An air cycle system for use in a vehicle having an internal combustion engine is provided. The circuit is operable in an active mode when the substrate moves and the power generating system generates energy or the energy storage device contains energy for powering the circuit and in a passive mode when the substrate is not moving and the energy storage device does not contain sufficient energy to power the circuit. The material maintains a vertically spaced part relationship between the shelf element and the frame, preventing them from rattling against one another.