FACILITIES power + cooling
Data centre retrofit delivers energy savings of more than half a million pounds
ONE of Europe’s largest telecoms providers has achieved dramatic reductions in energy consumption and carbon emissions thanks to EC technology from ebm-papst. Simply by upgrading their computer room air conditioning units to use EC fans, and harnessing this technology’s built in variable speed control, the telecoms giant is projected to achieve savings in excess of half a million pounds each year and dramatically cut carbon emissions.
The major telecoms provider approached both ebm-papst, Europe’s leading manufacturer of high efficiency fan and motor technology, and Emerson Network Power (ENP), to identify what savings could be achieved by upgrading its existing equipment.
Initially, ebm-papst and ENP measured the power input and air flow of the existing CRAC units, which were originally installed in 2002 and supplied cooled air via a raised floor. A trial installation on a single CRAC unit was undertaken to demonstrate the energy saving potential of EC technology in comparison to the original AC equipment. The three existing fixed speed backward curved AC fans in a single CRAC unit were replaced with three EC backward curved fans with integrated variable speed control. This activity required
the system, potentially causing the compressor to cycle more frequently to achieve the required duty, increasing power draw and wear. By using EC this added pressure on the system can be reduced.
“It is also important to consider that many legacy AC fans utilise separate motors with belt drives. Not only can these generate further losses, which equates to more wasted energy and additional heat, but they also need a regular maintenance programme for replacement and tightening. An unforeseen side-effect is that they can create belt dust that can intrude into the data centre and potentially block filters and damage the data centre’s core IT equipment.”
Precision airflow control
“The inclusion of an on-board microprocessor within EC fans opens up the opportunity for data centre operators to quickly and easily connect the 0-10v control input of the fans to an external control system, without the need to install additional equipment. This opens up the opportunity to manage air flow in accordance with requirements. Most data centres are built with redundancy and worst case scenario in mind which means under normal operation the system may be over performing for the cooling capacity needed.
In the vast majority of legacy AC equipment, this control is not possible, with fans running at a fixed speed, which means operators are missing out on significant energy saving potential. “The option to control fan speed presents a further opportunity to reduce energy
Endnotes
1. Source: Data Centre Dynamics, 2011 2. Source: Data Centre Dynamics, 2011 3. Source: Data Centre World survey, 2012
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minimal modification and took around two hours to carry out the installation.
The power input of the trial unit was then re-measured over a period of seven days, during which measurements were taken every ten minutes, when compared to the original measured data it confirmed that upgrading to EC technology could deliver energy savings of 58%, a figure which impressed the telecoms client. However, ebm- papst and ENP felt this could be improved upon. Having run the new EC fans at the same performance as the original AC fans during the trial, it was identified that the airflow could be reduced while still maintaining the required level of cooling. The speed of the fans was subsequently reduced, optimising airflow, and further measurements were taken, demonstrating a total energy saving of 78%.
As a direct result of the savings achieved by ebm-papst and ENP during the trial, the telecoms client has decided to go ahead with a complete upgrade of all CRAC units at the trial site, and also plans to roll this out to several of its other data centres in the UK, delivering projected energy savings in excess of half a million pounds each year and almost 3.3kT of CO2.
consumption within a data centre – more so than many may realise. The reason for this is found in the physics of fan laws. You may think that doubling shaft speed will also double the energy consumed, but it actually increases the power consumed by a factor of eight. Therefore it is extremely wasteful to run a fan faster than is actually required. This is particularly relevant when you consider redundant systems.
“A data centre may have a requirement for four CRAC (computer room air conditioning) units, running at 100% to achieve a required duty. An identical fifth CRAC unit may also be installed to offer n+1
redundancy.
However, it would be far more energy efficient to run all five CRAC units at 80% In the event that one unit fails, the building management system can tell the remaining four units to speed up and pick up the slack until the fifth unit can be repaired.
“The rationale for replacing legacy AC equipment with EC technology is very compelling and it is one that all data centre operators should take into account, even if they may not currently be looking at retrofit options. The dramatic reduction in energy consumed translates into tangible savings, which will positively impact on the bottom line.
Reducing energy consumption will also cut carbon emissions; this can further benefit the bottom line where firms are subject to the Carbon Reduction Commitment.”
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