The development in recent years of batteries powerful enough to drive drill rigs, heavy loaders and haul trucks in underground mines has made clear the advantages of battery electric vehicles (BEVs) over their diesel-powered counterparts.

BEVs are emissions free, require less maintenance and can yield increases in productivity and output. Seizing on those advantages, Sandvik Mining and Rock Solutions has become a market leader by developing and introducing an industry-leading suite of BEVs for underground mining applications. Sandvik is the only OEM with a full offering of underground BEVs.

To date, 26 Sandvik battery- electric loaders and trucks have logged hours in hard rock underground mines in Canada, the U.S. and Australia. As for drills, 13 Sandvik units have drilled well over 2.8 million metres at operations in Canada, Sweden and Finland.

Over the past five years, the company has introduced progressively more productive and technologically sophisticated drills, loaders and haul trucks. Last year, Sandvik introduced two new battery electric drill rigs, the DL422iE production drill and the DS412iE rock bolter. As part of its program to convert its entire fleet of drill rigs to battery power, the company will later this year unveil the DD422iE with Dual Controls, which can be used for development drilling, bolting, scaling or meshing.

Now, Sandvik is preparing to raise the bar yet again with the TH665B, a haul truck capable of carrying 65 tonnes of ore per load. The TH665B will be the largest underground electric truck on the market and represents a 30 percent increase in carrying capacity over the company's 50-tonne BEV truck TH550B.

"We're beginning our site acceptance testing at our research facility in California," says Brian Huff, Vice-President, Technology and Product Line, at Sandvik's Mining and Rock Solutions. "We're doing full load tests of the truck on a 20% ramp." The TH665B is scheduled to begin field tests by the end of 2022 in AngloGold Ashanti's Sunrise Dam mine in Western Australia. A preliminary production run is tentatively scheduled for late 2023 and the vehicles should be commercially available by 2024. The advantages of battery electric drills and vehicles have become clear as these new products log more operating hours. Eliminating diesel particulate, as well as the noise and heat generated by diesel-powered vehicles, benefits the health and safety of workers underground. 

The mining industry produces some 4% of greenhouse gas emissions and underground hard rock mining accounts for nearly one-fifth of the total. Switching to electric equipment aligns the industry with global initiatives to achieve netzero emissions by mid-century. The shift also appeals to investors, who are increasingly demanding that mining companies adhere to principles of environmental and social governance.

The economic case for electric over diesel is also becoming clearer with the passage of time, says Huff. Battery electric vehicles are pricier to purchase than diesel vehicles, but the real measure is total cost of ownership. On that basis BEVs are slightly cheaper. 

Electricity drawn from power grids is generally less expensive than diesel and that differential will only grow as fuel prices rise over time. Furthermore, eliminating diesel particulates reduces the demand on ventilation systems as well as heating and cooling systems. 

BEVs have also been shown to outperform dieselpowered loaders and trucks. "Our BEVs are 10-15% faster than diesel vehicles," says Huff. "That more than compensates for the time spent swapping batteries.

That said, batteries can be swapped in three minutes with Sandvik's unique Auto Connect and Auto Swap technology, which eliminates the need to install cranes or any other overhead infrastructure. The operators of loaders or trucks can swap batteries from the cabs of their vehicles. The vehicles are equipped with arms that lift the batteries and slide them into a charging station. Likewise, the arms are used to lift the replacement from the charging station and lock it into place within the vehicle. "You can charge a battery in less than an hour, but you're putting more strain on the grid," says Huff. "Our system allows you to charge the battery over two to three hours. You charge slowly to match charge time with run time. The battery is ready when you need it, but you've minimised the impact on the grid, minimised the heat generated in the charging process and you've reduced the strain on the battery.

Sandvik has also developed patented charging while drilling technology. Elina Pyykkö, Vice President Product Development and Product Management at Sandvik's Underground Drilling Division, says the charger is built into the drill rig. Once a rig is in position, whether it's a development drill, production drill or rock bolter, it is connected to the electrical grid within the mine. "When you are moving your booms or preparing for drilling, the power is used to charge your battery," says Pyykkö. "When you're drilling, the power is used to drive the drill. Power is shared automatically. It's embedded in the technology itself." 

Apart from that groundbreaking innovation, Sandvik's intelligent control systems allow the rigs to perform a drilling cycle autonomously. "You set the drill plan, which includes the number of holes and their positions," says Pyykkö. "The rig positions the booms and drills the holes automatically." The drills can also continue to work without an operator present, which means they don't have to be shut down during a shift change. And, when the work is done in one part of the mine, batteries are fully charged and the rigs can be moved elsewhere.

"You're using existing infrastructure," she says. "You just drive it to the next spot. It's always going to be charged and ready to go." 

There in increased interest in the mining market to introduce new BEV technologies and equipment. "We have customers who want to try the technology by replacing diesel units with BEVs in extensions of their mine, or when replacing or expanding their fleets," says Pyykkö. "The biggest benefit is for developers of greenfield mines." Permitting can be quicker and simpler. Regulators, as well as local communities, tend to look more favorably on all-electric mines because they have a much lower environmental impact. The capital cost of developing the mine can be substantially lower. "There are huge capital costs to digging and installing ventilation," says Huff. "By reducing the size of the shafts and the size of the fans for ventilation, you can offset and sometimes pay for a large part of you fleet just from the capital savings." There are substantial savings on the operating side as well. "Once you're installed, the rough numbers are you're using half the ventilation from a flow standpoint," Huff adds. "When you decrease the vent flow by half you save dramatically on electricity costs from the operation of the fans."

At the same time, Sandvik has been able to pack more horsepower and carrying capacity in its battery-electric loaders than is possible with diesel loaders of the same size and footprint. As Huff explains: "Your ventilation requirements are driven by the amount of horsepower you install. From a total mine economy standpoint, you want the smallest diesel engine that can get the job done." With battery electrics, there are no emissions and, as a result, no restrictions on installed horsepower. Thus, Sandvik's 10-tonne battery loader is the same size as seven-tonne diesel-powered unit and the company's 18-tonne battery model is the same height and has the same footprint as a 14-tonne diesel.

The company introduced its battery electric products in the U.S. and Canada before introducing them in Europe and Australia. Sandvik is now offering them globally. And why not. "We have the most extensive offering of battery electric equipment on the market," says Pyykkö.