A closer look at free cooling

The data center cooling challenge

Colocation continues to be adopted as part of a diversified infrastructure strategy. But the fact that these facilities are well-connected and provide space for high density configurations brings with it a challenge. Increasingly you can expect to see racks of less than 3 m², containing up to 20 servers, with a consumption of up to 6KW – and sometimes even much more. Now imagine a 30m² room with 60 of these ‘ovens’ running day and night. The need for very careful management of power and cooling is critical. And it requires a constant evolution in best practices and technologies to do it efficiently, and in an environmentally friendly manner.

What is free cooling?

Free Cooling is a technique that performs the cooling of a data center in the most efficient way. It refreshes the air within the data center without involving any cooling system. It simply takes the outside air, which has a lower temperature than that inside the facility – and after some humidity control and correction – is moved through the data rooms. Basic physics can then run its course.

Dependent on location, it may be possible to do this for most of the year. Aside from the ambient temperature in location, humidity is a key factor in defining the success of free cooling. If the air pulled into the data rooms is too humid, it can increase problems such as oxidation, whereas if it’s too dry it could increase static electricity, which poses its own challenges.

Key considerations in free cooling

Free cooling is optimal when the external temperature is lower than that expected within the IT rooms. In some locations this is very predictable, but in others you need to deal with those relative temperatures inverting. On a very hot day, additional steps must be taken to cool the outside air before it is sent into the IT rooms. This increases the overall energy requirement within the facility, and can reduce the relative value of a free cooling strategy.

To maximise free cooling (and minimise electricity consumption) the outside temperature must be lower than the IT room temperature for most the year. For some organisations this challenges their assumptions about where a facility should be located. Another take on the problem is to consider running IT rooms at a higher temperature. Again, this can go against the assumed ‘rule of thumb’, but the industry as a whole is now adopting higher facility temperatures, which supports further adoption of free cooling.

Free cooling – your environmental footprint

Cooling is perhaps the biggest challenge that data center managers face when looking to minimise their environmental impact, and the efficiency of cooling systems is a significant barrier to reducing the PUE for a data center. Historically most facilities have had a PUE above 1.8, but it’s becoming more common to see that decrease down to 1.2 where cooling has been optimised. Free cooling is one of the most adopted techniques to facilitate this change, and to help reduce your environmental footprint. DATA4 has continually assessed its environmental footprint, and sought reductions in our PUE score across our facilities. Free cooling has been now widely adopted in the majority of our data centers, and our newest facilities are now targeting a PUE of 1.25 or lower.