all major car manufacturers and suppliers. The following are three main points where it differs from other vehicle types:
Winter range concerns
Most of the credit for range is given to the non-thermal management aspects of battery energy density, overall vehicle electrical consumption, and wind resistance coefficient, but not so much in winter. In order to meet the comfort level in the cabin and the cold start of the high-voltage battery, a lot of electrical energy is consumed by the thermal management system, and a significant reduction in winter range is already the norm. The main reason is that the pure electric vehicle drive system heat generation is far more than the engine, the battery and temperature sensitive. Currently common solutions such as heat pump system, the drive system heat and environmental heat through the compressor cycle to provide the cabin and battery, there is also the Weimar EX5 in the use of diesel heaters, the use of a portion of diesel combustion heat to provide the battery and cabin preheating, there is another is the battery self-heating technology, so that when the battery is started with a small portion of energy to achieve the warming of each battery unit, thereby reducing reliance on external heat exchange circuits.
High power charging heat
Other types of new energy vehicle batteries are relatively small, the need for external plug-in charging occasions are also dominated by AC low power, while high-voltage high-power DC charging is almost a standard feature of every pure electric car, except for cars like Baojun E100 are more or less support tens of kilowatts of charging power. Although high-power charging is directly connected to the DC charging pile and the battery, there are no parts in the middle like the AC OBC, but the battery and cable heating under high-power is not to be underestimated. Especially in summer, even to meet the high power charging, such as 60kW charging power, need to use the cooling cycle involved in cooling the battery, or heat pump system. So it seems that although high-power charging shortens the charging time to improve charging efficiency, but the complexity and cost of thermal management is needed to meet such needs, so for different price models, and not want to improve to high-power can be improved.
Power electronics integrated heat dissipation
From the current trend of electric vehicle high-voltage system can be seen, the future of the power electronics will be more and more integrated, such as BYD's high-voltage three-in-one integrated vehicle charger, high-voltage to low-voltage DC/DC and high-voltage distribution box, and Geely new energy and geometry A with two-in-one integration of DC/DC and high-voltage distribution box and so on. The integration of power electronics inevitably brings the integration of the cooling circuit, which is a new problem for the thermal management system, the design of the cooling circuit inside the high-voltage integration and the pressure drop of the pipeline fluid. The benefits of integrated heat dissipation lie in the shortened piping length, shared cooling piping interface, and ultimately space saving and cost reduction.
