KeolisAmey’s Plans For The Rhymney Line
This document on the KeolisAmey web site details their plans for the new Wales and Borders Franchise.
The Rhymney Line has the following characteristics.
- It runs between Cardiff Queen Street and Rhymney stations.
- Most of the line is double-track, with a short length of single-track from Tir-Phil station.
- There is the Coryton branch line to Coryton station.
- From Cardiff to Bargoed station, there are four trains per hour (tph)
- North of Bargoed, an hourly service generally operates.
- \from Cardiff to Coryton station, there are two tph.
- Some services, run through Cardiff to Penarth or Barry Island stations.
- Services take sixty-one minutes between Rhymney and Cardiff.
- Services take eighteen minutes between Coryton and Cardiff.
What improvements will be made to the Rhymney Line?
New Trains
From 2019, cascaded Class 170 trains will run services on the line.
In 2023, these trains will replaced by new Tri-Mode Stadler Flirts.
Current plans, don’t envisage any of the Stadler Citylink Metro Vehicles working the line. But I don’t see any reason why they can’t, if say Transport for Wales wanted to run a service from Cardiff Bay to Coryton or any other station.
It could be that their batteries don’t have enough capacity for the Caerphilly Tunnel.
New Stations
The KeolisAmey document, states that a new station will be built at Crwys Road.
I’ve also read somewhere that there may be a station on the Coryton Line to serve a major new hospital.
Improved Services
In 2023, the following services will be in place.
- From Cardiff to Rhymney station, there will be four tph.
- From Cardiff to Coryton station, there will be two tph.
- Services will take forty-eight minutes between Rhymney and Cardiff.
- Services will take twenty minutes between Coryton and Cardiff.
The Coryton service is slower because of the proposed new station.
Electrification
The line will be electrified using 25 KVAC.
- There is a short tunnel at Bargoed station.
- There is a mile-long tunnel at Caerphilly.
- There were quite a few footbridges across the tracks.
- The margins on either side of the track seem adequate on much of the route.
It looks to me, that electrification of the Rhymney Line cshuld be possible, provided the design is good.
The Tri-Mode Stadler Flirts will have batteries, which will have these purposes.
- Provide traction power for the trains, where there is no electrification.
- Capture the energy generated by the traction motors under braking.
- Ensure that power is always available for the train’s control, driver and passenger systems.
On the Rhymney Line, battery power will also be used to provide traction power in the mile-long Caerphilly Tunnel.
I have been told that although the tunnel will not be electrified, there will be an overhead rail for the pantograph in the tunnel, which will not be electrified.
This means that the pantograph doesn’t have to be raised and lowered, as the train goes up and down the hill, as there is a continuous overhead rail and line for the pantograph to use all the way.
I believe that when the train is coming down the hill, that gravity and the onboard battery will give sufficient power to bring the train safely down the hill.
So is there any point in electrifying the downhill path?
- The two terminals on the line; Rhymney and Coryton stations, are single platform stations on single-track lines, which will surely be electrified.
- If necessary batteries could be topped up before on the single track sections, before joining the double-rack line to Cardiff.
- There is very little if any freight or engineering trains on the line. But these will be diesel-hauled.
- After the modernisation, all the passenger trains will be the new electric trains with batteries and/or diesel engines.
- Diesel trains and locomotives could continue to work the lines as required.
I don’t think there is any operational reason for the downhill path to be electrified.
It would reduce costs in both construction and maintenance.
Tri-Mode Stadler Flirts
I would expect that these trains are very similar to the bi-mode Stadler Flirt DEMUs, but that the power-pack would also contain a battery.
As an Electrical and Control Engineer, I wouldn’t be surprised that the power-pack, which accepts up to four Deutz diesel engines, can replace one or two of these with battery modules. This could make conversion between the two types of Flirt, just a matter of swapping a diesel module for a battery one or vice-versa.
Note that the three-car Class 755 trains for Greater Anglia have two diesel engines and the four-car trains have four engines.
This document on the KeolisAmey web site details their plans for the new Wales and Borders Franchise.
It gives a few extra details about the Tri-Mode Stadler Flirts
The KeolisAmey document gives extra a few extra details.
- The tri-mode trains are instended for Rhymney/Coryton <> Penarth/Barry Island/Bridgend via the Vale of Glamorgan Line.
- Main power source 25 KVAC overhead line with battery and diesel engine.
- 100% electric operation on transferred metro network.
I assume the following.
- That 100% electric operation includes battery operation.
- Batteries will certainly be used in the mile-long Caerphilly tunnel.
