Two energy efficiency strategies cover most of the fuel efficiency opportunities available to the rail freight sector.
Implement fuel efficiency improvements
A wide range of strategies and technologies exist to improve fuel efficiency in the rail freight sector including weight reduction, driver assistance software, improved aerodynamics and throttle management.
Examples of opportunities in these areas are outlined below.
Investigate weight reduction
Steel has traditionally been used to make freight cars for rail transport. There is potential to make cars out of lighter components such as aluminium, composites or plastics. The weight of rolling stock can also be reduced with improved design and by replacing mechanical control systems with electronic fly-by-wire systems.
Applying these strategies will lead to fuel savings by increasing each wagon’s load factor (payload of the wagon as a proportion of the total gross mass). This would then enable locomotives to pull greater freight loads without exceeding load limits and to save fuel on empty return runs.
For more information, see Weight reduction.
Invest in double-stacking
Double-stacking involves placing one high-cube (2.896 m high) container on top of another. A low-floor wagon is needed so that the double-stack is not more than 6.5 m above the top of the rail. Double-stacking can allow trains to carry 30–40% more freight by weight than similar length single stack trains with no additional power. Double-stacking also has the potential to reduce traffic on rail networks.
Double-stacking is prevented on some Australian routes as there are lower axle-load limits and smaller loading outlines. For example, it is permitted on the Parkes–Adelaide-Perth line, but restricted loading clearances on the North–South corridor prevent double-stacking. Infrastructure investment to support double-stacking would enable improved rail efficiency and reduced dependence on road freight.
For more information, see Double stacking.
Use driver assistance software
Driver assistance IT systems, such as portable loggers and GPS receivers, enable freight trains to optimise their fuel efficiency performance. The on-board computer calculates this based on the type of train, its location, weight, speed, fuel consumption, the gradient and curvature of the track, GPS location and driving techniques. The software provides instructions to optimise power, e.g. slower acceleration towards maximum permitted speed, coasting and running at lower speeds to allow more gradual deceleration before braking.
Examples of such software include:
- Freightmiser route-optimisation software – Pacific National has introduced this Australian designed software to help its drivers conserve 4–15% fuel and maintain schedules.
- LEADER (Locomotive Engineer Assist Display Event Recorder) – US software technology that calculates the optimum speed at which a train should travel based on line segment grade and curvature.
- Trip Optimizer – Software installed in GE diesel-electric heavy-haul locomotives is reported to enable fuel savings of 4%–13%.
- Consist Manager – Developed by the US Department of Energy and GE Transportation Locomotive Technology Program, Consist Manager utilises existing driver-guidance software to constantly check and select the optimal throttle positions of trail units. The system uses a multiple unit control system based on lead locomotive throttle-setting and operating conditions such as grade severity and train length. Consist Manager does this by constantly evaluating locomotives and load with the aim of optimising the distribution of power between locomotives. The system is reported to provide an additional fuel saving of 1–3% for each locomotive when used in combination with other driver assistance software.
For more information, see Driver assistance software.
New electronic control techniques safely enable freight trains to run closer to each other, allowing more trains to be on the same tracks at one time. The ability to increase the amount of freight carried by rail depends on the number of freight track lines and their length, the amount of load the trains can carry and the speed at which they can be unloaded and reloaded.
Modern switching can be done by moving just the containers across a platform horizontally, rather than shifting entire railway cars for loading. Twenty or more containers can simultaneously be switched from one train to another, or into a warehouse. Using such means, an entire goods train can be reconstituted in 15 minutes.
A significant amount of the energy used by freight trains is lost via air resistance. While studies suggest there is some potential to improve aerodynamics of locomotive engines, there is considerable potential to reduce aerodynamic-drag losses for certain car configurations, e.g. those that include empty cars and intermodal cars (two containers stacked on a flat car). Aerodynamic drag losses for intermodal cars can be as high as 30% of the energy used.
This issue can be addressed by various measures, including add-on components that don’t require replacement of rolling stock. For example:
- streamlining the sides and underfloor sections of trains
- minimising the gaps between cars
- filling gaps with air bags and covering open cars
- using wheel covers to reduce aerodynamic drag; it may be feasible to apply lessons from the trucking industry regarding easily managed covers
- appropriate design of freight cars.
Bearing in mind the significant volume of bulk rail freight, such as grain and minerals carried by unit trains, there is also considerable scope to improve the aerodynamics of wagon design and operation.
Studies have shown that a reduction in drag by 10% has equated to a fuel saving of 6–7%.
Software is available to rate the overall aerodynamic profile of a train by examining the frequency and length of gaps between wagons. For best results, the full length of the train must be considered. There is also software that can assess the best sequence of containers for a train.
A US modelling comparison between best and worst case scenarios found that fuel savings of as much as 2.2 L/km per train could be achieved.
For more information see Improved aerodynamics.
Use effective wheel/rail lubrication
Trains depend on friction to prevent wheels from slipping or derailing, especially along curving tracks. Wheel/rail friction makes up a significant component of the energy used in rail transport.
Lubrication to reduce friction levels can also reduce energy usage, wear and tear, and excessive noise, as long as it is done in a way that does not compromise wheel-to-rail contact. An Australian study suggested that 13% energy savings of can be achieved through effective lubrication.
Lubricants can consist of oil, grease or water. They can be applied automatically from systems installed on the side of the track (wayside) or from onboard lubricating systems, where the lubricant is mounted on the locomotive or lead car and applied on each curve. While wayside grease is generally more common, on-board lubricating systems are also starting to be used in Australia and around the world.
