Modern Railways – April 2019

Informed Sources Roger Ford

26 Modern Railways April 2019 http://www.modern-railways.com

haul challenge – hauling a

3,000-tonne iron ore train from

Port Talbot to Llanwern, including

the ascent of Stormy Bank

with its final 1:92 gradient.

Leaving the sidings, as soon

as we were on the main line at

10.59 the driver of the Class 60

selected full power. The mighty

Mirrlees MB275 then proceeded

to pour out its 3,100hp until, five

miles later, at 11.19, we topped

Stormy Bank, to a creep-scream

accompaniment, at 11mph.

So, 20 minutes at 3,100 is as near

as dammit 1,000hph. To supply

this you would need 3.3 tonnes

of Li Ion batteries at cell level.

SEDUCTIVE

Of course, the hybrid diesel-battery

locomotive hinted at in the report

would have a smaller engine with

a large battery pack to provide

extra grunt when accelerating

or climbing. With regenerative

braking some energy could be

recovered on down grades.

It sounds seductively simple.

But apart from pack-level energy

densities and the charge and

discharge limitations, there is

another issue with batteries.

Power equals volts multiplied by

amps. Freight traction involves

a lot of constant high power.

As you discharge a battery,

the voltage drops, which means

increasing the current to maintain

constant power. Increase the

current and the voltage drops

even faster. Batteries don’t like

this death spiral treatment.

AFFORDABLE?

Costs of Li Ion batteries have

been falling dramatically as

mass production has built up.

Car maker Tesla, with its own

battery ‘giga-factory’, claims to be

approaching $100 (£75) per kWh

at cell level. Other sources suggest

current commercial prices are around

$150 (£110) per kWh. Pack-level adds

around 30% to the specific cost.

But if someone wanted to

convert, say, a spare Class 47 to

demonstrate a diesel/battery hybrid

it wouldn’t cost an arm and a leg.

That’s something BR Research would

probably have done by now.

HYDROGEN

Of course, hydrogen is the

dream solution. I don’t think

anyone is contemplating a

hydrogen-powered Class 66

replacement, so I’ll keep it brief.

For a start, hydrogen fuel cells

lack ‘driveability’. You can’t just

couple the terminals from your

fuel cell to a traction inverter and

shove the controller into notch 7.

Fuel cells need a battery buffer to

provide the variable grunt needed

by electric motors. For example, the

latest Hyundai fuel cell car has a drive

motor rated at 120kW (161hp). The

fuel cell puts out 95kW (127hp) and

feeds a 1.56kWh (2.1hph) battery

that powers the electric motor.

Similarly, the production Alstom

Coradia iLint hydrogen multiple-unit

has a 200kW (270hp) fuel cell stack

feeding a water-cooled 111kWh

(115hph) Li Ion battery. This in turn

feeds the traction package. The aim is

to run the fuel cell at half power, with

the battery evening out the load.

Incidentally, in the course of

researching this article I asked

Alstom for the weight of the iLint

battery, only to be told ‘at this

stage the mass of the batteries

is not public’. How odd.

Anyway, when it comes to

freight traction, Ballard has

supplied a 250kW (335hp) fuel

cell to power a BNSF ‘switcher’

locomotive. So think Class 08

rather than Class 66 replacement.

CONTRARY

While the biggest reduction in

emissions will come from transferring

freight from road to rail plus a

rolling programme of electrification,

if freight diesels are to run on

long-term, we need to do our bit.

Consider diesel emissions

regulations (Table 1, overleaf ). These

are confined to carbon monoxide,

hydrocarbons, nitrous oxides and

particulate matter – the emissions

that damage people. But typing this

during the warmest-ever February

days, the absence of CO 2 , which

damages the earth, seems perverse.

CO 2 is the product of combustion.

The more fuel you burn, the

more CO 2 you produce.

Diesel engine fuel consumption is

measured in grams of fuel required to

generate one kilowatt hour (g/kWh).

In its day, the Mirrlees MB275 set

a new benchmark at 195g/kWh.

To illustrate how technology

has improved, the English Electric

12CSVT engines in the triple-headed

Class 37s that topped Stormy Bank

at 17mph when I first footplated

the iron ore trains in 1976 were

consuming 228g/kWh on full power.

MORTGAGE

Now comes the conundrum. The

more efficient an engine, the less fuel

it burns and the less CO 2 it generates

per horsepower. However, to get

NOx emissions down you have to

mortgage combustion efficiency.

When Wisconsin Central bought

the BR freight businesses and formed

EWS, it brought in Jim Fisk as Chief

Engineer. Back in the States, Mr Fisk

had been used to running heritage

General Motors locomotives with

lusty, but thirsty, two-stroke engines.

When he was buying the Class 66

fleet for operation in the UK, Jim

Fisk waxed strongly to me about the

perversity of the need to meet the

nitrous oxide (NOx) emissions, which

meant that the fuel consumption

of his new locomotives went to

pot. And the GM two-stroke was

nowhere near as fuel thrifty as

the Mirrlees in the first place.

To illustrate the effect of NOx

reduction on CO 2 production,

Table 2 shows the fuel efficiency

of the same model of MTU engine

under the United States Tier 2

and Tier 3 emissions regulations.

Tier 3 is the equivalent of the Euro

Stage III in Table 1. Some quick

calculation indicates that the

difference between Tier 2 and Tier 3

would save around 17kg of CO 2 on

that climb to Stormy summit.

So what can be done to

make diesel engines even

more fuel efficient?

Class 60 on steel: working 6H25, the Margam – Llanwern steel coils, approaches Llanwern

West Junction behind loco No 60091 on 23 September 2017. Peter Squibbs

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