Mechanical Technology June 2015

⎪ Sustainable energy and energy management ⎪

Having installed a 353 kW p 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. Solar installation reduces grid reliance by 40%

W ith 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 quirement of needing three comparative quotes, Rawlyn assisted in establishing an invitation-based request for proposals (RFP) to quote on the required 353 kW p 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. 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-

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.

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

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

Mechanical Technology — June 2015

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