Research and implementation of a load reduction system for a mine refrigeration system
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In this study, a system was developed to shift electrical load out of Eskom's peak period to the OR-peak periods. This system was designed, based on research done for load shift philosophies of a refrigeration system of a mine. The investigation focussed on the mining industry, for it consumes a large percentage of the electrical energy generated in South Africa. The research results ensured a successful implementation of a Demand Side Management (DSM) program on the ventilation and cooling (VC) system of a mine, where large energy savings arc possible. Load management is required because a prediction, based on a study done by Eskom, shows that the electrical load demand may exceed South Africa's installed capacity, by as early as the beginning of 2007. To counter this phenomenon, a DSM program was then initiated by Eskom to decrease the load demand in South Africa, via load shifting. New cooling plant controllers for the refrigeration system, which run in concurrence with the control philosophy of the entire mining system, are designed to ensure positive load shift results. These intermediate controllers operate within specified constraints for the refrigeration system. A simulation and optimised model was first created to test the controllers, and to verify whether the achieved results adhered to the safety regulations. After the model was finalised, the new controller system (consisting of these controllers) was implemented at a specific mine's cooling system. The installation of the new system's controllers and control philosophy, resulted in a successful load shift execution during the Eskom evening peak period. Additional to the load shift results, energy efficiency was also obtained through this implementation on the refrigeration system. The success of the research can be determined by the actual energy savings achieved, compared to the predicted savings. The annual estimated load shift averaged around of' 2.9 MW, with 3.5 MW during the nine summer months and 1.9 MW during the three winter months. The actual results, however, show an over delivered load shift of 3.6 iv/W during three summer months, and 3.1 MW during the first two winter months, at Kopanang Mine. Consequently, a monthly energy cost saving of around R 46 000 for the summer months and R 2 17 000 for the winter months was achieved. These results indicated a projected annual saving of over R 1.4 million for Kopanang Mine. These research results prove that DSM can be implemented on a mine's refrigeration system. Furthermore, the successful approach should by this research can be applied on the cooling systems of other mines. Should this be done, a large contribution can be made concerning better financial savings, and more efficient power consumption of South African mines.
- Engineering