THE LEADER VOLUME 19 • NUMBER 6
Dynamic trolley traction
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This issue comes immediately on the back of a hugely successful Electric Mine 2024 conference organised by our sister company International Mining Events and held May 21-23 at Crown Perth in Western Australia . One of the stand out talks was from Christoph Kettner , System Manager Truck-Trolley at Siemens Mobility & Michael Lewis , Senior Director – Decarbonisation and Electrification at Komatsu . They covered ‘ Dynamic charging of battery trucks – project insights and roadmap .’ It detailed the background and development of a trolley line developed at Komatsu ’ s Arizona Proving Ground ( AZPG ) near Tucson , a view of which is featured on this month ’ s front cover .
Kettner executed the project as Chief Engineer but pointed out from the outset that of course Komatsu and Siemens have a long history in supplying trucks and infrastructure for trolley assist operation of open pit mines . Their first joint reference dates back to 1986 when the first trolley line was commissioned at the Rossing Uranium mine in Namibia . Komatsu 730E diesel-electric trucks run off this line which has now been in operation for almost 40 years , during which time there have been several relocations of trolley lines and substations during mine expansions . Currently active lines are TL12 , 14 , 15 , 16 and 17 .
Kettner said that one of the major concerns raised relating to trolley assist is extra space requirements on the haul road – but then pointed out that even at Rossing it only involved an additional 50-80 cm to accommodate the poles and foundations . Of course the other major concern is a feeling that trolley is inflexible – again citing Rossing , at that one mine there have been more than 10 relocations since the 1980s .
Then Michael Lewis at Komatsu reviewed its product development roadmap for carbon neutrality – emphasising that it will not be one solution fits all with mining trucks – battery trolley with dynamic charging and battery with static charging will play a major role but so will hydrogen , e-fuel ICE , biofuels , hybrid and other approaches . He then talked about the importance of collaboration – such as its own GHG Alliance which now includes 12 mining companies working with Komatsu closely on truck electrification .
Lewis then talked about trolley specifically which for Komatsu covers its power agnostic diesel trolley truck and power agnostic battery trolley . For battery trolley , electricity from trolley lines powers uphill segments with battery power utilised for other segments – the battery is charged while on trolley and when retarding . The max trolley power transfer to each truck is 6.5 MW .
Highest efficiency is about 85 % from the line to wheel motor with speed increases of up to 90 % with obvious cost advantages over diesel in addition to the emissions wins . Due to the trolley upside in that it is one of the most cost effective ways to power a battery mining truck allowing in most cases continuous operation , Lewis said Komatsu decided quite early on that it wanted to have its own trolley line at AZPG . “ We wanted to learn about it , we wanted to be able to demonstrate it , we wanted to be able to evolve it over time .”
Battery truck development would benefit from the integration of trolley throughout the test and validation phases , improving quality . Having the test trolley line would improve operational understanding of the deployment and use of trolley plus it would support future projects such as autonomous trolley .
Kettner then continued the presentation with some details on Siemens ’ offering – a patented zero-emissions solution which combines on-board energy storage with off-board truck trolley . “ Our knowledge in Siemens Mobility is located in the Overhead Catenary System ( OCS ) and the substations .” Since the 1980s , Siemens has been providing this solution to different mines including Rossing and Kansanshi . But the latest version maximises modularity which in turn ensures flexibility – with standardised prefab substation buildings that are shipped pre-commissioned . The OCS is also standardised with a modular design from foundation to clamp . As stated the system is fully relocatable .
One of the other questions Siemens is often asked is about energy demand and how many trucks can be on the trolley at the same time . Kettner said : “ It doesn ’ t matter – as the system is modular we can adjust it according to requirements .”
Finally , details on the AZPG project came from Lewis – project planning kicked off 2020 with line assembly completed August 2022 with it being powered up February 2023 . The location was chosen also being close to the existing 24 kW grid transmission line , and the utility company was flexible in permitting 10 MW of power to be used on and off as required .
The 1.2 km trolley line has a curve radius of 60 m and starts flat then has a grade of up to 10 % inside the curve ; plus it was designed to enable connection of the pantographs on the curve . These were also firsts for the industry and have enhanced Siemens Mobility ’ s trolley offering . Plus , it has a switch over substation capability enabling a switch from 1.8 kV DC to 2.6 kV DC in only two minutes . This was a requirement to be able to test different electrical configurations on Komatsu trucks . Komatsu is also adding high power static charging at AZPG .
Given the timing during the tail end of the pandemic there were challenges with concrete and other material availability as well as logistics and electrical and steel worker availability . But it was a big achievement for both Komatsu and Siemens – and saw the first ever ultraclass battery electric mining truck running on trolley .
Lewis concluded : “ Working with a great partner brought us ultimately to success .” He also emphasised open communication , flexibility and a willingness to work together towards a common goal as a team .
Paul Moore Editorial Director paul @ im-mining . com
JUNE 2024 | International Mining 3