Jakob Carnemark, senior VP, Skanska Mission Critical Center of Excellence, says the eOPTI-TRAX technology can dramatically reduce water and power consumption by replacing the traditional chiller plant and air handling unit found in a data center.
In a traditional chiller plant, free cooling occurs when the outside environment is cold enough and no compressors are required, says Carnemark. This is more energy efficient, but that free cooling mode occurs only when the outside temperature is 45 degrees or below. "Our free cooling mode occurs when it's 85 degrees or below outside," he says.
That means a data center using the Skanska technology in many parts of the world would be able to operate in free cooling mode approximately 83% of the year, compared with about 24% of the year for a traditional chiller plant. It's an impressive claim, and even Carnemark acknowledges that it has been met with skepticism. So how is it achieved?
Skanska's approach to data centers comprises an aisle containment system and the eOPTI-TRAX. The aisle containment system comes in the form of an eHive or eComb. EHive is a standalone container building that can be placed adjacent to an existing facility or placed on a rooftop; an eComb can be placed in an existing or newly constructed data center.
The eComb or eHive uses liquid refrigerant coil technology combined with the eOPTI-TRAX to expel the heat from the computer hardware to the outside environment. Instead of cooling the data center using a raised floor design, where an under-floor air distribution system pushes cold air up and into the server racks using many fans consuming a lot of energy, eOPTI-TRAX reduces energy usage by improving air circulation in the server aisle. Heat is absorbed by coils lining the inside of the rear walls of the server rack. Tests have shown it can bring hot aisle temperatures down from 160 degrees to 75 degrees.
Carnemark says the coils are able to attain significant heat transfer without mechanical cooling, and what's unique is that the refrigerant can be changed from a gas back to liquid at temperatures as high as 85 degrees and be used over and over again, meaning as much as 80% less water is consumed compared with a traditional open loop chiller. Compressors found in traditional data centers cool the air through an evaporation method and thereby consume incredible amounts of water.
There are other technologies available to bring cooling closer to the rack. IBM's Rear Door Heat eXchanger replaces the backdoor of the rack and cools air before it exits the cabinet, reducing the need for air conditioning units and thereby reducing energy consumption.
Carnemark says traditional cooling systems require 90 watts to cool a single server, but the eOPTI-TRAX requires only 0.3 watts. This in turn lowers the overall mechanical power utilization effectiveness (PUE) reading. (It's important to note that mechanical PUE differs from traditional PUE, which also takes into account how much energy is wasted through a facility's power distribution system.)
Next: Other Approaches to Lowering PUE