Comparing environmental impact of conventional and high speed rail

Transcription

1 Planning and Regulation Route Planning New Lines Programme Comparing environmental impact of conventional and high speed rail

2 Executive Summary Comparing the Environmental Impact of Conventional and High-Speed Rail Introduction The New Lines Programme is to test the hypothesis that in 2020, the existing rail lines from London to the North and West will be operating at full capacity and the conventional and the next generation tools for increasing capacity will be exhausted. There will be the need for additional intervention. The programme aims to develop and evaluate the options for building new lines; including in this is the need to evaluate the environmental impacts of such an intervention in terms of expected energy consumption of new rolling stock, understand any step change in energy consumption between new versus existing rolling stock including diesel versus electric and to assess localised environmental impact during and after construction. As a result there is a need to better understand the environmental impact of building one or more new lines in terms of: 1) Performance (energy consumption) of rolling stock, both current high-speed (electric), conventional (diesel) rolling stock and future electric rolling stock; 2) Seating occupancy levels in high-speed versus conventional services; 3) Estimated direct and indirect greenhouse gas emissions from diesel and electric rolling stock (both in current and likely future electric mix); 4) Estimated emissions resulting from the construction, maintenance and decommissioning of rolling stock; 5) The potential energy consumption/emissions resulting from construction of new infrastructure in terms of materials used in the construction of infrastructure (and the energy consumption /emissions per kg of these materials) as well as the energy use/emissions resulting from infrastructure construction activities; 6) The role of energy consumption/emissions savings resulting from modal shift and factoring in demand generation in the overall comparison. This environmental study was carried out to assess the relative environmental performance of conventional and high speed electric rail services. The purpose of this work is to provide an objective comparison between the different options and the key assumptions that affect the outcome of the comparison. In doing this, the work also needs to take into account the long timeframes associated with planning and constructing large railway infrastructure projects including wholly new rail lines (e.g. around 20 years for both the Channel Tunnel Rail Link and Crossrail). Hence comparisons will need to be made on the anticipated performance of future high-speed and conventional rail rolling stock likely to be put into service in the timeframe. For the purposes of this study, high-speed rail (HSR) services are defined as services faster than typical UK intercity limit of 200 km/hour, typically over 250 km/hour and up to 350+ km/hour. Comparisons in this report are made for similar types of electric rail services for HSR vs conventional rail i.e. with conventional intercity service rolling stock (up to 200 km/hour), rather than rolling stock used in slower stop-start commuter services. The focus for the work for this project has been on energy consumption and greenhouse gas emissions. Other environmental impacts will be considered in more detail at a later phase and are not within the scope of this project. In order to obtain as up to date and accurate information as possible the project team consulted widely with experts in industry and academia, as well as with the Department for Transport (DfT). This was carried out via a letter of introduction and accompanying questionnaire and follow-up by and telephone interviews. ii

