Direct Current (DC) Power

Overview of DC Power in Data Centers

An alternative approach to conventional alternating-current (AC) power uses a direct-current (DC) power distribution scheme throughout a data center. Most data center server racks are not currently powered this way, but with the advent of servers on the market that can operate with either AC or DC, it is possible to use the DC powering approach, thus eliminating extra power conversion steps and losses. Other benefits include reduced cooling needs, higher equipment densities, and reduced heat-related failures.  

The videos below, produced by Berkeley Lab, provide an in-depth overview of how direct current power can be deployed in your data center to achieve gains in energy efficiency.

DC Power for Data Centers of the Future

A stakeholder group was formed by industry and the California Energy Commission to investigate:

1. Whether or not DC powered server(s) and/or server racks can provide the same level of functionality and computing performance when compared to similarly configured and operating servers (and/or server racks) containing AC powered server(s), as measured with industry standard measurement devices and software tools.

2. Document any efficiency gains from the elimination of multiple conversion steps in the delivery of DC power.

3. Feasibility for both facility-level as well as rack-level DC conversion and delivery.

4. Identify issues/best practices and make recommendations for implementation.

Sun Microsystems hosted two pioneering demonstrations — one where direct current is distributed at the facility level to racks of computers that have been modified to directly accept high voltage direct current (DC) and another where the DC power conversion occurs at the rack level and DC is then directly distributed to servers within the rack. In typical data centers, the loss in electrical power through conversions of alternating current (AC) to DC to AC to DC occurs for all power flowing to the IT equipment. Efficiency gains have a magnifying effect by reducing need for HVAC (e.g. 10% saving at the UPS level mean about 10% energy savings for the entire data center, compared to a very efficient AC baseline case and assuming the HVAC system consumes as much power as the IT equipment). Learn more about these demonstrations here. This project was organized by Lawrence Berkeley National Laboratory (LBNL), Ecos Consulting, and EPRI Solutions, and was supported by 40 industry partners. The full list of project participants, as well as more detail on the role played in the project, is available here

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Resources on DC Powering in Data Centers

  • DC Power for Improved Data Center Efficiency: The objectives of this demonstration project are to develop and demonstrate a power delivery system that does not contain as many power conversion stages using existing equipment and vendors where possible. This project implemented a power delivery system that distributes DC to the server racks. The system used a single rectification stage, thereby removing the conventional UPS, transformer, and the rectifier in the server’s first stage power supply. A standard AC distribution system is installed next to this DC system, server loads were connected and programmed to run identical routines. 
  • Calculating Energy Savings Using High Efficiency DC Power Architecture in a Server Application (Tool): This Excel-based calculator provides a first-order estimate of the magnitude of the energy savings based on converting an AC-based powering architecture to a DC-based powering architecture for a rack of servers. Comments/Suggestions for improving this calculator are welcome. Servers and other IT products in a data center run on low-voltage DC. The existing AC-based powering architecture in a data center requires multiple AC-DC-AC conversion that results in an overall system efficiency of AC-DC lower than 50%. A DC-based powering architecture reduces the number of conversion process and results in a better overall system efficiency.

Direct Current Power for Data Centers of the Future
Walkthrough of a DC Data Center