The air conditioning system of new energy vehicles is mainly composed of ventilation system, refrigeration system, heating system, air purification system and control system.
I. Working Principle of Air Conditioning Refrigeration System
The role of the refrigeration system is to cool the air inside the vehicle or the fresh air entering the vehicle from the outside, so as to reduce the temperature inside the vehicle.
1.Fan
2.Condenser
3.Compressor
4.Expansion Valve
5.Blower
6.Evaporator
7.Receiver-Dryer
1.Refrigeration route in the vehicle
Composition of the air conditioning refrigeration system for new energy vehicles
In a closed refrigeration system, refrigerant is charged and circulated by the compressor. The refrigerant condenses from gas to liquid at the condenser, releasing heat; it evaporates from liquid to gas at the evaporator, absorbing heat, thereby reducing the temperature inside the vehicle.
2. Battery Pack Refrigeration Route
The refrigerant circulation loop of the air conditioning system consists of two parallel branches: one for in-vehicle cooling and one for power battery unit cooling. Each branch has an expansion valve to independently control the refrigeration function.
The accumulator management electronics can control and open the expansion valve by applying voltage, allowing refrigerant to flow into the power battery unit for cooling. In-vehicle cooling is similarly conducted as needed, with the expansion valve before the evaporator controlled by the electrical and electronic system.
1.Condenser
2.Electric compressor
3.Liquid storage dryer
4.Power battery unit
5.Electric fan
6.Expansion valve
7.Heat exchanger
8.Blower
9.In-vehicle evaporator
10.Expansion valve for in-vehicle cooling
II. Working Principle of Air Conditioning Heating
In early electric vehicles, heaters typically used electric heating elements, but now more and more electric vehicles adopt heat pumps and air conditioning for heating. When the refrigerant in the air conditioning system flows in a specific direction, it operates in cooling mode: the condenser and evaporator each perform their functions, with the evaporator responsible for lowering the cabin temperature. When the refrigerant flows in the reverse direction, it switches to heating mode: the evaporator then acts as a condenser, responsible for heating the cabin.
The heating efficiency of air conditioning is 3 to 4 times that of electric heaters, making it more energy-efficient. For this reason, an increasing number of electric vehicles are switching to air conditioning-based heating systems.
1. Working Principle of PTC Water Heating Heater
Pure electric vehicles can use PTC heaters to directly heat the air or heat the coolant to warm the air. When a PTC heater is used to directly heat the air, it only requires replacing the warm water tank of a traditional vehicle’s air conditioning system with a PTC heater, supplemented by necessary control equipment, to be directly applied to pure electric vehicles.
2. Heat Pump Air Conditioning
Compared with PTC heaters, heat pump air conditioning can significantly reduce energy consumption and increase the winter driving range of vehicles. However, heat pump systems have low heating efficiency at low temperatures and higher costs, so most automakers still use PTC heaters for heating. In the future, with continuous breakthroughs in low-temperature heat pump technology, the application of heat pump air conditioning will become increasingly widespread.
Components of Heat Pump Air Conditioning System:
1.Expansion valve on power battery unit
2.Electric compressor
3.Cabin blower
4.Electric heating device
5.Expansion valve for cabin evaporator
6.Shut-off valve between condenser and receiver-dryer
7.Shut-off valve between electric compressor and heat pump heat exchanger
8.Heat pump heat exchanger
9.Receiver-dryer
The heating system of electric vehicle air conditioning has three working modes: air mode, coolant mode, and air-plus-coolant mode.
(1) Air Mode
The air conditioning compressor presses high-temperature, high-pressure refrigerant gas into the condenser. The refrigerant exiting the condenser flows into the thermal expansion valve, where its temperature drops slightly before entering two condensers for two-stage heating to enhance the heating effect. The refrigerant then flows into another thermal expansion valve and enters the evaporator. As the refrigerant in the evaporator is colder than the surrounding air, it absorbs heat and vaporizes. The low-temperature, low-pressure refrigerant gas finally returns to the compressor to start the next cycle.
(2) Coolant Mode
If the ambient air temperature is extremely low—lower than the refrigerant temperature in the evaporator—the refrigerant will flow into the heat exchanger. Inside the heat exchanger, two water pipes connected to the refrigerant interact with two pipes carrying coolant. Here, the refrigerant absorbs heat from the electric vehicle’s cooling system coolant. If the coolant’s heat is insufficient, an electric heater activates to warm the coolant.
(3) Air-Plus-Coolant Mode
The refrigerant flows to both the evaporator and the heat exchanger, absorbing heat from both air and coolant simultaneously. During vehicle operation, the control unit selects different working modes based on ambient temperature. There is also an intelligent mode: in cooling mode, the refrigerant flow direction changes, swapping the functions of the evaporator and condenser, with one condenser isolated by a partition to disable its operation. The electric vehicle’s cooling system features two three-way valves, enabling switching between large and small cooling loops.
III. Working Principle of Heating System
1.Working Principle of Hydronic Heating System
1.Heater core
2.Heater hose
3.Hot water valve
4.Radiator hose
5.Expansion tank
6.Water pump
7.Fan
8.Radiator
9.Engine
2. Working Principle of Heat Pump Air Conditioning Heating System
1.Evaporator
2.Electric fan
3.Electric compressor
4.Receiver-dryer
5.Power battery unit
6.Expansion valve for cooling pipes in power battery unit
7.Cooling pipes in power battery unit
8.Cabin blower
9.Expansion valve for cabin evaporator
10.Condenser
11.Heating heat exchanger
12.Electric heating device
13.Heat pump heat exchanger
14.Expansion valve for heat pump heat exchanger
15.Electric coolant pump
16.Coolant reservoir
17.Shut-off valve between electric compressor and evaporator (opens when unpowered)
18.Shut-off valve between evaporator and receiver-dryer (closes when unpowered)
19.Refrigerant check valve
20.Shut-off valve between electric compressor and heat pump heat exchanger (opens when unpowered)
21.Shut-off valve between expansion valve on heat pump heat exchanger and receiver-dryer (opens when unpowered)
