Facebook is revealing data about how the world's largest social network has achieved strong levels of water efficiency usage for cooling in the first building at its Prineville, Ore. data center.

Water efficiency usage (WUE) measures water used for cooling data centers only -- not any plumbing and or office usage elsewhere on site.

Specifically, as of the second quarter of 2012, the Prineville data center achieved a WUE of 0.22 L/kWh.

To put that into a better perspective, Daniel Lee from the Open Compute Project described in a blog post that figure is "a great result, but it should be noted that the WUE concept is fairly new." However, a specific goal for Q2 wasn't mentioned in the post.

More specific details about the nitty-gritty specifics behind the water cooling systems (including more details about the diagram below) are available on the Open Compute Project blog.

But as an overview, Facebook has implemented a mechanical system comprised of a built-up penthouse that utilizes 100 percent of outside air economization with a direct evaporation cooling and humidification misting system.

Lee asserted that most data center cooling systems don't actually employ outside air economization, instead recirculating up to 100 percent of the air used to cool the server room with a central chilled water plant and cooling towers. He added that consumes more energy and water.

By comparison, Facebook's mechanical systems don't have any chillers or cooling towers, relying primarily on air economization and the aforementioned misting system.

"It’s like using a window-mounted air conditioner to cool a room instead of putting a fan in a window when the outside temperatures are cooler than the temperature in the room," Lee described.

This marks the first time that Facebook has publicized its water usage efficiency measurement. Last week, Facebook also shared information about its carbon footprint, outlining a goal to earn at least 25 percent of its data center energy from clean and renewable sources by 2015.

Facebook is sharing this information as part of its commitment to the Open Compute Project. The Menlo Park, Calif.-based social media company is planning to continue to release water efficiency metrics on a quarterly basis.

That reporting process will get larger soon, starting with the second building at the Prineville data center when WUE metrics for that site are available next year along with the Forest City, N.C. facility as well.

Image via Open Compute Project

This post was originally published on SmartPlanet's The Bulletin blog.