HomeRail NewsLocos go bi- and tri-mode!

Locos go bi- and tri-mode!

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Guest writer: Keith Fender

Rail Engineer has previously looked at several innovative forms of traction for new passenger trains; from the Hitachi built bi-mode (electric / diesel) trains now widely in use in the UK (with other bi-modes such as the Class 769 conversions coming into service soon) to the iLint hydrogen powered train in passenger service in Germany (with several hydrogen powered projects announced in the UK too now).

However, until now, we haven’t looked in detail at the developing range of bi or tri mode locos now being designed and built for use in the UK and Europe.

Not a new idea

Dual mode, bi-mode, or electro-diesel locos are not new in conceptual terms. Diesel locos equipped with third rail pickup were developed for use by the New Haven Railroad in the mid-1950s in New York City, where steam and diesel usage was prohibited from 1903, leading to early electrification and time-consuming traction changes from steam to electric outside the city limits.

Siemens supplied electric mining locos equipped with auxiliary petrol engines to a diamond mine in South Africa as long ago as 1925!

British Rail and English Electric built a fleet of 49 Class 73 third-rail electric locos equipped with 600HP diesel engines from 1962 onwards and converted another ten older Class 71s to Class 74 (all since scrapped). 52 years later, some of the Class 73/1 versions are still in service, with the original engine, with freight company GB Railfreight, although others have been completely rebuilt as Class 73/9 with modern engines and traction equipment.

Last Mile vs. Main Line diesel

All of the major European manufacturers have developed bi-mode or hybrid locos in the last decade, but they vary considerably in terms of power rating – and orders received.

The initial trend of all the manufacturers was rather like the old BR Class 73/74 – to provide ‘Last Mile’ diesel power, enabling an electric loco to access non-electrified branch lines and yards. The diesel power installed was usually a small engine (around 180kW or 240HP, so around the power of half the old BR Class 73) hidden in an equipment cupboard inside the loco.

Bombardier and Siemens between them have sold the most ‘Last Mile’ equipped locos with Siemens selling 112 Vectrons fitted with 180kW diesel power modules and Bombardier 120 Traxx AC locos (90 of which were in use at mid-2019); the latest with 230kW diesel power modules and 40kW battery packs (used to provide a short term traction boost when the loco is operating in last mile mode).

Within these totals, Siemens is currently supplying 80 1,524mm gauge Vectrons (see top of page), each with two 180kW last mile diesel power packs, to Finnish state railway operator VR to enable replacement of diesel trip/shunting locos on non-electrified freight routes.

Bombardier has supplied ‘last mile’ diesel modules as an option since it launched the Traxx 3 variant of its long running Traxx design; the latest version, the Traxx 3 Multi System that is now undergoing final Europe-wide approval testing, can combine a quadri-voltage (1.5/3kV DC and 15/25kV AC) electric loco with a 230kW diesel power pack /40kW battery pack for last mile operation.

Austrian freight operator Wiener Lokal Bahn has six Class 187 ‘Last Mile’ equipped Traxx 3 locos on order. The locos are also equipped with remote control so can be driven in yards etc by staff on the ground. In the picture taken at Bombardier’s Kassel factory on 4 April, the loco is running on diesel and the driver is on the ground next to the loco. Side lights beside the driver’s doors illuminate when the loco is being driven remotely (they are different colours for diesel and electric operation).

WLC (Wiener Lokalbahnen Cargo) 187 324 diesel outside Bombardier’s Kassel factory, 4 April 2019. (Keith Fender)

New Trend – bi-mode main line locos

Before it sold its transportation, business based near Valencia in Spain to Stadler in 2016, Vossloh had identified the market opportunity for ‘go anywhere’ locos that could operate under catenary but which also have enough diesel power to operate through passenger and freight trains away from the electrified network.

Instead of just including a ‘last mile’ diesel module within a modern electric loco, the EuroDual loco range, which Stadler is now offering, is a capable electric locomotive that also has a powerful 2,800kW diesel engine.

