## Would Electrically-Driven Trains Benefit From Batteries To Handle Regenerative Braking?

There are two basic types of electrically-driven trains.

Electric trains, which include electrical multiple units and trains hauled by electric locomotives like the InterCity 225.

Diesel-electric trains, which include multiple units like Voyagers and the InterCity 125.

**Regenerative Braking**

In an electrically-driven train, the traction motors can be turned into generators to slow the train, by turning the train’s kinetic energy into electricity.

Many electric trains can do this and the generated electricity is returned through the electrification system, so that it can power other trains nearby.

This all sounds fine and dandy, but there is the disadvantage that all the electrification system must be able to handle the reverse currents, which increases the capital cost of the electrification.

**Batteries For Regenerative Braking**

Fitting batteries to a train, to handle the electricity that is generated by regenerative braking is an alternative.

**A Station Stop**

Suppose a four-car train that weighs 200 tonnes is travelling at 125 mph and needs to stop at a station.

My example train would according to Omni’s Kinetic Energy Calculator would have a kinetic energy of 86.7 kWh.

To put that amount of energy into context, the traction battery in a New Routemaster bus is 55 kWh.

So if a battery of this size was put into each car, there is more than enough capacity to store the energy of the train, when it stops at a station.

When the train leaves the station, a proportion of this energy can be used to accelerate the train back to 125 mph.

As regenerative braking is perhaps only eighty percent efficient at present, additional energy will need to be provided.

But even with today’s primitive batteries and less-than-efficient traction motors, there are still substantial energy savings to be achieved.

*Hitachi Class 800/801/802 Trains*

In Do Class 800/801/802 Trains Use Batteries For Regenerative Braking?, I looked at the question in the title.

I found 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**.

It was written in 2013 and I suspect every train designer has read it, as it gives a deep insight into the design of the trains.

The document provides this schematic of the traction system.

Note

- BC which is described as battery charger.
- The battery size is not disclosed.
- The APS supplies the hotel power for the train in two different voltages.
- Can the APS with the battery supply power to the Drive Converter?

After a lot of reasoning, I came to this 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.

Hitachi have not said, if the batteries on the Class 800/801/802 trains can be used for traction purposes.

Storing the regenerative energy in a battery can be used for one of two purposes.

**Hotel Power**

Hitachi’s Class 800 trains certainly use the electricity in the battery to power the hotel functions of the train like air-conditioning, doors, lights, power-sockets, toilets and wi-fi.

In a diesel-electric train, this could give benefits.

- The engines generally won’t need to run in a station to provide hotel power.
- Less fuel will need to be expended to provide hotel power.
- If say the train has to halt perhaps because of a signalling or track fault, hotel power can be provided without running the engines.
- If batteries are supplying the hotel power, the train may have more power for traction.

Overall, the diesel-electric train would be more efficient and would emit less carbon dioxide and pollutants.

**Traction Power**

There is no engineering reason, why the energy in the battery can’t be used to actually move the train.

But to implement it, could be complicated and expensive on an existing train.

**Some Worked Examples**

I’ll look at a few examples.

**InterCity 125**

The iconic InterCity 125s are unique, in that they are impossible to scrap. Just as they seem to beapproaching the end of their life, a devious engineer or marketing man comes up with a plan to keep them running.

As I write this, Great Western Railway and Abellio ScotRail are testing short-formation InterCity 125s and training drivers for services in the South West of England and Scotland. Both train operating companies appreciate the marketing advantages of Terry Miller‘s world-famous train, that was built as a stop-gap, after the failure of the Advanced Passenger Train.

So what size of battery would need to be fitted to each locomotive to handle the braking energy of a short-formation InterCity 125 with four passenger cars?

Consider.

- Each Class 43 locomotive weighs 70.25 tonnes.
- Each Mark 3 coach weighs 33.60 tonnes.
- An eight car InterCity 125 can carry about 500 passengers.
- I will assume that a four-car InterCity 125 can carry 250 passengers.
- If each passenger weighs 90 Kg with all their bikes, buggies and baggage, that adds up to 22.50 tonnes.

This gives a total train weight of 297.40 tonnes.

Calculating the kinetic energy using Omni’s Kinetic Energy Calculator for various speeds gives.

- 50 mph – 20.6 kWh
- 75 mph – 46.4 kWh
- 90 mph – 66.9 kWh
- 100 mph – 82.5 kWh

A fifty kWh battery in each locomotive would be able to handle the braking energy of the train.

The only problem, is that Class 43 locomotives have DC traction motors, no regenerative braking and air brakes.

But if any operator or rolling stock owner were bonkers enough to fit a new traction system, a diesel/electric/battery Class 43 locomotive is possible for a four-car InterCity 125.

This page on the Hitachi web site is entitled **V-TRAIN 2**.

Hitachi used a Class 43 power car to prove that diesel/electric/battery trains were feasible, before getting the order for the Class 800 trains.

So fitting batteries to Class 43 locomotives has been done before!

The simplest thing to do would be to use the batteries to provide hotel power for the train.

**Class 375 Train**

In this exercise, I shall consider a Class 375/6 train, with the following characteristics.

- Four cars
- Three cars are motored.
- Regenerative braking
- A weight of 173.6 tonnes.
- A capacity of 236 seated passengers
- An operating speed of 100 mph.

