The automotive industry is undergoing a technological renaissance – but I don’t need to tell you that. We all have a buddy with a Tesla, or perhaps you are the buddy with a Tesla. Societal pressure influenced by the desire of a greener and sustainable future has led to the next generation of vehicle drivetrain. This doesn’t stop at Tesla, Ford, Nissan, or what have you – the emergence of battery vehicles on a commercial level has also begun disseminating into industries such as agriculture, shipping & manufacturing, construction, and of course – mining. All industries have individual requirements and constraints when it comes to any form of technology, and mining may be one of the most arduous; as such, the requirements and constraints as it pertains to the operation of BEV in this application are quite unique. Today I’m writing about the present-day status of this technology in mining and my perspective on what the future holds.
Firstly, before we begin: Who am I? The people who tend to read these blogs generally know me – hey everyone! Although, I suspect that a post with a title like this has potential to attract a broader audience who may be questioning my expertise on this topic. Put simply – I am not an expert! There are certainly many other people who know more than I do about this particular BEV application and where it’s headed. Although, I’ve been involved in this sector since 2017 – I am a novice engineer at an underground mine whose load & haul fleet is primarily BEV (and has been for 10 years). My current responsibility is to aid in managing this fleet and provide technical insight on all things from electrochemical cells to the components of the vehicle drivetrain. We currently operate five 40+ ton capacity BEV trucks and twenty-four BEV loaders, along with 41 active chargers and 100+ batteries (ranging from approximately 4,500lbs to 18,000lbs each!), and I have learned a lot along the way. It has been a unique experience for our mine; we’ve developed a complex of in-house knowledge and have had a hand in the R&D of the equipment itself. As for me, I formally have a physics degree; but professionally, this is where all of my career has been focused. Regardless of what knowledge bracket my experience puts me in, there is an increasingly large amount of people interested in mining BEVs who haven’t had any experience with the technology. I’m writing this for you and to share my thoughts – if that’s worth anything. Let’s find out.
Present Day
Mining BEVs offer many benefits over their traditional diesel counterparts. They produce less heat, dust, and diesel particulate, which is particularly advantageous in an underground mine where ventilation requirements are strenuous. This was the motivating factor for our mine which is heavily constrained by low ventilation capabilities. Equally, the transition to mining BEVs satisfied our commitment to divesting from fossil fuels. In theory, an additional benefit of this transition is that mining BEVs yield lower operating costs since there is no need to purchase fuel – but it has been a challenge for us to achieve this due to the ongoing reliability issues we’ve observed (but this is improving as the technology does). The following section outlines some thoughts I have regarding the present-day BEV technologies and associated challenges.
Any novel technology goes through a post-concept but pre-optimization era. Arguably, this era is endless and all technologies are continuously improved upon as we gain an increased knowledge of materials science, chemical processes, or what have you – but what I mean to argue is that there comes a point where all manufacturers of the new technology adopt a relatively similar design and any potential improvements to the technology are minor, there aren’t any further paradigm shifts in that particular product line – until a new technology comes along. For instance, consider the wheel. I can’t predict the future, but I feel fairly confident in categorizing the modern day wheel as optimized. The first wheels were solid and made of clay, then civilization learned of the increased performance of a hollow and spoked wooden wheel. Now the standard vehicle tire is lined with rubber – but a lot of the same principles remain since the hollow and spoked wooden wheel. A more comparable technology to BEVs would be diesel engines. Diesel engines once had their pre-optimization phase too – and while I could speculate that the diesel engine has been fully optimized since it’s conception in the 1890s, it wasn’t until 1958 that the first electronic fuel injection system was implemented into commercial passenger vehicles. Perhaps there is another diesel paradigm shift ahead. Mining BEVs have not yet been optimized – they’re not even standardized. Manufacturers have not adopted one ubiquitous design or chemistry, nor the same drivetrain architecture. I can buy a Ford and then transition to a Subaru without much hassle; however, mining BEV manufacturers can not yet provide mines the same ease of access due to the non-homogenous technology. While not impossible, it would be a massive undertaking for our mine to transition to a different brand of BEV. I suspect that one day this disparity will vanish as one particular type of design prevails as the most optimal and all manufacturers assimilate to it, but this of course will require a paradigm shift. Paradigm shifts (like the fuel injector for diesel engines) often occur over long timescales, and I am certain that BEVs have many shifts to go. We have a lot of exciting developments to look forward to.
