By setting the room's return air temperature to 75 degrees, Iron Mountain cut energy consumption for cooling by between 10% and 15% compared with the company's traditional data centers. They operate between 70 and 72 degrees. The natural cooling also allowed Iron Mountain to boost power in the room to 200 watts per square foot, more than 50% above the 125 watts per square foot used in the other data centers located in the mine. Room 48 also cost about 30% less to build than they did because the design favored efficiency and cost reduction over specialty equipment.
For example, instead of buying expensive electrical equipment designed specifically for data centers, Iron Mountain went to the same electrical supply stores any electrician would frequent to purchase K-rated transformers or electrical load centers. "Anything you buy for a computer room is expensive," Doughty said.
Iron Mountain also installed low-energy T8 fluorescent lamps enclosed in tubes to reduce convection, although most of the time the room is dark because lights are controlled by motion sensors in each aisle.
While the mine's water isn't yet being used to directly cool server racks, Doughty said that will be incorporated into future design changes. He's convinced that all data centers will shift toward water-cooled racks. And he expects that geographical positioning using locations where natural cooling or energy resources can be exploited for efficiency will be the future of new data center construction.
Riding the geothermal wave
Iron Mountain is just one of several such experimental efforts under way using geothermal conditions to power or improve the cooling efficiency of data centers. In February 2008, American College Testing (ACT) in Iowa City, Iowa was the first data center in the U.S. to be awarded the Platinum certification in the Leadership in Energy and Environmental Design (LEED) program, a voluntary rating system for energy efficient buildings overseen by the U.S. Green Building Council.
The ACT operation has a 4,000-square-foot raised-floor data center cooled by a geothermal "bore field." The bore field consists of holes drilled into the earth and a closed-loop piping system filled with water or coolant that uses the cool underground conditions to exchange heat.
ACT isn't alone; other companies approved for Platinum status include Citigroup data center in Germany and Advanced Data Centers in Sacramento.
Google is hot on the technology as well and has invested more than $10 million in three companies developing geothermal energy systems. The technology, called Enhanced Geothermal Systems, replicates naturally occurring pockets of subterranean steam and hot water by fracturing hot rock and using the resulting steam to produce electricity.
And in July, Microsoft opened a 700,000-square-foot data center in Northlake, Ill., that uses outside air as part of the cooling system.
Interest in geothermal technology isn't surprising, said Doughty. "Energy costs are increasing exponentially so that the cost to operate the data center is becoming the greatest cost. People who can leverage the geographic location or a subterranean location will achieve the greatest benefit."