DIESEL has long been the principal form of traction used by heavy-haul railways, which often operates over long distances, and through remote and rough terrain. But while its high freight capacity means the sector is already more sustainable than other modes, pressure is mounting to further decarbonise.
The issue was highlighted during the International Heavy Haul Association (IHHA) conference held in Rio de Janeiro on August 27-31, under the theme of “Application of Heavy Haul Innovations for a Sustainable World.”
The conference showed there is no shortage of willingness and no lack of innovation within the sector to effect this change, but it will not happen overnight, with most railways talking of alternative traction technologies maturing by 2030 to support a goal of going carbon-neutral by 2050. There are also cost considerations, with railways operating on fine margins and wary of overspending on new technologies that may in turn provide insufficient levels of tractive power.
A key question to be answered is the calculation of the energy required to haul the train. This includes calculating the tractive power and the gravitational energy of going downhill, and against the rolling resistance, rail resistance, curving resistance, air resistance, and gravitational energy if going uphill. Key factors in energy use also include the length of the route, train weight and elevation gain.
This can be achieved using modelling and simulation but is also now possible through direct calculation using the data gathered from the locomotive.
“The question is how much energy input is required for the routes, and then how do you get that sustainably,” says Mr Shaun Robertson, principal advisor rail for the Rio Tinto group.
Australian freight operator Aurizon undertook technical modelling of the total energy requirements collated from 150 round trips across 13 rail corridors, to determine the current energy provided by diesel traction. The modelling also measured the potential energy that could be collected through regenerative braking, showing the remaining energy use that would be required from the new zero-emissions traction options.
However, the options for decarbonising while matching existing performance are currently limited.
Battery-electric
The most advanced option is the use of battery-electric locomotives (BEL). Around 40 are on order for heavy-haul applications around the world, with deliveries expected by 2026. Onboard batteries can also provide first and last-mile capability, an application especially conducive to mining railways by enabling battery charging while travelling at slow speeds during loading and unloading activities at ports and mines.
Brazilian mining company and rail operator Vale announced in July that it has launched a partnership with Wabtec under which the US supplier will provide three FLXdrive BELs, as well as collaborate on a project to test ammonia fuel as a potential clean alternative to diesel. The project supports Vale’s ambitious targets to reduce its GEE scope 1 and 2 emissions by 33% up to 2030 and become carbon-neutral by 2050.
“BELs have been selected to maximise energy efficiency, as the locomotives are equipped with regenerative braking.”
Alexandre Alves da Silva, Vale’s decarbonisation manager
“The decarbonisation of our operations is a journey in which we analyse all the options available and choose those that prove to be more effective,” says Vale’s decarbonisation manager, Mr Alexandre Alves da Silva. “In the case of railways, which are responsible for 10% of our emissions, we have arrived at the conclusion that the best options are green ammonia, ethanol and biodiesel.”
Vale will deploy the three battery locomotives on the Carajás Railway (EFC) following delivery in 2026. The railway’s trains are some of the world’s longest, often consisting of 330 wagons carrying up to 45,000 tonnes. The battery locomotives will supplement the three to four diesel units on a 140km uphill section in Açailândia, Maranhão, where the train’s fuel consumption is highest, replacing the two supplementary diesel locomotives currently used.
Photo: Shutterstock/DihandraPinheiro
The FLXDrive locomotives are expected to reduce diesel fuel consumption by up to 25 million litres per year when considering all of the EFC trains that will benefit from battery locomotive operation.
Alves da Silva says BELs have been selected to maximise energy efficiency, as the locomotives are equipped with regenerative braking. He says this is one of the most compelling arguments for introducing battery traction into heavy-haul operation as they can recover a significant amount of the energy currently lost as heat and noise when braking the heavy trains.
“[Regenerative braking] is such an incredibly simple concept, you wonder why we weren’t doing this before, but there’s a lot of work in the industry now to try to develop these options,” Robertson says.
Regenerative braking can be particularly suitable for railways that carry freight from a mine, typically at elevation, down to a port at sea level. Mining the ore above sea level creates “an enormous amount of gravitational potential energy,” Robertson notes.
Robertson pointed out that a tonne of ore at 500m elevation has around 1.3kWh of potential energy. “Think about a 20 million tonne per annum mine at 500m, you’re looking at 26GWh of energy that isn’t used at all at the moment,” he says. “You can think of your railway as an energy generator and you can get the physics and train configuration right to try and recover some of that.”
Hydrogen
Alternative technology such as hydrogen fuel cells are also being examined, but more research and development is needed to ensure these can be scaled to meet the needs of a heavy haul railway.
Nevertheless, a presentation by Ms Achila Mazini, an industrial engagement fellow at the Birmingham Centre for Railway Research and Education (BCRRE) in Britain, showed that the technology could be a viable alternative to diesel. The research presented by Mazini examined the feasibility of using hydrogen traction in freight railways in Brazil, and to assess whether hydrogen fuel cells would be sufficient to transport mining products or grain.
