The rail transport sector operates in a very competitive business environment. Small improvements in fuel efficiency or changes in fuel costs can have a big impact on profit and competitiveness.
Many energy-efficiency measures offer other benefits such as increased productivity and reduced maintenance costs.
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.
Double stacking is placing one high-cube container on top of another. This can enable carriage of up to 40% more freight than similar length single-stack trains with no additional power. It can also reduce rail traffic.
The benefits of double-stacking should be assessed against the effect on energy use created by weight increases and aerodynamic-drag. Be aware also that double-stacking is prevented on some Australian routes as there are lower axle-load limits and smaller loading outlines.
Speed and throttle management
Operating at lower speeds and restricting throttle use reduces drag and the need for braking.
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.
New electronic controls safely enable freight trains to run closer, allowing more trains to be on the same tracks at one time. The ability to increase freight depends on the number of track lines and the speed at which trains can be unloaded and reloaded.
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. An entire goods train can be reconstituted in 15 minutes.
Driver assistance software
Driver assistance systems, such as portable loggers and GPS receivers, enable freight trains to optimise fuel-efficiency. The software provides instructions to optimise power, such as slower acceleration towards top speed, and coasting at lower speeds for gradual deceleration before braking.
A significant amount of the energy used by freight trains is expended due to air resistance. Studies suggest potential to improve aerodynamics of locomotive engines. There is considerable scope to reduce aerodynamic-drag losses for certain car configurations, such as those that include empty cars. Drag losses for intermodal cars can be as high as 30% of energy used.
This issue can be addressed using methods that don’t require replacement of rolling stock:
- Streamline the sides and underfloor sections of trains.
- Minimise gaps between cars.
- Fill gaps with air bags and cover open cars.
- Wheel covers to reduce aerodynamic drag.
Software is available to rate the overall aerodynamic profile of a train by examining the frequency and gaps between wagons. There is also software to assess the best sequence of containers for a train.
Trains depend on friction to prevent wheels from slipping or derailing, especially along curving tracks. Wheel/rail friction makes up a significant portion of the energy used in rail transport.
Lubrication to reduce friction can also reduce energy use, wear and tear, and excessive noise. Lubricants can be applied from systems on the side of the track (wayside) or from onboard systems.
Electronically controlled pneumatic braking
Electronically controlled pneumatic (ECP) braking 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 speed with heavier loads. ECP braking systems also enable the use of longer trains and improved safety.
Optimum benefits are achieved where terrain allows faster downhill speeds. The increased inertia reduces the need for power and maintains higher speed when travelling up the next hill.
Anti-idling devices use engine management software to shut off the main diesel engine and restart it when certain parameters fall below threshold. Retrofitting devices is not difficult, but fuel savings depend on the length of time spent idling in normal operations.
In Australia, regulations prevent locomotives being switched off on main lines. However, anti-idling devices can be used on private rail freight lines.
Alternative drivetrain engine technologies
Alternative drivetrains can reduce energy loss and improve overall energy efficiency. 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 for improved wheel-to-rail traction. This can enable less powerful locomotives, or a smaller number of locomotives, to perform the same task.
AC traction motors have reduced maintenance requirements due to the smaller number of locomotives performing the same tasks and quicker servicing turnaround times.
Hybrid locomotives operate in a similar way to hybrid motor vehicles. Propulsion is provided by a large battery that is recharged by a small diesel generator. A regenerative braking system converts 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 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.
Solar powered trains
The world’s first 100% solar powered train began operating at Byron Bay New South Wales in December 2017.
In Europe, Bankset Energy Corporation is trialling a system of solar panels that clip over railway sleepers and produce 200Mw of electricity for every 1000km of track. The electricity generated would be used in overhead powerlines for trains, as well as feeding power to nearby business and residences. The company predicts that trains and rail will be 100% powered by solar energy and batteries in the near future.
The German and UK governments have invested in hydrogen trains as part of their efforts to combat air pollution.
In September 2018, 2 hydrogen fuel-cell powered trains took their first passengers on a 100km route in northern Germany. Emitting only steam and water condensation, the hydrogen powered trains perform similarly to their diesel rivals, comfortably cruising at 140km/h with a 1000km range and accommodation for 300 passengers.
The 30-year-old UK fleet will be retrofitted with hydrogen fuel cells and tanks. This will provide an alternative to electrification to cut noise and emissions on the majority of the network which is currently served by diesel trains.
Hydrogen has a lot upsides for transport applications, particularly regional trains that cover vast distances. The fuel can be loaded up and transported to where demand is, and when created from renewable energy it is entirely emissions-free.
Proponents predict that the lower running costs of hydrogen trains will mean the additional costs will pay back within 10 years.
See the Australian Renewable Energy Agency (ARENA) website for more information.
Project i-TRACE Australasian Rail Association
Transport case studies Clean Energy Finance Corporation