Electricity cost risks such as carbon tax, ECS and unavoidable tariff increases threaten the financial wellbeing of South African gold mines. Some of these proposed cost risks are however not enforced as yet. However, once approved, they could result in thousands of jobs being lost.The Eskom Integrated Demand Management (IDM) funding program for industrial projects has also been put on hold. With more than 97 large (367 MW total) projects already implemented on South African gold mines, these savings or projects were regarded as easier and with the largest savings. Therefore, new projects could be difficult to motivate due to longer payback periods of IDM funding being stopped.The aim of this study is therefore to investigate the total electricity cost risk reduction potential of one of the largest gold mining companies in South Africa. The electricity reduction potential will then be quantified in relation to the largest electricity consuming services and optimal production ratio.Benchmarking was used to provide the optimal point of production related to energy intensity. These results also provide electricity reduction targets for other South African gold mines.1.
Significant advances have been made in automation technology allowing systems to shift electricity consumption from peak periods to off-peak periods. Load shift projects have been implemented throughout South Africa for their electricity cost saving potential.This study shows how these load shift projects also reduce the carbon dioxide production at power stations by 91 kg/MWh shifted. This reduction is however not limited to load shift projects on the demand side, but also includes supply side load management. Technologies such as pumped storage schemes and carbon dioxide conversion to methane are identified as effective means of achieving supply side load management.A load shift project is shown to not only have an electricity cost saving but also an environmental cost saving. This emphasizes the need to continue implementing these projects as a method of reducing the environmental impact. Measurement and Verification (M&V) teams should therefore also report on this carbon dioxide reduction.
Compressed air supply and demand strategies have received significant attention since integrated demand management was initiated by Eskom. Due to the expensive nature of this vastly utilised energy carrier, every increase in the efficiency of a system is needed. Usually controlling the compressed air demand resulted in a reduced need for supply, ultimately leading to energy savings. The majority of compressed air optimisation projects on deep level mines in South Africa utilise demand side management initiatives to control or reduce compressed air usage. However, reduction in usage through control, leak repairs and reduced demand often results in system pressure build up. Compressed air supply must also then be reduced accordingly using capacity controllers. The existing capacity control is typically upgraded to reduce compressor output capacity automatically. The problem encountered is that not all compressor controls are created equal, and they produce different results in terms of efficient supply reduction. Inefficient compressor control is frequently encountered in industry today. On average, compressors operate at 16% below their maximum efficient point due to inefficient surge and capacity controllers. In contrast to this, intelligent compressor control resulted in compressors operating within 9% of their maximum efficiency point. In this case study, financial savings of R 3-million per annum could be realised.
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