Do Class 800/801/802 Trains Use Batteries For Regenerative Braking?
I ask this question, because I think that it could be key to the announcements about electrification yesterday, as reported in this article in Global Rail News, which is entitled UK Ditches Electrification Plans In Wales, The Midlands And The North.
If you look at all these Wikipedia entries for Hitachi trains being built for the UK.
You will find no reference to regenerative braking.
If you type “Class 800 regenerative braking” into Google, you will find this document on the Hitachi Rail web site, which is entitled Development of Class 800/801 High-speed Rolling Stock for UK Intercity Express Programme.
The only mention of the R-word is in this paragraph.
An RGS-compliant integrated on-train data recorder (OTDR) and juridical recording unit (JRU), and an EN-compliant energy
meter to record energy consumption and regeneration are fitted to the train.
If you search for brake in the document, you find this paragraph.
In addition to the GU, other components installed under the floor of drive cars include the traction converter, fuel tank, fire protection system, and brake system.
Note that GU stands for generator unit.
Traction System
I will start by having a detailed look at the traction system as described in the document.
The document provides this schematic of the traction system.
Note BC which is described as battery charger.
This is said in the text.
The system can select the appropriate power source from either the main transformer or the GUs. Also, the size and weight of the system were minimized by designing the power supply converter to be able to work with both power sources. To ensure that the Class 800 and 801 are able to adapt to future changes in operating practices, they both have the same traction system and the rolling stock can be operated as either class by simply adding or removing GUs. On the Class 800, which is intended to run on both electrified and non-electrified track, each traction system has its own GU. On the other hand, the Class 801 is designed only for electrified lines and has one or two GUs depending on the length of the trainset (one GU for trainsets of five to nine cars, two GUs for trainsets of 10 to 12 cars). These GUs supply emergency traction power and auxiliary power in the event of a power outage on the catenary, and as an auxiliary power supply on non-electrified lines where the Class 801 is in service and pulled by a locomotive. This allows the Class 801 to operate on lines it would otherwise not be able to use and provides a backup in the event of a catenary power outage or other problem on the ground systems as well as non-electrified routes in loco-hauled mode.
This is all very comprehensive.
But nothing is said about how regenerative brake currents from the traction motors are handled.
Any trained Control Engineer, of which I’m a life-expired example, can see all sorts of questions to ask.
- Could it be that all regenerative brake currents are fed into the Auxiliary Power Supply and then used for hotel power and to charge the battery?
- Is the generator unit switched on and off by a sophisticated control system, that uses GPS, train velocity, train weight, battery level etc.?
- Can battery power be used to move the train?
- How big is that mysterious battery?
In 2010, I wrote Edinburgh to Inverness in the Cab of an HST, after taking a memorable trip.
One memory of that trip is of the skill of the driver as he adjusted the twin throttles of the power cars and used the brakes, as the train travelled up hill and down dale.
This line will be Class 800 territory and I suspect that it will be worked by two five car units working as a ten-car train.
As I think that each five-car unit will have three generator units, does this mean that the driver will have six throttles?
Control Engineering has moved on in the forty years since the InterCity 125 entered service and I suspect that like an Airline Pilot, the driver of a Class 800 train, will have little control about how power is delivered. Except probably in a supervisory role.
So on routes like the Highland Main Line, the Class 800 will come into its own, using the generator units and stored energy as appropriate.
Obviously, the less the generator unit is used the better, as this minimises noise and vibration, and cuts carbon emissions.
Other features in the train design have been disclosed.
All Class 801 Trains Have At Least One Generator Unit
All Class 801 trains have at least one GU (generator unit), so it can obviously provide hotel power and probably enough power to limp to the next station, in case of overhead line failure.
Third Rail Class 800/801 Trains Are Possible
The layout of the traction system surely makes a third rail or even a dual-voltage version of the trains possible.
After all, their first cousin; the Class 395 train is a dual voltage train.
Locomotive Haulage Is Possible
As I said, the specification is comprehensive.
The document is also forthcoming in other areas.
