Identification model for cost-effective electricity savings on a mine cooling system

Abstract

South Africa has the world's largest reserve of platinum and gold. Despite this, the mining sector is struggling to stay economically viable. Increased costs in mining are one of the main contributors to the struggle of South African mines. Electricity is one of the fastest growing expenditures in the mining environment and there remains scope for electricity cost savings. Cooling systems are one of the larger electricity consumers on deep-level mines; often consuming 20% or more of the total electricity supply. These systems consist of numerous interconnected units. A need was identified to reduce the electricity costs of mine cooling systems without exceeding the cooling system constraints. Various strategies have been implemented to reduce the electricity cost of mine cooling systems. Improving the efficiency of cooling systems was identified as a desirable option for electricity cost savings on mine cooling systems. Reduced initial funding from Eskom has however limited ESCos to load shifting or bulk air cooler peak clipping projects. An integrated methodology was needed to identify scope for electricity cost savings on mine cooling systems due to the interconnected nature of these systems. Existing studies do not provide such a methodology. A decision diagram was developed to assist ESCos with the identification of possible electricity cost savings projects. The methodology was validated by testing it on a deep-level mine. An existing load shifting electricity cost saving initiative has already been implemented on the cooling system of the case study mine. The identification model was applied to this cooling system. The model showed that additional electricity cost savings could be achieved by incorporating a peak clipping initiative on the bulk air cooler. An average daily energy reduction of 14 000 kWh was achieved during summer and 6700 kWh during winter. This amounted to an electricity cost saving of R495 000 over a three-month period. Underground conditions remained within acceptable limits. Extrapolated over a year, an estimated annual saving of R2.1 million can be expected.