E electrification is the future, if underground machinery is to operate with zero emissions and without noise and vibrations. The power of batteries in tunnelling activities can speed up many projects all over the world and contribute to a sustainable mission as well.” That was the message of Erik Svedlund, Epiroc’s global marketing manager at Power Change Days in Sweden.
Epiroc put on the event following the launch of its second generation of battery powered 14t and 18t loaders, 42t truck and mid-sized drilling equipment family including face drilling, production drilling and rock reinforcement rigs.
In designing battery-powered machines to operate underground, it was necessary to draw on a range of experience.
“We developed this battery system with the benefits in mind of safety, vibration and heating,” says Svedlund. “There was no battery system that could match our needs. That’s why we decided to work together with the battery producer Northvolt to develop our own battery system, one that would be specifically designed for underground purposes.
“This battery system will be globally certified, and so quality assurance testing was required for all possible applications.”
Mining machinery needs to be capable of constant operation, working 24/7, but batteries have a limited runtime and would have to be recharged or replaced during a shift.
However, Svedlund argues that you only perform one advance at a time, and then you have to remove the excavated material from the face with a loader and truck.
“It only takes a couple of hours to unload the face. In tunnelling, the batteries would not be the limiting factor; a loader or truck would be provided with more than four hours at full speed/high productivity operation.
“It might be challenging for batteries to run on a mining schedule, where you have true 24/7 operation – you have to stop, but I don’t foresee any issues at all in tunnelling.”
Generations
The move from the first to the second generation of batteries has improved the battery capacity by up to 50%.
“The battery technology becomes better every year, now we are using NMC nickel-cobalt batteries. These are the best option in terms of safety, cost and performance.”
For a fast recharge, for situations where battery life is on the critical path, Epiroc has looked at and is offering its customers a battery-swapping operation that takes five minutes with an overhead crane, which lifts and swaps out the depleted battery for a fully charged one.
Svedlund clarified that there is no need to swap a battery after cleaning a face in a tunnelling application.
“You have between four and six hours of [operational downtime] for the battery to be charged,” Svedlund says.
“You can have a charger outside the tunnel and you go there to charge the battery.
Talking about the cost implication of a switch to battery technology, Svedlund says that battery machines are slightly more expensive than diesel machines. “But with the Battery at Service offering we remove the battery price from the initial purchase price, there is only a slight increase in the cost of the battery machine.
“The total cost of the whole operation is definitely lower. The total budget matches with the total cost of machine.”
Some diesel machines can even be converted to batteries.
“Of course we need to look at the feasibility of the model, whether it could be suitable and economically viable,” Svedlund says.
“It might be difficult to go electric all at once, so we need to work with the existing fleet and convert step by step the machines.”
Logistics implications
When it comes to noise and vibrations, many tunnelling operations have to stop during night to avoid noise disturbance in a dense urban area.
“But with electric machines this concept changes [for certain operations],” Svedlund says.
“Because the machines are so quiet it might be possible to continue operations at night time and accelerate the construction process. For this reason we are sure that the tunnelling industry will be one of the first to adopt zero emission technology.
“As the battery technology advances, battery systems will improve. The improvement rate is currently about 10% per year so we will be able to work full shifts with battery.”
Fire concerns
Amongst contractors, the common fear regarding batteries is fire. Svedlund explained that with the newer battery technology, manufacturers have removed all the hot surfaces from the machine, so there is nothing too hot to touch.
“The bigger risk of fire in machine is if there is oil spray and hot surface like the turbo, and of course you have an immediate fire,” he says.
“We have designed our battery system with these risks in mind and according to the safety onion; like an onion there is always another layer of safety if one should fail.”
Svedlund adds: “We have to control the temperature of the batteries; we have a thermal management system; the battery cells are water cooled.
“If there were a situation of thermal runaway in one individual cell, this should not spread to the next cell; but if it does then it should not spread to the rest of the modules; but if it does then it should not spread to the total battery pack.”
This layering process gives the user so many buffers and early warnings that you can take action in advance of a major problem.
“The action of fire in batteries is a slow process. If there is a problem in a battery machine, you will be aware of it, for example 30 minutes before the smoke starts spreading.
“The machine can still drive, and we have designed the system to be redundant and modular. So the part of the battery which has been affected or damaged can be shut down and you can still drive the machine to exit the tunnel. Compare that to a diesel machine, where there are no early warnings.
“You don’t know anything until the actual fire itself erupts from a combustion engine.”
Battery at service
Svedlund explained when they include “Battery as a Service” they take responsibility of the battery and its function, the customer will pay per use, similar to the price for a diesel.
“We get the full responsibility from production of battery to the end of life, when we have to recycle it,” Svedlund says. “The customer has a fixed and predictable running cost.
“We have to lower the threshold of financial risk and the initial investment to encourage our customers and the industry to zero-emission electrification. We are expanding and strengthening our footprint, we are committed to work globally and we want to offer this battery solution all over the world.”
