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Many industry experts have predicted the demise of data centre perimeter cooling due to the rise of alternative cooling strategies. It is clear today these predictions have proven to be unfounded.
Ten years ago perimeter based Computer Room Air Conditioning (CRAC) was the cooling of choice for the vast majority of data centre installations. Following the successive introduction of alternative technologies including In-Row, Rear Rack, Overhead, and Free Cooling systems the choice of cooling technology has increased significantly over the past decade.
One of the key principles of alternative technology is that by moving the cooling closer to the I.T load this will help reduce energy consumption through reduced fan power. The manufacturers of alternative technology would have you believe the days of traditional perimeter based computer room cooling are numbered!
However, the reality today is that whilst alternative cooling technologies have gained ground and do account for approximately 40% of new installations the overall growth in data centre capacity has compensated and helped maintain the volume of perimeter CRAC unit deployments.
Why Do We Still Relay on Perimeter Cooling
Perimeter cooling offers greater flexibility over closely coupled technology such as In-Row and Rear Rack systems. Perimeter CRAC cooling enables the independent deployment of equipment racks and cooling systems. This approach is still dominant in co-location and larger data centre environments.
The introduction of aisle containment and dynamic control functions in the late noughties has helped maintain the continued demand for perimeter based CRAC cooling technology.
With the introduction of state-of-the-art EC cooling fans, variable compressors, high efficiency coils, “next generation” perimeter CRAC units more than stand their ground against the newcomers on the block delivering excellent energy efficiency.
High Efficiency Next Generation Perimeter CRAC Units
Typical next generation air handling units are equipped with EC fans which are especially good at energy-saving in part-load modes of operation. Good data centre design enables the fans to operate at low speed for as long as possible. As a rule, fan speed corresponds with the compressor speeds and EEV valve which means that fan speed increases as soon as the smallest cooling load is present.
With smart cooling, however, the refrigerant control system increases the volume flow of cooling medium across the cooling coil; but the fans can remain at lower speeds. Fan speeds can be kept artificially low using the smart cooling function until a pre-determined point where they will speed up to keep up with room load.
Good Data Centre Design Practice
Through effective data centre design next generation low energy CRAC units can deliver a very credible PUE performance (sub 1.25). Typically, new builds are designed especially to support the maximum efficiency of airflow. Examples of good design include the forming of “hot corridors” which provide a direct link with hot aisles helping simplify airflow arrangements. When combined with aisle containment, underfloor air barriers, blanking panels and N+1 arrangements perimeter cooling will hold its ground well against “directly coupled” alternative cooling technology.
About Workspace Technology
Workspace Technology is one of the UK’s leading independent data centre design and build specialists. Workspace Technology has many years of experience in designing and building data centre projects for clients across UK.
As an independent design and build company Workspace Technology offers clients a wide choice of cooling technology. Recommendations are made to suit individual client demands and building environments.
Workspace Technology is GEA Heat Exchangers'* most experienced data centre Systems Integrator. Workspace Technology has helped a diverse range of clients to deliver excellent performance figures with perimeter based CRAC cooling through intelligent design and innovation.
* Formally GEA Denco
For more information please contract Roy Griffiths Technical Director at roy.griffiths@workspace-technology.com or call 0121 354 4894.