Thermal management of battery compartments of outdoor telecommunication cabinets using phase change materials (PCM)

Telephone operating companies have a long history of powering switching systems with batteries. Instead of large central offices, current trends are towards remote switches, closer to the customer. This poses new problems, since manpower is now required at multiple locations. The outside environment heavily influences the temperature within the remote terminals. The environmental conditions can be described by a -40°C to +65°C temperature range and solar loading. The life of a battery is directly related to the load applied, proper recharging and most of all, the ambient temperature of the battery which must be kept at optimum conditions. Batteries for back up service normally are stored in compartments attached to or inside outdoor cabinets. These compartments are exposed to solar loads, and must be kept at optimum temperatures, 77°F (25°C) as prescribed by the manufacturers. Furthermore, these compartments must allow for the proper venting of fumes that may be given off by the batteries in the course of their operating life. The use of phase change materials (PCMs) can lead to more stable operating environments for the batteries. The PCM allows peak or cyclic heat loads to be absorbed, and then rejected at a later time when ambient conditions allow their rejection. The issues associated with the use of PCMs for battery compartments are discussed in this paper