Energy costs eat up 25 percent to 60 percent of a data center’s operating expenses. For large facilities, that can add up to hundreds of thousands or even millions of dollars per year. Many data center operators have focused on the optimization of cooling to reduce energy consumption. While cooling systems certainly account for a large portion of the electric bill, uninterruptible power supplies (UPSs) also contribute to energy costs.

Traditionally, large data centers have used standalone “tower” UPSs with the capacity to support substantial loads. These units are typically overprovisioned to provide “N+1” redundancy and support data center growth. After all, UPS failure is the No. 1 cause of data center downtime.

In this model, a data center might implement three 500kVA UPSs to supply 1000kVA of power. That way, if one of the units fails or has to be taken out of service for maintenance, the remaining two units could provide the total capacity required. The problem is that each unit is operating at far below capacity. UPSs are most efficient when running at 80 percent capacity or more.

Large UPS systems also generate a lot of heat — as a rule of thumb, heat output is about 10 percent of UPS capacity. Many UPSs have an “ECO” or offline mode to increase efficiency, but it increases downtime risks.

That’s why it often makes sense to replace or supplement these monolithic UPS systems with smaller, modular units that are linked together. This allows you to more closely match capacity to load requirements and to scale up as needed by adding modules.

In this model, you might implement 21 50kVA units to supply 1000kVA of power with N+1 redundancy. Each unit will be operating nearer to its maximum capacity and thus more efficiently. Further, these units typically don’t have transformers, which boosts efficiency without the risk of operating in ECO mode.

Modular UPSs are smaller and generate less heat than standalone units. They are also hot-swappable, which means you can replace a failed unit without taking the entire system offline. “Smart” modular UPSs collect and analyze data to improve performance, and can be integrated with data center infrastructure management (DCIM) systems.

Now, there are some design considerations to keep in mind. Because modular UPSs are rackmount or cabinet-size units, they take up in-row space. In addition, you have to carefully position the units to ensure that capacity is located where it’s needed without over-provisioning. However, the potential energy efficiencies to be gained may far exceed these minor trade-offs.

Depending on the age of your data center, it may be a good time to evaluate modular UPSs. UPS systems have a lifespan of seven to 10 years, and many data centers have units that will need to be replaced in the short term.

As data center densities continue to increase to support growing volumes of data and connected devices, operators need to find new ways to improve energy efficiency while ensuring availability. Rahi’s data center experts can help you determine if modular UPS systems are right for your operations and calculate the potential energy savings.

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