How does an air conditioning system in electric cars work?
We all know how an air conditioner works in an internal combustion engine; or atleast a wee bit familiar with it. All vehicles, which are powered by internal combustion engines are equipped with a compressor. The compressor is powered by the internal combustion engine and circulates the refrigerant through the internal air conditioning plumbing into the chilling unit and cools the air before it is passed out into the cabin through the AC vents. But what about electric cars?
Nowadays, all the experts and analysts are of the opinion that going ‘electric’ is the future for automobiles. Electric powered or internal combustion engines, air conditioning with cooling and heating is a must have feature in any car. So how does an electric car achieve this functionality?
Several factors need to be taken into consideration while designing the air conditioning system in an electric car. The first major but obvious difference in air conditioning between IC powered cars and electric ones is the source of power. For example, in Tesla models, which are in the forefront as long as electric vehicles (EV) technologies are concerned, a compressor, which is very similar to the one used in our household refrigerators is used which works with 400 Volts of power. The compressor sits in front of the car and draws power for its operation from the car’s battery pack or Energy Storage System (ESS) as per the terminology of Tesla. The Energy Storage System sits in the back of the car. Similar to the one in the IC cars, the compressor in an electric car pushes the refrigerant through the cooling unit and chills the air before it reaches the vent. Simple, eh?
Now comes the tricky question. How does the heater work in an electric car? In a IC powered car, it is pretty straight forward wherein the heating system draws its heat from the coolant system which in turn gets the heat transferred to it from the engine. The incoming air is routed through a heater matrix holding the hot coolant. But, in an electric car, none of these exist!
In a Tesla model, the heater matrix is replaced by an electric heater which performs the job. In order to ensure not too much power is drawn from the Energy Storage System (EES) Tesla uses a positive temperature coefficient (PTC) heater. It is basically a resistor that increases its resistance to electricity with increase in heat. This ensures, the power consumption for heating is only optimal and also does not increase the temperature inside the cabin.
Another problem unique to electric cars is to keep the battery pack running at optimum temperature to increase life and performance. For this, Tesla uses a pump which circulates an antifreeze mix around the EES and acts as an independent cooling system. This ensures, temperature differences are minimal between the cells of the battery pack. Not so simple eh? Get used to it !