Technologies
Currently, there are two distinct conceptual designs for mining BEVs. There is the battery swap design, and the fixed fast-charge design. All of our trucks and loaders are battery swap capable, so my experience is wholly based on that system. The battery swap system is self-explanatory, there is a large battery in the loader or truck that is used until it needs charge and then it is swapped with one that is fully charged. This reduces vehicle idle-time as our batteries generally take 2-4 hours to charge. Some of our vehicles require an overhead crane to swap batteries as they cannot move and pick up a new battery themselves, but our newer equipment can do this (paradigm shift!). To facilitate this, there is a smaller, less complex fixed battery (the tram battery) that is relied upon to move the truck/loader from one main battery to another (the tram battery is only to be used over small distances) and the vehicle uses a built-in mechanical lift system to pick up and secure the charged main battery into place. The tram battery utilizes the vehicle’s regenerative charge system to charge itself while the truck/scoop is travelling. In my view, there are two challenges specific to this system: a complex mechanical battery lift system requires unique maintenance and introduces unique failures (especially when it’s lifting and carrying around a 18,000lb battery), and vehicle charge bays must be designed to accommodate multiple batteries.
The fixed fast-charge system is also quite self-explanatory; the vehicles posses only a main battery that remains fixed in the vehicle and utilizes a higher power fast-charging system to minimize vehicle idle-time (exactly how a fuel tank in a diesel truck remains fixed and periodically gets refilled quickly). Call me biased as I do not have experience with this type of system – but I have a lot of reservations about it based on my experience with this technology. I do not think it’s infeasible, but I think it poses significant risk on both the reliability and safety front; moreover, it requires more robust mine electrical infrastructure especially if the intention is to scale up the fleet. This is actually one of the reasons as to why our mine currently wouldn’t be able to transition towards a higher power fast-charge system – we would not have the electrical capacity/power allocation to do so for our fleet.
From a reliability and safety perspective, a battery needs to be accessible, easily isolated, and easily serviceable/transferrable. I’m not attesting that this is impossible in a fixed fast-charge system – but it is less practical than with a battery swap system. A properly monitored battery is a complex system comprised of thousands of sub-components. Our truck batteries are made up of 1536 cells alone – and they all need to be monitored in some capacity for at least their voltages and temperatures to ensure safe and proper operation. Optimized performance (balancing, cooling, etc.) requires more complex software and hardware. Any of these components (cells, monitoring boards, and so on) can fail at any time. I have been apart of discussions with manufacturers who have designed their batteries with configurations such that they are able to operate with some amount of failing cells/components up to a certain threshold – and in any fixed fast-charge system, this would be necessary. In its current form, batteries are inherently a high-maintenance product, and our battery program would not have succeeded if we were unable to easily separate the battery from the vehicle for servicing and repair. Conversely – batteries as an independent asset are still productive even if a vehicle is broken down for a non-battery related issue. Moreover, batteries degrade independently of the vehicle (exponentially so in hot or cold environments) and require replacing. Of course, this is not necessarily a novel concept, as many components of the traditional diesel machine require replacing at some point and are fixed to the vehicle – but a battery degradation/replacement cycle occurs more rapidly than most major diesel components; and in our experience, a lot quicker than manufacturer’s specifications since we operate them in much higher temperatures than what is considered nominal. Additionally, a fast-charge system could induce accelerated degradation than what we already experience, as higher charge currents lead to reduced cell lifetimes.
Another metric by which manufacturers diverge is cell chemistry. All BEV manufacturers currently utilize Lithium-Ion chemistry, although not all Li-ion cells are equal. The two prevailing sub-chemistries for mining BEVs are Lithium Iron Phosphate (LFP) and Lithium Nickel Manganese Cobalt Oxide (NMC). We use LFP cells. Tesla uses an NCA (Lithium Nickel Cobalt Aluminum Oxide) but is soon to be transitioning to LFP since it is more economical. Different chemistries offer different benefits – ours has less specific energy than NMC but more specific power, meaning that our LFP cells pound-for-pound against NMC are capable of powering larger vehicles but not for as long. NMC cells are also less thermally stable, posing increased risk for thermal runaway and ignition when subject to higher temperatures. We are apprehensive towards introducing any equipment with NMC chemistry into our mine because of this reduced thermal stability.
