Electronics Protection - September/October 2011 - (Page 8)

Feature Evaluating the Opportunity for DC Power in the Data Center Mark Murrill, Program Manager, Data Center DC Power Emerson Network Power With data center managers struggling to increase efficiency while maintaining or improving availability, every system in the data center is being evaluated in terms of its impact on these two critical requirements. The power system has proven to be one of the more difficult systems to optimize because efficiency and availability are often in conflict; the most efficient approach to critical power is rarely the most reliable. One solution to power system optimization that deserves serious consideration is DC power. Since utility AC power must ultimately be converted to DC for use by IT system components and because stored energy systems (batteries, flywheel, etc.) provide DC power for backup, a DC power architecture requires fewer total conversions from grid to chip and creates the opportunity to reduce costs and increase efficiency and reliability. A data center-optimized, row-based DC power protection system is now available to help data center operators take advantage of that opportunity. This system, combined with the availability of 48 VDC-powered IT equipment from major manufacturers, makes DC power a solution for small and midsize data centers seeking to optimize efficiency, reliability and scalability. Other applications include high-density equipment rows with a consistent footprint and pod-based data centers. introduces the potential for system downtime. Critical loads are no longer isolated from the mains or subject to the tight voltage regulation normally provided by the inverter, and complex synchronization circuits are needed to ensure reliable power transfer. Figure 1. In Eco-Mode, incoming power bypasses the inverter to increase UPS system efficiency. While the trade-offs with operating in eco-mode or with a transformer-free UPS may be acceptable for some applications, many users still require more robust operating environments combined with reduced total cost. This is where DC power offers several advantages. A Practical Approach to DC in the Data Center The second decade of the twenty-first century is one of incredible growth and change for data centers. Demand for computing and storage capacity has exploded, and many IT organizations struggle to deploy servers fast enough to meet the needs of their businesses. At the same time, the trend to consolidate data centers and centralize computing resources has resulted in fewer opportunities for planned downtime while increasing the cost of unplanned outages. The dramatic increase in data center energy consumption created both financial and environmental challenges. Energy costs, which once had been relatively inconsequential to overall IT management, became more significant as the rise in consumption was exacerbated by a steady increase in the cost of electricity. In addition, increased awareness of the role that power generation plays in atmospheric carbon dioxide levels prompted the US EPA to investigate large energy consumers such as data centers. The industry responded with a new focus on energy efficiency and began implementing server virtualization, higher efficiency server power supplies, and new approaches to cooling. Significant progress has been made in some areas, but the critical power system has yet to be fully optimized. While individual components have been improved, the overall system complexity is high, which can create inefficiency and add operational risk. Faced with the choice of increasing system efficiency or adding risk, many continue to choose more time-tested, established, traditional approaches that deliver high availability, but not the highest efficiency. A close examination of available options reveals that efficiency and total cost can be improved without sacrificing overall availability with DC power. In the last few years, AC UPS manufacturers have increased component efficiencies on traditional double conversion systems, and developed new products that focus on reducing energy consumption. In eco-mode (Figure 1) for example, efficiency is improved by bypassing power around the inverter; however, this 8 Background 48V DC power has a long history in telecommunication networks. It is inherently simple and reliable with few conversion stages to the point of use. In Alexander Graham Bell’s day, -48V DC was chosen as the standard for two reasons: number 1, DC power was felt to be more reliable than AC because it could be directly connected to backup batteries during grid outages. Number 2, 48 V was considered the optimal tradeoff between transmission distance and human safety because it is considered safe to touch during maintenance or accidental exposure. Today, telephone central offices (exchanges) are still powered by -48 VDC. These facilities exhibit levels of availability as high as 9-nines, as confirmed in a study of 23,000 DC power systems over 10 years by NTT Facilities. (Figure 2) Figure 2. In larger telecommunications installations, the 48 V DC power system is deployed as three distinct elements: 1. 480 V/208 VAC to -48 VDC modular power system 2. Battery banks for extended run time (at least 8 hours) 3. Load distribution cabinets (BDFB) September/October 2011 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - September/October 2011

Electronics Protection - September/October 2011
Contents
Crenlo Adds Rolling Transit Case to Lineup of Emcor Enclosures
Emerson Network Power Introduces Knurr DCM Enclosures for Nexus 7000 Series Switches
Evaluating the Opportunity for DC Power in the Data Center
An Update on Arc Flash: Revised Regulations and Best Practices Help Keep Workers Safe
Re-Designed Panelboards Proivde Savings for Hazardous Applications
MetCase Launches Retex Flat-Packed 19 Inch Wall Rack System
New SlimShield Two-Piece Board Level Shielding Offers Shield Heights Down to 0.060 inches
FrigoDynamics Launches Series of Two-Phase Heat Exchanger Coolers
Rogers Corp. Launches New Solutions for Thermal Management
SurgeX Space Savers Offer Maximum Protection with Minimum Footprint
Amphenol’s Expanded Neptune Connector Line Provide Better Environmental Protection
Industry News
Calendar of Events

Electronics Protection - September/October 2011