Electric vehicles and power distribution: considerations for underground mine operators

Mining relies on a wide range of heavy equipment, from assorted drills, haul trucks and load-haul-dump machines (LHDs) to lighter-duty equipment such as personnel carriers, logistics trucks, water trucks, boom trucks and graders.

While the introduction of battery electric vehicles (BEVs) in mining hasn’t changed what the equipment does, they’ve dramatically changed the infrastructure required to power and maintain it:

Diesel haul trucks and LHDs typically require:

• a maintenance garage
• fuel, oil and lube stations
• a wash bay

For the same equipment in battery-electric form, sites require:

• charging stations near where work is performed
• a maintenance garage with oil and lube stations
• a wash bay

At first glance, these requirements seem comparable, but in practice there are key differences:

1. To avoid efficiency losses, chargers must be near the work area to recharge between tasks. Otherwise, BEVs spend more time travelling, or charging, than producing. Smaller BEVs can travel farther with less support, but the range of a battery electric vehicle is less than an internal combustion engine.
2. Compared to fuel stations, more charging points are required for heavy BEVs, due to the charging cycle duration, battery capacity and other power constraints.

The mining industry has been moving away from traditional diesel power to electric power for decades. In the 1980s, trolley-assisted haulage trucks, such as Kiruna trucks, were already in use, and light rail systems may have used electric power even earlier. Today, equipment can be powered by trolley lines, tethers, batteries or hybrid systems.

Most major manufacturers still offer face drill rigs (a.k.a. mining jumbos) that rely on diesel engines for tramming, even though their electro-hydraulic drills require connection to an underground power distribution system for operation. Many of these manufacturers now offer fully electric jumbos that use batteries/electric motors for tramming and must be connected to the grid for drilling. Likewise, LHDs now come in diesel, battery-electric or tethered models.

Because underground mines have no built-in services, operators must create infrastructure for communications and electricity. Generally, power distribution starts with cables running from the surface substation down a ramp or shaft to the orebody. From there, the network branches out to meet the mine’s needs for reliability and redundancy.

Designing this system is complex. It must account for codes, standards, demand loads, voltage levels and other technical factors. Underground power distribution faces several constraints:

1. Cable ampacity (or capacity) is limited.
2. Higher voltage levels allow more power transmission within the same cable wire gauges but carries more safety risks and additional costs.
3. More power/voltage increases hazards such as arc flash, shock and electrocution.
4. Drifts (tunnels) have limited space to house cables safely and, with the increased demand, there may be more risk to personnel and equipment.

To determine power needs underground, a team would typically prepare a load list and load estimate, with accuracy depending on the level of study. This identifies both connected and demand loads, providing the basis for estimating overall power requirements. Power models and detailed studies then refine these estimates, ensuring the system is designed to meet operational needs.

Historically, a 10 MW feed was typically sufficient for underground operations. As more equipment transitions to electric power, demand has risen from 10 to 15 MW for small to medium mines and 15 to 20 MW for larger mines. When strategically viable, adding BEVs and/or other electric vehicles underground can push demand even higher by another 3 to 7 MW, depending on the charging philosophy (battery swapping vs on board quick charging).

BEVs introduce highly variable loads. Each unit can draw 120 to 500 kW depending on the size of charger and the time frame available for charging. The higher power peaks are associated with fast charging onboard the vehicle during mealtimes and breaks, where 12 to 14 LHDs, each drawing 500 kW, will yield an additional demand as high as 7 MW. Battery swap systems generally introduce less fluctuations and have a more constant demand. The fluctuations affect demand load, peak load, power quality, surface transformer size, switchgear size and feeder cable capacity.

Previously, a mine with a 10 W demand load may have had two 250 MCM or two 500 MCM cables installed to allow for 30 to 50% growth capacity. However, transient BEV loads, especially for onboard or fast-charging equipment that draw more power for a shorter period, can overwhelm these designs. A fully electric mine sometimes needs dedicated feeders, extra switchgear or more cables to support BEVs. To meet today's standard mine demand of ~10 to 15 W plus BEVs, three or even four 500 MCM 3-conductor cables, and possibly even more, are becoming more common. This trend increases capital costs, surface footprint and many other considerations.

With the right planning, BEVs can offer underground mine operators more than decarbonization: quieter operations, lower ventilation costs and improved worker health and safety (reduced risk of MSD, hearing damage and respiratory damage). The result is a more resilient, competitive mine ready for the next generation of production.

As underground mines move toward electrification, power requirements can no longer be treated as an afterthought or assumed in early estimations. From preliminary economic assessments through to detailed engineering, operators must account for the true cost of electrification and identify where BEVs, and other electric vehicles, are both feasible and beneficial.

Tools such as load lists, scheduling strategies and comprehensive power studies provide operators the clarity needed to define requirements and develop practical solutions. By integrating these analyses from the outset, they can make informed decisions that balance innovation with reliability and cost efficiency.