Energy cost optimisation of a complex mine pumping system

Abstract

The purpose of this study was to do an energy cost optimisation on a specific complex mine pumping system by means of load shift. A Real-Time Energy Management System (REMS) was installed on the mine and the pumps were controlled according to certain constraints. The results that were obtained were very satisfactory. This project was undertaken on Elandsrand Mine and was a part of Eskom's Demand Side Management (DSM) initiative. Eskom fully finances these load shifting projects to encourage Energy Savings Companies (ESCOs) to undertake load shift projects in order to reduce the national peak demand profile. The project entailed doing a detailed investigation of the mine's pumping system. The pumping system was analysed and simulated according to specific constraints that were specified by the mine. After the simulation was completed, an optimisation on this simulation was done and the pumping system was fully automated to react to the changing electricity tariff. This automation led to a successful load-shifting project. Load shift means that the demand, during peak periods, is decreased. This is done by moving the energy requirement to another time of day when the demand and therefore the cost is less. However, the total energy used for the day remains the same. Load shift decreases the energy demand during the peak periods and at the same time generate savings for the relevant energy user. The average load shift that was obtained for the 5 months (June -November 2004) was 3.66 MW. This load shift has resulted in an average monthly cost saving for the mine of R60 000. This project showed that with the necessary historical data and expertise, a load shifting project, and therefore a cost optimisation project, can be successfully implemented on a mine's pumping system. This method can also be successfully applied to other electrical components on the mine