Operationalizing Battery-electric Vehicles
There’s more to a successful BEV implementation than meets the eye.
By Carly Leonida, European Editor
At a Sandvik customer event held in Tampere, Finland in October 2022, Jeff LaMarsh, superintendent at the New Afton copper-gold mine in British Columbia, spoke to the audience about New Gold’s experience so far with BEV technology. The company has been working with Sandvik and other manufacturers since 2019 to introduce various pieces of battery-electric equipment; the latest addition were two Z50 Sandvik-Artisan mine trucks in mid-2022.
“We took delivery of our first BEV — an auxiliary piece of equipment — in 2019,” he told the crowd. “Since then, we’ve had eight BEVs on site, seven of which are unique, and some of which are vendor or acceptance trials.”
Because BEVs are relatively new in underground mining, there are still questions surrounding off-gassing from batteries and the risk of fire. Training for emergency responders and developing emergency procedures are a particular concern so that, should an incident occur, it can be dealt with quickly and safely. LaMarsh said it’s important that mines work together with OEMs to develop a project management plan, so that teams can make educated decisions on the fly where necessary.
“When it comes to engineering, we’ve trialed different designs for service bays and charging bays,” he said. “With charge bays, it’s critical to look at site conditions. For instance, is it on flat ground? Is the charge bay itself coming off a ramp? It’s important that the equipment approaches the charge bay level so that when it drops the battery, the battery stays on the same plane as the scoop, and it can be picked up again. Often batteries will creep or get tilted. When you’re doing three or four battery swaps a shift, positioning makes a big difference to the utilization of the equipment.”
New Afton has implemented fixed battery stands to help solve this problem. LaMarsh added that cable management in the charge bay also needs consideration as this can impact charge times, operator fatigue, and availability of the chargers and batteries themselves.
Another challenge is planning for the battery range. LaMarsh said that diesel equipment at New Afton has gas tanks that can usually last 1-2 shifts before refilling, but the battery equipment requires 2-3 battery swaps a day (the equivalent to 2-3 tanks of gas), so the location of charging bays has proven really important. “Typically, chargers should be as low in the mine as possible and/or close to the working area, and make them bigger than anticipated,” he explained. “Operators also need reliable information so that they can utilize the full range of power in each battery. If operators are too conservative and choose to swap out their batteries, say 30 minutes early, then that decreases the productivity benefits associated with BEVs.”
LaMarsh noted that, calculating BEV utilization and availability numbers is also more complex than with diesel units. Diesel equipment utilization is generally measured on engine hours whereas, with BEVs, some manufacturers measure utilization based on power pack hours or tram motor hours.
Another aspect is the maintenance strategy for both equipment and batteries; the batteries will need to be transported to and from the workshop for planned services. “We’re installing a dedicated battery service bay in the same vicinity as our charge bays to minimize any utilization loss associated with transport,” LaMarsh said.
“Moving into equipment performance, our operators like that the [BEV] trucks and scoops have more power than their diesel equivalents. Workforce acceptance is a big concern with new technology, and we’ve seen success through involving a couple of our best performing operators as well as a trainer and a maintenance person. They’re acting as the champions and spreading the word. And because they’re so positive, it resonates with the rest of the team. Our operators see BEVs as a big step forward and are starting to prefer them.”
Energy and Power
Owing to its nascent nature, few mines have the know-how yet to implement and manage BEVs effectively, and the first adopters are therefore leaning heavily on OEMs to bridge that gap. Epiroc recently created a curriculum for Collège Boréal in Sudbury, Canada, to help foster these skills and encourage new talent into the mining sector.
Trent Sears Global Product and Marketing Manager - Electrification - Chargers at Epiroc explained: “At the moment, there isn’t a steady pipeline of talent in mining when it comes to specialty roles in electrification. OEMs are at forefront of developing training packages and are working hard to bring customers up to speed, from the tender process to putting machines into production. Franck Boudreault, Underground Application Expert, Electrification, at Epiroc, added: “Mining companies have a lot of questions about the safety risks associated with having batteries underground. We’ve done a lot of homework, including burning some of our own battery components in a controlled lab environment to understand the heat and gases generated, and how long it takes before thermal runaway occurs. We did this in collaboration with the Research Institute of Sweden and a number of mining houses. All mines have to do their own risk assessments before bringing new technology underground, but we found that having this information helped to address any concerns.”
Sears said: “A fully electrified fleet can run from 8-10 megawatts worth of power demand, and power demand isn’t consistent during shifts. We recommend at least 30%-50% of additional charging capacity is installed to accommodate demand during peak periods. Installing an extra 8-10 MW of capacity on top of say, 25 MW of current capacity, puts a lot of pressure on mine energy infrastructure and can create challenges in energy availability. If the local grid can’t accommodate that then it’s worth looking at concepts like islanding and also energy storage.”
Boudreault explained: “With greenfield projects, there may be a chance to reduce ventilation power requirements which gives some extra power allowance for charging vehicle batteries. “However, switching to BEVs doesn’t necessarily entail infrastructure changes. We’ve received a lot of orders for battery- electric drill rigs. As drill rigs spend more time drilling than tramming, they are well suited to onboard charging without any impact on their performance. With no need for infrastructure, battery-electric drill rigs are, for many, a good entry level for the EV transition and in getting acquainted with batteries in mining applications.”
Battery ranges vary depending upon the type of vehicle they’re installed on and the duty cycle, taking into account tramming distances, ramp inclination etc. For drill rigs, battery autonomy is less of a concern than for loaders or trucks; Boudreault estimates that a typical drill rig would be able to travel approximately 6.5 km on a ramp or 900 vertical meters on a full charge, but that would very seldom happen in an underground mine. In comparison, a 14-metric-ton (mt) loader will typically provide around four hours of autonomy on a full charge.