Challenges
We are unique in our situation – we own and service all of our batteries in-house and employ a team of 13 electricians whose entire job is maintaining our BEV fleet all the way from the cell to the vehicle drivetrain (batteries, motors, inverters, hydraulics, etc.). This is certainly not the norm and will likely cease to be an option for other mines in the future (if it hasn’t already). To my knowledge, there aren’t any other mines with BEVs who enlist a similar program, so we certainly posses a unique perspective as it pertains to the challenges of operating BEVs. The following outlines some of them.
Our greatest challenge, by far, is ease of service. Particularly in the case of our truck batteries. When a battery needs servicing it has to be moved to our workshop and requires a crane to open up and “split” since it is enclosed in a bolted metal frame. Since the battery is usually inoperable in this scenario, it can’t move itself to the workshop via a truck – so we need to coordinate with our operations team to move the 18,000lb battery to our workshop with a scoop or flatbed. Regardless of how quick or tedious the repair job is, it needs to come to the shop as we do not have the physical capacity to open it up in our charge bays. Even in the case where we didn’t service our own batteries, we would still need to move them to a place where they could be serviced by the manufacturer’s technician, or worse – utilize shaft resources to send it to surface and off to the manufacturer. We are not a surface ramp-access mine, and our shaft has limited volume; as such, moving a battery to surface has significant impact to our operation. An ideal scenario would allow for the batteries to be more readily serviced in-field – whether that means designing all of our charge bays to have a 10-ton overhead crane and adequate space, or designing an alternate frame that allows for servicing without “splitting” the battery pack.
One of the more technical challenges we face is cell temperature regulation. Our mine’s ambient temperature is quite hot – and cells generate additional heat with use. Our vehicles use software to apply thermal limit protections at the cell-level (to mitigate thermal runaway and ignition), and once the cells begin to reach their upper temperature limits the truck reduces performance or shuts-down altogether. Without auxiliary intervention, the batteries reach these temperatures with ease (particularly on our larger trucks, hauling up-ramp). This has significant impact on our haulage production. Additionally – as mentioned previously, consistent high cell temperatures lead to accelerated cell degradation, reducing the lifetime of a battery. Some of the newer batteries we have are equipped with plumbing architecture to allow for coolant to pass through their components and cool the cells. This year, we’ve trialed this function and implemented some stationary cooling systems into two of our truck charge bays wherein coolant is pumped through our batteries while they are removed from the trucks, stationary, and on charge. A long-term solution to this issue would be for vehicles to be equipped with battery cooling systems as well, so that batteries can be continuously cooled when in-use and generating the most heat.
On the topic of degradation and disposal – not a lot of consideration is given to a battery’s end-of-life and disposal. When a battery has degraded to the point of no longer being effective for our mine (ie. not making enough trips to/from rockbreaker before needing charge swap) we retire it. However, the cells within these packs are not altogether useless, they are usually still capable of providing ~60% of their nominal capacity. LFP technology does not have profound recycling value – any materials worth recycling within them are only present in minimal quantities and do not render the process economical. This is different than NMC, NCA or other chemistries – the nickel, cobalt, and other valuable materials within those chemistries allow for economical recycling and mineral extraction. This points to a broader conflict when it comes to any application of BEVs, especially now that Tesla is transitioning to LFP chemistry, what is the end-of-primary-life plan for them? Demonstrably, these cells are still electrically useful as a means of energy storage. At our mine, we intend to build a stationary energy storage bank comprised of the cells we’ve retired that are still of use to us.
On a safety & risk mitigation level, more needs to be done to establish proper risk mitigation techniques. In the event of Li-Ion cell thermal runaway and ignition (for any chemistry), the mining industry is in need of widespread education and standardized firefighting techniques. Battery fires vary greatly in intensity in different conditions. When ignited, LFP cells produce hydrogen fluoride or hydrofluoric acid if dissolved in water – both highly toxic compounds that are produced in an accelerated rate when the cell is exposed to water mist. The dawn of a new technology poses new threats that require unique risk mitigation strategies. Moreover, the physical design of the vehicles and their batteries should allow for ease of access to the interior of the battery in order to eliminate any thermal activity at the cell level with an external source.
