Energy optimization for mine cooling systems through flow control

Abstract

The mining sector in South Africa accounted for 14.3% of all electricity supplied by Eskom in 2016. Up to 25% of this energy was consumed by mine cooling systems, suggesting that more focus should be placed on the energy consumption of cooling systems. Notwithstanding previous significant reductions obtained through energy efficiency in mine cooling systems, it was found that the current initiatives were not necessarily optimised to achieve their full potential. Through a review, several variable-flow energy-saving strategies were identified in the literature with the objective of ultimate integrated optimisation. In this semi-empirical investigation, an integrated simulation model was developed to fully quantify the overall cooling system’s integrated energy consumption. This model was subsequently coupled to a commercial optimisation platform to arrive at a globally optimised system. The novelty of the current study lies in the development of a mathematically optimised mine cooling system which is not currently found in the literature. The optimisation-friendly simulation model was constructed and verified through suitable component models and a component-based calibration process as a case study. For these verifications, modelling accuracies with root mean square of relative error (RMSRE) values between 0.0114 and 0.0651 were obtained. The components were subsequently coupled to form the integrated cooling system simulation model that was validated through a baseline simulation conducted on various isolated weekly datasets to confirm its integrity for simulation during and outside of the system calibration period. For these validations, RMSRE values in the range of 0.0362 to 0.0704 were obtained with average absolute error values between 2.44% and 4.61%. The baseline simulation validation was concluded with an hourly annual simulation that obtained an RMSRE value of 0.860 with an average absolute error of 6.22%. During the case study, it was found that the use of an integrated optimised mine cooling system has the potential to reduce the total average annual energy consumption by roughly 18%. This translates to an annual energy saving of more than 7.1 GWh for the particular mine. Because the majority of underground mines in South Africa utilise similar cooling systems, the adoption of integrated mine cooling optimisation systems could result in significant reductions of energy consumption in this sector.