30 January 2014
CIX operates a 1,860m2 (20,000ft2) data centre in Southern Ireland, and supplies communications for co-location and large enterprises including telecoms operators. The site has around 240 customer racks, 20 infrastructure racks, and runs round the clock all year.
CIX MD Jerry Sweeney says the data centre was built to use hot and cold aisle containment. The cold aisle has a glass roof to ensure the cool air does not mix with the warm air. The aisle is cooled using an underfloor air supply at 19°C to 20°C from a CRAC unit. This flows through perforated air tiles into the front of the racks. The hot aisle has no roof, which allows air at around 34°C to mix with ambient air before returning to the air plenums of the CRAC units.
Southampton-based ICS Cool Energy installed its free cooling Aptus chillers on the roof (see schematic) of the data centre, which allows them to use the low outside air temperatures to send chilled water to the CRAC units inside the data centre. The system has cut the compressors’ running hours significantly, saving money and achieving a PUE (power usage effectiveness) of approximately 1.15.
ICS estimates a data centre working continuously throughout the year would have to run the compressors for only 3,000 hours per year; the rest of the time it would run only pumps and fans.
“A modern data centre in Ireland, operating with a chilled water flow temperature of approximately 15°C, could achieve 100 per cent free cooling for eight months of the year (based on the average mean ambient temperatures) and the remainder of the year would offer partial free cooling helping to reduce the load on the chillers,” says ICS operations manager Craig Hodgson.
He adds that free cooling units can last 10 to 15 years, and chillers 10 years when properly installed and maintained. “Free cooling can almost double the life expectancy of the chillers as it reduces the wear and tear on them, helping reduce life cycle costs. If the free cooling systems were ever to go down, the chillers around the system would still be functioning so there would be no interruption to the process or data centre,” he says.
Hodgson goes on to explain that ICS installed a free cooling system in a Dublin site ready for the full design load. “After three years the centre is now 30 per cent full, and as the free cooling is so oversized for the current load, the chillers have only had to operate for a total of 70 hours,” he says.
Hodgson claims some projects pay back the investment in free cooling within 12 to 18 months. “After three to four years, the energy savings from free cooling have not only paid for the free cooling units but also the chillers. The lower the temperature of the water, and the higher the average ambient temperature, the longer the payback is.”