I will now go through my standard train kinetic energy calculation.

- I will assume three hundred passengers including standees.
- If each passenger weighs 90 Kg with all their bikes, buggies and baggage, that adds up to 27 tonnes.

This gives a total train weight of 200.60 tonnes.

Calculating the kinetic energy using Omni’s Kinetic Energy Calculator for various speeds gives.

- 50 mph – 13.9 kWh
- 80 mph – 35.6 kWh
- 100 mph – 55.7 kWh

It would appear that adding batteries to a Class 375 train would not involve large capacity batteries, especially if one was added to each of the three cars with motors.

As a Control Engineer by training, blending battery and electrification power could run the train more efficiently.

Probably naively on my part, I suspect that using batteries on Class 375 trains to handle regenerative braking, would be one of the easier installations.

**Other Electrostars**

All Electrostars are fairly similar, so if Class 375 trains could be updated, then I wouldn’t be surprised if all could.

**InterCity 225**

It looks like InterCity 225 trains will be used between London and Blackpool by Alliance Rail Holdings.

Other commentators have suggested that shortened sets run on the Midland Main Line between a diesel locomotive and a Driving Van Trailer (DVT) or two Class 43 locomotives.

I shall do the energy calculation for a five-car InterCity 225.

- A Class 91 locomotive weighs 81.5 tonnes.
- A Mark 4 coach weighs between 40 and 43.5 tonnes.
- A nine-car InterCity 225 seats 535 passengers.
- I will assume that a five-car InterCity 225 will seat around 300 passengers.
- I will assume each passenger weighs 90 Kg. with all their baggage, bikes and buggies.
- A DVT weighs 42.7 tonnes.

For a current nine-car train this gives the following.

- The empty train weight is almost exactly 500 tonnes.
- The passengers weigh 48 tonnes.
- This gives a total weight of 548 tonnes.

At 125 mph, the nine-car InterCity 225 has a kinetic energy of 238 kWh.

For a proposed five-car train this gives the following.

- The empty train weight is almost exactly 333 tonnes.
- The passengers weigh 27 tonnes.
- This gives a total weight of 360 tonnes.

At 125 mph, the five-car InterCity 225 has a kinetic energy of 156 kWh.

Reduce the speed to 110 mph and the kinetic energy drops to 121 kWh.

I suspect that using current technologies, there is not enough space in a Class 91 locomotive for the batteries.

Perhaps a short section of the coach next to the engine could be converted to hold a large enough battery.

*Five Mark 4 Coaches And Two Class 43 Locomotives*

This has been suggested in Modern Railways by Ian Walmsley and I wrote about it in Midland Mark 4.

Consider.

- A Class 43 locomotive weighs 70.25 tonnes.
- A Mark 4 coach weighs between 40 and 43.5 tonnes.
- A nine-car InterCity 225 seats 535 passengers.
- I will assume that a five-car InterCity 225 will seat around 300 passengers.

This gives the following.

- The empty train weight is 349 tonnes
- The passengers weigh 27 tonnes
- The train weight is 376 tonnes.

At 125 mph this train would have a kinetic energy of 163 kWh.

I’m sure that it would be possible to put a 100 kWh battery in the space behind the engine of a Class 43 locomotive, so I suspect that all the engineering solutions exist to create a train with the following characteristics.

- Two Class 43 locomotives with new traction motors to enable regenerative braking and a 100 kWh battery.
- Five Mark 4 coaches meeting all the regulations.
- The batteries would provide hotel power for the train.
- 125 mph operating speed.

It may be a fantasy, as the economics might not stack up.

*Five Mark 4 Coaches, A Driving Van Trailer And A Stadler UKLight Locomotive*

I wrote about this combination in Five Mark 4 Coaches, A Driving Van Trailer And A Stadler UKLight Locomotive.

I came to this conclusion.

Using the Mark 4 coaches or new Mark 5A coaches with a new 125 mph diesel/electric/battery hybrid Stadler UKLight locomotive could create an efficient tri-mode train for the UK rail network.

The concept would have lots of worldwide applications in countries that like the UK, are only partially electrified.

The concept or something like it, has possibilities.

**Voyagers**

In the July 2018 Edition of Modern Railways, there is an article entitled** Bi-Mode Aventra Details Revealed**.

A lot of the article takes the form of reporting an interview with Des McKeon, who is Bombardier’s Commercial |Director and Global Head of Regional and Intercity.

This is a paragraph.

He also confirmed Bombardier is examining the option of fitting batteries to Voyager DEMUs for use in stations.

The Voyager family of trains has three members.

- Class 220 trains – Voyagers – 34 trains of four cars – operated by CrossCountry.
- Class 221 trains – Super Voyagers – 44 trains of four or five cars – operated by CrossCountry
- Class 222 trains – Meridians – 27 trains of four, five or seven cars – operated by East Midlands Trains.

The trains are diesel-electric and I explore the possibility of using batteries in these trains in Have Bombardier Got A Cunning Plan For Voyagers?.

I felt is was a good plan.

**Conclusion**

In answer to the question, that I posed in the title of this post, I feel that handling regenerative braking in batteries on the train could be of benefit.

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