Train Configuration
This is said.
Trains have a unit configuration of up to 12 cars, including the ability to add or remove standardised intermediate cars and the generator units (GUs)
(generators with diesel engines) needed to operate commercial services on non-electrified lines.
So if say GWR wanted an eleven-car train, it would be possible.
Automatic Coupling And Uncoupling
This is said.
Because the coupling or uncoupling of cars in a trainset occurs during commercial service at an intermediate station, the automatic coupling device is able to perform this operation in less than 2 minutes.
This is definitely in line with Class 395 train performance.
Automatic Train Identification Function
This is said.
To simplify the rearrangement and management of train configurations, functions are provided for identifying the train (Class 800/801), for automatically determining the cars in the trainset and its total length, and for coupling and uncoupling up to 12 cars in
normal and 24 cars in rescue or emergency mode.
I suspect most modern trains can do this.
One Twelve-Car Train Can Rescue Another
See the previous extract.
Flexible Interior Layout
This is said.
The rolling stock is designed to facilitate changes to the interior layout to accommodate changes to services or to the number of cars in the train.
I suspect that was expected.
An Interim Conclusion
In answer to the question, I posed with this post, I suspect that the answer is in the affirmative.
Extra Evidence
I also found this article on the Hitachi Rail web site, which is entitled Hybrid Propulsion with a sub-title of Energy-saving hybrid propulsion system using storage–battery technology.
This is the introductory paragraph.
As a step toward producing environmentally friendly propulsion systems, Hitachi has supplied a hybrid propulsion system that combines an engine generator, motor, and storage batteries. This system provides regenerative braking which has not been previously possible on conventional diesel-powered trains, and enables increased energy savings via regenerated energy.
They list the advantages as.
- 10% improvement of fuel consumption
- 60% reduction of the hazardous substances in engine exhaust
- 30db reduction of noise in stopping at the station
They also give various links that are worth reading.
All of these pages seem to have been published in 2013.
Conclusion
I will be very surprised if Class 800/801/802 trains don’t have batteries.
Looking at the schematic of the electrical system, the energy captured will at least be used for hotel power on the train.
Will the Class 385 trains for ScotRail have similar traction system?
Class 710 Trains And Regenerative Braking
The new Class 710 trains for the London Overground, will be a next generation train, which could set new standards of energy efficiency. This is from a Bombardier Press release, that the company released when they received the order from London Overground.
The new trains will have similar features to the existing London Overground fleet (also manufactured by Bombardier), including walk-through carriages, air-conditioning and improved accessibility. These next-generation AVENTRA trains will feature an innovative design with optimised performance, including reduced weight, energy consumption, maintenance costs and high reliability, providing substantial benefits to both TfL and its passengers traveling on key London Overground routes, including the newly acquired West Anglia Inner Metro Service.
Note that there is no mention of regenerative braking, but this is mentioned in relation to the other Aventra trains on order; the Class 345 trains for Crossrail.
The Aventra has a slightly unusual and innovative electrical layout.
This article in Global Rail News from 2011, which is entitled Bombardier’s AVENTRA – A new era in train performance, gives some details of the Aventra’s electrical systems. This is said.
AVENTRA can run on both 25kV AC and 750V DC power – the high-efficiency transformers being another area where a heavier component was chosen because, in the long term, it’s cheaper to run. Pairs of cars will run off a common power bus with a converter on one car powering both. The other car can be fitted with power storage devices such as super-capacitors or Lithium-Iron batteries if required.
This was published six years ago, so I suspect Bombardier have improved the concept.
Could it be that the Class 710 trains consists of a two-car power unit sandwiched between two indentical driving cars.
The train could have a formation defined by something like.
DMSO+PMSO+TSO+DMSO or DTSO+PMSO+MSO+DTSO
The cars are as follows.
- DMSO – Driving Motor Standard Open
- PMSO – Pantograph Motor Standard Open
- DTSO – Driving Trailer Standard Open
- TSO – Trailer Standard Open
I’ve assumed there are a lot of powered axles as there are with the Class 345 train, but an appropriate number of trailer instead of motor cars can be used according to the demands of the route.
