The imperative to decarbonise the railway has been the subject of various reports, conferences, and research grants, although, in reality, little new operational hardware has been produced to meet this challenge since Jo Johnson’s call to remove diesels in February 2018.
Nevertheless, without any industry action, since then there has been a 37 per cent reduction in CO2 emissions from electric trains as carbon emissions from UK electricity generation fell from 276 to 177 grams per kWh. Carbon emissions from electric rail passenger vehicles are now only a fifth of those of diesel vehicles. This illustrates why electrification is needed if there are to be further significant carbon reductions. However, other than in Scotland, no further electrification schemes have been authorised.
Yet electrification cannot be a universal solution and self-powered alternatives to diesel traction are also required. Currently only one such train is approved for passenger service. This is the class 230 unit produced by Vivarail, the UK’s smallest train manufacturer.
Vivarail’s chief executive Adrian Shooter was chairman of Chiltern Railways for 18 years before he retired in 2012. He is clearly enormously proud of his company’s trains. This much was clear when he invited Rail Engineer to visit his company’s facilities at Long Marston in Warwickshire to see trains being produced for Transport for Wales and the Isle of Wight.
Adrian explained that Vivarail was founded in 2012 to address the shortage of diesel trains. His solution to this problem originated from a discussion with a school friend, none other than Rail Engineer writer Malcolm Dobell. At the time, Malcolm had just retired as London Underground’s head of train systems engineering and LU was about to replace its sub-surface D78 stock. In the late 1970s, Malcolm had been part of the engineering team that had introduced these trains and, as mentioned later, he agreed that they were ideal for conversion into main line diesel units.
There were, however, two drawbacks. The D78 is limited to 100km/h (62mph) and there were concerns that the converted units might be considered to be ‘London Underground cast offs’.
However, Adrian was not deterred. He knew that there are a number of routes on which 100km/h was not a constraint, provided that the new units had high acceleration and, on Chiltern, his experience was that passengers liked suitably refurbished older trains.
Thus, in November 2014, Vivarail signed a contract with London Underground for the purchase of 156 driving motor cars and 70 trailers of D78 stock, the first of which arrived in Long Marston in January 2015.
Vivarail’s prototype Class 230 diesel multiple units used three D78 vehicles and first ran on Long Marston’s test track in April 2016. Adrian explained that the train is intended for use on lines which could be some distance from maintenance depots. For example, West Midland Train’s Class 230 service on the Bedford to Bletchley line is remote from its Tyseley diesel depot in Birmingham. Hence, the requirement is to build a train that can be maintained trackside. This was done by providing an effective remote-condition-monitoring system, which, for example, activates an auto oil top-up system, and having equipment within easily detachable modules. Using a fork-lift truck, a Class 230 engine module can be replaced within ten minutes.
With over crowded diesel trains, a situation made worse by the cancellation of electrification projects, Adrian is sure of the demand for Class 230 units which, with its modular concept, can be used for any combination of traction, for example a diesel / battery hybrid. Furthermore, Vivarail’s patented fast-charging system could significantly increase the range of Class 230 battery trains on rural routes.
He has no doubt that Vivarail can make a significant contribution to railway decarbonisation and has become increasingly aware of the benefits of battery traction. He does not envisage diesel modules being used on future Class 230 units.
He stresses that the Class 230s also have the further environmental benefit of minimal embedded carbons from the reuse of bodyshells and bogies. Fitting new equipment to withdrawn vehicles with many years’ life remaining also offers significant economic benefits. Vivarail claim that the lease cost of their trains is half that of a new DMU.
Vivarail currently employs about 200 and has its workshop at the Quinton Rail Technology Centre in Long Marston and a centre of excellence at Seaham in County Durham. This opened in 2018 to undertake engineering design, component overhaul and the manufacture of subsystems, with emphasis on bogies and wiring.
Having secured a £1.5 million loan from the Midlands Engine Investment fund, the company is now able to move from Long Marston to a new manufacturing facility at Southam, near Leamington Spa. This will enable production, engineering, design, and stores to be in one building.
Vivarail has also signed a contract with Cambrian Transport for the use of a one-and-a-half-mile test track at Barry in South Wales.
London Underground’s D78 stock fleet consisted of 75 six-car trains, built by Metro-Cammell at Washwood Health in Birmingham, which entered service between 1980 and 1983. Each six-car train was made up of two, 55-metre long, three-car units. Each unit consisted of a driving motor coach (DM), a trailer car (TC) and an uncoupling non-driving motor car (UNDM). They are lightweight vehicles, the tare-weight of the DM and TC cars sold to Vivarail were respectively 30.7 and 21.2 tonnes.