Class 88 away from the wires – a guest appearance on the Severn Valley Railway in May 2018. (Keith Fender)

Vossloh also sold two versions of its initial UK-Dual design, based on the UK Class 68 (UK Light diesel loco) bodyshell, although deliveries were made by Stadler after they took over the business. Ten ‘UK-Dual’ – 4,000kW 25kV AC electric and 700kW diesel (using a Euro IIIB emissions compliant Caterpillar C27 diesel engine) – Class 88 locos were ordered by Beacon Rail in September 2013 for DRS using essentially the same body shell as the Class 68. Like the Class 68, the Class 88 used ABB traction equipment.

The Class 88 order was followed in October 2013 with an order for 50 similar but 1,067mm gauge locos for passenger services in South Africa, for delivery in 2015-16. A modified version of the ‘UK Dual’ bodyshell was chosen to accommodate the South African loading gauge. Whilst some of these were built, in advance of the UK Class 88s, deliveries have been suspended due to ongoing contractual problems in South Africa.

Late in 2018 came news of a planned new variant of the UK Dual Class 88 – but this time a tri-mode loco – with diesel, overhead electric and also battery power.  Beacon was once again to be the buyer, but the end customer would be UK stock-movement specialist Rail Operations Group. So far, the locos have not actually been ordered, so technical details are limited, but lithium-titanate batteries would be fitted to store energy from regenerative braking plus the overhead supply.

The design concept assumes use of the batteries to increase starting power, enabling heavier trains to be moved and to supplement diesel power for short periods, for example when going up gradients. The Class 93 may feature a slightly more powerful diesel engine than that used in the Class 88.

Pan European bi-modes

Some of the big European manufacturers are aiming to supply freight operators with locos that are powerful enough, as diesels, to handle freight on non-electrified secondary routes but also are powerful electric locos for use on electrified trunk routes. This is especially true in countries such as Germany or Austria, where most diesel-hauled freight currently operates for hundreds of kilometres under electric catenary (as much as 80 per cent of the time in Germany).

Very few ‘pure’ main line diesel locos have been built for use in Europe in the last decade; Stadler’s Euro 4000 six-axle design has taken the majority of orders, with Siemens and Alstom selling very few. Bombardier has sold 51 of its Traxx Multi-Engine (Traxx ME) loco to operators in Germany – this design has four small diesel engines instead of one large one, offering cheaper maintenance, the ability to operate with one or two engines switched off when running light, and redundancy.

Spanish manufacturer CAF built the first big European bi-mode locos over a decade ago. Nine six-axle ‘Bitrac’ electro-diesels were built for use in Spain, but CAF sold no more. These 4,500kW electric / 3,600kW diesel locos (fitted with two MTU 12V R43L engines) are now owned by Beacon Rail and leased to French Railways’ international freight subsidiary Captrain.

EuroDual for ELP under construction at Stadler’s Valencia factory in early 2019. (Keith Fender)

The Stadler EuroDual design, as already mentioned, is a powerful six-axle electro-diesel which utilises the same 2,800kW Caterpillar C175-16 diesel engine (as used UK Class 68 but the EuroDual uses the more-modern Stage IIIB version) in addition to offering 6,150kW (power at wheel rim) as a 25kV AC electric.

Stadler has sold 30 EuroDual locos, and agreed options for 70 more, to new Swiss-based leasing company European Loc Pool (ELP). Some are currently being tested whilst others are in production at Stadler’s Valencia factory. For the first batch of ten locos, ELP ordered two locos specifically for use in Scandinavia with winterisation (for temperatures as low as -40°C) and signalling systems for use in Norway and Sweden, plus eight locos for use in Germany. All ten locos are equipped for operation from 15kV/25kV AC catenary.