3 Summary of Analysis Results and Conclusions The results of the comparative analysis of conventional versus high-speed rail have been presented split between three source areas: 1. GHG emissions resulting from to direct energy consumption by the trains; 2. GHG emissions resulting from the construction, maintenance, use and disposal of new electric rail infrastructure; 3. GHG emissions resulting from the production, disposal and maintenance of electric trains. These results have demonstrated the following points: Per seat-km conventional rail uses less energy and produces fewer GHG emissions than highspeed rail. High-speed rail would be expected to result in around 9.3% more GHG emissions on average (at 12.8 gco 2 eq/seat-km) than equivalent conventional rail (at 11.7 gco 2 eq/seat-km) in 2025, according to calculations using central scenario values. This difference drops to 4.4% more over the 30-year lifetime of the trains, with HSR at 7.8 gco 2 eq/seat-km and conventional rail at 7.5 gco 2 eq/seat-km. This is because the importance of emissions from direct energy consumption decreases due to decarbonisation of electricity generation; Per passenger-km (pkm) HSR is anticipated to produce significantly lower GHG emissions than conventional rail. This is the case both when assuming typical differences in European occupancy levels between conventional and HSR and for the modelled differences in occupancy levels from the NLP Strategic Business Case. On average HSR (at 30.3 gco 2 eq/pkm) is expected to result in around 15% less GHG emissions on average than conventional rail (at 35.7 gco 2 eq/pkm) in 2025, according to the calculations using central values. This GHG emissions for HSR reduce further to 18.8% less (at 18.5 gco 2 eq/pkm) than conventional rail (at 22.7 gco 2 eq/pkm) when considering them over the 30-year lifetime of the trains. The differential increases further when modal shift and demand creation are factored in to 17.4% less (26.4 gco 2 eq /pkm and 32.0 gco 2 eq/pkm respectively for HSR and conventional rail) in 2025, and 23.5% less (15.1 gco 2 eq/pkm and 19.7 gco 2 eq/pkm respectively) over the 30-year train lifetime; Impact of electricity decarbonisation: When assuming current grid electricity emission factors and electric train models the GHG emissions due to direct energy use of the train accounted for over 80% of the total emissions (with 18% due to rail infrastructure and <1% due to indirect emissions due to trains). However, the direct train component drops to around 28% when assuming the use of new trains over 30 years from 2025 and the CCC s proposed rapid decarbonisation of UK electricity generation. In this case the emissions resulting from new rail infrastructure dominate, accounting for around 70% of the total. The majority of the emissions from construction of new rail infrastructure result from the use of concrete and steel. Significant gains might therefore be achieved by focussing on reducing the emissions footprint of these materials. Comparison of conventional and high-speed rail under central assumptions: Conventional and high-speed rail were compared for the different reference routes for services proposed under the NLP Strategic Business Case. Under the central assumptions the total average GHG emissions over the 30 year lifetime of the trains were calculated to be 18.5 gco 2 eq/pkm for highspeed rail and 22.7 gco 2 eq/pkm for conventional rail. When modal shift and demand creation effects are also included the average figures drop to 15.1 and 19.7 gco 2 eq/pkm respectively for HSR and conventional rail. The benefits of modal switching therefore outweigh the counter-action of factoring in demand creation. Due to significantly lower modelled average occupancy levels, the equivalent modelled services direct from Birmingham to Glasgow and Edinburgh have average emission factors around double these figures. Sensitivity analysis on occupancy levels and passenger numbers: The ±20% sensitivities on occupancy levels and passenger numbers show that as the average percentage occupancy levels of conventional and high-speed rail become closer together, the advantage high-speed rail has in terms of direct emissions per passenger-km is eroded. Parity is reached in their relative emissions when load factors for conventional rail are around 4% lower than those for high-speed rail. However, it is the total passenger numbers that are critical in the analysis, as this affects the allocation of emissions resulting from the rail infrastructure. Therefore a higher number of services with lower occupancy but high overall passenger numbers is strongly favoured over significantly less-frequent but high-occupancy services that potentially move fewer passengers. iii