They have a riveted aluminium underframe and bodyshell with four single-leaf doors per car, per side. As the trains operated on London’s District line, they were built to a loading gauge only slightly smaller than that of the main line.
Their 650-volt DC supply was provided from 3rd and 4th rails. Each motor bogie had two 300V DC traction motors in permanent series. A pneumatic camshaft-controlled traction resistor configured each bogie set in series or parallel control and provided two stages of weak field. A Train Equipment Panel monitored the operation of essential equipment.
In the late 1990s, the trains were fitted with new bogies as the original bogies were prone to fatigue cracking. The new bogies have a flexible frame design with a knuckle joint in each side frame. Brake equipment was renewed at the same time.
Between 2005 and 2008, the D78 fleet was refurbished at Bombardier’s Derby works in a £77 million contract to create a modern passenger environment equivalent to that on a new train. This included new seat shells and cushions, floor coverings, grabrails and more substantial metal armrests, as well as the provision of CCTV and improved public address.
London Underground’s wish to standardise its sub-surface fleet with S7 and S8 stock, which is compatible with its new signalling and control systems, resulted in the D78 stock being withdrawn ahead of its intended lifespan. Hence, Vivarail purchased trains with many years’ life left in them that were refurbished just over ten years ago and had relatively new bogies with little corrosion in their aluminium bodies. It seems they got a bargain.
Converting the D78s
Readying the D78 stock for diesel propulsion on the main line required a number of modifications. One of these was improved crashworthiness, as the converted D78 stock will be exposed to collision hazards, such as those at level crossings, that do not occur on the closed London Underground system. This required the provision of a cage in the driving cab and redesigning fittings around it. Additional plating was also installed below the window panel to prevent objects piercing the cab.
This arrangement was tested at Long Marston in May 2015 when a modified D78 driving motor car was pushed to a speed of 36km/h (22mph) and released 80 metres from a three-tonne tank of water placed at cab level. The test was monitored by TRL and showed that the enhanced safety structure preserved the driver’s survival space.
With mainline operation also presenting greater adhesion challenges than experienced on LU, automatic sanding and a modern wheel slide/slip system was also fitted. Gauging was another issue that had to be resolved before D78 stock could run on the main line. This required the body height of the unit to be lifted by 73 mm, which was achieved through the use of a suspension rubber on the bogie centre pivot and on the vertical dampers.
The original camshaft control was replaced by modern power electronics to improve efficiency and to enable the train to be powered from different power sources. The Dutch company Strukton supplied a traction inverter combined with an auxiliary power supply and a fast battery-charger for each power-car.
The traction system upgrade also included the replacement of the original DC traction motors with AC motors manufactured by Traktionssysteme Austria for improved efficiency and fine control of regenerative braking.
The diesel generator set was designed to fit within a standard raft of 2.9 x 0.9 x 0.9 metres with a common mechanical interface. It has a 110 kW Ford 3.2 litre engine, compliant to EU stage IIIB emission standards, which is coupled to an axial-flux three-phase alternator. The generator raft weighs 1.3 tonnes and the diesel-powered Class 230 units have two engine rafts under each driving motor coach.
Similarly, the protype battery train, 230002, has two battery rafts under each motor coach. This was built to test the concept of battery operation, rather than for a specific order, and initially used batteries from the 2015 Independently Powered EMU (IPEMU) trial.
The units are configured for up to three rafts per motor car and five rafts per trailer car. On diesel units, the fuel tank, which supplies two engine modules, takes up the space of one raft.
The generator and battery rafts weigh 1.3 and 1.7 tonnes respectively. An assessment of the vehicles’ dynamics confirmed that this extra weight was not a problem, given that the repurposed units will not experience the Underground’s crush loading.
Class 230 orders
The first planned passenger service for a Class 230 unit was a trial on London Midland’s Coventry to Nuneaton route from early 2017 until the end of the company’s franchise in October 2017. Much work had been done during the previous two years to obtain ORR authorisation to place the prototype diesel unit, 230001, into service. In December 2016, it was based at Tyseley for mainline testing and mileage accumulation as the final part of the authorisation process.
Unfortunately, it then suffered an engine fire. Vivarail’s report on the fire identified various issues with the original generator set which was a third-party design. These were addressed by the in-house redesign of the generator set. After the fire had thwarted the Coventry to Nuneaton trial, 230001 carried its first passengers in June 2017 whilst running the ‘Honeybourne shuttle’ at Rail Live.
