Development of an innovative heating and cooling system (ACU) for electric vehicles' batteries and cabin air conditioning.

The introduction of a new propulsion system for electric vehicles and therefore a completely different source of energy from the previous ones, brings with it the need for new systems for the management of these resources. The ESS (Energy Storage System) installed inside the vehicle, which stores the amount of energy needed to power the electric motor, must be kept at a constant temperature to allow proper operation, without loss of efficiency. For this purpose, a fluid conditioning system has been developed that allow to heat or cool, depending on the environmental conditions in which the vehicle is located and, at the same time, allows the temperature inside the passenger cabin to be regulated as the user desires; this system is called ACU (Active Cooling System). First of all, the state of the art concerning the refrigerant cycle and heat pumps was analysed, then different solutions were presented and analysed to control the temperature of the ESS, under different environmental conditions and according to the different requests of the user for the cabin temperature. Different types of components characterizing the refrigerant circuit were presented: compressor, thermal expansion valve, heat exchangers (evaporator, condenser), of which two types are reported: "refrigerant fluid - air" and "refrigerant fluid - liquid", respectively used for air conditioning of the cabin and the battery pack temperature controlling. The ACU, consisting of the entire refrigerant cycle, was designed using 3D modelling software respecting the customer constrain , and a first prototype was created. Subsequently, performance tests were carried out to verify the correct functioning of the system and that it complied with the parameters set by the customer,using instrumentation that allows to measure temperature and pressure in the points of the circuit where required or necessary, to evaluate the performance. The results are then analysed, it was emerged that same change are required, it is necessary redesign a new version of prototype, and consequently a second prototype was created and the same performance tests were carried out, obtaining better results with respect to the ones previously obtained with the old prototype.