Page 58 - European Energy Innovation - Spring 2016 publication
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58  Spring 2016 European Energy Innovation


The main types of free cooling for data centres are:                                  Operational Intelligence are
                                                                                      data centre specialists who work
Direct Air Side    Supply outdoor air into data hall, mixing, humidifying             collaboratively with operators to
                   when required.                                                     optimise their data centre reliability
                                                                                      and energy performance through
Indirect Air Side  Outdoor air used to cool data hall air via an air / air plate      consulting and education
                   heat exchanger. Allows more free cooling, particularly   
                   when hot but dry (adiabatic, evaporative cooling)

Water Side         Chilled water supplied to data hall cooling units uses
                   outdoor conditions for cooling rather than refrigeration,
                   e.g. via dry coolers or cooling towers.

widened in recent years. ASHRAE           not only for the mechanical plant
TC 9.9 (American Society of Heating,      but also the reduced electrical plant
Refrigeration & Air Conditioning          needed to support it.
Engineers Technical Committee
9.9 on Mission Critical Facilities        Of these, indirect air-side free cooling have       offers the best performance in most
worked with IT hardware vendors           cases. Direct air-side free cooling
to expand the recommended and             may use slightly less energy in cooler
allowable environmental ranges so         climates but there are risks associated
that data centre cooling systems can      with supplying air directly into the
run at warmer temperatures and            data hall. In addition, sometimes
capitalise on reduced refrigeration /     these systems are installed with a
increased free cooling operation.         refrigeration system for back-up,
                                          which has associated capital and
The upper temperature limit of the        maintenance cost implications, even
recommended range is 27C, however         if it does not run often. Water side
it is also possible to deviate from this  free cooling solutions have more heat
range, on occasion, into the allowable    exchange processes and therefore
ranges A1-A4 (A1 upper limit 32C,         offer fewer free cooling hours,
A2 upper limit 35C). With these           however they may be the preferred
requirements it is possible to design     choice for a retrofit solution where it is
and operate cooling systems without       difficult to move large volumes of air
refrigeration (i.e. 100% free cooling     adjacent to the data hall.
/ economizer) in most of the world,
particularly in European climates.        In all cases it is important to properly
This allows a significant operating       define the design brief and analyse
cost saving from reduced energy           the requirements so that technology
consumption; the facility’s overhead      is properly applied, rather than
factor, described by the industry as      purely looking for a product solution.
PUE (power usage effectiveness),          Frequently, energy efficient products
reduces from 100% of the IT load to       are purchased and installed but not
below 20%. There is also a reduction      properly understood or commissioned
in maintenance cost and capital cost,     and hence underperform once live. l

The European Code of Conduct for Data Centre Efficiency is a voluntary initiative launched by the JRC which publically
shares guidelines for energy efficiency best practice, including those described in this article.

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