4 Sensitivity analysis on the carbon intensity of electricity generation: The sensitivity on the electricity decarbonisation rate shows that varying the assumption on future decarbonisation of electricity generation has a 30-40% impact on the total greenhouse gas emissions and over 60% on the component due to direct energy consumption by trains. Under central (rapid decarbonisation) assumptions the range for the GHG emissions between 2025 and 2055 respectively was from 30.3 to 15.0 gco 2 eq/pkm for respectively HSR and 35.7 to 19.0 gco 2 eq/pkm for conventional rail (excluding the effects of modal shift and demand creation). Sensitivity analysis on embedded greenhouse gas emissions: The percentage of recycling of materials at the end of the life of infrastructure (and to much a lesser degree trains) has a very significant impact on the final results. Because of the dominating effect of embedded infrastructure emissions in the overall assessment this puts a high level of importance to designing recyclability into the design of new infrastructure as far as possible. The sensitivities on % tunnels on new line infrastructure and on the type of track also underline the importance of these elements in the overall analysis. Using ballastless track results in significantly higher GHG emissions in its construction compared to conventional track, but no detailed information was available on GHG savings due to reduced maintenance. More detailed evaluation of the GHG savings potential through avoided maintenance would be beneficial to inform the comparison should this option become preferred over conventional track in the future. The sensitivity on the % tunnels on new lines suggests that the alternatives to tunnelling should be investigated where possible. Sensitivity analysis on modal shift and demand creation: The analysis using information from the NLP Business Case showed that the benefits of modal shift from car and air tranpsort outweighed the counteracting demand creation element in the overall analysis. They also showed that the net benefits due to modal shift and demand creation for high-speed rail services are notably larger than those for conventional rail, further improving high-speed rail s relative performance. Because of the complexity in changes to rail services and passenger numbers on existing lines it was not possible to quantitavily factor in the impact if abstraction from existing rail. Overall Conclusions and Recommendations for Future Work Overall, this work has provided a comprehensive review and evaluation of the elements that contribute to the overall energy consumption and net greenhouse gas emissions from electric rail. Through detailed analysis and sensitivities this study has also explored the impacts of key assumptions on these elements on the overall comparison of the relative performance of future conventional and highspeed rail on proposed new lines. The work has clearly demonstrated the significant net benefit of high-speed rail services over equivalent conventional services in terms of energy consumption and GHG emissions per passenger-km in the context of proposed new line development. Factoring in the net effects of modal shift and journey creation adds to this advantage. Also highlighted is the overriding significance of the GHG emissions due to new rail infrastructure in the anticipated future where the electricity system is highly decarbonised. This in turn puts significant emphasis on the importance of minimising emissions from the construction of any new rail infrastructure, focussing on sourcing lower carbon materials and on the recyclability of end of life components. On the basis of the analysis for this study, the development of new lines to provide high-speed rail services appears to be highly desirable in reducing GHG emissions in the long-term. However, there will be very significant up front GHG emissions from the construction of new infrastructure in the short-term. The results of the work also suggest a number of areas for further research to help better understand and minimise the environmental impact of rail. More detailed analysis of specific proposals including other environmental impacts: This work has provided a preliminary scoping level assessment of the potential impacts of the development a high-speed rail service in terms of greenhouse gas emissions. However, a more detailed assessment would be beneficial once the preliminary proposals have been firmed up. At this stage an assessment of the other environmental impacts would be appropriate, such as emissions of air quality pollutants, noise and land-take. Research into ways to minimise the environmental impact of new rail infrastructure: The results on the relative importance of infrastructure emissions suggests a more detailed piece of research focussing on this element would be worthwhile to include other impacts such embedded emissions of air quality pollutants. Whilst a preliminary assessment of the impacts have been carried out here, a more in depth life cycle assessment is desirable. Research into the potential for minimisation of the GHG emissions footprint of new rail infrastructure through sourcing of less carbon intensively produced materials would also seem worthwhile. iv

5 Table of Contents Executive Summary ii Glossary and Energy Unit Equivalencies viii 1 Introduction Scope of work Information collection Report structure 2 2 Factors Affecting Comparisons of Energy Consumption and GHG Emissions Direct energy consumption and emissions from trains Indirect energy consumption and emissions from trains Energy consumption and emissions resulting from rail infrastructure Other factors affecting comparisons 24 3 Results of Comparative Analysis Definition of scenarios Breakdown of relative impacts Sensitivity analysis on key parameters 40 4 Summary and Conclusions 45 5 References 50 Appendices Appendix 1: Consultation Questionnaire 55 v