Search the Internet for “Class 710 train regenerative braking” and you find nothing official of with provenance.
I don’t believe that the Class 710 trains are not fitted with regenerative braking, as if you want to save energy on an electric train, it is one of the must-have features in the design.
But you need to be able to handle the electrical energy generated under braking.
Normally, the electricity is fed back into the overhead wires or third rail, so that it can be used by another train nearby. This technique is used extensively on the London Underground and third-rail electrification systems. Although, it is used on some 25 KVAC overhead systems like c2c, it means that the braking energy has to be converted to a high voltage to feed the electricity back.
So on the Aventra are Bombardier taking an alternative approach of using onboard energy storage to handle the energy generated by the braking?
Consider.
- Braking energy generated at a station stop, is immediately available to accelerate the train back to line speed.
- The onboard energy storage is designed to work with the traction motors.
- It is irrelevant to the drive system, if power comes from 25 KVAC overhead or 750 VDC third-rail.
- The overhead or third-rail power supply doesn’t need to be able to handle return currents.
- The train probably has enough onboard power to get to the next station at all times, should the power supply fail.
But the biggest factor is the amount of energy needed to be handled.
In How Big Would Batteries Need To Be On A Train For Regenerative Braking?, I calculated that the energy of a fully-loaded Class 710 train travelling at 100 kph is around 15 KwH.
So when a train stops, this energy will be released.
To get a better handle on how much energy is involved let’s look at these specifications for a Nissan Leaf car.
Nissan talks about 24 and 30 kWH versions of the car, So if this is the battery size, then one of Nissan’s batteries could store all the braking energy of a four-car Class 710 train.
This sounds absolutely unbelievable, but you can’t argue with the Laws of Physics. or the performance of modern automotive battery technology.
There are five lines, where the new Class 710 trains will run.
- Gospel Oak to Barking
- Chingford Branch
- Liverpool Street to Cheshunt
- Romford to Upminster
- Watford DC Line
How many of these lines are setup with the capability of accepting the return currents of regenerative braking?
The question is irrelevant if the Class 710 trains handle their own braking energy.
Conclusion
As the energy of a laden Class 710 train going at line speed is around 15 kWh, which is well within the capability of an automotive battery from a quality electric vehicle, I feel very strongly, that the Class 710 trains will handle regenerative braking using onboard energy storage.
How Big Would Batteries Need To Be On A Train For Regenerative Braking?
Let’s assume that we have a Class 710 train, trundling around North East London at up to 120 kph.
To calculate the kinetic energy in the train, which will have to be transferred to the battery, we need the mass of the train and its velocity.
I’ll start with the velocity of the train.
As it approached a station, it will be at whatever is the appropriate line speed, which to make things easy I’ll assume is 100 kph or just under 28 metres per second.
In most cases after stopping and discharging and loading a few passengers, it will probably return to a similar line-speed to go to the following station.
The mass of each car of an Aventra, is found at several places on the Internet, including this entry in Wikipedia which gives it as 30-35 tonnes. So the four-car Class 710 train could have a mass of 130 tonnes. Add 100 passengers at an average of 80 kg. each and this would make the mass 138 tonnes
Applying the standard formula gives a kinetic energy of 53240741 joules or in common-or-garden units 14.8 kilowatt hours. So the energy of an Aventra going at 100 kph could power a one bar electric fire for fifteen hours.
To get a better handle on how much energy is involved let’s look at these specifications for a Nissan Leaf car.
Nissan talks about 24 and 30 kWh versions of the car, So if this is the battery size, then one of Nissan’s batteries could store all the braking energy of a four-car Class 710 train.
Even a fully-loaded Class 345 train would only need a 50kWh battery.
Assuming of course, I’ve got the maths correct.
I have a feeling that using batteries to handle regenerative braking on a train could be a very affordable proposition.
As time goes on, with the development of energy storage technology, the concept can only get more affordable.
The Anonymous Widower 