Free Air Cooling At low outside temperatures, Cooling is direct with outside air. The outside air is conveyed into the contianer when the air flap is open. Therefore, when outside temperatures are low, energy-intensive compressor Cooling is not necessary. Mixed Mode Once the outside temperature exceeds a given threshold, Free Cooling alone is no longer sufficeint. then, in mixed mode, the runtimes of the compressor are kept to a minimum by the simultaneous use of Free Cooling and compressor Cooling. In this way, depending on the local temperature profile, the annual energy costs can be cut by a further 10%. The partial load mode of the air conditioner produces further potential savings.