Updating your Facebook status, uploading vacation photographs onto Flickr, streaming an old episode of “The Office” on Hulu and researching a term paper on Google sucks up more electricity than you can imagine. The growing power demands of the digital age are spurring increasing interest in something called the green data center.

Across the United States, data centers – buildings filled with high density computing equipment such as server racks used for data storage and processing – use an estimated 100 billion kilowatt-hours of electricity, according to the U.S. Environmental Protection Agency. That $7.4 billion annual light bill represents nearly 2 percent of the total U.S. electricity consumption. In 2006, just five years ago, the nation’s servers and data centers consumed about 61 billion kilowatt-hours.

The EPA estimates a 10 percent improvement in the energy efficiency of the nation’s data centers would save more than 6 billion kilowatt-hours each year, enough to power more than 350,000 homes.

Data centers use 30 to 100 percent more electricity per square foot than office buildings, in part because the stacks of servers generate heat, driving up cooling demands. Green data centers use more energy-efficient servers and, more importantly, design and technology to reduce energy demands for cooling and lighting. The Iowa City, Iowa green data center of ACT (also known as The American College Testing Program, Inc) uses a one-of-a-kind energy-efficient geothermal system to cool the building. The Prineville, Oregon green data center of social networking company Facebook uses an evaporative cooling system that negated the need for traditional chiller systems the company says helps cut energy use by up to 12 percent.

A common measure of how green a green data center operates is the power usage effectiveness (PUE) ratio that shows the amount of electricity needed to power the lighting and cooling systems compared to the electricity used by the computing equipment. The typical data center has a PUE of 2.5, according to the Uptime Institute. A green data center opened in March 2011 in Colorado Springs, Colorado by shipping giant FedEx has a PUE of 1.28, the company says.

Energy use is just one factor in attaining certification from the Leadership in Energy and Environmental Design (LEED) program, a voluntary rating system for energy efficient buildings overseen by the US Green Building Council. At least seven green data centers have achieved a Platinum rating, the highest level attainable under the LEED. Other World Computing, one of the LEED Platinum green data centers, uses a 131-foot tall wind turbine to provide the electricity for its green data center in Woodstock, Illinois.

The design and building measures necessary for LEED certification usually mean long-term savings. Fannie Mae in 2005 opened the nation’s first LEED-certified green data center and in a fifth anniversary celebration last year estimated the green design cut energy costs by 35 percent – a savings of $1.7 million over five years.

Green House Data, a 10,000-square-foot green data center in Cheyenne, Wyoming, is powered entirely through renewable wind energy. The company says its green data center uses approximately 40 percent less energy per square foot than comparable data centers.

The U.S. Environmental Protection Agency in June 2010 said that green data centers can earn the Energy Star label by being in the top 25 percent of their peers in energy efficiency according to EPA’s energy performance scale.

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