BACK TO BASICS – ELECTRIC TRAINS E-Trains – from definition to working principles
Calls for an electrification of railways are a constant in the debate on sustainable and climate-friendly mobility – but what exactly are the benefits of electric trains and what is the current state of the art of this technology? You will find the answer in this article.
Electric Trains: Definition
An electric train (E-Train) uses an electric motor powered by electricity from overhead lines, a third rail, or on-board energy storage such as a battery or a supercapacitor.
How do E-trains work?
Electric trains can get power from a rechargeable energy system like a battery or from a stationary source such as an electrified third rail or overhead wire. Traditionally, E-trains are distinguished by the type of electrical current they use - alternating current (AC) or direct current (DC). Early train systems used DC due to a lack of knowledge of AC and dangers around the high voltage lines as insulation wasn’t yet available.
Third rail systems utilize DC power. The train is equipped with a metal contact block called a “shoe” which makes contact with the electrified rail. Today, these third rails use side or bottom contact to enable protection of the electrified rail for railway workers and from weather.
Overhead traction once upon a time also used DC power but has evolved to AC, which is now more common and the system that is usually favored for new mainline and high-speed railways. Since DC locomotives usually run at low voltage, the equipment needed to be large to transmit enough power. High voltage AC systems enabled the use of low currents. The wiring infrastructure was lighter and cheaper and therefore more practical for long distance routes. Trains use a roof-mounted apparatus called a pantograph to contact the overhead wiring.
Once collected by the pantograph, electricity passes through a circuit breaker. The electricity undergoes a transformation inside the transformer, the rectifier and the inverter before reaching the traction motor where it is converted into mechanical energy.
The history of E-trains
In the discussion about climate-friendly mobility, E-trains may appear as a novelty and innovation. In fact, however, attempts to use batteries to move a railway vehicle date back to the 1830s, although the technology was only used for commercial purposes in the late 19th century on suburban and metropolitan railroads.
The first electric railway dates back to 1879 when Werner Von Siemens successfully demonstrated the technology at the Berlin Industrial Exposition in Berlin, Germany on May 31, 1879. The train, presented by the company Siemens & Halske, got its power through the two rails using a 150 volt direct current. The demonstration stunned those in attendance. Two years later, Berlin had the world’s first electric tramway. In 1894, Hungarian engineer Kálmán Kandó developed high-voltage three phase alternating current motors and generators for electric locomotives. He is considered to be the father of the electric train. By 1896, the city of Budapest would claim Europe’s first electric underground railway.
Meanwhile in the United States, the Baltimore & Ohio Railroad became famous as the first mainline railroad to electrify a short stretch of its Baltimore trackage in the 1890's. In 1904, the General Electric Company tested the first electric locomotive powered by a gearless drive bi-polar motor built for the New York Central Railroad. The New York Central Railroad therefore became the first steam railway in the U.S. to electrify any of its major trackage. The locomotive, known as the No. 6000, could run at speeds of up to 75 mph (120 kph). Current was supplied using a similar method to the B&O Railroad’s via a third-rail system – an electrified rail picking up the current using a "shoe" on the locomotive, and covered by a wood plank.
Electrification programs, including on mainline railways, were undertaken all over Europe after the First World War and, to a lesser degree, in the United States as well. In 1964, the first high-speed rail system began operations in Japan with the name Shinkansen, or “bullet train.” European high-speed passenger rail travel followed, starting with France’s TGV trains in 1981.
Today, the proportion of electrified tracks in the national railroad system varies between countries, from 100 % in Japan and Switzerland to only 32 % in the United Kingdom. Presently, the United States only has about 1 % of its tracks electrified.
Electric trains also continue to play an important role in the rail landscape, especially through high-speed passenger services like the French TGV, Japanese Shinkansen and to some degree in the U.S. with the Acela Express. China currently has the largest amount of kilometers of high speed rail with many more planned. The country dedicated USD300 billion to build a 25,000 km HSR network by 2020 and this has largely succeeded. E-trains are also the standard for urban rail lines, commuter lines and underground railways.
What are the advantages of E-trains?
Electric traction is generally considered the most economical and efficient means of operating a railroad, provided that cheap electricity is available. Electric locomotives have several advantages:
- Cost: The cost of electric train engines is about 20 % less than diesel locomotive engines on the global market. Maintenance costs are said to be 25-35 % less than for diesel engines. With some fluctuation for the price of fuel vs. electricity, it is estimated that it is 50 % less expensive to power a train by electricity than by diesel.
- Efficiency: They can draw on the resources of the central power plant to develop power greatly in excess of their nominal ratings to start a heavy train or to surmount a steep grade at high speed. A typical modern electric locomotive rated at 6,000 horsepower can develop 10,000 horsepower for a short period. In terms of efficiency, there is no contest. Diesel-powered trains are able to transfer 30-35 % of their energy to the wheels through the combustion process. Trains that get their energy from an overhead powerline transfer roughly 95 % of that energy to the wheels.