Looking Ahead
I cannot predict the future, but I suspect that the next paradigm shift (and many more afterwards) in mining BEVs will be major developments in cell chemistry. Diesel is currently far more energy dense than any Li-Ion chemistry; as such, the batteries required to operate standard sized haul trucks necessary for production are quite large and inconvenient to manage. Furthermore, some of the materials (see cobalt) which dominate the Li-Ion manufacturing space are not sustainable nor cheap to process – commercial implementation of BEVs (whether it be passenger or industry) will require a more sustainable and scalable solution. A potential option may be the Sodium Ion battery which is comprised of less rare materials that are more readily sourced; however, the technology is currently not as robust in terms of power delivery and cycle life as compared to Li-Ion cells. Other technologies on the rise include vanadium flow batteries, carbon nanotube electrodes, the emergence of silicone-based anodes, lithium-sulfur batteries, and many more – electrochemistry is an ever-evolving field that will be primarily responsible for the performance optimization of BEVs for the foreseeable future.
A potential challenger to mining BEVs (particularly for larger vehicles where batteries are currently impractical) is hydrogen-powered vehicles. Anglo American has been testing a Komatsu 930E (~300 ton payload) that has been converted from diesel to hydrogen/battery hybrid. I see a lot of potential in hydrogen technology; however, it is limited by the economics of its main facilitator, the fuel cell that “burns” hydrogen fuel and turns it into energy. Hydrogen fuel cells utilize platinum as a catalyst to separate hydrogen into its constituent protons and electrons, but platinum is rare and expensive, thereby limiting the commercialization of the technology. In order for this technology to become feasible as an alternative to BEVs, it must become more affordable to implement – particularly when it comes to fuel cells and electrolyzers (the component which converts water into oxygen and hydrogen fuel).
From a global responsibility perspective – a sustainable technology doesn’t stop at mine electrification. Mines that are located near urban centers are afforded the convenience of being able to tie into the local electrical grid; and in Ontario, our provincial power generation sources are primarily nuclear and hydro which are far more sustainable than fossil fuels. In terms of sustainability, this makes the transition to BEVs or hydrogen-powered vehicles compliant all the way from the source to the vehicle charger/electrolyzer (if hydrogen is being generated on-site, that is). However, for remote mine sites who cannot rely on local grid infrastructure, it is often the case that the majority (or large component) of mine electrical power comes from natural gas or diesel generators. While the introduction of BEVs/hydrogen vehicles in this case lessens the underground ventilation requirements, it does not make for a more sustainable technology if the electrical source itself is still fossil-fuel centered.
Summative Thoughts
Ultimately, I believe in BEV technology as a solution for the electrification of mining fleets. Perhaps in the longer term another technology will prevail as more practical and reliable (such as hydrogen – or if we’re feeling particularly ambitious, nuclear!), but presently BEVs are the most ready-to-implement from an economical and technological perspective. Certainly in the medium-term timescale, we will likely find uses for all sorts of varying technologies as they are all idealized for different applications. As for mines who are interested in transitioning to BEV, the first few things that ought to be considered are your current infrastructure (both physical and electrical) and evaluating whether or not your electrical supply is generated in a sustainable way (if that matters to you). What is your intended fleet size and is it likely to change in the future? How far do your trucks haul loaded up-ramp? Where would you locate your charge bays and are their locations optimized for vehicle regenerative charge? Is your mine design conducive to moving large batteries to serviceable areas or to surface if required? Does your mine have adequate power allocation to supply power for BEV chargers and cooling systems? If your company is doing this to satisfy a sustainability initiative – where is your mine electrical power coming from and is that source sustainable? Lastly, I would advise mines that due to the complex nature of BEV components and the immaturity of the equipment, they should expect to see increased reliability issues and potentially higher equipment operating costs until the technology develops and is optimized. That is simply the cost of being apart of this sort of development.
The intended purpose of this blog is to serve as a general educational resource for people who may be interested in the technology – I have tried to avoid specifics as much as possible. While I am passionate about the emergence and implementation of mining BEVs, the most frustrating component of my job is explaining these topics to others (which feels quite silly to say, but it is true). The frustration certainly doesn’t lie with the individual, but rather the global perception that this technology is established, optimized, and simple – it’s not. It is a massive undertaking to implement a mining BEV fleet, even if a lot of the maintenance burden is being outsourced to the manufacturer via a service agreement of some kind. It requires substantial mine infrastructure changes that are not required for traditional diesel equipment, it requires supplementary education, it requires unique operating processes, and so much more. Despite these challenges, I am eager to see what comes of it, I believe it to be the prevailing fleet electrification strategy for at least the medium-term timescale, and I am so fortunate to be afforded the opportunity to be involved.
(December 21st, 2021)
astronomine 