Life Cycle Assessment of Alternative Traction Options for Non-Electrified Regional Railway Lines

Abstract

The railway sector is facing significant challenges in addressing the increasing concerns related to climate change, environmental pollution and scarcity of resources. This especially applies to often non-electrified regional railway networks, with passenger services provided by diesel-driven vehicles. Innovative propulsion system concepts offer significant improvement of energy efficiency and reduction of overall environmental impact from train operation. This study presents a life cycle assessment of greenhouse gas emissions linked to the implementation of alternative powertrain systems in conventional diesel-electric multiple-unit vehicles employed on the regional railway lines in the northern Netherlands. The analysis encompassed the retrofit of a standard vehicle to its hybrid-electric, fuel cell-electric and battery-electric counterparts, and a comparative assessment of life cycle emissions during a ten-year time horizon. Results indicated significant impact of the production pathway for alternative energy carriers to diesel, namely hydrogen and electricity. The largest reduction in total emissions (96.80%) is obtained for a fuel cell-electric vehicle running on hydrogen produced from electrolysis, with slightly lower performance shown by the battery-electric configuration using green electricity produced from wind power (95.92%). Maintaining the diesel engine in the hybrid-electric alternative leads to a potential overall emission reduction of about 27%, as a result of improved fuel economy offered by the implemented energy storage system, and could be considered as a cost-effective transition solution towards carbon-neutral trains operation.

Full text

1
Life Cycle Assessment of Alternative Traction Options for Non-Electrified Regional Railway Lines
Marko KAPETANOVIĆ1, Alfredo NÚÑEZ 2, Niels VAN OORT1, Rob M.P. GOVERDE1
1Delft University of Technology, Department of Transport and Planning, Delft, The Netherlands
2Delft University of Technology, Section of Railway Engineering, Delft, The Netherlands
Corresponding Author: Marko Kapetanović (M.Kapetanovic@tudelft.nl)
Abstract
The railway sector is facing significant challenges in addressing the increasing concerns related to climate
change, environmental pollution and scarcity of resources. This especially applies to often non-electrified
regional railway networks, with passenger services provided by diesel-driven vehicles. Innovative propulsion
system concepts offer significant improvement of energy efficiency and reduction of overall environmental
impact from train operation. This study presents a life cycle assessment of greenhouse gas emissions linked to
the implementation of alternative powertrain systems in conventional diesel-electric multiple-unit vehicles
employed on the regional railway lines in the northern Netherlands. The analysis encompassed the retrofit of a
standard vehicle to its hybrid-electric, fuel cell-electric and battery-electric counterparts, and a comparative
assessment of life cycle emissions during a ten-year time horizon. Results indicated significant impact of the
production pathway for alternative energy carriers to diesel, namely hydrogen and electricity. The largest
reduction in total emissions (96.80%) is obtained for a fuel cell-electric vehicle running on hydrogen produced
from electrolysis, with slightly lower performance shown by the battery-electric configuration using green
electricity produced from wind power (95.92%). Maintaining the diesel engine in the hybrid-electric alternative
leads to a potential overall emission reduction of about 27%, as a result of improved fuel economy offered by
the implemented energy storage system, and could be considered as a cost-effective transition solution towards
carbon-neutral trains operation.
Keywords: regional railways, greenhouse gas emissions, life cycle assessment, alternative propulsion systems
1. Introduction
Regional railway passenger transport in the EU is often characterized by non-electrified lines, and diesel-electric
multiple unit (DEMU) vehicles as the only traction option. Complete electrification of such lines is often not
economically viable due to high capital investments required and low transport demand compared to the main
corridors. Facing stringent emission regulations [1], railway undertakings are thus seeking alternative traction
options to improve their environmental impact. Potential solutions are sought in advanced vehicle powertrains,
with hybrid-electric, hydrogen fuel cell-electric, and battery-electric propulsion systems [2, 3] being the most
prominent technology. Through improved fuel economy and/or use of renewable fuels, these systems offer
significant reduction of well-to-wheel greenhouse gas (GHG) emissions and potentially zero-emission trains
operation. However, to date, specific studies investigating the life cycle impacts of such solutions hardly exist.
Focussing on a case of regional railway services provided in the northern Netherlands, the aim of the present
study is to assess and compare the life cycle GHG emissions resulting from the implementation of the three
aforementioned alternative propulsion systems in the conventional DEMU vehicle. Hybridization of a standard
vehicle can be achieved by implementing an energy storage system, typically a Lithium-ion battery, that would
allow for the utilization of regenerative braking energy, reduced fuel consumption and related emissions. A
catenary-free fuel cell-electric system can be implemented by replacing the engine-generator unit with a
hydrogen fuel cell system, together with an appropriately sized energy storage system that would make up for
the slow dynamic responses of a fuel cell. Due to the lack of an on-board power plant, a battery-electric system
requires partial track electrification for charging the energy storage system, with stored energy later utilized on
non-electrified track sections. The results presented in the remainder of the study will provide railway
undertaking and decision makers with essential input in planning rolling stock and infrastructure investments.