Invest in electronically controlled pneumatic brakes
Electronically controlled pneumatic (ECP) braking involves a brake communication network that activates the entire train’s braking mechanism simultaneously. The alternative to date has been mechanical systems that operate progressively down the train.
ECP brakes enable trains to operate at higher average speeds and carry heavier loads while remaining within safety limits. Fuel savings can be achieved due to improved train handling, reduced wagon braking and lower compressor duty cycles. ECP braking systems also enable the use of longer trains and improved safety.<
Optimum benefits are most likely to be achieved where changing terrain allows higher downhill speeds. This enables the resulting increased inertia to reduce the need for power and maintains higher speeds when travelling up the next hill.
For more information see Electronically controlled pneumatic brakes.
Use anti-idling devices
Anti-idling devices use engine management software to automatically shut off the main diesel internal combustion engine and then restart it when the water temperature and battery charge (among other parameters) fall below a specified threshold that would impede a quick start or restart.Retrofitting devices is not difficult, but fuel savings depend on the amount of time spent idling in normal operations.
In North America, significant reductions in fuel consumption have been identified by shutting down locomotives when idling. For example, US rail company Union Pacific have equipped more than 70% of their locomotive fleet with stop-start equipment, through new locomotives and retrofitting. Union Pacific found that locomotive shutdowns can save 15–24 gallons of fuel, per locomotive per day.
In Australia, regulations prevent locomotives being switched off on main lines. However, anti-idling devices can be used on private rail freight lines in Australia. It should also be noted that in remote locations, driver comfort might require auxiliary power systems.
For more information see Idle management devices.
Take advantage of speed and throttle management
Operating at lower speeds and restricting throttle usage reduces the need for braking and can also reduce aerodynamic drag. The severity of the grade and percentage of speed reduction will cause fuel savings to vary. However, simulations suggest potential fuel savings of up to 8% are possible for limiting throttle usage and up to 11% for speed reduction with little or no capital cost.
A number of factors determine both the speed of a train and throttle position, including:
- instructions of the train controllers
- interactions with other trains
- loading and unloading.
Increases in travel time may raise service issues.
The US rail company Union Pacific is using speed reduction initiatives as one of its fuel saving strategies. Their ‘Conservation Speed 50 program’ shows that there are a number of tasks, which are not as time critical as others, where average speeds could be reduced.
For more information, see the Speed management.
Retrofit or replace older locomotives
The Australasian Rail Association (ARA) has developed a proposed plan of action to partner with government to address the ageing fleet of locomotives and put industry in line with international performance. ARA’s initiative includes a shorter term 10-year government-industry program of retrofitting and/or replacing up to 183 of Australia’s worst performing locomotives.
For more information
Use alternative drivetrain engine technologies
Alternative drivetrain engine technologies can reduce energy loss and improve overall energy efficiency.
Some examples of opportunities in this area are outlined below.
Replace DC traction with AC traction motors in locomotives
AC traction systems can replace conventional DC traction motors to provide improved levels of wheel to rail traction. This can enable less powerful locomotives, or a smaller number of locomotives, to perform the same task. SCT Logistics used AC Traction to achieve 30% more loading, and was able to replace four DC traction locomotives for two or three locomotives.
Other benefits of AC traction motors include reduced maintenance requirements due to the smaller number of locomotives performing the same tasks and quicker servicing turnaround times.
For more information see AC traction.
Investigate hybrid locomotives
Hybrid locomotives operate in a similar way to hybrid motor vehicles. Propulsion power is provided by a large battery that is recharged by a small diesel generator. A regenerative braking system can be integrated into the hybrid combination to convert kinetic energy back into electricity to be stored when braking. The hybrid system also allows the diesel generator to run at a constant speed (the most efficient operating point) and so reduce fuel consumption.
More research is needed to better understand the potential applications of commercial hybrid line-haul freight. Its application could be particularly applicable to long downhill runs or hilly terrain where braking is often used. Many rail lines from mines in Australia run downhill to the coast and could generate net energy output.
It is important to note that there could be rail gauge issues on these new hybrid locomotives which could limit their applicability to Australia.
For more information, see the Hybrid drivetrains.
For more information
- Fuel for Thought - Potential energy efficiency opportunities in the Australian road and rail sectors 2011
This report catalogues potential opportunities for energy efficiency improvements in the Australian road transport (heavy duty vehicles only) and rail transport sectors. It was designed to supplement energy efficiency assessments undertaken by transport operators involved in the Energy Efficiency Opportunities program.
Research and development is currently underway internationally in a number of areas to assist the improvement of fuel efficiency in the rail transport sector including:
- Diesel locomotive engines – fuel injection/combustion and in-cylinder controls, exhaust gas utilization, sensors and controls
- Locomotive systems – idle reduction, energy recovery, motors and drives
- Fuel use optimisation – operations optimisation, train fleet management, wheel/rail friction reduction, aerodynamics, rolling resistance
- Alternative drive-train engines and electrification of rail – hybrid engines, homogeneous-charge compression ignition (HCCI), fuel cells, gas turbines, locomotive electrification, dynamic braking
- Alternative fuels – compressed natural gas, liquefied natural gas, liquefied petroleum gas hydrogen fuel.
The Australasian Rail Association has developed a plan for R&D into alternative fuels for rail transport, including:
- compressed natural gas
- liquefied natural gas
- liquefied petroleum gas
- hydrogen fuel cells.
For more information