Cooling system of outdoor cabinet using underground heat pipe

Abstract

Currently the energy-saving strategy is one of the top priorities of Telecom Operators and Governments. In particular, the area of cooling has a heavy impact on the total electrical energy consumption, and needs to be optimized in order to increase overall performances, reducing both CAPEX/OPEX and the environmental impact. The present paper describes a new cooling solution for FTTC outdoor cabinets (where a significantly high amount of heat needs to be dissipated). This solution is based on geothermal cooling technique, that takes advantage of the ground heat (in this case ldquocoldrdquo) source, which is always available and has an enormous potential. The geothermal cooling unit has been used in conjunction with forced air circulation within a sealed cabinet. The cabinet prototype is designed with an independent and integrated ventilation system which ensures that the thermal load generated within the cabinet itself is dissipated into soil and atmosphere. The aluminum-ammonia heat pipe technology is applied to this geotherm cooling unit. Experimental tests were carried out in real outfield. The cabinet was submitted to solar radiation and real ambient conditions. To carry out the analysis, a data acquisition system was set in the testing environment during a period of more than 3 months, over 40 measurement points were set to monitor temperatures, operating parameters and working loads. The experimental results show that, for a prototype cabinet with 700 W heat load, this innovative solution cool the cabinet with COP value at about 110 for normal ambient condition of 30degC, which is comparatively higher than traditional air heat-exchanger solution (normally at 10-15). Moreover, the acoustic noise level is seriously reduced. The air flows through an independent underground ventilation system, and the air's temperature within the sealed cabinet can be reduced of about 5degC. The test data show that more than half of total consumption is dissipated into underground soil. Then, on a long-run perspective, the feasibility and the effectiveness of the described solution allow deep reduction of operational costs, with positive environmental impacts.