2
2. Methodology
A life cycle assessment (LCA) approach is used in assessing the GHG emissions linked to the alternative
propulsion systems implementation, namely hybrid-electric, fuel-cell electric and battery electric. A ten-years’
time horizon is considered, from 2025 until 2035, which denotes the end of the ongoing concession period and
the end of current vehicles’ service life. Due to the comparative nature of the study, and considered retrofit of
existing vehicles with electrification of already built railway lines, the analysis is restricted to the subsystems and
components varying with the alternative vehicle configurations. This approach also contributes to handling the
complexity, which is inherently high when the analysis entails infrastructure construction and vehicle production
from scratch. The system boundary (Figure 1) includes emissions resulting from: (i) production of the system
components used in converting the conventional vehicle, i.e., fuel cells and Lithium-ion batteries, as well as the
track electrification equipment required for the operation of battery-electric multiple units; (ii) the vehicle-use
phase, covering upstream emissions related to the production and distribution of fuel/electricity, and direct
emissions produced during vehicle operation; and (iii) the end-of-life phase that encompasses recycling and/or
disposal of particular vehicle components. Due to the much longer service life of railway infrastructure (typically
60 years) than the observed time horizon, end-of-life processes for track electrification equipment are omitted.
Depending on the nominal power of the fuel cell system, energy capacity of Lithium-ion battery and/or length
of the electrified track, corresponding life cycle emissions are estimated using emission factors provided in Table
1. Although hydrogen and electricity utilization in vehicle propulsion does not produce direct emissions, the
overall environmental impact of these energy carriers largely depends on the upstream processes related to
their production and distribution. To investigate the impact of these processes, and to allow for fair comparison
with the baseline diesel fuel, various production pathways are considered using a well-to-wheel approach.
Alternative hydrogen production pathways include steam methane reforming (SMR) and electrolysis of water
using green electricity obtained from wind power, while electricity production scenarios encompass a predicted
EU power mix for 2030, or renewable electricity obtained solely from wind power. Corresponding emission
factors are given in the remainder of Table 1, which are then coupled with the estimated fuel or electricity
consumption from vehicle operation in assessing the overall GHG emissions from the vehicle use phase.
Taking into account the significance and contribution of the use phase to the overall environmental impact over
a ten-years period, it is essential to obtain reliable estimates of the fuel or electricity consumption during the
train’s operation. For this aim, detailed MATLAB/Simulink individual train models based on a backward looking
quasi-static simulation approach [4] is employed. The modular structure and programming environment allows
for relatively easy development or customization of train propulsion system configurations and implemented
on-board power management [5]. We extend previous work on the model of a hybrid-electric [6] and fuel cell-
electric system [7] with a newly developed model of a battery-electric train. The simulation model requires
technical specifications for a variety of system components and infrastructure related characteristics, and
provides an estimate of fuel or electricity consumption during observed trips as an output. The obtained
estimates are then coupled with information on the annual days of operation, maintenance frequencies, and
the number of cycles performed per day in assessing the overall energy consumption during a ten years period.
Figure 1: System boundary for the LCA

