Energy efficient free cooled telecommunications shelter

A limitation with traditional air conditioning controls is that they operate HVAC equipment to a fixed temperature and are intended for human comfort. In order to reduce HVAC energy consumption in a telecom shelter, controls can be set to a higher temperature, but fixed operation may not be ideal for the longevity of battery systems or equipment. A fixed, year round set point will not take advantage of cool outdoor conditions when they are available. With energy costs trending upwards, together with ongoing maintenance costs for air conditioners, there is strong incentive to eliminate mechanical cooling altogether. The Canadian moderate temperate climate is ideally suited for free cooling of telecommunications shelters. Field trials show that intelligently devised controls can mediate summer days when outdoor temperatures might reach 35C, while utilizing cooler overnight temperatures to average-down interior temperatures. Cooler seasons will allow a variable speed fan to operate at lower speeds, noise levels and energy consumption rates. Effective and energy efficient free cooling strategies require a systemic approach to shelter design. Careful selection of electronic equipment that can operate reliably in a -5C to +45C environment is key. Heat producing equipment is located in the hot zone closest to the exhaust. As the interior temperature rises, so does the air flow to minimize the delta temperature between indoor and outdoor air. For year round efficiency, heater operation in winter is set to 12C, which achieves a balance with the battery capacity derating. Instead of traditional fluorescent lighting, LED fixtures are utilized as their output is insensitive to temperature fluctuation. Everything associated with the shelter (except the baseboard heater) operates from the -48 VDC power plant. Referenced to utility electrical input, the free cooled telecom shelters can operate at 90% efficiency.