30 Modern Railways April 2019 http://www.modern-railways.com
Informed Sources Roger Ford
traction power and range. Stadler’s
Class 93 ‘tri-mode’ locomotive
ordered by Rail Operations
Group (‘Pan Up’, February 2019)
provides an interesting preview.
It builds on the Class 88, which
adds a 700kW (940hp) Caterpillar
diesel engine to a 4MW 25kV AC
Bo-Bo electric locomotive. In
effect, when off the wire, you
have a Class 20 equivalent in
terms of traction horsepower,
ideal for taking container trains
in and out of the Felixstowe port
network if low-cost overhead line
electrification was installed on the
16-mile branch between Ipswich
and the Port of Felixstowe.
With the Class 93, some clever
packaging has squeezed a more
powerful 900kW (120hp) diesel
engine plus a Lithium Titanate Oxide
(LTO) battery rated at 400kW into
the Eurolight platform. This gives a
short-term (6-7 minutes has been
quoted) power boost to 1,740hp.
Stadler was unable to provide
information on the type of engine
or the capacity of battery pending
contract signature. What we do
know is that LTO sacrifices maximumenergy density in return for the type
of rugged battery needed for rough,
tough freight locomotive use.
Table 6 is from a company that
produces both types of Lithium
Ion battery. As you can see, for
a given capacity an LTO battery
will be heavier. On the other
hand it can use all of the charge,
can be discharged and charged
quickly and has a high output.FUTURE POLICY
Long-term freight traction policy
is full of known unknowns. The
extent of any rolling programme
of electrification that emerges
from the current revival, and routes
covered, is top of the list. Traffic to
be hauled is another – although
it is a reasonable assumption that
trains will be longer and faster.
Certainly diesel traction will
continue to be required. A basicperformance requirement built
round a really demanding CO 2
focused emissions specification, for
delivery starting from 2035, could
produce some innovative offers.
While there is some scope to
squeeze a bit more useful energy
out of each gram of fuel, a diesel
battery hybrid locomotive offers
a short-term power boost plus
regenerative braking. However,
to validate the concept, more
work needs to be done on freight
duty cycles on the key routes
in terms of power demand to
determine how much battery
boost would be needed.FLIGHT PARALLEL
Interestingly, a European study into
electric-powered airliners under the
Clean Skies research programme
showed that the most effective
option was to use a battery topower an electric motor providing
extra power to the fan of the jet
engine during take-off and climb.
This would allow the use of
smaller turbofans to run at the
more efficient constant operating
point during the cruise (see the
MTU data mentioned above). A
theoretical 10% fuel saving was
predicted. Mind you, that study
assumed double the energy density
available from today’s batteries.
As for the last mile conundrum,
while the Class 93 looks promising, it
is oriented towards Rail Operations
Group’s specific range of services. If
you need to fit diesel engines and
batteries into an electric locomotive
specifically for freight then a Co-Co
configuration gives you another
20 tonnes on a 17.5-tonne axle load.
I am conscious that readers may
see my argument that electrification
is the only credible replacement
for freight diesel locomotives as
a counsel of despair in the face
of global warming. But as the
cold numbers show, rail freight’s
CO 2 emissions are infinitesimal
on a national transport, let
alone global transport, scale.
If we are to keep freight moving
with the lowest environmental
harm, the steel wheel on steel rail –
even with diesel traction – is, if not
the best, the least worst option. aTABLE 4: CURRENT DIESEL FREIGHT FLEETS
Class Fleet size Rating kW Emissions Built Age (years)
Nominal
withdrawal date
59 15 3,000 1985-95 24-34 2025-35
60 27 (1) 3,100 1989-93 26-30 2029-33
66 407 3,300 1998-2016 3-21 2038-56
67 30 3,000 1999 20 2039
68 44 3,800 IIIA 2012-19 0-7 2052-59
70 37 3,690 IIIA 2009-17 2-10 2049-57
73 (2) 11 1,600 IIIA 2018 2 2058
TOTA L 571
1) Remainder in store, 2) Re-engined with MTU 1600 Series engine. Fleets with modern emissions-compliant engines highlighted in green.TABLE 5: FREIGHT ELECTRIC LOCOMOTIVE FLEETS
Class Number Built Age (years)
Nominal
withdrawal date
86/7 22 1966 53 2006
88 (1) 10 2016 3 2056
90 34 1987-90 29-32 2027-30
92 32 1993-96 23-26 2033 36
TOTA L 98
(1) Incorporates last mile diesel engine.TABLE 6: COMPARISON OF LI ION TECHNOLOGY PERFORMANCE
Carbon anode LT O
Energy density 120-200Wh/kg 70-80Wh/kg
Cycles 4,500-8,000 15,000-20,000Class 93 tri-mode: ROG is taking delivery of 10 of these electric / diesel / battery machines from Stadler.022-030_MR_Apr 2019_informed 1.indd 30 12/03/2019 15:01