- Batteries will be charged when running on electrified lines or by capturing regenerative breaking energy whilst descending to Cardiff.
- The diesel engine will be used for primary power on the Vale of Glamorgan Line, which is without electrification and nearly twenty miles long?
There will be a lot of commonality between the two types of Flirts and I suspect driver and other staff training for the two variant will be the same.
How Big Will The Batteries Need To Be?
Consider a three-car Tri-Mode Stadler Flirt
- I reckon, that the weight of the train will be around 130 tonnes.
- Rhymney has an altitude of 287 metres.
- I will assume 150 passengers at 80 Kg. each, which gives a weight of 12 tonnes.
This means that the train has a potential energy of 111 kWh at Rhymney station.
On the way down the hill from Rhymney the regenerative braking will convert this potential energy into electricity, which will be stored in the battery.
But also consider.
- There will be losses in energy conversion in the regenerative braking process.
- Energy will be used running the train’s systems.
- Energy will be used stopping and starting the train at each station.
- Energy will be used bringing the train through some sections without electrification.
- Energy will be used keeping the crew and passengers comfortable.
- Energy can be burned off using braking resistors on the roof of the train.
When you consider that the battery on a London New Routemaster bus, has a capacity of 75 kWh, I think it is highly likely, that Stadler can design a battery module to fit one of the two spare engine positions in the power-pack.
Now, consider a four-car Tri-Mode Stadler Flirt
- I reckon, that the weight of the train will be around 150 tonnes.
- Rhymney has an altitude of 287 metres.
- I will assume 200 passengers at 80 Kg. each, which gives a weight of 16 tonnes.
This means that the train has a potential energy of 130 kWh at Rhymney station.
Looking at the weight of Bombardier’s 50 kWh batteries, I suspect that it would be possible to design a battery module with the following characeristics.
- 100 kWh capacity
- A weight less than that of the Deutz engine, which is around 1.3 tonnes.
- Plug compatibility with the diesel engine.
Doing this calculation with real data, is the sort of mathematics that I relished doing in my twenties.
How Far Would A Full 100 kWh Battery Take A Three-Car Flirt?
In an article in the October 2017 Edition of Modern Railways, which is entitled Celling England By The Pound, Ian Walmsley says this in relation to trains running on the Uckfield Branch, which probably has a terrain not much different to the lines to the South and West of Cardiff.
A modern EMU needs between 3 and 5 kWh per vehicle mile for this sort of service.
This would mean that a 100 kWh battery would take a three-car train between six and ten miles. It might even take the train from Cardiff to Barry Island or Penarth and back..
Conclusion
It looks a very interesting concept.
- Most of the energy is provided by the electrification, which would power the train up the hill.
- Coming down the hill, the batteries would be recharged using the regenerative braking.
- Battery power would used to take the train on routes without electrification to the West and South of Cardiff.
- When the battery power was low, the diesel engines would cut in.
Energy efficiency would be high.
The Greening Of The Valleys
This document on the KeolisAmey web site details their plans for the new Wales and Borders Franchise.
The documents gives these two definitions.
- South Wales Metro – Includes the full set of local services around South East Wales. This includes what is currently known as the ‘Valley Lines’, plus services between Cardiff and Ebbw Vale, Maesteg and extending to Severn Tunnel Junction and beyond.
- Central Metro -Refers to the sub-set of the South Wales Metro train services which run from Treherbert, Aberdare, Merthyr Tydfil, Radyr, Rhymney and Coryton, through Queen Street to Cardiff Bay, Cardiff Central, Penarth, Barry Island and Bridgend.
For these services around Cardiff and on the Cardiff Valley Lines, KeolisAmey Wales intend to acquire the following fleet.
- 11 x four-car Stadler Flirt DEMU
- 7 x three-car Stadler Flirt Tri-mode MU
- 17 x four-car Stadler Flirt Tri-mode MU
- 36 x three-car Stadler Citylink Metro Vehicles
This diagram from the document shows the routes and the frequencies.
They also say the following surrounding the map in the document.
- Maintains all existing connections to Cardiff Queen Street and Cardiff Central stations.
- Service pattern easy to understand
- Most frequencies even in the hour ‘clockface’ (e.g. 00-15-30-45 past)
- Vale of Glamorgan, Barry, Penarth and City Lines integrated into Central Metro solution.
- 2tph from Pontypridd station ‘divert’ via City Line but don’t terminate at Central i.e. Aberdare – City Line – Central – Merthyr
Note that Aberdare, Merthyr Tydfil, Rhymney and Treherbert stations all get a total of four trains per hour (tph)
The Trains In More Detail
Stadler Rail are building the three fleets of rail vehicles.
