Saving Energy on the Other Side of the Rack: UPS and Transformer Efficiency

Written by Joe Kozlowicz on Wednesday, July 2nd 2014 — Categories: Colocation, Disaster Recovery, Green Data Center

A lot of the focus in the data center energy efficiency world is placed on cooling, and rightly so: cooling servers can consume as much as 37% of a well-designed data center, according to Emerson. But there are opportunities to improve efficiency on the other side of the rack, too. The power delivery systems, including Uninterruptible Power Supplies (UPS) and transformers, can deliver significant energy (and cost) savings.

UPS and Transformer EfficiencyThe UPS maintains electrical power loads during outages and conditions incoming power under regular circumstances to smooth out surges and other irregularities that could damage equipment or lead to downtime.

Most UPS systems lose energy in the inverter and transformers. Newer systems have power management systems that control switching between the inverter and transformers to increase efficiency. Energy Star rated UPS systems could increase efficiency by 30-55%. Both UPS systems and Power Distribution Units (PDUs) can benefit from newer models with efficient transformers, cutting an additional 2-3% of energy loss.

When choosing efficient UPS systems, it’s important to consider redundancy as well as the average power load. In an average data center, that’s maybe 60%. Power ratings are often measured at 100% while redundant N+1 systems will share the load to each sit at around 30-50%.

In the new Green House Data facility, efficiency gains are also found in the exterior transformers. Two transformers switch 13,200 down to 480 volts, moderating the 5MW of power on opening day.

In an electric transformer, losses basically come down to friction. No load losses are produced from the magnetic field in the core, with the biggest contributor being hysteresis losses. Hysteresis losses are magnetized and demagnetized laminations of the magnetic core (hysteresis translates as “to lag” as this flux lags behind the magnetic force). Load losses result from the heat generated from friction as electrons move along the conductor.

The Green-R-Pad distribution transformers we chose boast up to 70% reduced no-load losses. A single 1,000 kVa unit saves seven tons of C02 emissions annually.

Upgrading power systems might take some upfront investment, but the energy savings can be worth it down the road: the Department of Energy pegs annual savings of $90,000 from just a 5% increase in UPS efficiency for a 15,000 square foot data center.

Posted By: Joe Kozlowicz

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