K+S tests electromobility underground at Werra potash mining operation

Fertiliser and salt producer K+S is testing the use of electromobility in its German mines. The suitability of the charging infrastructure and safety underground are currently being tested in addition to the everyday suitability and range of the vehicles in a mine at the Werra integrated plant. In the long term, electric vehicles are to replace diesel-powered vehicles in all K+S mines.

“Electric vehicle operation in a mine poses special challenges,” explains Lars Rickfelder, Head of Underground Technology at K+S’s Mining central function. Due to general conditions such as high ambient temperatures of up to 50°C, uneven road surfaces, and large inclines, all vehicles must have good off-road capability, which also has an impact on power consumption. Many of the off-road vehicles and pickups are on the road all day in multi-shift operation, covering up to 100 kilometres per shift.

They can only ever be charged for short periods in between, and charging facilities cannot be made available everywhere in the mines. “It’s comparable to a cab that’s on the road around the clock,” says Rickfelder. “Making sure the vehicles are ready to go at all times is not a trivial task, certainly not in a mine.”

The current e-mobility project at the Hattorf-Wintershall potash mine of the Werra integrated plant consolidates previous isolated tests of electric vehicles in the German K+S mines. The small electric fleet for tradesmen and area supervisors includes six pick-ups based on a tried-and-tested off-road vehicle. Instead of the diesel engine, the automotive supplier has installed a high-voltage battery, the necessary charging electronics, and an electric motor. According to the manufacturer, the unit has a maximum output of just under 120 hp and a range of around 110 kilometres. A standard all-electric van for eight passengers is also in use.

In more detail, the vehicles running in Werra are converted Toyota Land Cruisers – referred to as Electric Cruisers – supplied by technology supplier and integrator, Huber Automotive. The Electric Cruiser e-drive system comprises standard components from leading suppliers, for example from Bosch Rexroth. These are arranged into a new architecture that best exploits their individual strengths. This is all made possible thanks to the core element of the system, Huber’s innovative control unit that uses a 32-bit power architecture to extract peak performance from the individual components under ideal thermal conditions.

There is currently no standard electric replacement for the diesel-powered all-terrain vehicles and pick-ups that have been used as access vehicles in the mines to date. In recent years, models with low-emission diesel engines have been purchased to reduce emissions. In the meantime, however, the first manufacturers have announced that they will no longer sell their off-road vehicles with diesel engines from 2023. “Due to the ban on combustion engines decided by the EU, vehicles with diesel engines will no longer be available in the long term anyway – the switch to electric vehicles must also be made in the mines, and we must prepare this well,” says Rickfelder. In addition to the suitability of the vehicles for everyday use and their range, important aspects include a suitable charging infrastructure and safety in the mine.

“The operation of electric vehicles also poses new challenges for the mine rescue teams,” reports Patrick Kniest, Head of Mine Rescue and Fire Protection at the Hattorf-Wintershall mine. Although the risk of fire in electric vehicles is fundamentally lower than in cars with combustion engines, the fire behaviour differs. The adapted fire protection concept therefore provides for the mine fire brigade to prepare for a possible operation with burning electric vehicles through exercises and with special equipment. “We have analysed everything in detail and are well prepared for a possible operation,” says Kniest.

“Another focus of the trial operation is the charging infrastructure,” says Sebastian Hühne, Head of Technical Staff at the Hattorf-Wintershall mine, who is supporting the project. A separate 400-volt charging network was set up specifically to enable the batteries to be charged quickly. Since the mine vehicles are on the move during the shift, the only time left to charge the batteries is during the shift change. This is feasible, as experience to date has shown, although the challenge will increase with more than 300 battery cars in the mine in the long term: “Then we have to use and distribute the available energy as effectively as possible,” says Hühne. The intelligent charging technology used already allows the charging processes at the current twelve charging boxes to be monitored, controlled, and statistically analysed by computer.

Another aspect of the introduction of e-mobility in the mine is the training of employees. At present, the vehicle manufacturer is still taking care of all the necessary work. “In the long term, of course, the e-vehicles will be maintained and repaired by our own employees. For this purpose, the colleagues have to be trained accordingly,” says Hühne.