In May 2018, Vivarail entered into an agreement to supply three two-car Class 230 diesel units for use on the Marston Vale line between Bedford and Bletchley. Units 230003, 230004 and 230005 entered service on this route in April 2019, immediately after receiving their OOR authorisation to operate. Each unit has a fully accessible toilet, dedicated space for cycles, wheelchairs, and pushchairs. They have a mix of airline seats, bays of four seats around tables, and some remaining tube-style side-seats. There is a USB socket at every seat.
In July 2018, it was announced that Vivarail was the preferred bidder to supply five three-car Class 230 units to KeolisAmey for the Wales and Borders franchise, to operate Wrexham-Bidston and Chester-Crewe services. These units, 230006 to 230010, are the UK’s first diesel/battery hybrid units. They have two 100kWh battery rafts on each driving motor car and four diesel generator rafts under the trailer car. This configuration has been tested on the prototype battery unit, 230002, which achieved a range of 40 miles under battery power only.
These units are geofenced to ensure that their diesel engines will only idle in built-up areas. As they are hybrid units, their engines can be limited to 2,000rpm for improved reliability. The diesel-only units have a maximum speed of 2,500rpm.
Their interiors feature a power supply at all seats, air-conditioning, high-speed Wi-Fi, air-cooling, wheelchair and bike spaces, an accessible toilet, and a new walk-through gangway design. After slippage in the testing programme, these three units received their authorisation to operate from the ORR in August and will then be ready to transfer to Transport for Wales Rail Services.
In September 2019, Vivarail received an order that did not require modular traction rafts. Instead, their repurposed D78 stock will become Class 484 units, refitted with collector shoes, to operate on the Isle of Wight’s third-rail network. Five of these two-car units will replace the 80-year old tube stock that currently operates on the Isle of Wight. These new trains will be introduced in April 2021 after a three-month blockade of the 14-kilometre line for enhancement works, which includes raising platforms for the new units.
Adrian advises that Vivarail had suggested that it could supply its Class 230 battery trains to operate the route to enable the 53-year old third rail system to be decommissioned. However, this was not considered to be the best option perhaps because of the high initial cost of battery rafts.
As the class 320 concept was developed, it became increasingly clear to Adrian that battery electric multiple units (BEMUs) were the future for shorter distance services. However, their utility is limited by slow battery charging. To address this issue, Vivarail teamed up with Petalite, which specialises in high-speed, high-power battery charging, to apply for an award from Innovate UK’s Accelerating Innovation in Rail initiative.
Their project was for an innovative rapid-charging technology with static-energy storage to exploit low-rate cheap energy for high-rate charging. In July 2017, Innovate UK announced that it would fund £642,000 of this project, with Vivarail and Petalite contributing respectively £185,000 and £100,000.
This project used Vivarail’s protype two-car battery unit, 230002, which was sent to the Bo’ness preserved railway in Scotland for tests in October 2018, including three days of free public trials.
During these trials, the train’s batteries only needed charging for a few hours overnight from a mobile charging unit.
This trial gathered useful performance data and demonstrated that the battery train could provide a reliable service and the functionality of the electronic control systems. It also demonstrated that the unit could accelerate at 1m/s² up the steep gradient on the Bo’ness railway.
In December 2018, Vivarail announced it would be working with Hoppecke to design and integrate batteries for its trains. This includes the provision of air and water-cooling systems in the raft and battery packs to dissipate heat from the charging current, which is in excess of 1,000 amps.
Adrian explained that the fast charging system uses short lengths of 3rd and 4th rails These are only energised after a ‘handshake’ between the train and the charging system, which uses proximity sensors and RFID tags, has proved that it is safe to do so. The shoe gear is made of ceramic carbon to withstand the heat from the large charging current, which is controlled by the train.
The problem of supplying such high currents at wayside charging locations is overcome by having a large battery bank that is trickle charged between train charging. Typically, this will be the size of a 20-foot container for a half-hourly service on a short branch line.
The final hurdle for the fast charge system is its approval for use. As would be expected for such a novel system, this has its challenges. However, after much work, it is expected that approval will be granted soon.
The end of the 12-month fast charging project was marked by a demonstration at Long Marston in March 2019, when representatives of Innovate UK and the Department for Transport observed a Class 230 being recharged in seven minutes.
