What is the working principle of air conditioning in electric vehicles?
3 Answers
Air conditioning in electric vehicles operates based on signals from various sensors that detect internal cabin temperature, evaporator temperature, engine coolant temperature, and other relevant switch signals. These signals control the operation of components such as the radiator fan, condenser fan, compressor clutch, blower motor, and air control motor to automatically regulate the cabin temperature. Thermoelectric air conditioning has the following characteristics: thermoelectric components require DC power; reversing the current direction can switch between cooling and heating effects; thermoelectric cooling modules have minimal thermal inertia, enabling rapid cooling—achieving maximum temperature difference in under one minute with proper heat dissipation and no load on the cold side. By adjusting the operating current, cooling speed and temperature can be precisely controlled, with a temperature accuracy of up to 0.001°C, allowing for continuous energy regulation. Under proper design and application conditions, cooling efficiency can exceed 90%, while heating efficiency is significantly greater than 1. The system is compact, lightweight, and structurally efficient, helping to reduce the overall weight of electric vehicles. It offers high reliability, long lifespan, and easy maintenance. With no moving parts, it operates without vibration, friction, noise, and is highly resistant to impact.
The biggest difference between electric vehicle (EV) air conditioning and internal combustion engine (ICE) vehicles lies in the heating system. For cooling, both use electric compressors to circulate refrigerant, similar to household air conditioners. Heating is more complex: entry-level EVs use PTC ceramic heating elements, functioning like large hair dryers that directly consume battery power – turning on the heater in winter can reduce range by one-third. Premium EVs employ heat pump technology, which transfers heat from outside to inside the cabin, using 60% less energy than PTC systems while still functioning in sub-zero temperatures. However, heat pumps are more expensive and feature more complex refrigerant piping – if the pipes get damaged, the entire system fails. Some vehicles also offer heated seats and steering wheels, which are far more energy-efficient than blowing hot air.
The biggest fear of driving a Tesla in winter is turning on the heater, as the battery drains alarmingly fast. The principle is actually explained in the manual: in summer, cooling relies on an electric compressor to circulate refrigerant and absorb heat. In winter, heating takes two paths—older models use PTC heaters that consume electricity for warmth, while newer models switch to heat pump air conditioning. A heat pump works like a reverse refrigerator, extracting heat from the air even at -15°C outside and delivering it into the cabin. I tested it myself: at -5°C with the AC set to 22°C, the heat pump consumes 1.5 kWh less per hour than the PTC. However, slow heating in low temperatures is a pain point, so the smartest move is to preheat the car via the app before getting in.
