The provided air conditioning system includes a self-sustained power supply apparatus, a motor coupled to the apparatus and receiving a first power supply, a first transmission system coupled to the motor and transmitting a first kinetic energy, a second transmission system coupled to the engine of a transportation tool and transmitting a second kinetic energy, a compressor coupled to one of the first transmission system and the second transmission system, receiving one of the first kinetic energy and the second kinetic energy and generating an air conditioning operation to an inner air of the transportation tool, and a switching apparatus coupled to a second power supply and employed to make one of the following results happen: the first transmission system is connected to the compressor, the second transmission system is connected to the compressor and the first and the second transmission systems are both separated from the compressor.