The Hybrid Air Car uses compressed nitrogen, which is held in a tank called the high-pressure accumulator.
A hydraulic pump and piston compress nitrogen in the accumulator. When the nitrogen is released (by pressing the accelerator), the pump runs in reverse. Acting now as a motor, it harnesses the energy of the moving hydraulic fluid to send power to the wheels.
After the hydraulic fluid passes through the motor, it flows to the low-pressure accumulator, where it is stored for later use.
A gasoline engine supplements the air power when accelerating or going up hills. This could be an 82-hp 1.2 L I3 for subcompacts and a 110-hp 1.6 L I4 for compacts.