| dc.description.abstract | South Africa is experiencing severe electricity supply shortages, leading to rolling blackouts and soaring electricity prices. In response, demand-side management (DSM) measures are crucial to ensure grid stability and to alleviate electricity costs. Alongside load shedding, mandatory load curtailment by key consumers is being enforced during critical periods to alleviate the strain on electricity supply. As a result, mining operations have been significantly impacted by the enforced load curtailment measures.
Mine dewatering systems have long been considered suitable for DSM measures, with load shift away from peak time-of-use easily implemented due to the built-in water storage capacity in the systems. Additionally, pumping systems have been halted for prolonged periods as part of load reduction strategies for Eskom's load curtailment, intensifying the strain on mine dewatering systems. It is, therefore, challenging to find a balance between load reduction, meeting dewatering requirements, and maintaining load shift.
A lack of information regarding the cost of load curtailment on mine dewatering systems presents a significant challenge in devising clear strategies for load reduction and comparing alternative load reduction approaches. Currently, there is no existing model that relates the incidence and duration of load curtailment events to the electricity cost of mine dewatering operations, necessitating an in-depth investigation.
This study aims to quantify the cost of load curtailment on the mine dewatering systems. A method was developed to assess the cost implications under various load curtailment scenarios at mine dewatering systems, involving the creation of a digital twin simulation model of the dewatering system.
The method was implemented at a case-study mine shaft A, located at mining operation 1. The simulation was adjusted iteratively to examine the relationship between load curtailment duration and pumping electricity cost, DSM performance, and meeting dewatering requirements over a 30-day test period.
The case study simulation results revealed that pumps can be stopped for up to 135 hours a month while still meeting dewatering requirements. The cost of electricity for pumping increases with each additional instance of curtailment, totalling R5.52 million in winter and R990 thousand in summer for 135 hours of load curtailment, based on 2023/24 tariffs. Peak pumping is necessary after 32 hours of pump stoppages, and load shift performance declines after that. Nevertheless, the evening load shift project performance remains above the 6.7 MW target, as curtailment often aligns with evening peak periods.
Initiating diesel generators for load reduction costs around R80 000 per hour, totalling R11.4 million over 135 hours. Pump stoppage costs start low but peak at R90 000 per hour after 127 hours in winter. Therefore, it appears that pump stoppages represent a viable load reduction strategy at shaft A for up to 123 hours per month in winter and 135 hours in summer.
The developed method proved effective in determining the cost of load curtailment on mine dewatering systems for any given shaft. The findings of this study will help mining industries to devise more informed strategies for managing load curtailment while ensuring the efficient and cost-effective operation of their dewatering systems. | en_US |