The research applied a Hybrid Train Simulator (HTS) developed by the University of Birmingham to a representative service operated by Brazilian freight operator VLI Logistics, taking into consideration the route alignment and elevation, fleet characteristics, and the configuration of existing diesel consists to measure the energy and power requirements which were then compared with the outputs of an equivalent hydrogen fuel cell system. The simulator creates a model that predicts a train’s motion under specific conditions like gradient, train mass, friction, and applied traction forces by combining mathematical formulae.
“It’s not a problem that one railway can solve all by themselves or one vendor can solve by themselves so as an industry we’ve got the opportunity to collaborate more here.”
Shaun Robertson, principal advisor rail for the Rio Tinto group
VLI Logistics currently hauls trains of up to 80 wagons on the stretch simulated by the model, a 720km section of the 4400km North-South Railway, which runs from Açailândia in the state of Maranhão to Estrela d’Oeste in São Paulo.
“The simulations conducted in this paper demonstrated that the use of hydrogen on freight railways in Brazil and on this specific route is a feasible and competitive option for decarbonising the sector,” Mazini says. “Specifically, the study found that hydrogen traction could meet the energy and power requirements for transporting mining products by rail, and it also found that for this specific journey, refuelling stations and additional tankers to improve range and power supply were not required.”
While further research is needed to assess the economic feasibility of implementing this technology, including the costs of production, storage, and distribution of hydrogen fuel, the study answers important questions about whether hydrogen can provide the tractive effort required by heavy-haul operation.
Other options such as methanol have been suggested, while Class 1 railways in the United States are exploring renewable fuels and biodiesels. Vale says conversion from diesel to ethanol, still for internal combustion engine use, is another promising alternative. Numerical simulations and initial bench tests with ammonia following the signing of the agreement with Wabtec in July are also evolving with promising results.
Most likely, heavy-haul railways will use a combination of these options to achieve their decarbonisation targets (see panel below).
Electrification
Until these new developments progress, electrification remains the only mature option for full zero-emission operation. Some heavy-haul networks around the world are electrified, but there are a number of challenges to more widespread use.
Rail electrification can have a big impact on the electricity supply network, particularly due to the high amount of energy needed to power a heavy-haul train. There are also safety considerations when installing the system, and maintenance costs. Ease of maintenance can also be an issue due to the remoteness of many heavy-haul lines.
The upfront cost of installing overhead electrification and purchasing new electric locomotives can be prohibitive, and these costs can grow if the installation of electrification results in a need to upgrade the signalling to prevent interference, or a desire to fully utilise the higher line speed electric operation allows, which may in turn require track upgrades.
However, Mr Richard Wales, director of consultancy services at Australian company Andromeda Engineering, proposed during the conference that changes in technologies and engineering standards were making electrification, either full or partial, more feasible.
The introduction and development of static frequency convertors (SFC) could reduce the impact on the energy grid. New studies have also shown that the depth of the piles on which catenary masts are installed could be reduced from 5m to 2.5-3m, while the distance between masts could be increased by up to 30%, further reducing costs.
The developments in battery technology could also further support the introduction of partial electrification. “The island could be 1km long, it could be 100km long, it really comes down to the operating model on your network,” Wales says. “With island electrification, you can adapt it to your particular operating model and the particular points where you use the most energy.”
Electrification can also be paired with regenerative braking. “The batteries can get full, so we can recover even more energy into the electrified islands and return it back to the grid,” Wales says.
Ultimately, Robertson says, there is not yet one easy solution. However, he says it is encouraging that railways around the world are considering and testing similar options.
“It’s not a problem that one railway can solve all by themselves or one vendor can solve by themselves so as an industry we’ve got the opportunity to collaborate more here,” Robertson says. “You’re probably already noticing the duplication in the presentations so the more that we can do to talk together and collaborate together, work together on this solution, I think the better for the industry and ultimately, the better for the world as well.”
Aurizon continues path to decarbonisation
THERE’s no one-size-fits all approach when it comes to decarbonisation for Aurizon, Australia’s largest rail freight operator.
The company, which carries approximately 250 million tonnes of coal, iron ore, minerals, agriculture and general freight annually, owns and operates 5000km of heavy-haul rail infrastructure. This includes the 2200km Tarcoola - Darwin line, and the 2670km Central Queensland Coal Network (CQCN), 2000km of which is electrified, making it one of the world’s few electrified heavy-haul networks. The railway also has 670 active locomotives across the fleet, ranging in gauge and weight.
Aurizon has a goal to become net zero by 2050, reducing its greenhouse gas emissions, which in the 2022 financial year totalled 835,000 of CO2-equivalent scope 1 and 2 emissions.
“If we are to reach our 2050 goal, it’s necessary to be much more deliberate and future-facing, to reach that goal we need to introduce new technology.”
Roger Buckley, Aurizon fleet decarbonisation manager
Aurizon fleet decarbonisation manager, Mr Roger Buckley, says this objective is complicated by the complexity of Aurizon’s network, which also includes operation on lines it does not own and a mix of standard-gauge and narrow-gauge operation. To meet these challenges, the fleet decarbonisation programme includes both immediate and near-term measures together with long-term changes.
In the short term, this includes reducing idling through the deployment of automatic engine start-stop systems to prevent extended engine use; exploring the use of zero-carbon drop-in fuels containing renewable diesel or synthetic diesel; and the deployment of train energy management systems.