The 126 tonne locos have a starting tractive effort of 500kN (under both diesel and electric power) and a top speed of 120km/h (although they could be geared for 160km/h if required). The three-axle bogies are an improved form of those used under the Stadler Euro 4000 CoCo diesel design and each bogie has three asynchronous traction motors. Initially, the ‘German’ locos are only designed for use in Germany, although Stadler intends to secure approval for operation in other countries in the future.

Further orders

In addition to the ELP order, Stadler has orders for ten EuroDual (15kV/25kV AC bi-mode) locomotives for German operator HVLE. ITL (owned by SNCF French Railways via Captrain) also ordered four locos in the same configuration for use in Germany in late 2018. The prototype EuroDual, which is a 25kV AC/1.5kV DC bi-mode version, has been sold to VFLI in France – unlike the other locos this loco is equipped with French safety systems.

During 2019, Stadler has announced an order for seven locos for Turkish open access operator Körfez Ulaştırma, due for delivery in 2021. Körfez Ulaştırma will use the locos to operate 2,000-tonne oil trains in Turkey. Stadler will also maintain the fleet.

Stadler says it has now sold 74 of its new EuroDual six axle locos. Stadler has also announced orders for 22 bi-mode locos for Spanish national rail infrastructure manager ADIF for delivery in 2021/22 – technical details for this order have not been announced.

Siemens presented the first of its new ‘Dual Mode’ (DM) version of the Vectron locomotive in March 2019. Designed as a mid-power diesel loco (2,400kW) and mid-power AC electric loco (2,000kW) in one four-axle loco, the Vectron DM offers the maximum flexibility to freight operators for traffic that originates or is destined for places on non-electrified lines but which uses the electrified main line network for the trunk-haul part of their routes.

Siemens estimates that German freight operators, currently using over 700 older diesel locos, could save 53 per cent of their energy and maintenance costs, plus reduce CO2 emissions by 950 tonnes annually per locomotive, by using the new Vectron DM instead of an existing diesel loco.

Siemens developed and built the first German Class 248 Vectron Dual Mode loco from scratch in six months. This fast concept to prototype period was possible as the Vectron Dual Mode uses bogies and traction motors from the existing diesel-only Vectron DE platform and these were already available as, so far, only nine Vectron DE Class 247 locos have been built since the model’s launch in 2010.

The Vectron Dual Mode will now probably replace the Vectron DE in Siemens’ range, although the company would potentially continue to offer it to customers outside Germany if the order quantity was economically attractive.

The 90-tonne loco is capable of 160kmh. It is equipped with a 2,500-litre diesel fuel tank and the German PZB signalling system (although it is pre-equipped for ETCS). Whilst not designed for passenger operation, Siemens says it could be equipped with electric train supply for air conditioning etc if that was requested. Siemens is currently testing the two prototypes and seeking orders for the new Vectron Dual Mode with delivery from Q4 2020 promised.

The MTU 4000 engine used in the Vectron Dual Mode, fitted with a set of large air filters, meets EU Stage V emissions standards (as does the four-engined, pure-diesel Bombardier Traxx ME).

NJT ALP 45DP leaving Seacaucus Junction, New Jersey, June 2017. (Keith Fender)

Across the Atlantic

Bombardier has also built bi-mode locomotives, but not for use in Europe. Its ALP 45DP BoBo electro-diesel has been supplied to commuter rail operators in New Jersey (USA) and Montreal in Canada. New Jersey Transit (NJT) has a fleet of 35 and is currently adding a further 17.

The 4,000kW (electric), 2,700kW (diesel) ALP45DP has an axle loading of 34.1 tonnes (compared to 22.5 for the four axle European Siemens Dual Mode). The North American loco is fitted with two Caterpillar 3512C HD engines and, in the case of the NJT locos, works from two traction voltages too (12.5kV 25Hz AC and 25kV 60Hz AC) at up to 125mph (electric only).

Siemens has also built bi-mode locos for US commuter operator Long Island Railroad in the 1990s (23 DM30AC electro-diesels delivered from 1996).

Adding a third dimension – battery power

While developments in battery technology are leading to all major manufacturers looking at battery power for passenger trains, it is increasingly being considered for locomotives too.

