Since launching our Fleet Electrification Program in 2015, MacLean has conducted ramp trials with a battery electric, on-board charging material haulage unit - a BT3 Boom Truck - at underground mines in Ontario and Quebec.
The tests have proven a crucial point in the real mining environment - that with a minimal amount of in-cycle or lunch break opportunity charging into mines’ existing electrical grids (via an umbilical charge cable and standard jumbo plug), a high-tramming service vehicle such as a boom truck can deliver full-shift operation while also providing a zero emission, low noise, low heat, low vibration operator experience.
The other interesting data output from MacLean’s EV trials has been the documenting of energy usage for equal work on the same MacLean BT3 model – one battery electric, one diesel – at the same mine on the same duty cycle. It’s well understood that battery electric drives compared to diesel engine drives are significantly more efficient because they don’t convert a large part of their stored energy into heat. What MacLean was able to measure during our latest ramp trial, where our EV BT3 travelled some 300 kilometres of mine ramp, was that the unit used 88% less energy than one of our diesel BT3 boom trucks for the exact same duty cycle.
This delta is due in significant part to the ability of the EV unit to regenerate power when it goes down ramp, from 20 to 35% of the power the unit consumes on the level or going up-ramp, based on harnessing the ‘free’ energy of gravity.
Some quick math brings the comparative efficiency of EV drives and their regenerative capacity into sharp relief.
A diesel-powered MacLean unit with a four-cylinder engine holds 160 litres of fuel and a typical Maclean mining truck can burn through some 15,000 litres of diesel fuel in a year working underground. This represents $15,000 dollars just to fill up, using just the round number of $1 per litre as a ‘price at the pump’ instead of a truer cost (distribution, storage) of double that, or even higher, at remote mines that have to transport their fuel to site over seasonal ice roads or open shipping lanes.
In contrast, the EV ‘gas tank’ on a MacLean battery drive unit holds 92 kilowatt hours of electricity and a year’s worth of work underground would represent $1,500 to refill at a standard rate in Ontario - eight cents per kilowatt hour. (This grid rate can be even lower in mining jurisdictions that benefit from access to hydropower and solar power, e.g. Nevada where it can be as low as 3 cents per kilowatt hour during the daytime and 1 cent per kilowatt at night.) The energy use equivalency math is based on 1.25 kWh of battery electric energy being able to do the same amount of work as one litre of diesel fuel burned.
What’s more, this favourable cost comparison doesn’t even attempt to quantify the health and productivity benefits of an emissions-free work environment. Ask an operator at Goldcorp’s Borden Gold project in Ontario, what they think of working with EV units all day as opposed to the diesel alternative and I’m sure they’ll say that it makes a significant difference for how they feel coming up at the end of a shift. Then there is the lower maintenance cost from half the required planned maintenance over the full lifecyle on EV units compared to diesel units (i.e. no more regular oil changes), and the opportunities for mine design efficiencies in the context of all-EV fleet (smaller heading sizes, fewer ventilation raises required, reduced surface ventilation infrastructure, etc.).
So, it all adds up to the EV switch in mining making sense for multiple reasons, simultaneously. Time to plug in, charge up and head out... to an emissions-free underground work environment.