Trolley assist has had something of a renaissance in recent years – with new systems up and running or under construction at a number of major mines from Collahuasi to Los Pelambres.
Today these are conventional diesel trolley systems using diesel-electric drive trucks, but with a view to being able to accommodate battery trolley operation in the future – with Komatsu’s Power Agnostic 930E dump truck currently at Boliden Aitik expected to be one of the first to achieve this once is it fitted with a battery pack – expected sometime in 2026. Caterpillar’s Dynamic Energy Transfer (DET) can also transfer energy to both diesel-electric and battery-electric large mining trucks.
These trucks are all rigids – but what about the potential for so called wide body dump trucks to operate under trolley – whether conventional or battery? In some parts of the world these trucks – with payloads up to about 100 t – are taking significant market share from smaller rigid mining trucks, as their initial cost is lower and maintenance and parts costs are also lowering than that for rigids.
China’s Zoomlion has already explored this with its 70 ton class ZT115DPEV, a trolley wide body truck based on its all electric ZT115EV model. It has already been put into experimental trolley operation in a mine in China, and the OEM says has achieved good test results.
Zoomlion: “The bottleneck in the application of new energy products, especially electrification products, in mining machinery is mainly the high use and huge power demand, while the energy density of power batteries is currently insufficient…frequent energy replenishment affects productivity; battery swapping will increase the procurement cost of power batteries.” It points out that at present, new energy products are often used in areas of the mine with low work intensity or where the trucks can self charge thanks to regeneration on fully loaded downhill hauls.
It adds: “However, most open pit mines do not have the conditions for heavy loading downhill, and dump trucks need to carry loads out of the pit and even to the waste area, a situation where the range and duration of existing power batteries are generally low and require frequent charging or replacement. For this reason, mainstream manufacturers at home and abroad are exploring new energy solutions that are suitable for most scenarios…until the advent of the ideal energy source, a combination of existing technologies may be the best solution.”
The ZT115DPEV truck operates as part of a dual-source power solution for all electric wide-body mining trucks with overhead power lines. “The core of this solution is to solve the problem of insufficient power battery life with electricity supply from the grid, and the vehicle does not need to be specifically charged or the battery replaced, so as to achieve unlimited range, greatly improve operation efficiency, and completely solve the industry pain point.”
The ZT115DPEV model allows the reduction of the capacity of the power battery. When driving directly below the overhead line, the current obtained by the pantograph from the overhead wire is converted to the electric wheel motor to drive the vehicle, while also charging the battery. When leaving the overhead line range, the vehicle state switches to normal driving, and the truck operates on its own as an all electric battery truck.
Zoomlion: “Usually in a working cycle, heavy load ramps are the slowest operating link, and ordinary diesel vehicles on continuous ramps generally have a speed of only 8-11 km/h. Ordinary all electric vehicles are limited by power battery power and thermal management.”
The Zoomlion ZT115DPEV is not limited by the battery power under trolley, and uses a dual-motor with a four-speed automatic transmission, allowing for a speed of >15 km/h on a continuous 10% slope, thereby reducing cycle time and increasing productivity.
Zoomlion says that large rigid trolley trucks of around 8 m width can only accept a lateral shift of the pantograph of about 2 m, otherwise they will lose power. Their width also means wider ramps are needed to accommodate trolley operation. The ZT115DPEV wide body truck has a width of only 4.2 m and is equipped with a double-adjustable self-following pantograph.
It can move horizontally by ± 1 m, plus has rotational movement by ± 0.7 m, while the total adjustable range of the sliding line and the pantograph is 5.3 m. The small turning radius still allows easy and fast driving, greatly improving flexibility and the driving experience.
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