“However, if we are to reach our 2050 goal, it’s necessary to be much more deliberate and future-facing,” Buckley says. “To reach that goal we need to introduce new technology.”
Aurizon has identified three end-state platforms as the building blocks to its future fleet composition: a battery electric locomotive (BEL) for short-haul operation up to 400km; a BEL tethered to a battery electric tender (BET) for medium-length hauls up to 850km; and a BEL tethered with a hydrogen electric tender (HET) for longer hauls up to 1800km. For journeys greater than 1800km, such as from Broken Hill in New South Wales to Kwinana near Perth, either hydrogen refuelling stations or additional onboard hydrogen will be needed.“
These programmes will systematically eliminate our emissions as the required solutions and infrastructure are developed,” Buckley says. “However, these programmes will by their nature be slow to start as will their contribution to our emissions reduction, hence why it’s necessary for us to have that first stream of emissions reduction.”
Retrofit
In May, Aurizon announced it had awarded Caterpillar subsidiary Progress Rail a contract to retrofit an existing class 4000 diesel locomotive with battery traction. Conversion of the locomotive is expected to be completed by early 2025, with on-track trials commencing in the first half of 2025.
With the class 4000s making up a quarter of its fleet, Buckley says the focus is on retrofit. “Due to their relatively young age they’ll still be with us in 2050, so we will need to find a decarbonisation pathway for them,” he says.
The project will deliver 4.5MWh of battery capacity, with the batteries positioned above and below the existing underframe. The project includes installing a new electric compressor and blowers and will provide individual axle control. The battery will be charged using a 1.4MW inverted pantograph located in the depot.
“Our aim is to build a replacement locomotive with a 20-tonne axleload with similarly compatible tractive effort to the existing diesel locomotive,” Buckley says.
The next stage of the programme is the development of the BET.
“To progress the BET technology we did not want to wait for the existing BEL manufacturers to deliver a tender as their roadmaps either don’t contain tenders or do not contain them fast enough for us,” Buckley says.
“So in order to progress with the prototype development of the BET concept, it’s been necessary to consider the modification of an existing locomotive such that we can use the tender as a source of energy. This allows us to consider and explore multiple modes of operation, all of which are of significant interest to us. It’s possible to run in a diesel-only mode, in a battery-only mode, and finally in a true hybrid mode. We’re continuing to work closely with a supplier and we look forward to sharing more information around this exciting project in the future.”
Work is also continuing on the HET.
In December 2021, Aurizon and global mining company Anglo American entered into an agreement to conduct a now-completed feasibility study to explore the application of Anglo American’s proprietary hydrogen fuel cell and battery hybrid power units in heavy-haul freight rail operations.
The study focused on the potential deployment of the hydrogen power technology on Aurizon’s Moura rail corridor between Anglo American’s Dawson metallurgical coal mine and Gladstone Port, and the Mount Isa rail corridor from the North West Minerals Province to Townsville Port, via Aurizon’s Stuart Terminal.
“To progress the BET technology we did not want to wait for the existing BEL manufacturers to deliver a tender as their roadmaps either don’t contain tenders or do not contain them fast enough for us,”
Roger Buckley
“That work concluded that the hydrogen electric tender was the preferred configuration given the space constraints on our physically smaller locomotives,” Buckley says.
Aurizon, working with First Mode, has since developed a system that can incorporate the hydrogen storage, fuel cells, the cooling system, batteries and dc-dc converters required into a standard 40-foot container, with only an electrical connection to the BEL.
As well as examining the energy demands over a specific route, Aurizon is also modelling the total cost of ownership across the lifetime of the various traction types. The model includes the replacement of the components during the life of the asset, such as the replacement of batteries based on the number of cycles or fuel cells based on operating hours. The model also estimates the reduction in cost of technologies such as batteries and hydrogen fuel cells over time, based on Aurizon’s research, government figures, and “reliable sources.” Importantly, the model includes capital costs for the locomotives, tenders, and charging and refuelling infrastructure, as well as taking into account energy costs and lost revenue associated with the payload loss from pairing a tender with each locomotive on the train.
“This model shapes our strategy on project funding and customer engagements,” Buckley says. “The model is continuously updated as we get information from trials of the technology, performance, and costs.”
The modelling predicts that by 2030, the three zero-emissions platforms will be similar in price to diesel traction and will be much cheaper than renewable diesel or using hydrogen in a combustion engine, due it its lower efficiency compared with fuel cells.
“We will maintain our total cost of ownership view as the technologies mature and emerge,” Buckley says. “But as you can see, the model outcomes support our relentless focus on the three-platform approach and the results have not changed for us despite the many technical changes over the last four years.
“Our immediate action is to focus on renewable energy. We’ve already taken the commercial steps to get to 25% green energy by 2025 (for electrical energy supply to the Central Queensland Coal Network). The second is to find a retrofit pathway for our two dominant classes, which we’ve kicked off with our Progress Rail BEL, and to further look for a long-term solution for our standard-gauge fleet which is the basis of our growth in the bulk business.”
