Demand side management opportunities for a typical South African cement plant

Abstract

The South African electrical system is under threat of supply shortage. This is because, in the last decade, the maximum electrical demand has been encroaching on the net maximum capacity and the reserve storage margin has become smaller. Eskom, the country's electricity utility, has implemented a demand side management (DSM) programme in an attempt to alleviate the threat. Investigations into demand side reductions have been encouraged by the utility in sectors with high electricity consumption, such as the cement industry. As part of the non-metallic minerals sector, it is responsible for 5% of the electrical consumption for the mining and industrial division of the country. It has also been estimated that by 2020 the sector will be ranked as fifth for energy savings potential. Therefore, there may be opportunities to reduce the power demand of cement plants thus assisting Eskom in reducing the country's electrical consumption. This can be done by implementing DSM programmes, such as energy efficiency and load management. This dissertation investigates the global opportunities for energy efficiency in cement plants and determines their feasibility for the South African cement industry. It also investigates the potential of a load-shifting scheme to reduce evening peak loads and save electrical costs. To evaluate DSM potential for an undisclosed South African cement plant, historical data on electrical consumption was used in a simulation programme which the author wrote. This was done to determine a possible load-shifting scheme which could be implemented to save costs and reduce peak-period demand. A pilot study was performed to evaluate how shifting the load of raw and cement mills would affect the production and electrical costs of the plant. Results showed that, although in theory there is good opportunity for cost savings, it is highly dependent on the reliability of the mills and the change in production demand. Therefore, load-shifting schemes have to be highly adaptable on a daily basis to shift load when possible.