The cutting-edge Diamond Light nSource scientific reserach facility in Oxfordshire has made major energy reductions thanks to more straightforward EC technology
In 2012, computer room specialist Stulz asked ebm-papst UK to carry out a site survey for upgrading some of its computer room air conditioning (CRAC) units.
Normally this type of unit is used for data centre cooling, but in this case the equipment was being used to cool electronic equipment rooms around the perimeter of the Diamond Light Source synchrotron.
The synchotron fires electrons at almost the speed of light, via a series of particle accelerators, around a 560 m circular structure. Effectively this creates a range of extremely bright beams of light, which can be used for everything from high-intensity X-rays to microscopic investigations of atomic and cellular structures.
Phase 1 of the project was to upgrade 27 of Stulz’s downflow CRAC units from their traditional AC forward curved centrifugal blowers to EC backward curved impellers.
The initial site survey was carried out to ascertain such factors as power draw and performance in the existing units and their suitability for upgrade. The blowers would be replaced by EC backward curved impellers, but due to the limitation of the scoop which feeds the air into the room, the EC solution had to be mounted within the CRAC unit enclosure rather than below.
The proposed solution was to use ebm-papst’s energy efficient RadiCal 560 mm impeller. The fans would be mounted into bespoke metalwork frames to angle the airflow to assist with the air delivery into the room.
An initial survey was carried out, showing a 39 per cent energy saving over the original configuration and the results were presented to Stulz and the end client. To support the findings, in January 2013, the trial installation of one unit was carried out by Cinque Energy Solutions.
Initial results showed a 43 per cent improvement in kVA compared with the original AC fans. For the trial the unit was not physically modified, which allowed the client to revert back to the original set-up if required. It was agreed that the floor of the CRAC unit would be opened up further to allow the new fans a less restrictive system resistance, thus increasing efficiency further.
The most important measured parameter for the customer was the temperature at rack level. The trial unit airflow was adjusted to match the previous ambient conditions. Due to the control of EC fans, a simple manual 0-10 V controller was fitted to the CRAC unit to allow each unit to be tuned to the room requirements.
The upgrade of the 27 units was scheduled for a two-week shutdown period in August 2013. Two teams from Cinque Energy Solutions were deployed to work on units simultaneously. All 54 fans were delivered to site and positioned near the units to cut down on delays during the four-step conversion:
- Remove the original AC fans and motor system;
- Enlarge the outlet holes in the floor void to maximise airflow with the EC fans;
- Fit new EC fans and frames;
- Reconnect supply to fans and fit manual speed controller.
After the installation, the original unit, which had previously been measured for the trial, was re-measured following the floor pan being opened up to the new requirements.
Added to the fine tuning of the fan performance, this gave energy benefits. The improvement in kWs, even with the skew of improvement in power factor (0.6 to 0.9), gave an improved result compared with the initial estimations.
From the 27 units, a 55 per cent energy saving was achieved, equating to a carbon reduction of 46 tonnes per year. This, based on an industry average of 10p/kWh, would achieve savings of £32,000 a year. On top of this, further benefits were revealed by the conversion. Due to the sensitivity of the equipment being used in the synchrotron, improvements in noise and vibration from using EC fans were also an advantage.
In addition, the following advantages were noted:
- Extended fan life;
- Extended unit life;
- Reduced maintenance – no belts;
- No belt dust being blown into the equipment rooms;
- Controllability of cooling capacity;
- Greater flexibility for capacity management.
The client’s report reveals a high level of satisfaction: “Obviously the financial savings from reduced energy consumption and increased reliability were of great importance. Other key benefits from the modifications ebm-papst offered were the reduction in both noise and vibration. These can affect our operations significantly.”
Phase 2 of the project, to convert the remaining Stulz cooling units, is scheduled for upgrade at the next shutdown.