6 List of Figures Figure 2.1: Typical composition of energy demand for high-speed and conventional rail services 4 Figure 2.2: Energy flow diagrams for passenger trains with and without regenerative braking 5 Figure 2.3: Energy conversion losses for a German ICE electric multiple unit 7 Figure 2.4: Comfort function demands for a train in UK winter (0 C) 7 Figure 2.5: Typical breakdown of components in electric multiple unit trains by weight 10 Figure 2.6: Typical breakdown of components contribution to drag in electric trains 10 Figure 2.7: Energy consumption of current and future rolling stock (kwh per seat-km) 13 Figure 2.8: Trend between energy use (kwh/seat-km) and speed (km/h) for European trains 13 Figure 2.9: Low and High Scenarios for Future Carbon Intensity of UK Grid Electricity 15 Figure 2.10: Proportional breakdown of materials used in electric rail rolling stock and corresponding net emissions of greenhouse gases for production and disposal at different recycling rates 18 Figure 2.11: Breakdown by electric rail infrastructure element of the net embedded greenhouse gas emissions for (at a 50% recycling rate), annualised over the infrastructure lifetime 21 Figure 2.12: Proportional breakdown of materials used in electric rail infrastructure and corresponding net emissions of greenhouse gases for production and disposal (at a 50% recycling rate) 23 Figure 2.13: The core New Line only options from London considered in the New Lines Programme Strategic Business Case (NEW LINES PROGRAMME, 2009) 26 Figure 2.14: Speed Assumptions for the New Lines Programme Strategic Business Case (NEW LINES PROGRAMME, 2009) 26 Figure 2.15: Detail on the full option (MB1.4.1) considered in the New Lines Programme Strategic Business Case (NEW LINES PROGRAMME, 2009) 27 Figure 2.16: Train Service Specification for Full Option (MB1.4.1) considered in the New Lines Programme Strategic Business Case (NEW LINES PROGRAMME, 2009) 27 Figure 2.17: Modal share of high-speed rail services and flights by journey time 30 Figure 2.18: Assumptions on the projected improvement in the greenhouse gas emissions from cars and domestic air transport 31 Figure 3.1: Breakdown of the total GHG emissions from conventional and high-speed rail per seatkm for different routes (assumes current trains and carbon intensity of electricity) 35 Figure 3.2: Breakdown of the total GHG emissions from conventional and high-speed rail per seatkm for different routes (assumes future trains and carbon intensity of electricity) 36 Figure 3.3: Breakdown of the total GHG emissions from conventional and high-speed rail per passenger-km for different routes (assumes future trains and carbon intensity of electricity) 37 Figure 3.4: Breakdown of the total GHG emissions from conventional and high-speed rail per passenger-km by impact area 38 Figure 3.5: Summary comparison of the relative performance of conventional and high-speed rail at different timeframe assumptions (NLP-SBC Total) 39 Figure 3.6: Sensitivity analysis breakdown on the impact of varying occupancy levels and passenger numbers on the comparison of total GHG emissions from conventional and high-speed rail 40 Figure 3.7: Sensitivity analysis on the impact of the assumptions on the future decarbonisation electricity generation to the comparison of conventional and high-speed rail 41 Figure 3.8: Sensitivity analysis on the impact of the assumptions on the % recycling of end of life infrastructure and trains to the comparison of conventional and high-speed rail 43 Figure 3.9: Sensitivity analysis on the impact of the infrastructure assumptions on the % tunnels and type of rail track to the comparison of conventional and high-speed rail 43 vi

7 Figure 3.10: Sensitivity analysis on the impact of the assumptions on modal shift and demand creation to the comparison of conventional and high-speed rail 44 List of Tables Table 2.1: Principal contributors and example values for the three Davis formula coefficients 6 Table 2.2 Elasticities for efficiency measures on total energy consumption for current electric trains 8 Table 2.3 Modelled impacts of efficiency measures on energy consumption for Japanese Shinkansen HSR 8 Table 2.4: Summary of measures to reduce energy consumption from trains 9 Table 2.5: Characteristics of current and future rolling stock used for conventional and high-speed rail 12 Table 2.6: Total greenhouse gas emissions (in kgco 2 eq per tonne material) resulting from different stages of the material lifecycle (production, recycling, other disposal) 16 Table 2.7: Material breakdown for typical electric rail rolling stock and corresponding net emissions of greenhouse gases for production and disposal at different recycling rates 18 Table 2.8: Characteristics of current and future rolling stock used for conventional and high-speed rail and the net greenhouse gas emissions under the central recycling scenario 19 Table 2.9: Estimated energy and water consumption per train-drive km for train maintenance and refitting 19 Table 2.10: Estimated embedded emissions for electric rail infrastructure based on ballasted or ballastless track, breakdown by element 22 Table 2.11: Estimated annual in-use activity elements for electric rail infrastructure and equivalent 2007 emissions factors 23 Table 2.12: Typical load factors for European high-speed rail services 25 Table 2.13: Modelled average load factors for conventional and high-speed services from the New Lines Programme Strategic Business Case (NEW LINES PROGRAMME, 2009) 28 Table 2.14: Modelled average modal switch and journey creation for conventional and high-speed services from the New Lines Programme Strategic Business Case (NEW LINES PROGRAMME, 2009) 30 Table 3.1: Summary definition of the Central, Low and High scenario assumptions used in the analysis 32 Table 3.2: Assumtions for scenarios on the projected greenhouse gas emission factors for electricity, passenger cars and domestic flights 32 Table 3.3: Detailed definition of the Central, Low and High scenario assumptions for passenger numbers, occupancy and the proportion of tunnels on new lines for different services 33 Table 3.4: Comparison of services in the New Lines Programme Strategic Business Case with typical European high-speed rail services 34 Table 3.5: Definition of the Central, Low and High scenario assumptions for modal shift and demand creation on new lines for different services 34 Table 3.6: Sensitivity analysis on the impact of the assumptions on modal shift and demand creation to the comparison of conventional and high-speed rail (NLP-SBC Total) 44 vii

