247 energy. With 2025 prices for diesel (1.16 €/Liter) and for electrical energy (120 €/MWh) the potential of yearly savings is 2.4 Mio €. 4. BATTERY TECHNOLOGY FOR BEV – TROLLEY TRUCKS With the given trolley installations, a battery equipped trolley truck could dynamically charge the battery during trolley operation at an average power level of 500 kW. Together with downhill recuperated energy this is sufficient for charging the energy which the trucks need in their haulage cycle off the trolley line. For the specific situation at the Erzberg mine with ramps where trolley assisted haulage is enabled a battery capacity of 500 kWh would be sufficient. On uphill loaded haulage cycles with trolly assistance as well as on downhill loaded cycles without trolley assistance the discharge of the battery would be around 50 kWh. The 500 kWh battery could run on a regular 45 to 55% duty which means a depth of discharge (DoD) ratio of 10% to maximise battery lifetime. For sufficient traction power off the trolly the 500 kWh battery must meet a ratio of charge/discharge speed relative to its capacity (C-rate) between 2 and 2.5. The C-rates between 2.0 and 2.5 result in power between 1000 kW and 1250 kW and enable loaded uphill haulage without trolley assistance. On the other hand, quick charging is possible in the same power range. The 500 kWh battery capacity would assure to handle one or more full cycles without trolley assistance in case of unexpected failure of the trolley system. The battery chemistry which fulfils the above C-rate requirement is lithium-ion based with nickel-manganese-cobalt based cathodes (Li-NMC). For Li-NMC a battery lifetime of 6000 cycles at a DoD ratio of 10 % can be expected whereas lithium-ion based with iron phosphate-based cathodes (Li-FPO) would offer >10000 cycles for a 10 % DoD ratio in use (Chian, 2019). Parameters like additional truck dead weight, quick charge requirements, battery costs and battery second life use should be considered and the resulting total costs over the lifetime of a battery equipped trolley truck need to be compared to choose the right battery type. 5. FURTHER MINING EQUIPMENT ELECTRIFICATION POTENTIAL Due to the inhomogeneous ore body and the necessity of ore quality blending at the Erzberg mine, the equipment used for mining operation (ore and waste rock handling) needs to be flexible. Therefore, the use of cable-bound equipment (like drill rigs or excavators) is possible but would involve costly and time-consuming workload. At Erzberg mine two of the three substations for the trolley installation are situated in close distance to operating benches for ore and waste rock (see Figure 8). The involved 10 kV AC switchgears could handle cable bound electrical connection either for a direct supply to mining equipment or for charging stations for battery electric mining equipment.
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