Innovations in rail travel are making trains faster, safer, more efficient and environmentally friendly. Of all the transportation modes, rail is leading the way in new technologies.
Electric railways are becoming more common in response to both environmental and cost concerns. High-speed rail technology is promising speeds beyond 300 mph in a matter of a few years. And, without a doubt, rail transport is more autonomous than other forms of transportation.
Trends in railway electrification
Let’s start by taking a look at what is happening with regard to railway electrification.
Most high-speed trains today get their electricity from overhead wires or catenaries using a pantograph. That’s because, given current designs and technologies, batteries can’t be sized to supply the necessary power and still fit on the train. Diesel engines turning generators don’t meet new environmental mandates. Plus, the weight, storage demands and costs of diesel fuel, along with fire safety concerns, create added challenges. Another option has been to use a shoe to take electricity from a third rail (similar to light rail), but this has proven to create too much friction between the shoe and rail at high speeds.
A major challenge when using pantographs to take power from the catenary is maintaining consistent contact between the two without creating too much friction. Most pantograph systems work on compressed air. An auxiliary compressor can deliver the needed air supply, but this method has proven costly and the compressor takes up valuable space that could be put to better use in optimizing capacity for freight or passengers.
Several companies have invested in alternatives. Parker eliminated the need for an auxiliary compressor by designing a compact, fully integrated “plug and play” control system, which contains all the pneumatic functions along with a reservoir. The redesigned main control module system is linked to the reservoir, from which the pantograph system draws compressed air. This solution is attractive since it’s lightweight, space-efficient, less expensive and requires fewer components that need to be maintained and replaced.
Another issue that crops up with catenaries is ice on the overhead wires. To combat this problem, some trains are deploying two pantographs so that the first one knocks off the ice. To handle travel in either direction, train makers often package a pair of pantographs in the same overhead fairing, mounting them face-to-face.
Energy-waving, high-speed rail technologies
Along with the desire to convert more diesel locomotives to electricity is an interest in minimizing or reusing electric energy. Beyond the obvious environmental benefits are cost advantages, since energy (fuel) represents the largest cost component in total transport costs. This has led to an increased interest in many energy-saving technologies like regenerative braking that converts the kinetic energy from the braking motion into electric energy for purposes of energy reuse. Electricity is then fed back through the overhead lines so it can power an accelerating train on another track or be stored for future use.
Challenges remain, however, to find sufficient space for storing electricity. When there is no place to store or use the electricity, it gets burned off in roof-mounted braking resistors (rheostatic braking) or the train switches to friction braking.
Energy storage systems
Energy storage systems are currently available in multiple forms. Some of the more common include flywheels, electric double-layer capacitors, batteries, fuel cells and superconducting magnetic energy storage devices. In evaluating the various options, attention is paid to their high energy density and power density, as well as their total cost, environmental impact, space efficiency and weight.
In general, battery-based energy storage systems have higher energy densities but their capital costs are often higher, and they have more limited lifespans. The market is looking for technology breakthroughs that will lower the cost of the storage systems. By 2030, for example, it is expected that the cost of lithium-ion batteries will drop considerably due to technology advances regarding their design and production. There are, however, environmental drawbacks of batteries since they use toxic materials. Flywheels offer the greatest environmental appeal, but the future ideal solution is seen as one that will combine the advantages of different energy-storage technologies.
Regenerative braking is preferred because, in addition to its obvious energy efficiency, it minimizes wear and tear. Another option, however, is the use of linear eddy-current brakes which consist of electrical coils positioned along the rails. The coils serve as magnets with continually switched north and south poles. When the magnets move along the rail, their changing magnetic field creates another field in the metal rail, which creates electrical tension and eddy currents to provide enough resistance to slow the train.
Improving train aerodynamics is yet another way to significantly affect energy usage, since up to 60% of the tractive force can be lost due to drag and friction. Covering roof-mounted equipment with streamlined fairings also reduces drag and limits the booming sound trains make when traveling through a tunnel.
Exploring alternate energy forms
Solar rail is a relatively new concept for producing clean energy for railways.
Australia has been effectively using solar panels on the roofs of its electric rail cars since 2017.
Hydrogen power is also being explored for greater sustainability. With this technology, fuel cells would consist of an anode, cathode and electrolyte membrane. Hydrogen would pass through the anode where it splits into electrons and protons. As the electrons are pushed through a circuit, they would generate an electric charge that is stored in lithium batteries or directly used by a train’s electric motor.
As is the case with some other technologies designed to conserve energy, the hydrogen concept needs to be perfected to ensure cost competitiveness and safety.
High-speed trains to reach even higher speeds in the future
Research is ongoing to make trains even faster and more energy efficient in the future.
In the area of high-speed rail technology, superfast maglev trains are gaining momentum. Key to their ability to reach unmatched record speeds is the use of magnets that float carriages above the ground without wheels. The technology already is being used in Europe with a second-generation technology being promised to hit the market by 2027 offering speeds in the 300+ mph range.
Elon Musk is additionally touting a hyperloop that would hit speeds up to 700 mph. The hyperloop consists of a vacuum-sealed tube that reduces air resistance and carries “pods” using passive maglev technology.
These examples represent just a few of the many innovations being explored to accelerate the speed and energy efficiency of today’s railways.
With the higher speeds, however, come greater concerns regarding safety and the added burden on various components, including increased vibration and heat.
Fire safety was a focus of Europe’s EN 45545 initiative which outlined new safety requirements for railways, especially regarding fire concerns. Parker was the first hose manufacturer in Europe to develop rail hoses using a new rubber compound that meets the requirements of EN 45545, while also offering cost savings and easy installation with its improved bend radius.
This article contributed to by Dave Walker, market development manager, Rail, Motion Systems Group, Parker Hannifin.