Class 230 BEMU
Vivarail’s battery trains and their fast charging system is an impressive concept, yet questions remain about range and the cost of batteries. Adrian advised that a Class 230 BEMU has a range of between 60 and 100 kilometres, depending on the number of stops. This could be extended if it was acceptable for trains to stop every 80 kilometres or so for a seven-minute fast charge.
Network Rail’s Traction Decarbonisation Network Strategy (TDNS) has concluded that, of the 15,400 single track kilometres of UK unelectrified network, the elimination of diesel traction requires, respectively, 13,040, 800 and 1,300 single track kilometres of electrification, battery, or hydrogen traction. TDNS, like Vivarail, considers that battery trains have a maximum range of 100 kilometres, although TDNS did not seem to consider the potential of fast charging systems. As an example, Adrian points out that the 196 kilometres between Glasgow and Fort William could be powered by a battery train if trains stopped at the mid-way point of Crianlarich for a seven-minute fast charge.
The cost of batteries also determines the most appropriate decarbonisation option. A two-car Class 230 BEMU has four battery packs, each costing around £100,000, with a seven-year warranty that requires a 20 to 80 per cent state of charge to be maintained. The unit monitors battery output and charge status and provides this information to the manufacturer to confirm that batteries are being operated as required for the warranty. The cost of the wayside charging battery bank also has to be considered.
For customers who may be deterred by the high up-front battery costs, Vivarail offers the option of paying for batteries on a per mile basis which, as Adrian pointed out, is likely to be less than the per mile operational and maintenance cost of diesel vehicles.
In line with the philosophy of having removable modules for any type of traction, Vivarail has been considering powering its trains from a 25kV supply and hydrogen. Adrian advised that six months have been spent developing a transformer/rectifier raft to power a Class 230 from the overhead lines and charge its batteries. Such a unit would require at least 25 per cent of its route to be electrified to keep its batteries charged.
Vivarail have also considered how a Class 230 could be adapted to become a hydrogen train, for which the problem is storage of a large volume of compressed hydrogen gas, which has a low energy density. This problem is exacerbated as cylindrical tanks are not an efficient storage arrangement. Vivarail’s proposed solution is a four-car unit with a mix of 315mm and 420mm diameter cylinders underneath two trailer cars with two battery and one hydrogen fuel cell raft underneath each of the driving motor cars. This arrangement would have fuel cells with a total power output of 400kW, batteries with a capacity of 400kWh and storage for 282kg of hydrogen, giving a range of 1,000 kilometres.
Another form of hydrogen generation is Steamology’s ‘water-to-water’ concept, which is an energy-dense turbine powered by steam generated from compressed hydrogen and liquid oxygen. The company was awarded a £350,000 grant for the total cost of producing a protype that fits within a Vivarail Class 230 raft. The purpose of this innovation is not clear, as it increases the problem of fuel storage on hydrogen trains by requiring the storage of both compressed hydrogen and liquid oxygen.
Over the past five years, Vivarail has succeeded in producing a flexible, modular platform which offers an alternative to diesel trains on short-distance services. Indeed, the prototype battery train, 230002, is the only potentially zero-carbon self-powered vehicle authorised for main line operation. The authorisation of new innovative trains is no small task, especially for such a small company.
On routes with frequent stops, the higher acceleration of a Class 230 BEMU offers a journey time that is less than that of diesel trains with a higher maximum speed. However, for journeys requiring more than a few miles of main line running, the Class 230’s 100km/h maximum speed is unlikely to be acceptable.
With 1,000 vehicles of the sprinter fleet reaching 40 years of age between 2026 and 2031, it remains to be seen how much of the D78 stock that Vivarail has stored at Long Marston will be used to replace these vehicles. Yet it is quite possible that this stock might find service overseas, leaving few coaches available to be repurposed as Class 230 units in the UK.
Adrian reports that there has been much overseas interest in the Class 230 concept. Indeed, on the day of Rail Engineer’s visit, a representative from an undisclosed overseas railway was assessing its potential after he had just completed his two weeks self-isolation.
The two-car battery prototype unit is also to be showcased in the United States early next year. The Railroad Development Corporation, a major investor in Vivarail, is to use the unit to demonstrate its Pop-Up Metro concept, in which the lightweight Vivarail trains could be used on little-used freight lines in urban areas with very little infrastructure expenditure.
If D78 stock is to be used overseas, perhaps the technologies that Vivarail has developed, such as the fast charging system, could be used to repurpose other rolling stock and, by doing so, remove the current 100km/h restriction on its technology. Whatever the future holds for Vivarail, the company has shown itself to be adaptable and capable of delivering innovative operational solutions for UK rail’s decarbonisation challenge.