design & facilities management
Of course, with greater
computing power comes higher
energy consumption. But the
computers themselves are not the
only technology to consume more
electrical power. It is also used to run
the equipment designed to dissipate
the increased heat generated by
more sophisticated computers –
namely, condensers, air handling units
(AHUs), cooling towers, and so on.
Indeed, one of the biggest energy
users in a data centre is not the
computing technology itself, but the
means of keeping this equipment
cool, which is essential to prevent
downtime and ensure data centres
run at their optimum.
Furthermore, because cooling
equipment is required to work harder
as computers become ever more
sophisticated, the risk of breakdown
(and, therefore costly downtime) is
that much greater. This is what makes
maintenance so important.
A measure of success
A useful measure of the energy efficiency of
a data centre is power usage effectiveness
(PUE). This is the ratio of total amount of
energy used by the data centre to the energy
delivered to computing equipment.
Heating, ventilation and air conditioning
(HVAC) can be responsible for up to 45 per
cent of the energy cost of a data centre and
three per cent of the UK’s total electrical
energy usage is thought to be attributable to
data centres.
Improving PUE focuses largely on the
supporting cooling system. Cooling towers
and air handling units draw in air from the
outside that is potentially full of dust, leaves
and pollen, all of which can clog system filters.
Keeping filters clean and in good working
order is a simple maintenance step that can
offer big fuel bill savings and reduce the
potential for equipment breakdown.
Air intake screens stop airborne debris
from entering a system in the first place,
to ensure cooling is kept constant, risk of
breakdown is reduced and maintenance
requirements are cut. This can be achieved
by external, pre-filtration media. It is a solution
that can be applied at the specification stage,
or retrospectively, to improve the operational
efficiency of existing cooling equipment.
Working with AMEY, ECEX conducted a
controlled, long term field trial to accurately
measure the energy saving benefits of
using air intake screens. At Westminster
City, AHUs were monitored initially without
air intake screens and then with, and
revealed a 4.9 per cent reduction in power
consumed and a significant reduction in
maintenance requirements.
Maintenance
The cost of a sound Planned Preventive
Maintenance (PPM) programme is
ridiculously low compared with the
cost of unplanned downtime caused,
for example, by having to deal with
a catastrophic AHU breakdown or
condenser failure (which can lead on
to failure of the data centre itself).
As well as preventing such
disasters, effective maintenance
also makes a significant contribution
to the bottom line by ensuring that
plant is energy efficient and therefore
produces lower power bills and higher
environmental performance.
But, the most compelling
argument in favour of a properly
implemented maintenance strategy is
that it guarantees reliability. And just
about every indicator in a business –
safety, environmental performance,
morale, retention, customer service –
improves if you establish reliability as
a core value of your organisation.
Broadly, maintenance is a five
step cycle:
1. Determine where you are now
with an audit.
2. Decide where you want to get to
by setting performance targets.
3. Plan how to get there.
4. Implement the plan.
5. Continuous improvement demands
that you return to step 1.
Unfortunately, there is often a
crushing sense of complacency
over the way asset care is planned
and organised.
The good news is that there is
much that can be done to improve
how a data centre cooling system
operates through simple maintenance
steps. For example, there is
technology to tackle high volumes
of pollen and falling leaves, which
can increase the strain on chillers,
in particular, by clogging filters and
restricting airflow.
As well as reducing the possibility
of cooling equipment failure, this
also has an enormous impact on
energy efficiency. A study in the
US by Johnson Controls’ Institute
of Building Efficiency, for example,
found that when condenser flow
rates are reduced by 20 per cent in
mechanical and absorption chillers
full load energy consumption is
increased by three per c ent.
The message is clear – investigate
every opportunity to reduce the
burden in cooling equipment.
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