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Electric cars

Air conditioning in an EV – how does heating work in an electric car?

20 January 2023

The engine in an electric car does not generate heat, so EVs must use specially designed heating and cooling systems. Maintaining the right temperature in the cabin in winter is not only a matter of driving comfort, but above all safety, since the windows must not be fogged up or frosted. You should know how an air conditioning system works in order to use it optimally. 

The principle of air conditioning in the car 

The air conditioning system works in conjunction with the car's heating system and is responsible not only for cooling the interior in summer, but also for warm air in winter. The common element of both systems is the refrigerant, which, depending on the mode of operation, receives heat from the heater or is cooled in the radiator. Circulation of the refrigerant at as high pressure as 17 bar is forced by a compressor driven by a multi-ribbed belt, which in turn transmits the drive from a pulley on the engine's crankshaft. In the cooling system, the refrigerant enters a condenser cooled by a momentum of air or a fan and changes from a gaseous to a liquid state. From there, the liquid is transported to a dehumidifier and then an expansion valve, where it transforms into a -4 °C gas. It then cools the evaporator, through which the air blown into the cabin flows. In a heating mode, on the other hand, the same refrigerant takes heat from the engine and transfers it to the heater, which heats the air flowing through it. An engine-driven fan is responsible for blowing cooled or heated air into the cabin. Knowing how air conditioning works in a combustion car, it is easier to understand the principle of this system in electric cars. 

Air conditioning system in an electric car – what is the difference? 

The electric motor does not emit heat, but this does not mean there is no heating in the car. The mechanism of operation of cooling and heating systems in electric cars is actually not very different from those found in combustion cars. The main difference is the power source of the compressor. It is not the crankshaft in this case, but the batteries for electric cars. Compressors in EVs have their own built-in electric motor, an inverter that converts direct current drawn from the battery into AC, and a separator that separates the compressor oil from the refrigerant. Among the advantages of the solution, where the compressor is powered directly from the battery, is the ability to run the air conditioner while parked, with the engine off. In new electric cars you can also find a heating system based on a heat pump, which somewhat resembles the split air conditioners used to heat buildings. The air-to-air heat pump can operate in both heating and cooling modes. In a heating mode, the warm air it produces is directly blown into the cabin, while in cooling mode it goes to a condenser, followed by a dehumidifier, expansion valve and evaporator. The heat pump is also powered by a lithium-ion battery using an inverter. 

How to heat the interior of an electric car? 

Turning on the car's heating increases the energy demand for the compressor, which in the case of electric cars is associated with faster battery drainage. Given the small number of fast chargers and the extended battery charging time in cold weather, BEVs seem like a good option only for city trips, and that's provided you have your own charging point at home. However, there are ways to reduce the electricity consumption of electric vehicles and hybrid cars in winter. First, preheat the car's interior even before hitting the road. It's best to plug it into a charger, or if that's not possible, set it up in a sunny location. Secondly, while driving, it is a good idea to turn on the economy mode that reduces the energy consumption of individual systems to a minimum. If the car is equipped with heated seats and steering wheel, you can set the interior temperature to the lowest level or opt for no heating in the car. However, energy consumption for heating the interior depends not only on skillful energy management, driving speed and battery operating temperature, but also on the type of heating and proper insulation of the car's interior. 

The use of fan heaters 

There are several different types of heating in electric cars, but the most common is an electric heater connected to a blower. Although the power of such heaters is mostly small, as low as 2 to 4 kW, in negative temperatures they greatly accelerate the process of battery drainage. It has even been tested in practice how long an electric car battery lasts in winter. Tests conducted by the American Automotive Association showed that in temperature conditions below -7°C, the average range of an electric car drops by up to half compared to optimal conditions of 24°C. This problem does not occur in warm climatic conditions, but in northern Europe or America, for example, where there are sometimes very harsh winters, the use of such heating in the car can make it impossible to travel long distances outside the city. 

Advantages and disadvantages of a heat pump in the car 

Heat pump is an increasingly common type of heating in electric cars. By properly compressing and expanding the heating medium, free heat energy drawn from outside can be used to heat the vehicle cabin. Tests in winter conditions have shown that this requires less energy than a traditional system with an electric heater, but only within a certain range of outdoor temperatures. At temperatures between 0 and 10°C, the heat pump is estimated to consume about 1 kW of energy, so it saves 1-2 kW for every hour of operation. At lower temperatures, the situation changes to the disadvantage of the heat pump. It is also often emphasized that the heat pump is a good solution only if the car is used for city driving and has a battery with a relatively small capacity. If the car is to cover longer distances, it is more profitable to invest in a model with a more capacious battery and a system based on a traditional resistance heater. 

High Voltage Heater – what is it and how does it work? 

The High Voltage Heater (HVH) is a device that is small in size and weighs just 2.7 kilograms, yet is very efficient. Unlike heat pumps, this technology is based on a water heating model instead of air heating. It can be used for both maintaining a comfortable temperature in the cabin and preheating or cooling the traction engine. The HVH heater is designed to operate over a wide range of supply voltages from 100 to 450 V, while its maximum heating power is as high as 7 kW. The high efficiency of this solution makes it applicable to large vehicles, such as trucks and buses. The most common application of this technology is electric parking heating of the driver's cabin used in trucks, but it is also successfully used in passenger cars. Automobile design is increasingly combining all of these technologies in various combinations, or using the most comprehensive solutions possible to provide the greatest benefits. 

Insulating materials and the range of an electric car 

A very important aspect from the point of view of maintaining a comfortable temperature in the vehicle cabin is not only to produce heat or cold efficiently, but also to retain it where it is needed. In this regard, automotive components made of EPP foamed polypropylene, which features excellent thermal insulation, impact and deformation resistance, and minimal weight, are perfectly applicable. Even today, EPP has become a leading material that is widely used by car seat manufacturers. Among other things, it is used to manufacture seat fillings, headrests, armrests or car door panels, and even body components for passive safety. The excellent moldability and electrical properties of this material have also led to its use in the production of batteries for electric cars. Battery components molded from it protect sensitive cells from extreme temperatures, surges and mechanical damage. Thus, they make it possible to increase the range and safety of electric cars in many ways. 

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