Should You Implement an Air-Side Economizer for Your Data Center?

Jan. 15, 2018

In the right conditions, you can save on data center cooling.

The need for efficient data center cooling is growing quickly, as its global market is expected to reach $20 billion by 2024, according to a study from Market Study Report. Facilities managers need every advantage to reduce energy spend from data centers, and for many facilities, using air-side economizers is the best choice to reduce costs for cooling.

Air-side economizers cool data centers by bringing outside air into a building and distributing it to servers. They are integrated into a central air handling system with ducts for intake and exhaust, and its filters reduce contaminants from entering the data center. When properly integrated, they can reach up to 30% energy savings on cooling, although in many cases they don’t reach this potential due to poor design and implementation, as an American Council for an Energy-Efficient Economy describes. These systems require proper planning because of some of their inherent limitations.

One significant problem with air-side economizers is that they do not always lend themselves to retrofits. Because many data centers are located in the interiors of lower levels and basements in buildings, an air-side economizer might not be the most cost-effective solution because the data center is hard to reach. If you can get it to effectively reach your data center without too much expense and difficulty, they can be especially effective.

Climate Concerns with Air-Side Economizers

But because the air is brought in and out of the building without recirculation, the outside air needs to be under the right conditions. In cooler climates, they work exceptionally well. According to Lawrence Berkeley National Laboratory, if the outside air is cool enough, only the fans need to be run and the mechanical cooling equipment can be shut down, contributing to energy savings. Even when it isn’t cooler outside, air-side economizers can operate.

“If the outside air temperature is higher than the required supply air temperature but lower than the temperature of the air returning to the cooling equipment, it can still provide partial cooling and reduce the load on the cooling equipment,” says Berkeley Lab. “The effectiveness of this scheme depends on the local climate and the ability to move a relatively large volume of air simultaneously into and out of the building.”

One simple way to reduce the heat of the air used and get the most out an air-side economizer is to make sure outside air intakes are located on the north side of a building because there is significantly less solar heat gain compared to the south side, explains the Department of Energy.

Even if your facilities are in a warmer climate, you still have options for savings with an air-side economizer, says ENERGY STAR: “Because data centers must be cooled 24/7, 365 days per year, air-side economizers may even make sense in hot climates, where they can take advantage of cooler evening or winter air temperatures.”

The wrong combination of heat and humidity can decrease the savings potential of an air-side economizer. For example, cool air that is very dry might require you to spend a considerable amount on humidifying the air, which cuts into the savings your economizer would otherwise provide. ASHRAE provides recommendations for where air-side economizers work best. Be sure to consult with engineers about how one might work in your climate.

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