3
Component/Energy carrier
Unit
Value
Reference
Fuel cell
kgCO2e/kW
43
[8]
Lithium-ion battery
kgCO2e/kWh
83.5
[9]
Track electrification
kgCO2e/km/year
1750
[10]
Diesel
kgCO2e/l
3.303
[11]
Hydrogen (SMR)
kgCO2e/kg
15.9
[11]
Hydrogen (electrolysis)
kgCO2e/kg
0.432
[11]
Electricity (EU mix 2030)
kgCO2e/kWh
0.259
[11]
Electricity (wind energy)
kgCO2e/kWh
0
[11]
Table 1: Greenhouse gas emission factors for energy carriers and alternative technology components
3. Case Study of Regional Railways in the Northern Netherlands
The methodology proposed in the previous section was applied in estimating the energy consumption for each
of the considered alternative propulsion systems, followed by the calculation of related life cycle GHG emissions.
The following sub-sections provide the description of the selected benchmark DEMU and railway line, followed
by a comparative analysis of the different scenarios.
3.1 Reference Vehicle and Railway Line
The presented LCA approach is applied in a case of a two-coach DEMU GTW 2/6 from Stadler, employed on the
network’s main railway line connecting the cities Leeuwarden and Groningen. Due to the difference in line
resistances and maximum speed limits for the two opposite directions (Figure 2), the vehicle round trip is
analysed, based on the actual periodic timetable and vehicle circulation plan provided by the railway
undertaking. A vehicle performs eight round trips during working days, and six round trips during weekends. A
three weeks out-of-operation period is assumed per year for maintenance purposes. Commercially available fuel
cell modules from Ballard [12] and Lithium-ion batteries from Toshiba [13] are used in vehicle retrofit, with the
number of modules determined from the estimated power and energy demand, while satisfying the maximum
weight and volumetric space constraints [7]. With stations Leeuwarden and Groningen already connected to the
national traction grid, the battery-electric scenario considers electrification of the first track sections stretching
from these two stops, namely Leeuwarden – Leeuwarden Camminghaburen and Groningen – Zuidhorn. Table 2
provides the main specifications for alternative scenarios. In addition to the initial retrofit, both fuel cells system
and Lithium-ion battery energy storage system are to be replaced once during the observed ten-years period
due to the limited service life of these technologies, i.e. number of working hours or charge/discharge cycles.
Component
Propulsion system
Conventional
Hybrid-Electric
Fuel Cell-Electric
Battery-Electric
Diesel engine
2×390 kW
2×390 kW
-
-
Fuel cell system
-
-
6×70 kW
-
Lithium-ion battery
-
106×1.24 kWh
157×1.24 kWh
499×1.24 kWh
Electrified track
-
-
-
15.036 km
Table 2: Technical specifications of alternative propulsion system configurations

4
Figure 2: Railway line Leeuwarden-Groningen: track layout, geometry, and speed limits
3.2 Results
The estimated fuel or electricity consumption per single trip and for the overall ten-years period is provided in
Table 3. The total life cycle GHG emissions are further calculated using emission factors (Table 1), propulsion
system configurations (Table 2) and the assumptions related to the periodic replacement of components, with
estimates for the six scenarios summarized in Figure 3. Figure 3 also shows the relative GHG emissions reduction
potential of alternative systems compared to a baseline conventional DEMU vehicle as the highest emitter, with
estimated total GHG emissions of almost 9 million tons of CO2e, attributed completely to the vehicle use phase
(production and consumption of diesel fuel).
Conversion of a conventional DEMU to its hybrid-electric counterpart leads to a potential overall emissions
reduction of about 27%, as a result of improved fuel economy offered by the implemented energy storage
system. A significant impact of upstream processes related to the production and distribution of an energy
carrier is most evident in the case of fuel cell-electric vehicle configuration, which demonstrated both, the lowest
(9.66%) and the highest (96.80%) emission reduction potential if hydrogen produced from SMR and electrolysis
is used, respectively. A slightly higher emission level compared to the aforementioned best alternative is shown
for the battery-electric powertrain with green electricity used for traction and charging the energy storage
system. A high contribution of the energy carrier pathway is notable here as well, with emission savings potential
reduced to about 77% for electricity based on the 2030 EU mix, as still significant part of the electricity
production is expected to rely on fossil energy such as coal and natural gas [11].
Propulsion system
Energy carrier
Per trip
Over 10 years
Conventional
Diesel [l]
106.40
2,719,584
Hybrid-electric
Diesel [l]
77.45
1,979,622
Fuel cell-electric
Hydrogen [kg]
19.80
506,088
Battery-electric
Electricity [kWh]
255.80
6,538,248
Table 3: Estimated energy consumption from train’s operation

