Warwick University data centre benefits from energy-efficient cooling solution

The removal of heat and saving energy are major environmental challenges facing data centres. Building on its successes as one of the UK’s designers and manufacturers of air conditioning, Eaton-Williams Process Cooling (EWPC) has applied it expertise to the cooling issues faced by the IT industry in particular data centres and has moved away from traditional methods of cooling and focused on rack based cooling technology.

Working closely with IBM in the US, Process Cooling has developed a number of products specifically for data centre environments including CDUs (Cooling Distribution Units) and rear door heat exchangers (RDHx) that remove heat at source using chilled water as the coolant. This approach has proved so successful in reducing costs, energy consumption and freeing up floor space that its RDHx won the Silicon Valley Leadership Group’s (SVLG) sponsored ‘Chill-Off’ in 2008 for being the most energy efficient data centre cooling product.
One of the first customers in the UK to benefit is the Centre for Scientific Computing (CSC) at the University of Warwick. Rapid growth in the use of High Performance Computing (HPC) resources in the CSC by academics; post-doctoral researchers and PhD students, meant that the department’s existing data centre facilities needed to expand to cope with demand.

The performance of servers and storage has increased exponentially over the last few years as has the heat generated by the hardware. The problem facing the university was to temper the need for expansion with the control of heat and limited floor space.

Eaton-Williams has successfully provided temperature controlled solutions for numerous commercial and industrial applications and designed solutions for many of the UK’s leading telecoms providers including BT, Orange, Vodafone and Belgium’s national provider, Belgacom with energy efficient cooling solutions for data centres, co-location sites and network hubs.

Addressing the cumulative issues of increasing heat densities and environmental sustainability are a key part of the company’s on-going strategy with Process Cooling focusing on the specific requirements of the data centre industry.

Warwick, working closely with its consulting engineers, Couch Perry Wilkes Partnership (CPWP) was aware of Process Cooling’s successes and sought a solution that addressed its environmental concerns whilst providing an effective and reliable cooling solution with capacity for future expansion.

Process Cooling’s approach moved away from traditional CRAC (Computer Room Air Conditioning) units with the recommendation of a more robust, compact and energy efficient solution using its rear door heat exchangers and CDUs.

With initially six cabinets housing forty servers in each, six RDHx units were installed in conjunction with a Downflow CRAC arrangement to remove up to 15kW of heat from each rack using a traditional chilled water system.

Each RDHx offers condense free operation using controlled water from the CDUs. The RDHx high specifications include refrigeration grade coils pressure tested to 45, hermetic construction, sealed copper brazed, under floor manifolds pressure-tested to 20-bar, leak detection and leak-free quick release couplings and hose sets rated to 53 bar. The secondary circuit working pressure fed by the CDUs in ‹4 bar gives an excellent safety margin.

The units substantially reduce the heat output from the servers which can be in excess of 45°C by as much as 50%, removing it from the hottest part of the servers (back) and rejecting it into the cooling coils  in the rear door which then cools the rejected air down to close to room temperature (approximately 20°C).

In an adjacent room as well as two CRAC units there are two Process Cooling CDUs that control the temperature of the water for the RDHx units. Each CDU incorporates full run/standby capability (N+1). The CDUs feature internal manifolds with leak free quick release couplings for easy installation and connection. An externally sited chiller provides chilled water which is delivered to each CDU unit at a temperature of 10°C increasing free cooling capabilities more effectively than a CRAC only based system.
The RDHx requires no additional fans or electricity and is designed to cool without opening or removing the doors. Because the heat exchangers are in the back of the racks and in the door itself, the actual footprint of the racks and floor space is barely impacted.

A major benefit is that as the RDHx cools the air before it leaves the rack there are no hot spots and cooling air at source is very energy efficient. (150kW of heat can be rejected to the primary chilled water system via RDHx and a CDU, consuming only 2.6kW of pump power. A CRAC system would consume around 10-15kW to do the same job and with a much larger footprint.)

The under-floor manifolds have been designed to enable up to a maximum of 19 racks and RDHx units to be installed without any downtime and minimal M&E work. The room has been designed to accommodate an ultimate design load of 19No. computer racks at 15kW per rack which is cooled by a combined conventional air system and Rear Door Heat Exchanger (RDHx) arrangement. With the air system ultimately providing up to 7.5kW per rack and RDHx providing up to a further 7.5kW per rack cooling to achieve the agreed high performance computer loading of up to 15kW for each computer cabinet.

Process Cooling’s solution has enabled Warwick to introduce high density equipment with zero thermal impact into its data centre and has set a benchmark which the university plans to implement in its other data centres.