Micro-Modules Use Warm Water for Cooling

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Several R.A.S.E.R. HD enclosures from Elliptical Mobile Solutions.

As modular data center solutions have emerged as a viable deployment model, most vendors have continued to offer 20-foot and 40-foot enclosures, sticking with the ISO-standard sizes used in the early container models from Sun Microsystems and Google.

Elliptical Mobile Systems (EMS) has pursued a different course, specializing in "Micro Modular Data Centers," smaller enclosures that can house a single rack of IT equipment and a heat exchanger. In early testing, the company's latest model, the R.A.S.E.R. HD, has shown the ability to cool IT equipment using warm water - a capability that offers major energy efficiency gains.

The R.A.S.E.R. HD is a 42U enclosure designed to handle IT loads from 20 kW to 80 kW. It can be deployed indoors or outdoors, and features active fire suppression, electronic security, environmental monitoring and building automation.

Warmer Water = Higher Efficiency

Many data center cooling systems set the chilled water temperature in range between 45 to 55 degrees. Recent testing found that the R.A.S.E.R. HD can cool high-density loads using water in a range of 65 degrees all the way up to 85 degrees.

Using a higher water temperature in a cooling system provides two benefits - it allows you to either use your chiller less, or not at all. Higher inlet water temperature maximizes the number of hours in which "free cooling" is possible through the use of water side economizers. Additionally, chiller efficiencies increase at a higher supply water temperature.

The testing was conducted at the United Metal Products facility in Tempe, Arizona, with the enclosures placed outdoors on a 100-degree day. The testing used a 23kW load bank to simulate IT loads. After working effectively with 65 degree water, the unit was able to maintain a server inlet temperature around 85 degrees after the water temperature was raised to 85 degrees. While not all companies are comfortable running their data centers at that temperature, the test illustrates the potential to gain savings by running warmer.

"The R.A.S.E.R. HD provides solutions for eliminating chiller systems altogether while maintaining very low PUEs,” said Scott Good of gkkworks, who conducted the testing on behalf of EMS and has authored a white paper (PDF) detailing his findings.

Uses Air/Water Heat Exchanger

The cooling system for R.A.S.E.R. HD consists of an air loop and a water loop. The fans of the cooling unit draw warm air from the rear section of the cabinet and into an air/water heat exchanger. The air is cooled and then blown into the front area of the cabinet. Inside the air/water heat exchanger, the heat energy of the warm air is transferred to the medium of water. The heat exchanger is connected to an external reciprocal chiller unit, where the water is cooled again.

“The closed loop/coupled design offers consistency in cooling performance, independent of the raised floors, floor tiles, and fans associated with traditional cooling," said Good. "These products scale to successfully support the full gamut of rack loads, from minimal to high density. A user with a closed-loop, close-coupled design knows that a predictable capacity is available as operations grow.”

Elliptical Mobile claims that the R.A.S.E.R. HD can achieve Power Usage Effectiveness (PUE) ratings of 1.1, an extremely efficient performance. Good said he is confident that given an IT load to test he could the unit accomplishing a PUE of 1.03.

Intriguing Deployment Options

One of the intriguing aspects of the R.A.S.E.R. HD is that it offers the potential to deploy IT equipment in a small space, without the need for a controlled data center environment. The enclosure could easily replace an IT closet or small server room, making it ideal for small businesses, satellite offices and remote worksites.

But with the R.A.S.E.R. HD, Elliptical Mobile also sees the potential to solve problems that have vexed larger data center operators, offering a different vision for how high-density IT capacity might be deployed efficiently and in bite-sized installments.

"Close-coupled cooling embodies two of the industry's favorite buzzwords: modularity and scalability," Good said. "Instead of building larger spaces and installing more air conditioners, professionals can 'right-size' from the very beginning instead of trying to reinvent the wheel."

In this video, Good provides an overview of the testing and a closer look at the enclosures in action.