5
Figure 3: Total life cycle greenhouse gas emissions produced during the observed period and relative
greenhouse gas emissions reduction compared to the standard diesel vehicle
Regarding the relative share of different components to the overall GHG emissions produced during the
observed period (Figure 4), the vehicle use phase (energy carrier production, distribution and consumption) has
the far largest contribution in all scenarios, except for the battery-electric vehicle running on green electricity –
as the only alternative that offers net-zero emissions from a well-to-wheel perspective. The fuel cell system is
linked with slightly higher life cycle impact than the considered Lithium-ion battery for this powertrain
configuration. Although the battery-electric configuration considers a significantly larger battery system, its life
cycle emissions are almost three times lower than those associated with the track electrification.
Figure 4: Relative contribution of different components to the overall greenhouse gas emissions produced
during the observed period
4. Conclusion
This study presented a comparative assessment of life cycle GHG emissions related to the implementation of
various alternative powertrain configurations in a conventional diesel regional train, namely hybrid-electric, fuel-
cell-electric and battery-electric. The results indicated significant impact of the production pathways for the

6
alternative energy carriers, with the highest potential benefits identified for the fuel-cell electric system running
on green hydrogen. Similar performance is obtained for the battery-electric vehicle using green electricity from
wind power. Although internal combustion engines produce other harmful emissions such as local pollutants, a
vehicle retrofit solely by hybridization of a conventional powertrain demonstrated significant fuel savings and
emission reduction, and could be considered as a cost-effective transition solution towards carbon neutral trains
operation. Future research will include economical aspects related to the implementation of presented
propulsion systems, together with the alternative production pathways for hydrogen and electricity, by an
integrated LCA and life cycle costs (LCC) approach.
Acknowledgment
This work is supported by Arriva Personenvervoer Nederland B.V. within the PhD project “Improving
sustainability of regional railway services” of Delft University of Technology.
References
[1] UIC and CER, “Moving towards sustainable mobility: A Strategy for 2030 and Beyond for the European
Railway Sector”, Paris, 2012.
[2] W. Klebsch, P. Heininger, J. Geder, and A. Hauser, “Battery Systems for Multiple Units: Emission-free drives
powered by lithium-ion cells”, VDE Report, Frankfurt am Main, 2018.
[3] W. Klebsch, P. Heininger, and J. Martin, “Alternatives to diesel multiple units in regional passenger rail
transport: Assessment of systemic potential”, VDE Report, Frankfurt am Main, 2019.
[4] L. Pröhl, “OPEUS Deliverable DO2.1 - OPEUS simulation methodology”, EU-project OPEUS (S2R-OC-CCA-02-
2015), 2017.
[5] L. Pröhl, “OPEUS Deliverable DO2.2 - OPEUS simulation tool”, EU-project OPEUS (S2R-OC-CCA-02-2015),
2017.
[6] M. Kapetanović, M. Vajihi, and R. M. P. Goverde, “Analysis of Hybrid and Plug-In Hybrid Alternative
Propulsion Systems for Regional Diesel-Electric Multiple Unit Trains”, Energies, vol. 14 (18), p. 5920, 2021.
[7] M. Kapetanović, A. Nunez, N. van Oort, and R. M. P. Goverde, “Analysis of hydrogen-powered propulsion
system alternatives for diesel-electric multiple unit regional trains”, J. Rail Transp. Plan. Manag., Under
review, 2022.
[8] M. Pehnt, “Life-cycle assessment of fuel cell stacks”, Int. J. Hydrogen Energy, vol. 26 (1), pp. 91–101, 2001.
[9] Ö. Andersson and P. Börjesson, “The greenhouse gas emissions of an electrified vehicle combined with
renewable fuels: Life cycle assessment and policy implications”, Appl. Energy, vol. 289, p. 116621, May
2021.
[10] T. Baron, M. Tuchschmid, G. Martinetti, and D. Pepion, “High Speed Rail and Sustainability. Background
Report: Methodology and results of carbon footprint analysis”, UIC, Paris, 2011.
[11] JRC, “JEC Well-to-Tank report v5. Well-to-Wheels analysis of future automotive fuels and powertrains in
the European context”, Luxembourg, 2020.
[12] Ballard, “FCmove,” 2021. Available at: https://www.ballard.com/about-
ballard/publication_library/product-specification-sheets/fcmovetm-spec-sheet.
[13] Toshiba, “SCiBTM Rechargeable battery,” 2021. Available at: https://www.global.toshiba/ww/products-
solutions/battery/scib.html.