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What Can UPS Do For You?

By August 30, 2016December 26th, 2021Briefs
What Can UPS Do For You?, Michaels Energy

Package Delivery

You’re probably familiar with UPS. You know, the brown trucks that drive around delivering packages. They keep businesses operating, and are often vital to business success. They are generally reliable, but a small percentage of the packages sent through them are lost en route (some estimate that 0.05% of packages are lost[1]). It can be a complex process to take a package from Ft. Myers, Florida, put it on a truck bound for Orlando, take it from the truck and get it on a plane to Seattle, take it off the plane and put it back on a truck, which takes it to, say, Olympia. That process offers many opportunities for packages to be lost.

The Real UPS

This isn’t really about that UPS, but rather the data center power reliability equipment known as Uninterruptible Power Supplies (or UPS). That whole package delivery analogy was an attempt to relate the two very different UPSs. Here, the “packages” are electricity flowing through a UPS. The “packages” go through a complex process on their way through the UPS, and this process results in a loss of some of the “packages”, i.e. energy is lost as heat.

Each UPS takes electricity from the grid, converts it from alternating current (AC) to direct current (DC), uses that DC electricity to maintain charge on a battery bank, and then converts it back to AC. This process results in electricity that is free from large spikes or disruptions. The batteries ensure that the electricity supply will be “uninterrupted” for a period of time if there is a brief loss of power. These are beneficial traits for data center equipment, like servers, which need high quality power.

How to Make UPS More Efficient

Since UPSs operate 24/7, and there are energy losses associated with the AC to-DC to-AC power conversions, they waste considerable energy. Also, their conversion efficiency gets worse as the load on the UPS decreases. Most UPSs are operated in the 20-40% of capacity range (EATON Corporation Product Brochure), so they are near minimum efficiency. There are some fixed losses, regardless of load, but the load-dependent energy losses are most substantial.

If a UPS is more than five years old, it likely has poor efficiency (87%, see graph[2]) at its most common operating loads. There are two primary solutions to this problem. One could simply operate the UPS at higher loading levels while keeping another UPS on standby for redundancy. Or, one could purchase a new, high-efficiency UPS that has a much flatter efficiency versus loading curve and peak efficiencies approaching 99%. Some new models have features that bypass the DC battery circuit completely when charging isn’t necessary, if the power quality coming in is satisfactory. This provides near 100% efficiency when in this bypass mode and high efficiencies at low loads.

Packaging It All Up

By making sure UPSs are highly loaded, or that the UPSs in use have efficiencies at low (30%) loads that are more than 90-95%, it can operate at maximum efficiency. Oh, and as a bonus, cooling savings from reduced heat generated by the UPS! It’s a two-for-one deal!

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