Reducing carbon emissions during open-pit operations is now a major driver for global mining companies, who are going back to the future by employing trolley assist systems for trucks to limit diesel fuel usage and costs, while at the same time boosting speed-on-grade for greater throughput, write ABB’s Mehrzad Ashnagaran and Michel Serres*.

Haul road electrification technology has been in development for decades, but the emergence of a new generation of diesel-electric trucks that already have an electrical system on board to tap into – making it easy to attach them on a trolley line – means the concept has recently begun to gain significant traction as a commercially viable way to facilitate the all-electric mines of the future.

One of the key challenges when it comes to reducing diesel fuel usage is cycle times. There is no technology today that enables miners to fill the truck’s tank and complete a shift without stopping; either you have to increase the speed of the mobile equipment or the size the fleet itself – both of which have a direct impact on capital expenditure.

Trolley assist systems have returned to the market in the last two to three years in places such as North and South America, Africa and Turkey, mainly due to CO2 emission taxes, the removal of tax advantages from diesel, and premiums offered by energy suppliers to incentivise companies to use electricity.

Going forward, there are many synergies with using trolley lines, which offer huge benefits in terms of CO2 reduction.

Large trucks regularly carry 3,000-5,000 litres of diesel in the tank and consume around 300-400 litres per hour while travelling up a 17 km ramp in half an hour.

By going electric, the vehicles, when on-trolley, only use around 30-50 litres an hour, which equates to a reduction in diesel consumption of as much as 350 litres an hour, making operations much more CO2 efficient. In addition, the speed of the trucks will increase, meaning you have a higher throughput at the mine. Operators can also start to think about parking some of their fleet, which will bring additional indirect value to overall operational improvements through better maintenance planning to improve fleet availability and fleet longevity.

One example of the revival of trolley assist systems is at the Aitik open-pit copper mine in Sweden. Here Boliden, ABB and partners trialled the electrification of four haulage trucks on a 700 m trolley line, with the goal of reducing annual diesel usage by 800,000 litres and carrying 70 Mt of ore every year at the mine without using fossil fuel.

Reduced diesel consumption at Boliden mines

Boliden has now moved on from the 700 m trolley line trial at Aitik to confirming it will install an additional 3 km of trolley line at the mine, plus 1.8 km at Kevitsa (in addition to the accompanying conversion of diesel-electric haul trucks). By doing so, Boliden says it will reduce its diesel consumption by 5,500 cu.m/y when its investment is complete. That is a big number.

Aitik is currently the only mine in an arctic climate where electric trolley has been installed. Overall, with the further three kilometres of electric trolley line, greenhouse gas emissions from transportation over the life of mine are reduced by nearly 15%.

In Kevitsa, 13 mining trucks are converted for electric trolley lines at the same time as the 1.8-km-long electric trolley line is being built. The investment means that greenhouse gas emissions over the life of this mine will be reduced by 9%.

In addition, productivity gains are added as the electrically powered trucks can run at a higher speed, and the working environment for the drivers is also improved, not least through lower noise levels.

Today’s mine design

Diesel-electric trucks have an electrical powertrain in the wheels, meaning they can be driven fully electric, and have an electrical genset on board, so they generate electricity as they go.

However, due to the limitations of existing battery technologies at surface mines, we cannot yet manage large payload trucks of 280-400 tons (254-363 t) fully battery equipped. Companies are therefore trying to close the gap between the trolley and the loading or dumping point using battery packs and other solutions.

Constraint management

The transformation from diesel to electric is bringing new advantages in terms of CO2 reduction but also new constraints in terms of mine planning and fleet management. Energy costs represent almost one third of a mining company’s total cost base; helping industry to manage these costs is therefore key.

Switching OEMs on to electrification

Having initially adopted a ‘fast follower’ approach to new digital technologies, the risk-averse mining sector has also been slow to embrace electrification. Operators are looking to technology leaders such as ABB as well as more niche players to make change happen.

A lot of mining companies are looking to the likes of ABB to influence mining equipment manufacturers and engage them in the electric transformation, and so accelerate the process.

A clear technology roadmap and shifting workforce skill are key to this transition.

The biggest challenge is that customers are nervous about redesigning existing diesel-powered mines to integrate new electrification systems. Asset lifecycle strategies, ownership models and duty cycles are all subject to change. Ultimately, the customer needs a very clear technology roadmap and finding the right partner for this major undertaking is key.

According to Accenture’s resources practice, the profile of the future mining workforce could change by up to 80% by 2024, driven by increased adoption of advanced technologies. The onus is therefore on mining companies to demonstrate a progressive commitment to electrification to attract and retain the next generation of digitally literate talent.

Today the worldwide situation with COVID-19 may accelerate these changes faster than forecast.
Current skill sets will have to be re-evaluated for the all-electric mines of the future, and so the need for change management is key. Tomorrow we will need more workers understanding the concept of electrification, in addition to digital and planning skills – so the shifting skill profile is an important consideration.

*Mehrzad Ashnagaran is Global Product Line Manager Electrification at ABB, while Michel Serres is VP Innovation and Digital North America at ABB