Mechanical Technology June 2015

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Mechanical Technology — June 2015 25
⎪ Sustainable energy and energy management ⎪
With the increasing costs
and decreasing reliability
of grid power, together
with a gradual decrease in
the cost of photovoltaic technology, self-
generated alternative energy is becoming
more common and viable as industries
seek a more profitable, sustainable busi-
ness model.
The voestalpine Isando facility manu-
factures railroad turnouts mounted on
sleepers for use to guide trains across
changing tracks. “Our design of an
optimum solar-powered solution for
voestalpine was based on an analysis
of the plant’s energy load profile prior
to the installation; the availability of
elevated north-facing roof space, which
was checked and to see if it was strong
enough to support the panel; as well as
an electronic solution that
would minimise or prohibit
the flow of power back into
the grid,” explains voestal-
pine’s energy consultant
Warwick Stark, director of
Rawlyn Consulting.
As per voestalpine’s re-
quirement of needing three
comparative quotes, Rawlyn
assisted in establishing an
invitation-based request for
proposals (RFP) to quote on the required
353 kWp solar photovoltaic plant, a plant
size determined by analysing voestal-
pine’s past annual average load profile.
Rawlyn then assisted voestalpine in the
evaluation of the proposals on a techni-
cal basis in order to determine the final
winning bid.
In order to further reduce the capi-
tal expenditure, Rawlyn assisted with
an application to the Department of
Trade and Industry for Manufacturing
Competitiveness Enhancement Pro­
gramme (MCEP) ‘green energy’ project
funding for 30% of the total cost of the
project.
De s i g n e d t o y i e l d a u s a b l e
483 412 kWh/year, the photovoltaic
installation will effect annual savings
of over R600 000 against an annual
electricity bill of R1 374 000 prior to
the installation.
Having installed a 353 kWp solar photovoltaic grid-tied installation at its Isando manufacturing plant, voestalpine
has offset its reliance on the national grid by 40%. The resulting savings to the plant’s operational costs will
repay the R7.3-million investment within nine years.
Above: The voestalpine Isando facility has 1 384
photovoltaic panels installed across the north-facing
roof spaces. The panels provide a low-maintenance
solution that will last 25 years.
Left: The panels form an array of strings that feed 20
high-quality SMA dc to ac inverters that effectively
handle the fluctuating electrical quality of the grid
power.
Solar installation reduces grid reliance by 40%
The 353 kW installation consists of
1 384 photovoltaic panels, each measur-
ing 1 640 x 990 mm, forming an array
of strings that feed into 20 dc to ac in-
verters, as well as associated ac cabling.
The project was contracted to
SUNCybernetics, the local partner of
SUNFarming. SUNCybernetics has
identified SMA Solar Technology as
its preferred inverter supplier, which
it believes produces the most reliable,
consistent interface with the fluctuating
quality of South Africa’s electrical grid.
The inverters also throttle the incoming
transfer of solar power according to the
needed load, preventing the electricity
from feeding back into the grid.
The voestalpine Isando facility will
also benefit from SUNCybernetics’ part-
nership with the North-West University’s
engineering department, through which
research on power quality and power
factor improvement analyses will
be conducted and performance and
savings reports presented to voestalpine.
An optimum cleaning regime will also
be devised, taking into account the en-
vironmental conditions endured by the
panel array.
The installation requires minimal
maintenance, and with the correct clean-
ing regime, PV panels are rated to last for
a period of 25 years, at which point their
production efficiency will have dropped to
80% of their performance rating.
SUNCybernetics also trains nomi-
nated plant personnel in the use and op-
eration of the photovoltaic system. “This
installation is in line with voestalpine’s
progressive approach to creating opera-
tional sustainability. We have previously
optimised the electricity consumption
at its Isando and Kimberley facilities
through the replacement of high bay
lighting systems with induction lamps,”
Stark concludes. q