D ATA C E N T R E S C O O L I N G
Free Fresh Air Cooling
What’s Free, Renewable and Cool?
By Alan Beresford, Managing Director, EcoCooling.
Alan Beresford
explains the benefits
of free fresh air.
Since the dawn of (data centre) time,
we’ve all been conditioned to believe
that we need refrigerated air to cool
our sensitive IT kit. Yet if you only
blow hard onto something with slightly
cooler air you make it colder. So,
says Alan Beresford, Technical and
Managing Director of EcoCooling,
why not apply that same principle
in the data centre and do away with
refrigeration?
Data centre cooling air doesn’t need
to be cold, it only needs to be a little
cooler than the thing you’re trying to
cool. What really matters is the volume
of slightly cooler air that ‘blows’ onto
the item being cooled. Thanks to
changes to both server designs and
the guidance from ASHRAE (the
standards body for data centre cooling)
it is now possible to use free Fresh Air
to achieve the newly redefined ideal
operating temperature range for IT
equipment of 21C to 27C.
Where in Europe and the top half
of the northern hemisphere can you
find an endless supply of air at 21C
or less on most of the days of the
year? Just about everywhere - because
we’re talking about plain, ordinary
fresh air and it’s available for free by
the thousands of billions of cubic
metres. Giants like Facebook with their
120MW Lulea data centre in Sweden;
and one of Europe’s largest Telco’s are
using Free Fresh Air to cool their data
centres and digital switching centres.
And neither has deployed any form of
expensive, energy-guzzling, auxiliary
refrigeration plant.
How are these two giant data
centre operations overcoming the
problem of the occasional ‘hot’ (21C+)
days? Facebook’s strategy is simple
and elegant. Having done much
analysis and modelling on the effects
on reliability and uptime, Facebook
concluded that for them the most
cost effective solution to the few ‘hot’
days in Lulea is simply to allow the IT
kit get a bit warmer and on the very
hottest days evaporative cooling. On
the other hand, the major European
Telco I mentioned has been busy
de-installing all of its expensive to run
refrigeration plant and is installing
adiabatic (evaporative) CRAC-like
units in its data centres and telephone
exchanges to cope with the ten per
cent or less of days that are ‘warm’.
These units are far cheaper and less
space consuming than refrigeration
plant and consume only 10 per cent of
the power.
Key to the Free Fresh Air strategy
however is designing the whole system
so that this evaporative cooling only
kicks in on the hottest of days. As
a result, the overall cooling cost is
reduced phenomenally. That’s because
for around 95 per cent of days the
only ‘cost’ of cooling is that of running
electrically commutated (EC) fans to
blow and extract the correct volume
of Free Fresh Air through the data
centre or telephone exchange. In both
of these examples, the operators are
looking at true annualised PUEs less
than 1.1.
Not Free For All
There is no standard solution for cooling. Every application is unique.
16 NETCOMMS europe Volume V Issue 4 2015
We’re currently installing Free Fresh
Air cooling at 70 sites, and as more
data centre operators realise what is
actually possible and conduct their
own investigations we will doubtless
see significant movement to this
methodology throughout the top half
of the northern hemisphere and the
bottom half of the southern one. But
this solution isn’t suitable for every data
centre. Strangely, the thing that you’d
probably most expect to be a problem
with Fresh Air – relative humidity (RH)
- generally isn’t a problem. However,
RH combined with the wrong sort of
dust or p \