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CONSTRUCTION WORLD
SEPTEMBER
2017
50
ALTERNATIVE POWER
Craig Bouwer, projects and product
manager at Zest WEG Group’s Generator
Sets Division spoke to Construction World
and explained why it is essential to ensure
that this alternative power solution is fit for
the purpose intended.
“While generator sets do not specifically
offer energy consumption reductions,
through careful selection of the major
components such as the engine and
alternator it is possible to reduce diesel
consumption and subsequently the
operating cost of these machines,”
Bouwer says.
Historically, commercial properties have
tended towards a single large generator set
which, according to Bouwer, is not always
ideal. He says that, while it is common
practice to install such a unit to supply the
necessary back up power in the event of a
power outage, there are numerous benefits
to be received by installing multiple smaller
synchronised generator sets in parallel.
Benefits
Firstly, it is more efficient to run smaller
generator sets at full load than one large
generator set at half load. This eliminates
the burning of unnecessary fuel as well as
possible damage to the generator set.
“Not only does this improve fuel economy,
it also reduces the capital outlay for a
commercial property, and most importantly
it will facilitate operational flexibility,”
he says.
This local manufacturer of generator sets
offers standard off-the-shelf units as well as
purpose engineered solutions, and Bouwer
is quick to point out that it is advantageous
for the company’s technical team to be
involved from early on in a project to allow
for the most practical and cost effective
solution to be applied.
Multiple smaller synchronised generators
sets with synchronised controllers
communicate with each other, allowing
optimisation of the load demand. System
reliability and generator set availability is
also improved when installing more than
one set in parallel onto a common bus. This
means that should the first generator set not
start, for any reason, the remaining units will
then provide the power required.
“Zest WEG Group Generator Sets Division
can assist contractors, consultants and
architects at the design stage of a project
to ensure the system can be engineered
to shed less critical load and supply all
essential load from the remaining available
generator sets,” he explains.
FIT-FOR-PURPOSE
power
solutions for commercial buildings
Generator sets have long been accepted in the built environment as a
reliable and constant means of power generation, either as the prime
source of power for continuous operation or as standby to the utility.
This mitigates against a total power outage
situation as would have been experienced if
the system was designed with only a single
large generator.
This type of power solution with
synchronised generator sets facilitates
operational flexibility and means that there
will always be an available unit to supply
critical loads in a breakdown or maintenance
scenario. In addition to this, when there is
more than one generator set operating in
parallel partially loading a generator set will
be avoided and the generator management
system will ensure that only the required
number of generators is operated under low
load scenarios ensuring the units run at their
optimum designed power rating.
When multiple synchronised generator
sets are installed, it is easy for the end user
to expand the backup power supply should
the on-site load increase as the controls and
parallel switchgear are already in place.
Optimising load demand
Chris Watkins, manager drives & automation
at Zest WEG Group, says that it is possible
to further optimise the load demand by
selecting the correct electric motor and
Variable Speed Drive (VSD) combination for
the application.
A large commercial building could have
anything from 40 to 100 electric motors
operating, for example, the HVAC system,
a fire system, a water treatment plant and
compressors for refrigeration. In such a
scenario, significant cost savings could be
achieved if the motor driven applications
are optimised by using top premium
efficiency motors and VSDs as starting/
control method instead of traditional direct
online starters.
“By doing this, it is possible to achieve
further operational savings and by using
VSDs it is also possible to reduce the size of
the generator set,” Watkins says. “Where this
is not done, in some instances the generator
The Zest WEG Group generator installation at the Promenade Shopping Centre in Mitchells Plain.