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Considering direct fresh air free cooling..?

With the cost of energy representing one of the largest operating overheads associated with data centres, finding more energy efficient ways of supporting IT systems is a major driver for our industry. Ancillary systems, most markedly power and cooling infrastructure, present one area of tangible improvement and these systems have seen huge gains in energy efficiency over recent years.

The creation of metrics such as PUE and DCiE have not only given us an easy way of tracking improvement within existing data centres but has also given Marketeers a simple way of comparing one facility or solution to another.

As most of you reading this will know the aforementioned professional group have, in some cases, abused these metrics. However what their wholesale use has done is bring the concept of data centre energy efficiency to CFOs, CEOs, COO and end users in a simple and accessible format.

This can only be a good thing and over the last 10 years data centres have seen average PUEs fall from 3 to sub 1.5 in all types of facilities, from enterprise to micro.

So what has this got to do with choosing direct fresh air free cooling?

As a vendor neutral data centre designer there are a huge number of products and solutions available to help me reduce a data centre’s PUE. Often an effective place to start is by incorporating compressor free cooling.  These cooling systems fundamentally fall in to two camps – direct and indirect.

Indirect systems use cooling coils or heat exchanges to transfer a data centres waste heat to atmosphere. These cooling systems maintain separation between the data centre’s clean environment and the outside world.

Direct air systems remove the data centre’s hot air by replacing it with cooler air from outside.

Direct fresh air cooling systems have been used for many years and there is no doubt they can be very energy efficient. Future-tech has installed a broad range of these systems over the years and achieved annualised, full facility, PUEs of 1.12. Many of these solutions have been retro fitted to existing live data centres resulting in significant energy savings for their owner operators.

Although these systems have worked well it should be noted that direct fresh air solutions are definitely not a silver bullet for energy efficient data centre cooling.

Over the last 5 years I have seen a number of direct fresh air systems installed by data centre design companies and owner operators who have not thought the risks through properly. Where this has gone wrong has been with regard to external contaminants found in the local environment and the inability for standard filtration to remove such contaminants.

The most common contaminant I have experienced has been sea salt. I have met and spoken with a number of data centre owner operators with facilities located up to 5 miles from the sea who have experienced high saline levels in their data centre’s incoming air.   Some of these data centres have been located further from the coast but within a similar distance of tidal estuaries or rivers.

When talking about the risks presented by high saline levels it is often difficult to provide “real world” evidence. This is because organisations that have experienced such problems don’t really want to make it public knowledge. On this occasion, though, an organisation has.

The photos below were provided by an organisation who, against Future-tech’s advice, installed a direct fresh air system and, although they will remain nameless, wanted to get the evidence out there to help other owner operators avoid the same issues. Below is the result after just 3 years of operation in an area that is not deemed to be a “maritime environment” and has a moderate saline content.

Obviously this is pretty scary stuff… If a powder coated cabinet can look like this within 3 years imagine what the inside of one of those server must be like.

The problem is standard filtration such as EU4 and EU8 will not effectively remove saline contamination form the incoming air.

Other contaminants such as pollen and diesel particulates can also cause issues but with correct filtration (EU4 and EU8) these issues are normally only operational. By this I mean the filters get blocked quickly and require frequent changing.

If the filters are not changed the static pressure of the cooling system will increase. This will make the fans work harder and use more energy.

If incorrect filtration is used these foreign particulates will make their way in to your data centre and IT equipment. I have visited data centres with this problem and on one occasion seen pollen caked onto the front of  cabinets, much like the salt on the photos above.  However the owner operator in question was not willing to allow me to take photos.

If your organisation is looking for ways to make its data centres more energy efficient, whilst avoiding potential risks, please contact Future-tech on 0845 9000 127 for some impartial advice.

Bio. James Wilman is a Data Centre Design Consultant at Future-tech EMEA. He is represented on the British Standards TCT/7/3 expert panel which is working on the new data centre design, construction and operation standard. James has a passion for resilient energy efficient data centre design and operation.