8 Glossary Term/Abbreviation Definition/Explanation Carbon footprint A measure of the impact human activities have on the environment in terms of the amount of greenhouse gases produced Catenary The system of overhead wires suspended above the track that deliver power to electric trains. CH 4 Methane CO 2 Carbon dioxide eq CO 2 or CO 2 eq Carbon dioxide equivalent: a quantity that describes, for a given mixture and amount of greenhouse gas, the amount of CO 2 that would have the same global warming potential (GWP), when measured over a specified timescale (usually 100 years). EMUs Electric Multiple Units a type of electric train that has powered vehicles across the train formation, rather than a single power vehicle/locomotive at either end with unpowered carriages. GHG Greenhouse gas GWP Global Warming Potential IPCC Intergovernmental Panel on Climate Change LCA Life cycle assessment Load Factor The fractional or percentage occupancy of a train N 2 O Nitrous oxide Pantograph A pantograph is a device fitted to the roof of the train that collects current from the overhead wires. passenger-km or pkm Passenger kilometre = Unit of measure representing the transport of one passenger over one kilometre. RE Renewable energy seat-km or skm Seat kilometre = Unit of measure representing the movement over one kilometre of one seat available in a train (or other mode of transport) Tare mass The technical term for the total unlaiden mass of a train TOC Train Operating Company Energy Unit Equivalencies From /To - multiply by GJ kwh Toe Gigajoule, GJ Kilowatthour, kwh E-05 Tonne oil equivalent, toe viii

9 1 Introduction The New Lines Programme is to test the hypothesis that in 2020, the existing rail lines from London to the North and West will be operating at full capacity and the conventional and the next generation tools for increasing capacity will be exhausted. There will be the need for additional intervention. The programme aims to develop and evaluate the options for building new lines; including in this is the need to evaluate the environmental impacts of such an intervention in terms of expected energy consumption of new rolling stock, understand any step change in energy consumption between new versus existing rolling stock including diesel versus electric and to assess localised environmental impact during and after construction. As a result there is a need to better understand the environmental impact of building one or more new lines in terms of: Performance (energy consumption) of rolling stock, both current high-speed (electric), conventional (diesel) rolling stock and future electric rolling stock; Seating occupancy levels in high-speed versus conventional services; Estimated direct and indirect greenhouse gas emissions from diesel and electric rolling stock (both in current and likely future electric mix); Estimated emissions resulting from the construction, maintenance and decommissioning of rolling stock; The potential energy consumption/emissions resulting from construction of new infrastructure in terms of materials used in the construction of infrastructure (and the energy consumption/emissions per kg of these materials) as well as the energy use/emissions resulting from infrastructure construction activities; The role of energy consumption/emissions savings resulting from modal shift and factoring in demand generation in the overall comparison. This environmental study was carried out to assess the relative environmental performance of conventional and high speed electric rail services. The purpose of this work is to provide an objective comparison between the different options and the key assumptions that affect the outcome of the comparison. In doing this, the work also needs to take into account the long timeframes associated with planning and constructing large railway infrastructure projects including wholly new rail lines (e.g. around 20 years for both the Channel Tunnel Rail Link and Crossrail). Hence comparisons will need to be made on the anticipated performance of future high-speed and conventional rail rolling stock likely to be put into service in the timeframe. 1.1 Scope of work Definition of High-Speed Rail and Evaluation of Environmental Impacts For the purposes of this study, high-speed rail (HSR) services are defined as services faster than typical UK intercity limit of 200 km/hour, typically over 250 km/hour and up to 350+ km/hour. Comparisons in this report are made for similar types of electric rail services for HSR and conventional rail i.e. with conventional intercity service rolling stock (up to 200 km/hour), rather than rolling stock used in slower stop-start commuter services. Although there are a wide range of environmental impacts resulting from rail, the focus for the work at this stage is primarily on energy consumption/ greenhouse gas emissions. Other environmental impacts (e.g. air quality, noise and land-take) will be considered in more detail at a later phase and are not within the scope of this project. 1

