REDUCING ENERGY CONSUMPTION OF MINE COOLING SYSTEMS BY CONTROLLING CHILLED WATER DEMAND OF MOBILE COOLING UNITS

Energy costs are increasing rapidly. Energy efficiency strategies are required to reduce electricity consumption for energy intensive operations. Cooling systems of deep level mines consume approximately 25% of their total electricity consumption. Cold water supplied by these systems is reticulated throughout the mine. Water reticulation can account for a further 42% of the total electricity consumption of a typical deep level mine. Underground working areas in deep level mines must be cooled to account for temperatures of up to 60 degrees C. Mobile cooling units are often used to cool underground working areas. These units require significant amounts of chilled water. Adequate supply of chilled water to these units is crucial to comply with health and safety regulations. It is often found that the water supply to mobile cooling units is not properly managed. Energy savings can be achieved on the cooling systems as well as the reticulation systems by reducing the water consumption of mobile cooling units. Various valves were identified as possible equipment to be used to manage water consumption on mobile cooling units. A case study proved that flow reductions on the mobile cooling units are possible. Worker safety and mine production was not affected by the installations. Electrical energy savings were achieved through reduced pumping and reduction in refrigeration energy consumption. Water consumption for one mobile cooling unit was reduced by 237 kl/day. This is equivalent to an average saving of 37.5 kW per unit. This saving includes the reduced power consumption on the chillers and pumps. Installing the valve on 26 MCUs would potentially result in a total saving of approximately 1 MW, an annual saving of R 2.8 million.