Battery powered locos are not new – the first named “Galvani” was demonstrated by its inventor Robert Davidson between Edinburgh and Glasgow in 1842!

During the 19th century, many manufacturers built small battery shunting locos but, using lead acid batteries, they were heavy, slow and had limited range.

A British battery loco that is 102 years young this year, and still in daily use, seen at Hythe in August 2019. (Keith Fender)

The Hythe Pier railway in Hampshire uses two small Brush-built electric locos delivered as battery locos in 1917 to work in an armaments factory. They are still in use, although converted to third rail operation, as this August 2019 picture shows!

Battery technology has moved a long way in the last few years. Batteries are now being used daily for trams in many cities – although often only for short sections – and they are now seen by all the major manufacturers as a key traction option for the future. As mentioned earlier, the Beacon/ROG Class 93 design would use batteries, primarily to enhance starting performance but also to store energy.

Combining modern battery technology with electric traction systems and, in some cases diesel engines, as well, could be the next trend in locomotive design. Some such locos already exist – Chinese rail engineering firm CRRC has delivered electric locos with battery packs, charged via regenerative braking or ground supply, for use operating engineering trains on metros in Sydney (Australia), Hong Kong and Guangzhou (China). Maximum Speed using battery power is 40km/h.

CRRC loco for DB at Innotrans 2018. (Keith Fender)

CRRC has also supplied two diesel-battery hybrid shunting locos to German Rail operator DB for use operating maintenance trains on the Hamburg S-Bahn network (one was displayed at Innotrans in 2018). A total of four locomotives are on order, to be equipped with lithium-titanate batteries capable of generating 150kW of traction power (or, with the 250kW diesel engine, a combined 400kW).

In August, Welsh rack-railway operator the Snowdon Mountain Railway announced it has ordered two battery-diesel hybrid locomotives from British manufacturer Clayton Equipment. The new locos will replace older diesels and will use regenerative braking on the descent to generate energy for use on the next ascent to the summit of Snowdon.

Several smaller European manufacturers, including Gmeinder, are now offering battery hybrid options for previously diesel-only designs; the Gmeinder DE75 BB four-axle shunter has a 354kW Caterpillar engine and a lithium-ion traction battery pack producing 600kW of traction power between them.

Russian manufacturer Transhmash unveiled a diesel battery hybrid loco in 2019, equipped with a 200kW diesel engine plus a 240kW lithium ion battery pack.

Vossloh Locomotives, which is being bought by Chinese firm CRRC, offers its DE18 four-axle diesel with 150kWh battery packs in addition to the standard ‘straight’ 1,800kW diesel version.

Turkish manufacturer Tülomsas has rebuilt mid-1980s vintage Turkish State Railways DE11000 diesel locos with smaller 300kW diesel engines plus 400kW of lithium-ion battery power. The resultant hybrids are able to run on either or both power sources as required.

DB Regio H3 operating in battery mode at Nuremberg Hbf on 13 December 2016. (Keith Fender)

Alstom has been building diesel-battery hybrid locos designed for trip freights, shunting industrial plants and empty stock moves in Germany for five years. The ‘H3’ three axle design equipped with Nickel-Cadmium batteries has sold fairly well and is in use in Germany and central Europe. A bigger four axle development of the technology – the ‘H4’ – has been developed, but the only order so far for Swiss Railways (SBB), who have ordered 47 Class Aem 940 locos for infrastructure trains. These are classic electro-diesels equipped with two Caterpillar C18 diesel engines.

In 2017, CAF announced it had won a contract to supply twelve 1,000kW electric/battery hybrid locos to Paris metro and rail operator RATP to operate engineering trains on the RER network. The locos will be produced at CAF’s French plant and incorporate ten tonnes of nickel-cadmium batteries, as well as traditional pantographs for overhead power collection.