10 1.2 Information collection Comparing the Environmental Impact of Conventional and High-Speed Rail In order to obtain as up to date and accurate information as possible the project team needed to consult widely with experts in industry and academia. This was to enable the collection of more detailed information and develop of a more nuanced understanding of the issues than could be achieved from a simple review of the available literature. As part of this consultation an introductory letter was sent out in March 2009 requesting cooperation. A questionnaire (provided in Appendix 1) was also provided alongside this request to help identify key information for the analysis. The letter and questionnaire was subsequently followed up in and telephone conversations and interviews. Advice and information was gratefully received by the project team from the following organisations and individuals which has informed the work: Alstom; Association of Train Operating Companies (ATOC); DeltaRail; Department for Transport (DfT); Forum for the Future (FFF); Greengauge 21; Hitachi; Professor Roger Kemp (University of Lancaster); Rail Industry Association (RIA); Rail Industry Forum; Rail Research UK (RRUK); Rail Safety and Standards Board (RSSB); Siemens; Steer Davies Gleave; International Union of Railways (UIC). 1.3 Report structure The aim of this report is to provide a preliminary assessement of the relative environmental impact of conventional and high-speed rail to help inform the wider business case being developed for the New Lines Programme. The report provides a summary of the results from this project, including the review of literature and consultation with stakeholders, results from comparative analyses, sensitivities and conclusions. This report is structured as follows: The theoretical background to train energy consumption, measures available to reduce this and, discussion of the different elements affecting the comparison of high-speed and conventional rail are provided in Section 2. A summary and discussion of the comparative analysis is presented in Section 3; The summary and conclusions for the work are presented in Section 4, together with recommendations for future work; References for source material are provided in Section 5. 2

11 2 Factors Affecting Comparisons of Energy Consumption and GHG Emissions This chapter provides a discussion of the major elements that influence the overall energy consumption comparison of conventional and high-speed rail. For the purposes of this work, the comparison is restricted to energy use and greenhouse gas emissions. To properly consider the relative impacts a range of factors need to be evaluated. These can be loosely grouped into the following major categories: 1) Direct performance (energy consumption) of the rail rolling stock: In making comparisons it is important to understand both the current situation and the anticipated performance of trains that would be supplied to service new lines (i.e. most likely not going into service before 2025). Comparisons between different trains are most usefully made in terms of the average energy used per seat-kilometre (i.e. total energy used per kilometre for the whole train divided by the total number of seats). 2) Seating occupancy levels and service frequency for high-speed versus conventional rail: Seating occupancy levels (also known as the load factor) directly influence the net energy use / emissions per passenger. There are significant differences between different types of services, with high-speed services typically having higher occupancy levels. Together, average seating occupancy and service frequency provide a measure of the intensity of the use of the rail infrastructure. This is important to enable the embedded emissions from infrastructure to be allocated on a per passenger-km basis. 3) Direct and indirect greenhouse gas emissions from electricity production (current and likely future electricity mix): Assumptions on the projected carbon intensity of electricity in the future will significantly impact on the relative importance of the components of direct energy consumption by rail vehicles versus other elements such as the indirect/embedded energy consumption/emissions from rolling stock and infrastructure production and disposal; 4) Indirect emissions resulting from the construction, maintenance and decommissioning of rolling stock: A complete assessment of the impact or rail rolling stock needs to factor in the energy consumption and emissions resulting from the production, disposal and maintenance phases, as well as the direct energy consumption considered in earlier sections. There may be differences between the types or volumes of different materials used for conventional and HSR rolling stock that will affect their relative impacts; 5) Energy consumption/emissions resulting from construction and use of new rail infrastructure: These can be very significant in size and could potentially significantly alter the picture if there are significant differences between conventional rail and HSR in the total passengers carried on rail new infrastructure. Elements include: a) Materials used in the construction of infrastructure (and the energy consumption /emissions per tonne of these materials); b) Energy use/emissions resulting from infrastructure construction activities; c) Annual variable energy use/emissions from infrastructure use and maintenance. 6) Energy consumption/emissions savings resulting from modal shift and factoring in demand generation: Modal shift (e.g. from car and air transport to rail) and journey creation have effectively opposing impacts on the overall evaluation. Whilst modal shift from other modes of transport will provide additional benefits, demand creation effectively reduces the benefits of the higher occupancy rates (and total passenger numbers) typically achieved by high-speed rail. It is therefore important to provide a quantitative estimate of their respective impacts in the overall evaluation. Abstraction from existing rail services is much more complex to quantify due to changes in the type and frequency of service provision affecting the total energy consumption and passenger-km. The primary focus of the project work was initially on the first three categories. However, it was important to consider the other areas where they may influence the relative comparison between HSR and conventional rail. The analysis presented in Section 3 has shown the importance of including the 3

