DC Powered Infrastructure Efficiencies

Research Overview

Research Lead:  Greg Hidley, GreenLight Project Manager, Calit2 

It is estimated that companies could save billions of dollars each year in capital costs and ongoing energy savings by using all-DC distribution in their data centers.

In a traditional server facility AC power is provided at a high voltage and converted to DC in the UPS system to charge batteries and condition the power. From there it is converted back to AC to drive the power supplies of computing equipment to run CPU, memory, disks, and communications components. Skipping or consolidating the above conversion steps can save considerable electricity usage overall in the power distribution chain and in cooling.

In 2006, a temporary installation, utilizing best-in-class equipment, was slightly modified to prove that further research was merited. In cooperation with Berkeley Lab and others, Direct Power Technologies, Inc. provided both equipment and design assistance. GreenLight has now installed first-generation 380 VDC equipment specifically manufactured to enable this technology to evolve to the next level of commercial availability.

The researchers hope to prove that switching to an all-DC power distribution should increase the 'computing work per watt' - a key barometer of energy efficiency in computing environments. In addition to significant energy savings, other potential benefits include improved power quality, reduced cooling needs, higher equipment densities, reduced heat-related failures, improved reliability (from fewer components) and ease of use of renewable sources of DC power. The DC power researchers also point out that the industry has the opportunity to make this a worldwide standard through the ongoing collaborative efforts.

Two of the seven racks of servers in GreenLight's Sun Modular Datacenter have now switched from standard AC-DC to DC-DC power. Five Oracle Sun Fire X4270 servers and five Intel 2600s have been outfitted with Delta Electronics, Inc. custom DC-DC power supplies. The Delta power supplies and an Emerson 20-kilowatt DC power rectification system were tested extensively by the independent, non-profit and Palo Alto, Calif.-based Electric Power Research Institute (EPRI). The rectification system is located in the rack enclosure as part of the DC-DC design concept, offering 400 volts of DC power (VDC), while the Delta power supplies run on 380 VDC.

This is one of the first installations in the United States to utilize system components specifically manufactured for this (380v) DC power system topology. Direct Power Technologies worked with Emerson Network Power to provide the rectifier system; Spectrum Power Management Systems for 380v DC rated plug strips; and Anderson Power Products to provide connectors and cords specifically manufactured for the UCSD project's system topology.

The server functionality in this dual AC and DC power supply model is independent of ultimate power source, whether it be AC, DC, fossil fuel or renewable energy. Each system is capable of operating in both AC-DC and DC-DC power modes via separate power feeds. By switching two breakers, operators can change the mode of operation from AC to DC.

Distributed energy resources that utilize renewable energy and produce DC power are rapidly growing nationwide. UC San Diego itself has an ambitious program for the deployment for an additional 2 MW of photovoltaic panels, multi-megawatt electricity energy storage systems, and a 2.8 MW fuel cell that utilizes currently flared methane gas from the local wastewater treatment plant.

The DC-DC experiment will provide a fully instrumented environment to measure the achievable efficiencies when using DC power at the server, rack and data center levels - and to compare those efficiencies to the energy profile of GreenLight's existing AC-DC instrument racks. According to Berkeley Lab's Tschudi, the overall system efficiency of AC systems in data centers is lower, whereas a DC-based powering architecture results in better system efficiency by reducing the number of AC-DC conversions. In the future, further efficiency gains are possible by directly powering variable speed fans, pumps and chillers with DC along with lighting systems. These devices operate on DC today, so the transition to DC would be relatively straightforward.

Many industrial partners cooperated to support this experiment, which is one of the first in the United States using components specifically manufactured for this 380VDC power topology.

Technical White Papers

DC Power 2011
DC Power 2010