infoTECH Feature

November 11, 2014

How the Evolution of Power Has Become More Efficient

With the recent passing of the Energy Efficiency Improvement Act of 2014 (H.R. 2126) in March, new opportunities for data center efficiency have emerged.  In alignment with this, legislation also introduced the TENANT STAR (News - Alert) (News - Alert) certification to ensure best practices for energy efficiency in commercial buildings and federally operated data centers, which has had a tremendous waterfall effect across the entire data center ecosystem — reducing energy loss and improving reliability.

Traditionally, data center power distribution models involve multiple (and inefficient) voltage power conversions between the electric utility and the server.  Distribution transformers, uninterruptible power supply (UPS) systems and power distribution units (PDU) all introduce AC (alternating current) to DC (direct current) conversions and voltage transformations in the power chain, oftentimes resulting in wasted energy.  The typical distribution model can include a:

  1. Conversion from 480VAC to 480VDC within the UPS system;
  2. Conversion from 480VDC back to 480VAC within the UPS system;
  3. Transformation from 480VAC to 208VAC at the PDU; and
  4. Conversion from 208VAC to DC voltages within the server power supply

In order to eliminate many of these unnecessary power conversions, energy can be distributed at a DC voltage directly to the server power supply as opposed to converting the DC power in the UPS back to AC power and then converting back again to DC at the server.  Depending upon the age and technology of power equipment, conversion to a DC power distribution model can result in efficiency gains of 10 to 20 percent thanks to a reduction in the number of power conversions. 

Although DC power distribution in the data center industry is nothing new, modern technological developments have made this system more attainable and efficient than previously.  In fact, many telecommunications companies have taken advantage of the efficiency and reliability of DC power systems for decades.  Benefits of DC power distribution over AC power distribution include:

  1. Fewer power conversions between AC and DC voltages results in a smaller parts count, which improves reliability and reduces maintenance costs;
  2. Fewer power conversions increases system efficiency and reduces energy costs;
  3. Less equipment may reduce capital investment costs of a comparable, new AC distribution system;
  4. Less equipment also reduces the footprint required on site; and
  5. Harmonic (News - Alert) distortion and phase balancing are not a concern with DC power distribution, which eliminates the need for power filtering and minimizes stranded capacity.

Thanks to recent innovations and advancements, DC power systems are now more readily available, prompted by the successful deployment of DC distribution in Asia and Europe and due to groups like EMerge Alliance which have developed standards for the commercial adoption of DC power.  Noting the potential of this shift in data center power distribution, several manufacturers are now producing DC circuit protection and power supply cord connectors which address concerns with user safety related to DC voltage and arc protection.




Edited by Stefania Viscusi
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