Green Grid Warns Electric Harmonics Cause Data Centre Waste

Organisations with efficient data centres may still be wasting power thanks to harmonics in the power supply, according to the Green Grid.

Data centres maybe optimised to use low power, and produce a little waste heat as possible, but electrical loads can cause a dirty current signal, and data centre managers need to know how to reduce the losses this causes, according to a White Paper that is being presented at the annual European conference of the Green Grid IT efficiency consortium, held this week in the Siemens Centre in Brussels.

Tune up your power

“There can sometimes be a danger of harmonics being overlooked when it comes to data centre efficiency, possibly because it can be perceived as a complex subject to understand,” said Ian Bitterlin, EMEA technical work group chair at the Grid. “However, it has a major part to play in the health and effectiveness of data centres, and it is important for organisations to begin analysing whether their PSUs [power supply units] are affecting the power and efficiency of their systems.”

Ideally, electrical power supplies are a regular sine wave, but resonance, and loads on the system can produce harmonics, where a higher frequency signal is overlaid on the basic supply. This causes inefficiency by creating eddy currents in transformers and other effects where energy is wasted.

Eliminating harmonics completely is usually too expensive, and may cause different kinds of waste, as systems may have to be massively over-specified to clean up the signal.

However, the Green Grid and its members have been achieving such success with basic measures of efficiency such as PUE (power usage effectiveness), a green grid metric which is being included in a forthcoming international standard, and “best practice” documents such a the EU Code of Conduct for data centres, that Bitterlin thinks it’s time to add harmonics to the list of things to work on.

“It is of particular importance to data centre owners who are advanced in their energy efficiency programmes,” he said. “For example, when we are talking about taking a data centre’s PUE down from 1.3 to 1.2, harmonics can be a sizeable contributor to success.”

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