LOAD MANAGEMENT AND ENERGY SAVING IN REFRIGERATION SYSTEMS ON DEEP MINES IN SOUTH AFRICA

Deep South African mines use extremely large refrigeration capacities with high power consumption to cool their workings. In particular Impala Platinum, which is the second largest platinum producer in the world, has an installed refrigeration capacity of 150 MW. In pursuit of energy savings and reduced 'carbon impacts', Impala have embarked on a novel energy management program which includes storing cooling at certain times of the day and releasing the stored cooling capacity at other strategic periods.The thermal storage concepts include: Thermal storage on ice banks Cold water mass storage in Squat dams with a novel bladder system to separate different temperature water masses Tall dams with stratification separating the different temperature water masses Shaft steel work and surrounding rock mass The control systems charge the thermal storage with large refrigeration machine load during the cold periods of the day at high coefficients of performance. Subsequent discharging of the cooling storage takes place during hot periods of the day with lowrefrigeration machine load. Thus, these control systems achieve overall-cycle efficiency as well as load shifting out of peak tariff periods. This paper describesthese systems at Impala with different thermal storage concepts some of which save up to 10 MWh per day.