Government agencies looking to buy modular (or containerized) data center solutions should request air-side economization capabilities from their vendors. The free-cooling features significantly increase energy efficiency of the solution and reduce time and cost to deploy it.

These are some of the key conclusions in the new report published recently by the US Department of Energy’s Lawrence Berkeley National Laboratory. The report’s authors, LBNL’s Henry Cole and Mark Bramfitt, a utility consultant, were tasked with producing a modular data center procurement guide for federal agencies.

"For users, specifying ‘second-generation’ modular data centers featuring air-side economizers will ensure not only significant energy and operational cost savings, but also lower deployment costs due to a reduced need for support infrastructure," an introduction to the paper reads.

Some of the ‘early-generation’ modular data center designs are inferior to traditional data centers in terms of energy efficiency, the authors explain. Deploying such solutions can be complicated by their infrastructure needs, not the least of which is the need to supply chilled water.

Such early-generation units can still be an appropriate choice for some uses, such as short-term deployment during rehabilitation of an existing facility, or when the local climate is not appropriate for free cooling. "It should be noted that some recent designs using early generation cooling approaches provide excellent energy use performance."

The second-generation products the paper refers to have their own air-side economization features, working in tandem with an evaporative-cooling system. This approach provides for better energy efficiency and for quicker and cheaper deployment.

The paper’s authors analyzed thermal-performance data they received from six modular data center vendors. The analysis revealed that solutions requiring a chilled-water supply had an average PUE of 1.16, while second-generation units’ PUE averaged 1.02.

Since the researchers were looking at modular data centers, the way they calculated PUE was different from the formula used for traditional facilities. It omits lighting, UPS, external power transformers and backup generators.

The metric, in fact, was called PUE* to differentiate it from the common PUE metric. Here’s the formula they used:

PUE* = (total power supplied to the module + power to produce externally acquired chilled fluid) / IT power

Download the full report by clicking here