I was interested to see that Red Engineering Design’s green data centre package was a runner-up in the 2008 Building Services Awards (BSj 07/08). I congratulate the firm on its achievements, especially as there is such focus on energy usage today and data centres, by their nature, are large energy users.

As designers of data centres ourselves, the brief synopsis of the project undertaken by Red prompted a few queries. The synopsis mentioned that Red had developed a package of measures that reduce energy use and CO2 by more than 30%. The first query was what was the benchmark that Red was comparing with?

Attendees at the DatacentreDynamics Conference will be aware that one of the benchmarks used for data centre energy performance is the power usage effectiveness (PUE) of the building. This is the ratio of the total power consumed by the building divided by the IT load. For example, for a PUE of 2, 3600kW of power would be required to produce 1800kW of IT data power.

Benchmark PUE figures for data centres presented by Hewlett-Packard are:

PUE of 1.6 = ideal
PUE of 2.0 = target
PUE of 2.4 = average
PUE of >3.0 = poor.

Hewlett-Packard’s worldwide research indicated that no sites achieved the ideal PUE of 1.6 and only 5% hit the target of 2.0.

With a client and industry partners, we have developed a data centre design model that operated last year on an average of 1.44, with scope for improvement. While we are proud of this achievement, confidentiality agreements mean we are unable to discuss and publicise project details. We are, however, curious to establish how the Red design compares to the PUE benchmark.

Our second query concerned Red’s use of open-circuit cooling towers in a data centre application. Other designers and building operators will recall the powers invoked by local authorities in the past when there have been outbreaks of legionella. In the event that the local authority was unable to establish the cause of the outbreak, there was a blanket ban on the operation of cooling towers in the local vicinity – obviously a high risk to a building’s operation, especially a data centre. Presumably a back-up method of heat extraction was incorporated into the design.

As the growth and demands of data centres increases, it is reassuring to see CIBSE members taking up the challenge of providing world-class designs and performance.

Alan Affleck, associate, RSP Consulting Engineers