By Jim Stark, P.E. Principal of Engineering, Electronic Environments Corporation

With promises of increased energy efficiency and reliability, the idea of using DC power in the data center is not a new one. But, advancements today in the distribution system make it more viable than ever.

Traditional data center power distribution includes several 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 which lead to wasted energy. A typical power distribution system can include:

• Conversion from 480VAC to 480VDC within the UPS system
  

• Conversion from 480VDC back to 480VAC within the UPS system

• Transformation from 480VAC to 208VAC at the PDU

• Conversion from 208VAC to DC voltages within the server power supply

Distributing power at DC voltages eliminates unnecessary power conversions. DC voltage can be distributed directly to the server power supplies, rather than converting the DC power in the UPS back to AC power and then converting back again to DC at the server. The reduction of power conversions can result in efficiency gains of 10 to 20% depending on the age and technology of the power equipment. DC power distribution is not a new concept in the data center industry, but recent developments have made it more feasible and practical than in the past. Telecommunications companies have appreciated the efficiency and reliability of DC power systems for decades. Some of the benefits of DC power distribution over AC power distribution include:

• Fewer power conversions between AC and DC voltages increases system efficiency and reduces energy costs

• Fewer power conversions results in a smaller parts count which leads to improved reliability and can reduce maintenance costs

• Harmonic distortion and phase balancing are not a concern with DC power distribution which eliminates the need for power filtering and minimizes stranded capacity

• Less equipment may reduce capital investment costs of a comparable, new AC distribution system

• Less equipment also reduces the footprint required on site

Telecommunication companies have traditionally standardized on low voltage DC systems (48VDC); however, the higher power consumption requirements of data centers fits better with 380VDC systems. The higher power densities of data center servers would result in extremely high current draw at 48VDC and would require much larger conductor sizes. The use of 380VDC eliminates this need. The 380VDC standard also fits well within the typical server power supply limits. An additional benefit of 380VDC is the ability to integrate with renewable energy sources such as photovoltaic (solar) arrays and fuel cells, since they operate in the same voltage range.

Recent advancements have overcome two issues that have delayed the acceptance of 380VDC systems in the past: (1) the availability of DC power systems and server power supplies, and (2) safety concerns related to high voltage at the rack and server level. DC power systems are now more readily available, driven by the successful implementation of DC distribution in Asia and Europe, and due to groups like EMerge Alliance creating standards for the commercial adoption of DC power. 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.

Exciting changes and new efficiencies are beginning to take shape across the data center landscape as 380VDC and other sustainable practices become integrated into data centers. Join us on December 9th at DatacenterDynamics Converged in Dallas, Texas, to explore this topic further when we present, “Is it Finally Time for 380VDC Power in the Data Center?” in the Power & Cooling Track at 12:20 pm. For more information, please visit the DCD Dallas web site program.

To meet with Mr. Stark during the event, please email info@eecnet.com and to learn more about EEC, visit www.eecnet.com.