Epiroc has opted for a different battery chemistry to most other OEMs — it has chosen nickel-manganese-cobalt (NMC) over lithium-ion thanks to its scalable nature. Boudreault said that the behavior of the battery is also very predictable and linear even as the size increases which equals greater safety. “We selected very small cells so that, if an event does occur at a cellular level and a small amount of energy is released, then there’s less risk of propagation than with larger cells,” Boudreault explained. “As of today, we have no operational fires to report. NMC also offers very high energy density — almost twice that of other chemistries — which allows battery size and weight to be kept to a minimum. And we will continue to increase the energy density. Eventually, we’ll reach the point where a loader can go a full shift with just a little bit of trickle charge during the break and then battery swaps won’t be required mid-shift. But there are a few things that need to be addressed before that can happen.”
In April 2022, Epiroc also signed a memorandum of understanding with Blu- Vein, a joint venture between Australian mining innovator Olitek and Swedish electric highways developer, Evias. The aim is to fast-track development of the BluVein1 underground dynamic charging solution for BEVs. The system consists of a rail with conductors that is fixed to the roof of the main decline. As electric vehicles descend, they use regenerative charging to replenish their batteries. When it’s time to ascend, the vehicle automatically connects to the slotted rail, accelerates to full speed using power drawn from the rail, and additional power is used to top up the battery. Epiroc is supplying an MT42 electric-drive truck for testing with the aim of having a commercially viable system by 2024-2025.
One of the major technical challenges linked to electric vehicles is thermal management of the battery. Proper cooling limits the likelihood of thermal runaway and fires. TotalEnergies is developing new fluids to address this.
David Kupiec, Head of Performance Fluids for EV transmissions and industrial applications, explained: “Efficient cooling increases the reliability of the battery and extends its life; for every 10°C increase in temperature, the battery life is cut by half. This particularly important in mining infrastructures where, in the future, mines will have to store expensive batteries as spare parts. Proper cooling also helps to reduce equipment downtime through faster charging. A more compact cooling system also reduces the size and total cost of ownership of the battery pack.”
Current cooling technologies use standard water-glycol coolants and, because water is conductive, they cannot come into direct contact with the battery. Cooling is achieved indirectly through heat exchangers, and as a consequence, the process is not as efficient as it could be. TotalEnergies has developed an innovative range of dielectric fluids called Quartz EV in which any type of battery can be fully immersed to allow optimal cooling.
“With this technology, we’ve been able to demonstrate much better fire-risk management,” Kupiec told E&MJ. “During testing, we stressed batteries in many different ways and showed that thermal runaway does not propagate in the way that it does with standard cooling technologies. It also decreased the length of charge times by up to four times and lowered the total cost of ownership and weight of the battery pack.”
TotalEnergies has also created a sub range of products — Rubia EV — specifically for mining applications. “The vast majority of underground electric vehicles use standard water-based cooling technologies,” said Kupiec. “But with the development of dedicated BEV fluids, we feel there is now room to start trials in underground mines and we are initiating discussions with partners for this. We are also investing to accommodate testing of electrical equipment, such as gears, motors, batteries etc. alongside our standard combustion engine testing.”
Adjusting Mine Design,
Planning and Scheduling
There is a common misconception that electrification changes everything but, diesel and battery-electric trucks or loaders are essentially the same piece of equipment with the same functionality; their main differences lie in their energy requirements, performance and maintenance. For greenfield operations, there’s the chance to design the mine layout and planning over different time horizons to best suit the needs and capabilities of BEVs.
Steven Donaldson, Partner and Cofounder of Australian industrial mathematics specialist, Polymathian (which is in the process of being acquired by Sandvik), explained: “With greenfield projects, engineers can optimize the design and layout to accommodate the different operating methodology that BEVs require. The same applies for brownfield projects, although there is usually less flexibility.
Colin Eustace, Head of Simulation at Polymathian, added: “There are potentially scheduling challenges when the life of a battery is similar to or shorter than the cycle time for a certain piece of equipment. For example, if a haul is quite long, there may not be enough charge in the truck battery to complete the cycle. Scheduling needs to consider how to get the most out of each battery and when to charge. Those decisions can have a big impact on the way mines operate. In contrast, if the hauls are fairly short and the truck can complete several cycles before swapping batteries, then that wouldn’t impact production scheduling as much.
Simulation and mathematical optimization can be very helpful in resolving scheduling conflicts and in finding the best possible operating strategy given the incumbent variables and limitations, particularly where schedulers have limited experience with BEVs. Eustace explained: “Simulation is a great tool to test how a system would operate with different constraints and variables. We can use it to represent the existing operation and then make changes to gain forward visibility of performance with a change in operating strategy, layout, or vehicle performance. Where there are complex scheduling requirements associated with the introduction of BEVs, optimization to be used to mitigate the impacts of those constraints or even improve the operations.”
Polymathian worked with OZ Minerals to assess ways in which BEVs could be integrated into production at its Carrapateena mine as part of an expansion to 12 million mt per year. The findings showed that production levels could be maintained when diesel loaders were replaced with BEVs with modifications to the operating strategy. “We worked with OZ Minerals to simulate alternative operating strategies that would minimize the amount of equipment required to meet production targets,” Eustace told E&MJ. “We also looked at developing a production level that was as efficient as possible with BEVs. We then compared and contrasted the performance for those strategies to work out the best solution for introducing BEVs into the operation.”
Some of the main KPIs used to evaluate performance included the number of machines required to reach target throughput, and also the maximum throughput that could be gotten from the block cave. By reducing the interactions and delays as part of the loader cycle, some operating strategies were able to utilize less equipment to achieve the same throughput. Also, by scaling up the amount of equipment, the teams were able to achieve much higher capacity than expected.