Battery power for passenger trains

Hitachi has announced plans to develop battery-powered trains for the UK market and has already delivered them in Japan. The wider Hitachi group is already a major automotive battery supplier and Hitachi Rail Europe has previously said it expects the rail market to piggyback the developments in battery technology for road transport; the market for which, on a global scale, is many times bigger than the market for rail.

The company has been developing hybrid and battery technology since 2003, largely in Japan. In 2007, it fitted a Class 43 HST power car with battery technology and ran trials in the UK in partnership with Network Rail. The train, named Hayabusa, completed over 100,000 km. The result was a 15 per cent fuel saving and a silent and emission-free movement out of stations.

In 2017, Hitachi delivered the BEC819 series ‘DENCHA’ (Dual Energy Charge Train) BEMU to Japanese operator JR Kyushu. Now in passenger service, it is operating for 50km route on battery power, between recharges.

Hitachi is now planning to add batteries to its UK bi-mode trains, which will be used alongside diesel engines to form a tri-mode hybrid power system. Hitachi expects not only to boost acceleration rates, but to cut fuel consumption (and costs) by 10 per cent or more. Hitachi also point out that batteries can benefit station environments too. Using them for initial operation in and out of busy stations can cut noise and air pollution, which is highly significant as air quality at some UK stations breaches safe legal limits significantly due to diesel emissions.

Siemens battery train on test in Austria.

Siemens, using lithium-titanate battery units, and Bombardier (lithium-ion batteries) are already testing battery equipped EMUs in Germany and Austria respectively.

Alstom’s new iLint hydrogen-powered train, which is now in service in Germany, is a hydrogen/battery hybrid with a sophisticated control system that uses batteries to store energy from regenerative braking and minimise fuel-cell load variations. As hydrogen fuel has a greater energy density than batteries, it clearly has some passenger multiple-unit applications and has also been used for shunting locos in America and China. However, it currently seems unlikely that hydrogen will have any major role in locomotive design.

Stadler has developed and sold battery-equipped versions of its Flirt EMU – 55 battery/15kV AC overhead power trains for use by NAH.SH (the public transport system in Schleswig-Holstein) in northern Germany and 24 tri-mode 25kV AC/ diesel and battery versions for use in the Welsh valleys by Transport for Wales.

Batteries with everything?

The convergence of differing propulsion systems, with both electric traction equipment and even diesel engines becoming more compact and needing less space in a locomotive car body, plus the likely future development of battery technology, could lead to the disappearance of ‘simple’ diesel or electric locos. If batteries are cheap and powerful enough, they can power movements in depots or assist with self-rescue for failures and could become standard.

One major European freight operator calculated that simply restarting an older, 1960s vintage diesel loco and moving it from one end of a yard to the other costs around £50 a time! With batteries, such costs disappear.

Battery technology for transport use is developing rapidly, and billions are being spent by the automotive industry to enable this. The UK Automotive Council estimate that the energy density of batteries could quadruple by 2035, yet even this is only one tenth of the energy density of diesel.

Hence, for more demanding rail applications such as heavy freight, high speed trains or even high-frequency metro-style services, it is unlikely that batteries will ever have a major role – although anyone re-reading this in 2050 might know better!

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  1. I have been watching the development of battery and hydrogen powered trains for some time.

    I have a quote from Bombardier, that Aventras are built to take a battery or super capacitor.

    Having stood on a platform, whilst a Class 345 Aventra has passed. They are a very quiet train. Noise is often the product of turbulence, which increases the drag, as a train, car or plane passes through the air.

    If you look at the nose of an Aventra, it is carefully curved and smoothed and I wonder if Bombardier have used aerodynamic expertise from their aircraft division to reduce the drag. This would mean that a train can cruise at the operating using less energy, which would mean smaller and lighter batteries.

    I have done calculations, which I believe show that there is little difference between the drag of a HST and a Hitachi Class 800 train. That is not very good progress over forty years.

    Is it significant that the new AT-300 trains for the Midland Main Line have a reprofiled nose?


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