Datacentres explore ways to cut energy use

Proliferation of centres sparks conference on power-efficiency

Putting datacentres on decommissioned ships and reusing hot water from cooling systems to fill the town swimming pool were among the wackier ideas floated at the recent Datacentre Energy Summit in Santa Clara, California.

Datacentre 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, such as improving air-flow management and using outside air in colder climates to cool equipment.

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

Subodh Bapat, vice president for energy efficiency at Sun Microsystems, described a perfect storm of factors that are forcing datacentres 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 US have increased by about 12% on average for the past three years and are expected to keep climbing.

That's forcing some datacentres to consider unusual solutions. One large healthcare centre is looking at reusing hot water expelled by its cooling systems to do its laundry, Bapat said. A hosting company in the US 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 datacentres on ships docked at port, giving it "the biggest heat sync 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. Staff from several large datacentres 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 air-flow management, so that cold air pumped in to cool equipment doesn't mix with hot exhaust air coming out, said Bill Tschudi of the Lawrence Berkeley National Laboratory.

Many datacentres 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 tested "hot-aisle containment" at a datacentre in Austin, Texas, 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 datacenters, 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.

Another case study looked at air-side economising, which is "basically just a fancy name for opening the windows" and using outside air for cooling, Sun's Bapat said. The air must be filtered and de-humidified, he said.

A colleague of Bapat's at Sun, Dean Nelson, said datacentres should consider raising their overall temperatures. Sun tested modular cooling systems on five-year-old servers and they operated without any problems even when aisle temperatures reached 85 degrees Fahrenheit (29 degrees celsius) .

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

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