Earlier this year, social networking giant Facebook finished construction of its newest data center in Pineville, Oregon. In a press release, Facebook officials touted the new facility as "setting new standards for environmental responsibility in data center design and operations." Those standards incorporate renewable energy tactics such as rainwater reclamation, solar energy, and heat recycling.By now, the energy-saving advantages of environmentally friendly efforts in IT are clear - even if companies don't always practice them. Even rather token efforts that make grossly inefficient data centers slightly less so can result in significant cost savings, given the escalating cost of electricity. But it's clear that energy efficiency will become only more important in the years ahead. That's especially true for data centers, as the demand for IT horsepower increases. So what are the best next steps in efficient data center operation? And is there a place for renewable energy sources such as solar and wind in the current data center equation?Measuring efficiencyThe common metric used in measuring the energy efficiency of a data center is a simple one: PUE (power usage efficiency) = total facility power\/IT equipment power. The desired PUE number is 1.0 - a\u00a0one-to-one ratio between the energy being used to power the IT equipment and the total energy being expended in the data center facility. Unfortunately, most data centers operate at a PUE of about 2.0 at best, according to industry sources.That's why vendors tout the PUE of their green compute technology. For instance, Hewlett-Packard claims its POD (performance-optimized data center) systems, which are self-contained high-end computing units, operate at a PUE as low as 1.05. That energy efficiency mainly comes from the systems' use of "innovative cooling techniques," says Jon Mormile, HP product marketing manager for POD. Keeping hot-running computer servers cool while they chug away is a major factor in the PUE discrepancy.For its part, Facebook claims a PUE of 1.07 for the data center design it employed in its Pineville facility, a design it has made public in support of its "Open Compute Project." Unlike its Web 2.0 rival Google, which keeps its data center designs highly proprietary, Facebook launched its "open source" data center effort "to share our designs and collaborate with anyone interested in highly efficient server and data center designs," said Jonathan Heiliger, VP of technical operations at Facebook, in a statement.Nonetheless, that impressive efficiency number does not include the energy Facebook is generating with it solar-panel array. That energy will be used to provide electricity to the office areas that support the data center, according to Facebook.Which doesn't surprise Jack Pouchet, director of energy initiatives at Emerson Network Power, a division of multinational Emerson Electric. Because data centers are "energy dense" they're "not a perfect fit for solar," says Pouchet, who refers to himself as Emerson's "green guy." Renewable energy sources such as solar panels and wind turbines usually don't generate the volume of electricity needed to power a data center completely. They also come with inherent limitations, which include the requirement for generous amounts of sun and wind along with the space needed to set them up.His conservatism is ironic, given the fact that Emerson Network Power is one of only a handful of organizations in the country that powers its data center at least in part using solar energy. Emerson incorporated a 7,800-square-foot rooftop solar array as part of a new global data center opened at company headquarters in St. Louis in 2009. However, the solar energy generated by the photovoltaic panels represents only about 16% of the electricity needed to power the Emerson facility. A good way to approach using alternative means of generating electricity is as just such a supplemental energy source, whether contributing directly to the data center or to support systems around the facility, Pouchet says. And sun and wind aren't the only renewable alternatives, he points out. There's energy from biomass when it's burned, and naturally occurring geothermal energy, both of which can be used to power steam engines. And just because the federal government isn't likely to build another Hoover Dam anytime soon doesn't mean hydroelectric power isn't available. "Most geographies have multiple ways of achieving renewable or alternative energy chains," Pouchet says.Getting off the grid There is one data center in the United States that runs solely on solar power. It's operated by Affordable Internet Services Online Inc., or AISO.net, and was founded in 1997 by Phil Nail, who serves as the company's chief technology officer. "We started off small," Nail says. Our first client was a Mexican restaurant."AISO.net's data center is located in Temecula, Calif., an hour north of San Diego, which contributes to its ability to use solar power. It also helps that the facility is energy efficient from top to bottom, from its rainwater cooling units to its solar fluorescent lights. Wind turbines turned by the air-conditioning fans power the thin-client desktop computers used in the office. "We've been totally solar since 2001," Nail says, adding, "We're off the grid." Another key ingredient in AISO.net's energy efficiency success: server virtualization. "Everybody who comes to us allows us to take their physical servers and virtualize them," Nail says. Which helps explain why a "relatively small" data center with only "about 15 [server] racks" can support "thousands of customers worldwide," including the San Diego Convention & Visitors Bureau, Krispy Kreme Doughnuts, and the Indianapolis Zoo - all powered only by the sun. Be committed, collect incentivesIt may be an extreme example but AISO.net points to an important lesson: When it comes to data center design and operation, dramatic and meaningful energy efficiency has to be a commitment, not a whim or an afterthought. "You can't just piecemeal it," Nail says.Many organizations support energy efficiency initiatives, and an increasing number are data center oriented, such as The Green Grid (www.thegreengrid.org). Facebook's Open Compute Project (http:\/\/opencompute.org\/) is backed by AMD, Dell, Goldman Sachs, Hewlett-Packard, and Intel, among others.Energy efficiency and the use of renewable energy are not just feel-good initiatives; there are real-world deliverables in terms of federal and state tax incentives. One place to find out about those is DSIRE, Database of State Incentives for Renewables and Efficiency (www.dsireusa.org).Still, insiders say IT management too often takes a "not my job" attitude about data center efficiency. "It depends on who's running the budget," says Tony Cooper, IT product manager for Rittal Corp., which manufactures server cabinets and provides help with data center design. "I've talked with IT managers who don't care about their power - they're not measured by it, it's not in their budget." When it comes to energy, that's just bad policy. John Soat is a freelance journalist who's been writing about the intersection of business and technology for more than 25 years. Reach him at firstname.lastname@example.org.