Passive ambient conditioning systems for telecommunications systems

The features of passive and semipassive ambient conditioning systems inside a telephone shelter are described. Passive systems do not require the use of moving mechanical parts. They are based on the structural features of the shelter itself and on static components which do not require power to operate. Semi-passive systems limit the use of electromechanical components (small blowers and pumps) and can provide a performance range that existing passive systems cannot yet meet. These systems are based essentially on three principles: thermal filter, temperature shift, and thermal diode. Particular emphasis is given to the operating principles of the semipassive system. System reliability is discussed, and energy savings for passive systems are examined. >