Project GreenLight Powers Up Direct Current Servers

Project GreenLight added direct current-powered (DC) servers as one of its instrumented server facility capabilities. This enables real-world experiments to gauge whether large computing facilities can operate on less power if they take alternating current (AC) out of the equation.

The experiment at the University of California, San Diego (UCSD), is part of Project GreenLight's modular data center, which measures the energy efficiency of information and communication technologies. Data from the project will help researchers build greener information technology systems and software.

At UCSD, engineers switched a set of servers in a campus data center to operate continuously on 380-volt DC. The switch to DC power holds great potential on a campus where supercomputers and other high-technology facilities represent a disproportionately large share of energy consumption. 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.

At traditional server facilities, AC power is converted to DC power in the uninterruptible power supply system to charge batteries and condition the power. From there it gets converted back to AC to drive the power supplies of computing equipment to run central processing units, 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. Each conversion loses power and generates additional heat, both of which reduce the overall power and cooling efficiency of the server facility. Directly providing DC to the server facility bypasses many conversion steps and generates less heat, leading to overall higher efficiency.

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