DCN August 2016 - Page 25

cooling Intelligent choices Since its opening in 2009 Stulz UK has supplied the cooling systems at NGD’s mega data centre in South Wales, a Tier 3 facility offering both private and shared colocation data halls across 750,000ft2. With up to 180MW power available from a direct SuperGrid connection, the facility has proved increasingly popular with enterprise and service provider organisations operating high density environments such as those found in HPC and cloud. Two years ago, in response to increasing requirements from customers to further reduce PUE, NGD evaluated alternative solutions to the DX direct expansion systems originally supplied by Stulz. This included an adiabatic system (IAC) and though demonstrating very energy efficient PUE figures it was rejected due to the major infrastructure works involved, large footprint/low cooling capacity, high water usage and treatment requirement, as well as on grounds of cost. Stulz UK subsequently replaced the DX systems with its latest cooling solution which intelligently determines the optimal mode of operation according to the dictates of the external ambient conditions and data hall requirements. This solution enables the system to operate in free cooling mode for the majority of the year, to compensate for these hotspots is costly. For cooling higher density racks, HACS incorporating doors, ceilings, in-row cooling systems and variable speed temperature controlled fans may provide a more efficient solution whilst ensuring server availability. This only providing supplementary cooling in times of elevated external ambient conditions. The scalable system design is based on the glycol free cooling GE system and features a unique pipework arrangement: a low loss header within the dry cooler compound and individual flexible pipes for distributing to each individual CRAC unit. The pipes are double insulated and have both an inner and outer pipe. In the event that the inner pipe leaks it transfers into the outer pipe which has its own leak detection installed. The pipes can be made in any lengths therefore minimising joints and can be installed in a fraction of the time it would take for a traditional piping system. The first GE system was installed and commissioned within five weeks and the annualised PUE figure achieved was 1.18. The cost of the system compared to the IAC was almost 60 per cent lower and the ROI for the GE system was three years compared to six years for the IAC. Thanks to this intelligent cooling solution NGD has been able to move in line with customer requirements, delivering solutions from a standard 4kW rack up to 60kW per rack and beyond with resilience at a minimum of N+20 per cent. is because HACS is a self-contained ‘room within a room’ system that removes server exhaust air from the data hall at large and precisely targets cold air to specific racks or rows. By maintaining higher return temperatures HACS will also ensure cooling unit capacities are maximised whilst the power consumed (including by fans) is reduced. Apart from saving energy this will optimise the potential for free cooling days. HACS can also be deployed without impacting the existing cooling architecture – unlike CACS – as it does not affect the temperature of the entire computer room. 25