Electrification is one of the enablers to achieve future net-zero targets. With current battery technology, as close-to-surface deposits are depleted, the need for metals and rare earths is pushing underground mines deeper into the Earth’s crust.

Underground mines have traditionally relied on diesel-powered load-haul-dump (LHD) machines in their loading and hauling operations. These machines are powered by internal combustion engines (ICEs) that emit exhaust gases, diesel particulate matter (DPM), and heat. Battery powered LHDs have been used in underground mining since the early 2010s, with Canada the earliest adopter of this technology. Battery electric vehicles (BEVs) use electric engines that enable higher energy efficiency than ICEs and do not produce exhaust. Therefore, they have the potential to facilitate cleaner air and reduce ventilation demand, thus reducing costs.

This research investigated and analysed how the implementation of battery electric (BE) LHD machines affects current underground mine loading and hauling practices and operations. When BEVs are used instead of diesel LHDs, they bring with them additional aspects that are crucial to explore, such as the perception of the personnel and how BEV LHDs differ from a productivity perspective, specifically when using battery swapping. Furthermore, when changing the machine type from diesel to BEVs, it is important to know what differences this will make to the required ventilation and air conditioning demands, as these have traditionally been established based on the number of diesel machines in the underground mine and their engine power.

This research was initiated by exploring the points of view and perspectives of underground mining personnel and management and analysing how these perspectives differed. Then, productivity and operational studies were conducted using two case study mines: a block cave mine and a sublevel caving (SLC) mine. The research investigated alternative configurations of LHDs for optimised productivity and identified queues and the required number of extra batteries for BEV operations using discrete event simulation (DES). Subsequently, field measurements were conducted in the case study SLC mine to quantify the potential reduction in the ventilation requirements, as ventilation-related energy consumption can result in half of the mine operation’s energy use. Finally, diesel, electric, and BEV LHDs were compared based on machine specifications.

The results suggest that independent of their experience with BEVs, the management chose the same three primary reasons to use BEVs: they wanted to make the working environment healthier, reduce carbon emissions, and reduce air conditioning and ventilation-related costs. The main reasons why mines were not considering BEVs in their future operations were related to their high price and being unproven. Independent of their experience of working with BEVs, the underground mine personnel liked them because of their quietness, spacious cabins or modernity, and absence of exhaust fumes; however, they shared concerns specifically related to safety and fire risk aspects.

According to the DES simulation results, BEV LHDs can achieve, on average, 8.9-12.1% higher productivity with a loop hauling strategy than with direct hauling in an equivalent gear. Additionally, the BEV LHDs achieved, on average, 6.5-10.3% higher productivity than diesel LHDs in equivalent scenarios. In terms of queueing, when there were enough batteries in the system, the BEV LHD queueing did not accumulate when there was a maximum of 12 LHDs with four charging stations and a maximum battery swap of one hour because “working groups” were formed. Eight BEV LHDs using from 16 to 20 batteries (2-2.5 batteries/LHD) reached minimal queueing. Field measurement results showed the potential to reduce airflow by at least 70-77% in the studied area of the case study SLC mine. Finally, a comparison of power types showed no significant differences between them in terms of maximum (rimpull) force, standard bucket size, breakout force (tilt and lift), operational (empty) weight, and tramming capacity.