This is a vertical acting reciprocating type engine. This produces the cold required for operating the plant. The high pressure air enters through inlet valves at the start of downward motion, the inlet valve closes and entrapped air expands. During upward stroke, outlet valve remains open and inlet valves remain closed. In downward stroke air enters the cylinders & expands. In the upward stroke the expanded air is pushed outside. The electric motor is used initially to start the machine. There after, the engine is moved by the air pressure itself and during which time, the engine motor retains the speed by action as a brake.