- Environment: Electric locomotives are quieter in operation than other types and produce no smoke or fumes benefitting the environment both from an emissions and noise pollution standpoint. As not all trains are currently electric, eliminating diesel-powered locomotives would reduce pollutants such as soot, volatile organic compounds (VOCs), nitrogen oxides, and sulfur oxides. This would have an effect on public health as well as the environment. E-trains can have even greater environmental benefits if the source of electricity comes from renewable energy.
Challenges for the electrification of railways
The high cost of electrifying lines to power electric locomotives, either by third rail or overhead catenary, continues to be one of the main obstacles to this technology. Maintenance costs for the infrastructure such as the traction current wires and structures and power substations are also a factor.
A lack of political will to build regional or nationwide infrastructure may also be lacking. Germany currently has approximately half of its rail network electrified. The government aims to have 70 % of the rail network electrified by 2025. However, in 2019, less than half a percentage point was added to the total. Progress can be slow.
Innovation for high-speed electric trains
One challenge for high-speed trains comes from the connection between the pantograph and the overhead line. The pantograph sits on top of the train connecting it to the powerline and therefore must maintain good contact with the overhead powerlines. In some places such as the UK mainline, pantograph height can vary by roughly two meters due to differences in terrain such as tunnels, level crossings and bridges. Research is underway to develop active pantographs that improve contact eliminating contact loss due to dramatic changes in the height of the overhead line or due to high winds.
High-speed trains are in competition with the airline industry. Speed and reducing travel time are important goals that affect the amount of passengers who will consider high-speed train travel. When the developers of Alstom’s AGV train wanted to improve upon the TGV’s top travel speed of 320 kph to 360 kph, they needed to completely rethink their design concept. Traditionally, Alstom’s very high-speed trains used a power car concept (another name for an electrical locomotive), which is a dedicated car for the motor, power equipment and driver. Each train therefore needs two power cars. For the AGV, the designers developed an innovation that got rid of the need for power cars. They designed the bogies – the chassis that carries the wheelset – to carry the train’s motors.
The new architecture positioning the specially developed bogies between the carriages of a train, instead of in their traditional positioning under the carriages. The advantages include less NVH inside the carriages, better damping, and also improved safety in the case of a derailment. The carriages do not deform and the increased rigidity helps to keep the AGV upright. The removal of the locomotives has the added benefit of increasing the passenger capacity of the train by about 20 %.
Design innovations are also constantly evolving to solve challenges. The extremely long noses characteristic of recent versions of the Japanese Shinkansen bullet trains, are designed not for aerodynamics, but mainly to eliminate sonic booms caused by the "piston effect" of trains entering tunnels and forcing compression waves out of the other end at supersonic speeds.
Who are the main manufacturers of E-trains
CRRC Corporation Limited is the world’s largest rolling stock manufacturer by revenue. The company and its subsidiaries produce both diesel and electric powered trains. In summer of 2020, CRRC unveiled the first of its Shen 24 28.8 MW electric six-section locomotives. The 24-axle locomotive is intended for hauling coal trains. Another workhorse electric locomotive made by CRRC subsidiary Datong Electric Locomotive is the HXD2 model. This 13,000 horsepower locomotive was built in cooperation with the French multinational manufacturer Alstom.
Alstom is among the world’s biggest rail manufacturers and is known for its products such as the AGV, TGV, Eurostar, Avelia and Pendolino high-speed trains. Its AGV train broke a speed record on a test run in 2007 reaching a speed of 574.8 kph.
In an effort to compete with the market share of CRRC Corporation Limited, there have been a number of mergers and attempted mergers in the past few years. Most significantly, in September of 2020, Alstom signed an agreement to acquire the rail division of its competitor Bombardier Transportation.
Bombardier Transportation is well known for its metro rolling stock such as the fully automated and driverless Innovia Metro. Many of its trains can be found transporting passengers within the transit systems of cities all over the world. The company also produces a number of E-train locomotives including its TRAXX (Transnational Railway Applications with eXtreme fleXibility) modular platform. All variants within the platform feature two bogies with two powered axles each and three-phase asynchronous induction motors. Riders of the New Jersey Transit in the U.S. will recognize the Bombardier ALP-46 as the electric locomotive driving riders to and from their destinations.
With its long history of innovation in E-trains, Siemens AG is still a major manufacturer in the railway industry. The company has been involved in the production of Deutsche Bahn’s high-speed ICE train originally as part of a consortium with ABB and AEG and in cooperation with Bombardier to manufacture the latest version, ICE 4. This newest generation of ICE is based on the power car design concept in an entire traction system is contained in one car, including the transformer, traction converter, traction cooling unit, and four traction motors.
