54
GREEN DATA CENTRES
Improving
sustainability
By Alan Luscombe, Director,
Uninterruptible Power Supplies
www.upspower.co.uk
UPS systems can make a valuable
contribution to overall efficiency
Data centre operators are under steady pressure to run
a facility with visibly green attributes. Not only does
this become increasingly important as electricity prices
inexorably rise, but it also improves a data centre’s carbon
footprint in line with corporate responsibility endeavours.
This contributes to an amenable working environment and
enhanced relationships with local communities, while at the
same time meeting legislative pressures and incentives to
create and maintain ecologically responsible businesses.
Many large undertakings qualify for participation in the
Energy Savings Opportunities Scheme (ESOS) – an energy
assessment and saving scheme run by the Environment
Agency. Organisations that meet these definitions must
carry out an ESOS assessment covering all their energy use,
unless they have an up to date and comprehensive ISO
50001 energy management system that’s certified by an
accredited certification body.
ESOS compliant energy audits must identify energy
saving opportunities, although these should be reasonably
practical and cost-effective to implement. Participants
will probably wish to implement any such opportunities,
provided the money saved by reduced energy use exceeds
the cost of implementation. However, there is no regulatory
requirement to do so.
Any participant comprising or including a data centre,
will almost inevitably contain a power protection system
complete with an uninterruptible power supply (UPS). This
can offer opportunities for energy savings depending on the
type of UPS installed, and how it’s being used. Ideally the
on-site installation utilises a modern modular design that
can deliver great power efficiency, as well as other benefits
including high availability and scalability. However, in reality
many sites have older legacy systems and these are where
the energy reduction opportunities can mainly be found.
Transformerless technology vs legacy installations
Energy savings arise firstly from a move to modern
transformerless technology made possible by advances in
power semiconductor technology, and the advent of Insulated
Gate Bipolar Transistor (IGBT) devices. The technology is more
efficient than the earlier, transformer-based designs with an
overall improvement in efficiency across the load spectrum of
around 5%. This yields substantial reductions in heat losses
and energy running costs.
Transformerless systems also bring the input power
factor closer to unity with less load dependence. Input
current magnitude is decreased, with associated reductions
in switchgear and cable sizing. In some cases, electricity
costs are also reduced. Legacy systems are often operated
below their optimum efficiency because they’re not easily
scalable. This lack of scalability means that until recently
many systems were significantly oversized to allow for the
prevailing load and any expected future growth. The graph
in Fig. 1 demonstrates this by showing an expected load
profile that starts at 35% of the data centre capacity, with a
projected growth to 90% of capacity over 10 years.
The same graph also reveals that a UPS sized for 100%
data centre capacity was installed, yet in reality the load
only ever reached 35%. Accordingly, the UPS remained
significantly underloaded, which seriously impacted its
efficiency over its lifespan. A legacy UPS has a maximum
efficiency of about 93% when fully-loaded, dropping to
about 90% at 50% loading, and even less at the levels
shown in the graph.
www.networkseuropemagazine.com