Trolley Assist Haulage Systems: Championing decarbonization of the mining industry

Advances in electric-drive haul truck technology over the past 20 years have been remarkable.? Digging Deep takes a closer look at the trolley-assist haulage systems and their role in championing the decarbonization of the mining industry.

What is a trolley-assist haulage system?

Trolley Assist is a system in which haul trucks in open pit mines are propelled by electric energy along a designated?haul road segment. This can lead to high savings on fuel costs, productivity, CO2?emission, and engine life, but is associated with limitations in?mine planning.

How do trolley-assist drive systems for haulage trucks work?

The drive systems for these trucks consist of two electric drive motors that are integrated through gears into the rear wheels of the trucks, an electric generator, and a powerful diesel engine. The characteristics of the drive system allow it to harness electrical power directly. In some parts of the world, electrical power can be generated inexpensively and with less emissions, depending on the fuel source.

Truck trolley systems, which simply substitute electricity for diesel fuel, may offer another avenue for further advancement. Instead of generating electricity from the diesel engine and the electric generator on the truck, it’s sourced from a dedicated substation and transmitted via an overhead catenary to the drive motors on the truck.

What is the history of trolley-assist haulage systems?

The use of truck trolley systems dates to 1882 when Werner von Siemens developed?the first electrical-driven wagon that followed overhead power lines. This system has been evolving ever since and has been used in the mining industry since 1967 when it was implemented in the Chino Mine in New Mexico.

Due to the lack of large trolley equipment, the truck trolley system has never been widely used. The energy crisis in the 1980s led to the development of a trolley system for mines. However, the interest revived again when Caterpillar introduced their first diesel-electric truck in 2006 with a payload of 345 tonnes.

Today, 西门子 is a leading supplier of trolley technology and infrastructure and the company has seen a lot of renewed interest, primarily due to diesel fuel consumption.

What role do haul roads perform in effective trolley-assist systems?

The truck trolley system is most cost-effective on the ramps, where the most energy is required. As illustrated in the diagram from Siemens below the truck trolley system has the highest benefits when driving uphill on a 6 to 10 degrees ramp.

The rest of the haulage route, i.e. flat areas and downhill ramps, will be powered by a diesel engine. It is extremely beneficial to put trolley lines on both uphill and downhill hauls to recover the braking energy. Some mines are now considering trolley assist for flat hauls just to reduce diesel consumption and extend the life of the truck engine.

What are the pros and cons of using trolley-assist haulage systems?

Like any other technology in mining, there are definitely pros and cons of trolley-assist haulage systems. These are the pros:

? High flexibility and reliability

? Low capital costs

? Compatible with all types of material

? Possibility to mine selectivity

? Fewer emissions due to the substitution of diesel fuel with electricity

? Higher uphill speed which leads to shorter cycle times

? Extension of the interval between engine overhauls

On the contrary, there are also cons to trolley-assist haulage systems. Given below are the cons:

? High operational costs

? Labor intensive

? Mine roads need to be maintained

? Inefficiency due to traveling empty trucks

? Extra investment due to the installment of the trolley line system

Where in the world are trolley-assist haulage systems being used?

Different OEMs manufacture trolley-assist haulage trucks and these include Komatsu , Hitachi , Liebherr Group and Belaz . Given in the table below are some of the different types of mines utilizing trolley-assist haulage systems around the world.

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