Stadler Flirt DEMUs
Over a thousand Stadler Flirts have been sold to operators around the world. Most have been or will be built in Switzerland.
From the pictures, the trains, that will be delivered to Wales, look very much like the Class 755 trains, that have been ordered by Greater Anglia. These trains will enter service next year.
Stadler Flirt DEMUs gives more details of these trains and the closely-related fleets.
The trains will operate services between Cardiff and Ebbw Vale, Maesteg and extending to Severn Tunnel Junction and beyond.
Tri-Mode Stadler Flirts
I would expect that these trains are very similar to the bi-mode Flirt DEMUs, but that the power-pack would also contain a battery.
Tri-Mode Stadler Flirts gives more details of these trains and how I think they will operate.
The Tri-Mode Stadler Flirts are intended for Rhymney/Coryton <> Penarth/Barry Island/Bridgend via the Vale of Glamorgan Line.
There will be a lot of commonality between the two types of Flirts and I suspect driver and other staff training for the two variants will be the same.
Stadler Citylink Metro Vehicles
The Stadler Citylink Metro Vehicles in the KeolisAmey document. look very similar to Sheffield Supertram‘s Class 399 tram-trains, that are providing a tram service in Sheffield and will soon be running on the heavy rail network to Rotherham.
Stadler Citylink Metro Vehicles gives more details of these trains and how I think they will operate.
From Cardiff Queen Street To The Flourish
It looks like the Metro vehicles will use the batteries for power on the extension to the new terminal station at The Flourish.
I describe the proposal for the extension to the Flourish in The Flourish Station Is The Focus Of The South Wales Metro.
Electrically-Efficient Operation Of The Metro
I have a feeling that Stadler are bringing some of their mountaineering experience from Switzerland to the valleys of South Wales.
It is interesting that both the Tri-mode Stadler Flirts and the Stadler Citylink Metro Vehicles will have batteries.
Climbing The Hills
The main purpose of the batteries is to make the climb and descent to the terminals at the heads of the valleys as energy efficient as possible.
Efficient climbing of the hills will need all uphill tracks to be electrified.
The KeolisAmey document states this about the electrification.
Discontinuous overhead line electrification to 25 KVAC with permanently earthed sections around restricted structures, saving 55 interventions e.g. rebuilding bridges/no need for wire in Caerphilly tunnel.
Battery power would be invaluable for jumping the gaps in the electrification.
Coming down, I believe that the trains and tram-trains will use the batteries to handle the energy generated by regenerative braking.
This means.
- The electrification can be simpler.
- There might be no need to electrify the downhill track in double-track sections.
- Trains can use the battery power to cross sections without wires or restarting from stations, when going downhill.
- Tram-trains going to The Flourish will arrive at Cardiff Queen Street station with enough energy in the batteries for the return trip to The Flourish.
- The Cardiff Bay Line doesn’t need to be electrified, which saves money and possibly increases safety and reduces visual intrusion.
It is not only energy efficient, but it saves construction costs and time.
Why Aren’t Citylink Metro Vehicles Used On The Rhymney Line?
There are several possible reasons.
- Calculations have shown, that the battery capacity of the smaller Citylink vehicle might not be enough to go uphill through the Caerrphilly tunnel.
- The route may need more powerful vehicles.
- More capacity may be needed on this line, so the larger Tri-mode Stadler Flirts will be used.
- The Flirts could use their diesel engines to rescue a train stuck in the tunnel.
But whatever the reason, I’m sure it’s a good one!
Could Downhill Tracks Not Be Electrified?
I think this may be possible, as vehicles coming down the hills could use gravity and small amounts of battery power.
Regenerative braking would also be continuously charging the batteries.
It would certainly be simpler, than having to constantly swap between overhead and battery power on the descent, where the electrification was discontinuous.
As the lines are going to have a more intensive service, there will be additions of a second track in places to allow trains to pass.
Any electrification that could be removed from the project would be beneficial in terms of building and operational costs.
How Would Discountinuous Electrification Be Handled?
I discus this in How Can Discontinuous Electrification Be Handled?
The Lines In More Detail
Click these links to find out more about the individual lines.
Conclusion
The two types of compatible vehicles, allows the plans for the South Wales Metro to be a cost-effective and very green solution for Cardiff’s transport needs.
It is a model, that can be used elsewhere.
Will railway engineers in future talk of the Cardiff Model, just as they talk of the Karlsruhe Model?
The Anonymous Widower 