The rapid growth of integrated networks and systems has led to an increasing demand for dependable and continuous power. To support a reliable supply of electrical energy to power these networks and systems in the event of an outage on the electric grid, the uninterruptible power supply (UPS) system serves as a source of nearly instantaneous backup power. Strings of batteries typically power these UPS systems, providing energy that is available to support critical operations when an outage occurs.
As integrated networks and systems quickly evolve, new challenges arise that demand innovative solutions to meet the changing needs of UPS systems. These challenges include occupying valuable indoor space, exposing backup batteries to the UPS system’s radiant heat and consumption of additional energy to power air conditioning at a low enough temperature to maintain an optimal environment for backup batteries. A viable response to these challenges is to take your battery backup system outside using the proper batteries along with a thermally managed outdoor enclosure.
EQUIPPING THE BATTERY BACKUP SYSTEM FOR OUTDOOR PLACEMENT
When selecting a battery, the Institute of Electrical and Electronics Engineers (IEEE) recommends sizing it at its lowest expected temperature, which is typically 68°F (20°C) for outdoor applications and 77°F (25°C) for indoor applications. An ideal ambient temperature can be difficult to maintain if the battery backup system is not equipped with thermal management technology, especially for cooling. In the UPS system, it is easier to direct cooling air to the electronic components than it is to the batteries, which often get little or no cooling, even though electronic components typically tolerate a much wider range of temperatures than batteries.
When this equipment is located indoors, the task of maintaining temperatures that are ideal for the UPS and other backup power equipment is complicated. Many UPS systems lack adequate cooling for the backup batteries, especially in the case of modular and containerized UPS systems. This often places additional energy demands on the facility’s air conditioning system, as the indoor environment must be kept cool enough to safeguard backup batteries. The placement of UPS battery systems indoors also takes up valuable facility space, which can be used for other, more revenue-producing equipment and additional workspace for personnel. This is especially critical in operations with a high value on floor space, such as hospitals.
If you’re looking to maximize the value of your indoor floor space, an alternative solution for your battery backup system is to “take it outside;” i.e., to move the system outdoors in an enclosure designed for outdoor use. Thermal management technology, which includes air conditioning and heating, provides an environment for top performance and longevity of UPS batteries that are housed in outdoor enclosures.
Most air conditioning units deployed in support of outdoor enclosures are closed-loop systems based on a vapor compression cycle: The refrigerant changes from liquid to gas (evaporation), which absorbs heat from within the enclosure and transfers it to the outside air. This cools and removes humidity from the enclosure. Air conditioning is energy efficient, as there is a small amount of energy loss during the cycle, and it can manage a large heat load, making it reliable in even very high-temperature climates. Managing a large heat load makes air conditioning among the highest performing thermal-management technologies, as it is able to cool an enclosure’s interior far below high ambient air temperatures. Thermal management technology will also heat the interior far above low ambient air temperatures.
THE THERMALLY MANAGED OUTDOOR ENCLOSURE
The use of thermally managed outdoor enclosures for backup batteries in UPS systems helps maintain optimal operating temperatures, leading to the following benefits:
Additional indoor space: Moving the housing of backup batteries for UPS systems outdoors will make additional space inside of the facility available for other equipment and personnel. Even though the battery backup system is outdoors, it is still protected from the elements and extreme temperatures.
Placement adjacent to UPS system: The battery backup power system can be installed in a position that is adjacent to modular, containerized UPS systems, which normally lack adequate cooling to protect the batteries from premature failure.
Air conditioning set at higher temperatures: If a thermally managed outdoor enclosure is installed inside of the facility, it is no longer necessary to set the air conditioning at a lower temperature for that room, provided all other equipment in the room will tolerate higher temperatures, which is typical of most installations. By using the enclosure’s air conditioner to maintain a temperature specified for the backup batteries, the facility’s air conditioning does not need to be set at an artificially low temperature, which reduces cost and consumption of energy.
Thermally managed enclosures help enable batteries to operate for their entire service life, reduce maintenance, and require less frequent replacement by protecting the batteries from extreme temperature, inclement weather, and other outdoor conditions, with minimal power consumption and reduced cooling costs.
Additionally, the outdoor enclosure should include passive ventilation that mitigates hydrogen gas and be constructed to protect backup batteries from earthquakes in compliance with such seismic certifications as IBC (2015), ASCE 7-10, CBC (2016) and California OSHPD health care infrastructure requirements. It also should be certified for safety in compliance with UL® 1778. A range of voltages and breaker ratings to accommodate a wide variety of battery backup system requirements should also be available.
Other important features of an outdoor enclosure include thick insulation, which reduces the impact of solar loading and power consumption, and built-in security features, as well as optional center tap cabling, circuit breaker reporting, and actuator options.
THIN PLATE PURE LEAD (TPPL) BATTERIES FOR UPS APPLICATIONS
While a thermally managed outdoor enclosure is a critical component to the overall power and energy management system, the batteries also play a vital role. Needs have changed from the 15-minute rate discharges required of UPS systems to support mainframe computers of the past to rate discharges of five minutes or less that modern, globally interconnected networks now demand. Trends such as cloud storage, the availability of data/communications equipment and bandwidth to retail customers for rent, and modular and containerized power, as well as shorter run times and higher ambient temperatures, have placed new demands on UPS batteries.
In response to these demands, TPPL batteries are providing greater conductivity and lower resistance by greatly reducing both grid corrosion and grid growth common in conventional alloyed lead acid batteries, which may experience calcification. An advantage of the high-purity materials used in these batteries reduces gas generation within the cell, which extends the operating temperature range and reduces cooling costs. The lack of impurities also improves the battery’s service life, and extends shelf life by as much as three times that of conventional batteries.
The use of pure lead in TPPL batteries enables plates to be made as thin as 1 millimeter (as opposed to a thickness of 2 to 4 millimeters for conventional alloyed lead acid batteries). Pure lead plates are denser and require less space between them. This results in increased surface area, better active material utilization, and greater power density. With this energy-dense design, smaller, lighter batteries are able to achieve the same run times as larger conventional lead acid batteries with reduced recharge rates.
The enhanced density of TPPL batteries provides discharge rates from 30 seconds to five minutes, and a wider operating temperature range that requires less cooling of the UPS system’s environment. TPPL technology also enables the battery to have a higher cyclic capability, as much as 25% longer service life (seven years or longer) and a longer shelf life (17 months) than lead calcium batteries at 77°F (25°C).
BATTERY BACKUP SYSTEMS FOR UPS APPLICATIONS
A battery backup system comprised of batteries designed for UPS applications housed in a thermally managed enclosure enables the power and energy management system to be placed outdoors, placed adjacent to modular and containerized UPS systems, or even placed indoors with room air conditioning set at temperatures as much as 10°F (approximately 5.5°C) higher.