Data centers explore novel ways to cut energy use

Putting data centers on decommissioned ships and reusing hot water from cooling systems to fill the town swimming pool were among the wackier ideas floated at the Data Center Energy Summit in Santa Clara, Calif., on Thursday.

Data center operators came together to compare notes about the best ways to tackle rising energy consumption at their facilities. Ideas ranged from the exotic to the more down to earth, like improving airflow management and using outside air in colder climates to cool equipment.

After a brief lull a few years ago, a new wave of data center construction and expansion is under way, stretching the power and cooling capacities of existing facilities and putting pressure on utilities' electrical grids, speakers said.

Subodh Bapat, vice president for energy efficiency at Sun Microsystems Inc., described a "perfect storm" of factors that are forcing data centers to become more power-efficient.

The electricity consumed by microprocessors is increasing by 16% per year as they become more powerful, he said, which contributes to a 14% increase in the power consumed by each new generation of servers. At the same time, energy prices in the U.S. have increased by about 12% on average for the past three years and are expected to keep climbing.

That's forcing some data centers to consider unusual solutions. One large health care center is looking at reusing hot water expelled by its cooling systems to do its laundry, Bapat said. A hosting company in the Northeast is freezing water overnight, when the cost of electricity is cheaper, and then blowing air over the ice during the day to provide cold air for cooling systems.

Another company hopes to put portable data centers on ships docked at port, giving it "the biggest heat sink in the world [the ocean] to get rid of waste heat," Bapat said.

Most people at the summit here were looking for more down-to-earth solutions. They were offered by several large data centers who discussed results from pilot tests designed to help show the real-world savings offered by from various energy-saving techniques.

One of the most effective is better airflow management, so that cold air pumped in to cool equipment doesn't mix with hot exhaust air, said Bill Tschudi, a researcher at the Lawrence Berkeley National Laboratory.

Many data centers use alternating hot and cold aisles to keep warm and cold air separate, but that method is only partially effective because the air mixes in the spaces above the aisles, Tschudi said.

Oracle Corp. tested at a data center in Austin "hot-aisle containment," which involves building an enclosure around server racks so that the hot exhaust can be siphoned off. Cooling systems account for as much as half the energy consumed by some data centers, said Mukesh Khattar, who heads Oracle's energy efforts.

The hot-aisle containment allowed Oracle to reduce the fan speed in its cooling system by 75%, which reduced the fan's power consumption by 40%, Khattar said. It installed a variable-frequency drive to control the fan and got payback for the investment in nine months, he said.

Yahoo Inc. tested cold-aisle containment and then installed a wireless sensor network to monitor temperature and humidity around the room. The sensor network allowed the company to gradually increase the temperature in its data center without creating heat spots that could damage equipment. The setup can reduce cooling energy costs by 25%, said Christina Page, head of Yahoo's energy and climate strategy.

There are upfront capital costs to consider. Sensor networks cost $6 to $8 per square foot to implement, said Troy Mitchell, sales director at SynapSense Corp., which sells sensor equipment. Doing hot-aisle containment in a 43,000-square-foot data center like Yahoo's would cost $250,000 to $300,000, he said.

The containment systems must not interfere with sprinkler systems. Yahoo used flame-retardant PVC connected to the racks with "fusible links" that would collapse at 130 degrees Fahrenheit in the event of a fire, allowing the sprinklers to operate, Mitchell said.

Another case study looked at air-side economizing, which is "basically just a fancy name for opening the windows" and using outside air for cooling, Bapat said. The air must be filtered and dehumidified, but in cooler climates such as San Francisco, it can be used for most of the year, he said.

Dean Nelson, senior director of global lab and data center design services at Sun, said data centers should consider raising their overall temperatures. Sun tested modular cooling systems on 5-year-old servers, and they operated without any problems even when aisle temperatures reached 85 degrees Fahrenheit.

"It makes me wonder," he said, "why are we running our cold aisles at 65 degrees?"

Accenture Ltd. is publishing the results from the case studies on its Web site, along with an overview that compares their effectiveness.

Copyright © 2008 IDG Communications, Inc.

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