Optimising deep-level mine refrigeration control for sustainable cost savings

Common problems faced when considering the implementation of load management initiatives on gold mine refrigeration systems are the implementation costs and time. Expensive infrastructure upgrades are often also the norm in the industry when considering the implementation of load management. In addition to these challenges, the old Eskom Demand Side Management (DSM) model often resulted in rapid deterioration of cost savings after the ESCo's contractual obligation expired. A new DSM model was introduced to rectify this. This study addresses the challenges of implementation constraints and the sustainability of cost savings for load management initiatives on refrigeration systems under the new DSM model. Through optimised control strategy modelling, load management initiatives were implemented on two South African gold mines with limited capital expenditure. This allowed for a quick, low-cost implementation which resulted in sustainable cost savings. The average evening load shift on the two respective mines during summer months resulted in 7.28 MW and 2.00 MW over a period of eight months. This accumulates to an annual cost saving of R 1.76 million and R 215 000 for the two mines, calculated with the 2016/2017 Eskom tariffs. The simulation models predicted the results with an average error of less than 2%. The sustainability of cost savings through optimised control on deep-level gold mine refrigeration systems thus become evident.