Powering mines sustainably with trolley assist

When it comes to sustainable mining, electric drive haul trucks powered by overhead trolley lines might be described as the killer app, combining speed, efficiency, and carbon reduction in a single solution. Implementation, however, requires wide stakeholder involvement and many months of careful planning. In this edition of Experts Corner, two experts – ABB’s George Shehata and SMS Equipment’s Dillon McKinnon, answer our questions about the steps involved and the many benefits that make the journey well worth the effort.

What advantages does trolley assist provide compared to traditional diesel?

George: There are three main areas that people consider. The first is the high cost of diesel fuel, which keeps rising. The second is the drive by the industry to reduce emissions. The third is speed – diesel powered haul trucks move fairly slowly on steep grades when fully loaded, and trolley assist electric drive trucks can travel at nearly twice that speed. So having a single solution that mitigates all three considerations is pretty significant.

Dillon: Adding to what George mentioned, I think there are also internal and external drivers when considering trolley. There’s a social driver to engage in decarbonization efforts from the communities in which mines operate, and there’s a big push from investors. Then there are the financial drivers based on the costs mentioned, mainly because rising fuel prices create unpredictability versus more stable pricing for electricity from the grid. And then, of course, there are pressures from governments as well around emissions for a mine operator.

Where are the best opportunities for trolley assist?

George: First of all, trolley assist is not a blanket solution for every situation, and there are certain criteria that make it viable. Number one, you have to have significant grades involved – if you’re just running on flats all the time, you’re not going to achieve sufficient fuel reduction at a level to provide good ROI. Number two, your electrical energy source has to be reasonably priced. It doesn’t make sense to put trolley assist on a remote mine where you have to run a diesel generator and then convert that to electric. And third, these trucks consume a lot of energy, so you will need all of the upstream electrical infrastructure to deliver that capacity.

Dillon: I would add that you get the highest carbon reduction when the electricity is generated from sustainable sources, such as what we have in British Columbia with hydroelectricity and an extremely low carbon intensity. This means that a mine like Copper Mountain can run its haul trucks on 96% sustainable energy, which can take a mine a long way toward net zero.

What’s involved with implementing trolley assist?

George: The three significant areas for that are building the mine roads that are suitable for trolley assist, getting the electrical infrastructure in place, and making adaptations to the haul trucks themselves. Mine roads need to be as straight as possible. They don’t have to be perfectly straight, but straightening them helps reduce the overall installation costs. We then have to create the electrical infrastructure. This includes what we call an overhead catenary system (OCS), which provides the trolley lines that power the trucks. The OCS is fed by a dedicated trolley substation that takes the power from the grid and converts it to DC power used in trolley assist.

Dillon: One of the things that makes this solution so attractive is that our trucks are already electric - when they run on diesel, that powers a generator that feeds power to the wheel motors. So, with trolley assist, we’re feeding those wheel motors directly by drawing power from an overhead catenary. The interesting part is that the onboard diesel engine only generates half the power that the wheel motors can handle. That’s because those motors have to be sized to support dynamic braking. So, we’re actually utilizing the unused potential of those motors. This makes trolley assist trucks much more powerful, more efficient, and faster.

How does trolley assist impact the day-to-day operations of a mine?

George: What I have seen is the kind of cultural change that typically happens when you introduce a new technology. In this case, you need buy-in and collaboration from the team that will eventually use it. That includes operators, maintenance staff, and a change management plan that will adapt the workflow to accommodate faster trucks. So, it’s important to begin those conversations early.

Dillon: There has to be a lot of consultation because you’re changing people’s jobs, but a lot of that is positive. When you sit in the cab on one of these vehicles, it’s amazingly quiet – it feels like you’re just gliding along. That’s a big change if you’re used to the noise of a diesel-powered truck running at high RPMs. So, operators really like that, and there’s less fatigue.

What’s involved in putting it all together?

George: This is a collaborative effort between multiple parties. In addition, to input on the infrastructure and equipment side, we also need mining engineering input, expertise and commitments from the electrical utility providers, and input from the government. So, it has to be a team effort, and that has to start very early in the process.

Dillon: The key is collaboration, bringing in the experts in the respective fields. We’re experts on the trucks and how to match them to the mine’s work requirements, but we rely on others to advise on the infrastructure, including ABB. The decision-makers must understand all aspects, including building and maintaining the roads, ensuring there’s enough power, and installing and supporting all of the electrical infrastructure. So, you might see SMS Equipment, ABB, the electrical utility, government representatives, and mining engineers all sitting at the table together, hashing out all these details.

The Bottom Line:

With its ability to mitigate fuel costs, reduce carbon emissions, improve speed and efficiency, and lay the foundation for upcoming battery electric haul trucks, trolley assist is uniquely positioned to play a major role as mines pursue their GHG emission targets. ABB and SMS Equipment are working as collaborative partners with a number of mines in North America to help make these projects a reality.