For a UPS system to perform as part
of an energy storage system and fulfil a
role within the National Grid’s STOR
programme it must be capable of using
Lithium-ion technology or some other
battery capable of frequent charge/
discharge cycles and there’s the rub.
Car manufacturers such as BMW, Tesla
and Toyota are harnessing Lithium-ion
technology for their electric vehicles, but
few UPS manufacturers have launched
Lithium-io n enabled back-up systems.
Yet, Lithium-ion provides several
advantages over traditional VRLA
batteries.
Firstly, this battery technology is better
suited to the rapid and frequent charge/
discharge cycles required for energy
storage. A downside is battery cost and
the complex charging system required to
optimise charging current and prevent
thermal runaway.
Lithium-ion batteries are more
compact than an equivalent Ah-rated
lead-acid battery set, with potential
footprint and volume reductions of
about 60 per cent. Weight may also be
reduced by a similar factor leading to
reduced physical space requirements
within a data centre or server rack.
Lithium-ion batteries are more
temperature tolerant than lead-acid
batteries. Lead-acid requires an
operating ambient of 20-25°C and for
every 10 per cent ambient temperature
increase above 30°C the design life can
halve. Lithium-ion batteries are less
susceptible to temperature variation.
This has implications on cooling within
data centres and where a UPS and its
battery can be installed; important as
the ASHRAE standard pushes up white
space operating temperatures, in a bid to
reduce cooling energy consumption.
Lithium-ion batteries may also be
more predictable in terms of working
life and less prone to erratic failure.
Working lives for Lithium-ion battery
sets of 10 years or more as standard
compare well to the 3-4 and 7-8 year
typical working life spans of 5-year and
10-year design life batteries making the
economic argument for Lithium-ion
batteries even stronger.
Conclusion
As with any UPS system and critical
power investment, one thing that clients
always consider is the Total Cost of
IT INFRASTRUCTURE
Image courtesy of
Yuasa Battery Sales
Ownership (TCO). Lithium-ion
batteries typically carry a 30-40 per cent
premium over lead-acid and their
capacity range, while increasing, still
limits them in terms of the kVA/kW
size of UPS in which they can be used.
This can be offset against the ‘extra’
life these batteries should provide over
lead-acid leading to fewer replacements.
Other potential cost benefits include
reduced cooling for a Lithium-ion
enabled UPS operating within a higher
ambient environment. Finally, in the not
too distant future, UPS with lithium-ion
batteries could be connected to the grid
and receive an annual connection fee
plus generation tariff based on usage.
Not only would this help to provide a
quicker payback. It would also help to
boost the capacity reserve on the grid.
SOFTWARE & SERVICES
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NETCOMMS europe Volume V Issue 6 2015 45