Cost-benefit to the cement industry by shifting evening load to off-peak periods

Cement manufacturing is an energy-intensive processwhereelectricity costs account for up to 15% of the total manufacturing costs. The increasing electricity tariffs in South Africamake it imperative for cement producers to implement or become involved in DSM initiatives in order to remain competitive. In this paper, a case study of a load shifting project that was implemented at a typical South African cement plant is presented. The focus is on an energy management system that schedules the operation of the mills to shift load from peak to off-peak periods. The operating schedules are calculated on the basis of a simulation that minimises the operating costs of the mills, based on Eskom's variable cost, time-of-use tariffstructure. The simulation takes into consideration various factors, such as scheduled maintenance, equipment reliability and silo storage capacities, to provide accurate operating schedules that maximise load shift potential without adversely affecting production targets. The simulation also predicts thelevels of the various silos, which is invaluable information for production planning. The results of the implementation of the load shift project, obtained over a period of three months, is provided as confirmation of the considerable cost-benefits that can be achieved by shifting evening load of the mills to off-peak periods.