Energy Efficiency Guide: Aisle Containment

facebook-containment

A look at a cold-aisle containment systems installed by Facebook in one of its Silicon Valley data centers.

Containing the air in the data center - separating cool supply air and warm exhaust air - is an important energy efficiency strategy that figures prominently in energy efficiency optimizations at major companies. It makes sense to isolate chilled air and waste heat as much as possible, rather than to allow hot and cool air to mix, which requires the continual use of additional energy to cool a larger volume of air.

Back in 2004, data center managers at Oracle confronted the issue at a data center in Austin, Texas that was experiencing rising heat loads. They improvised chimneys affixed to the top of the rack to allow heat to rise up to an enclosed ceiling-level plenum and recirculate to the CRAC (Computer Room Air Conditioner) unit. Oracle's team disproved myths and confirmed the energy savings.

Since then, many products and techniques have evolved in the realm of hot aisle/cold aisle containment. Capping either aisle can prevent waste heat from recirculating and mixing with cool air from the CRAC units, which usually allows you to reduce the overall airflow by adjusting the fan speed in computer room air handlers (CRAHs) .

Which method is better? Major vendors take different approaches. APC by Schneider favors hot aisle containment, while Emerson Network Power offers a cold aisle containment product. A 2008 study by Lawrence Berkeley National Labs compared the two approaches. But either strategy can capture energy savings by isolating the hot and cold air. Here's a look at how some companies have implemented containment strategies.

Hot Aisle Containment

For hot aisle containment in its lab environments, Google recommends a simple and cost-effective method of using metal-end caps on rows and vinyl plastic curtains, such as those used in meat lockers. This limits air of different temperatures from mixing, while giving the flexibility to add racks easily.

Sun Microsystems also used clear vinyl curtains to contain hot aisles  in a data center project in Broomfield, Colorado that consolidated 165,000 square feet of legacy data center space into just 700 square feet.

Others, such as Microsoft in Dublin, use server pods featuring a hot aisle containment system using a fixed structure, with the cabinets housed in a fitted opening in the side of a fixed enclosure.

In its newer buildings, Yahoo's Computing Coop module features louvers along the side of the building that allow fresh air to enter into the data center. In the equipment area, the fresh air enters the front of the servers, and then exits into a contained hot aisle, which is topped by a chimney that leads into the upper chamber of the “coop.” Depending on the conditions, the warm air can either be recirculated or vented through the cupola. “The building itself is an air handler,” said Scott Noteboom, the Director of Data Center Operations for Yahoo. “The entire building is meant to breathe, and there’s a lot of louvers and dampers to control the airflow.”

WrightLine and its partners worked with data center developer Advanced Data Centers to create a prototype flexible containment system that keep air separated and add such features as swinging doors for access to the hot aisle and clear panels to allow ambient light to the hot aisle.

Cold Aisle Containment

Game operator CCP Games used a cold aisle containment system to deploy a 12-cabinet cluster of servers for the EVE Online virtual universe. The installation in London houses the Tranquility (TQ) cluster, which powers the EVE Universe of more than 330,000 players.

HP uses white cabinets in a cold aisle containment system that houses servers at its Wynyard data center located on the North Sea in the UK. Temperature in the contained cold aisle is maintained at 24 degrees C (75.2F).

Last year Facebook retooled a 14,560 square foot facility in Silicon Valley, which was equipped to use fresh air to cool the servers (air economizers).  The high-density site was designed with a cold aisle that was eight feet wide, a broader configuration than Facebook normally uses, to provide additional cooling capacity. Facebook then installed a cold aisle containment system, with a plastic roof overhead and sliding doors at the end of each aisle of racks. Director of Datacenter Engineering Jay Park and his team then swapped out tiles, replacing two rows of perforated floor tiles with solid ones. The containment system allowed greater control over the airflow, allowing Facebook to lower the frequency of its server fans

Last year Emerson Network Power produced the SmartAisle system, which combines cold-aisle containment, in-row cooling and management tools to provide data center managers with more control over the temperature and energy use in their environments

Fire Suppression

The implementation of containment solutions has presented new issues with building features such as fire suppression systems. There has been innovation there with the addition of products which address fire suppression, such as "drop-away" panels from Polargy Systems that have sensors that detect raises in temperature due to fire and automatically have panels to drop away from the containment system. Enclosure systems from WrightLine feature a “fire-activation” ceiling, which  opens to allow overhead fire suppression systems access to the equipment inside the containment system.

Data Center Knowledge guest columnists, including Electrorack, have discussed combating thermal issues with next-gen tools for containment.

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