Kawasaki Heavy Industries is also a major player and well known for its metro rapid transport platforms. The company has the additional distinction of manufacturing the Japanese Shinkansen bullet trains. Throughout its 56-year history, not a single passenger has been killed or injured on Japan’s high-speed network. The next generation of bullet trains, known as ALFA-X, is being tested at speeds of almost 250 mph (400 kph), although the trains will only operate at 225 mph (362 kph).
E-Train usage worldwide
Europe, Japan and Russia lead the way in regard to E-trains, while North and South America still rely heavily on diesel to power their railways. For example, electrified rail makes up less than 1 % of U.S. railroad tracks. In nearly all regions, passenger rail is significantly more electrified than freight. Countries and regions that have more urban and high-speed railways typically have a greater share of electrified railways.
High speed rail is a specialized area of electric train operation. China currently leads the world in kilometers of high speed rail followed by Spain, Japan, France, Germany, and Sweden.
As of 2018, Switzerland was the only country in Europe to have all of its railway lines in use electrified. At 95.3 %, Luxembourg had the highest share of electrified railway systems of the European Union member states. The EU average was 54.3 %.
Why does the U.S. lag behind?
Despite being world leaders in railroad innovation for much of the 20th century, the U.S. now lags behind other advanced nations that have invested in electric-powered railroads for many years. In the first half of the 20th century, steam engines were replaced by cleaner and more efficient electric locomotives as well as diesel or diesel-electric hybrids. Due to the significantly lower initial cost of investment, U.S. railroad firms chose diesel despite their higher costs to operate and maintain over time.
Unlike other countries, U.S. railroads were private companies and were not owned by the state, making it less attractive to invest in and finance electrification upgrades to rail systems.
Are E-trains the future?
The global electric locomotives market is expected to decline from USD6.53 billion in 2019 to USD6.4 billion in 2020 mainly due to the COVID-19 global health crisis. Post-pandemic, the market is expected to recover and reach USD7.85 billion in 2023.
Electrified railways are considered the most environmentally friendly mode of transport. But what about when electrification is not economically viable or can be impractical for other reasons? As noted above, in Germany, for example, just over half of the tracks are electrified. For sections of track that are not electrified, a hybrid powertrain can be a solution. However, traditional hybrid powertrains utilize a diesel motor for operation on non-electrified track, thereby reducing the environmental benefits achieved through electric trains. Siemens Mobility developed the new Mireo Plus regional train platform to tackle this problem, giving railway systems the ability to run their operations efficiently and economically without local CO2 emissions.
Siemens Mobility developed a completely new system architecture with the latest-generation fuel cells and high-performance batteries integrated in a modular design. The flexible vehicle concept allows both a purely hydrogen-powered multiple unit for longer, non-electrified routes and a battery-electric train for only partially electrified routes, or any combination in between. The Mireo Plus H variant features both a fuel cell and battery. A two-car train has a range of up to 800 km, while a three-car train can reach up to 1,000 km on non-electrified track. This is enough to cover the longest regional routes in Europe. If the electricity or hydrogen comes from renewable energy sources, then the Mireo Plus can claim to operate completely emission-free.
In early 2020, Alstom also announced its first contract to supply battery-electric regional trains (the Coradia Continental BEMU) for Germany’s Leipzig-Chemnitz line. Looking forward, hybrid concepts that incorporate hydrogen fuel cells and/or batteries are likely to help fill the gap in electrified rail networks.
Typically used for special purposes such as in mines or industrial facilities where an errant spark from an electric line could have disastrous consequences, battery-electric trains are starting to gain traction in more traditional railway settings. In 2020, Hungary’s railway operator MÁV launched a public procurement procedure to acquire 50 battery-electric trains. The new trains will replace the country’s costly and pollution-heavy diesel trains with new zero-emission rolling stock. The Hungarian company expects significant improvement in terms of energy efficiency once the new fleet is acquired and a direct cost savings of HUF3.6 billion (EUR10.18 million) annually. Unfortunately, at the time of writing, the tender has been withdrawn after questions from interested parties about technical specifications. It has been reported that the company does plan to reissue the tender.
So are E-trains the future? The answer depends on the country and region. Clearly countries in Europe as well as Japan and China have already invested heavily in electrified rails and high-speed train infrastructure making the cost of continued E-train investment favorable.
Hybrid solutions will help to connect non-electrified sections of track. However, in countries such as the U.S. that currently lack significant distances of electrified track outside of urban areas, there is a high bar to entry for widespread E-train use. Increasing public awareness of climate change issues may help to make the case for investing in the infrastructure needed for widespread electrification of U.S. railways.