12 other elements in the comparison, particularly the embedded emissions from construction of new rail infrastructure. The following sub-sections provide a more detailed discussion of the different elements and a summary of the default and sensitivity data used for the analysis in Section Direct energy consumption and emissions from trains Theoretical background to energy consumption The direct energy consumption of electric train systems from electric substation to wheel-rail interface can be broken down into four main areas: Energy required to overcome the train s resistance to movement; Energy lost due to inefficiencies in the traction system between pantograph and wheel; Energy used for on-board passenger comfort functions; and Losses in the electrical supply system between the substation and pantograph. Figure 2.1 shows the breakdown of energy demand for power taken from the catenary for high-speed and conventional electric trains; it can be seen that the majority of demand for energy is to provide motive power to overcome running and inertial \ grade resistance. Figure 2.2 shows the energy flow for trains with and without regenerative braking (which feeds power back into the catenary that would otherwise be dissipated as heat in friction brakes). Figure 2.1: Typical composition of energy demand for high-speed and conventional rail services Regional (with regeneration) 35% 37% 28% Regional (without regeneration) 53% 27% 20% Intercity (with regeneration) 10% 68% 22% Intercity (without regeneration) 19% 61% 20% High Speed (with regeneration) 9% 69% 22% High Speed (without regeneration) 17% 63% 20% 0% 20% 40% 60% 80% 100% Inertia and grade resistance Running resistance Comfort functions Notes: Reproduced from UIC EVENT (2003) Project report p27 4

13 Figure 2.2: Energy flow diagrams for passenger trains with and without regenerative braking a) Energy flow diagram for a passenger train without regenerative braking Energy fed in at electric substation Net energy intake Train Mechanical energy at the wheels (train motion) Catenary losses Comfort functions Losses in traction system Inertia and grade resistance Air resistance and friction Eventually dissipated in brakes b) Energy flow diagram for a passenger train with regenerative braking Energy fed in at electric substation Net energy intake Train Mechanical energy at the wheels (train motion) Catenary losses Energy returned to catenary Inertia and grade resistance Regenerative braking Air resistance and friction Comfort functions Losses in traction system Dissipated in brakes Losses in traction system Notes: Reproduced from UIC EVENT (2003) Project report, Figures 2 and 3. 5

14 Energy required to move the train The energy required by the traction system accounts for around three-quarters of a train s direct energy use in service (UIC EVENT 2003), as indicated earlier in Figure 2.1. Traction energy demand falls into two main categories: energy required to overcome inertial (ie accelerating the train) and grade resistance, and energy needed to overcome running resistance (friction and drag). The energy needed to overcome inertial and grade resistance is caused by and hence directly proportional to train mass. Energy used is not dissipated but stored as kinetic and gravitational potential energy respectively, and thus is theoretically fully recoverable. Regenerative braking aims to recover as much of this energy as possible, but inefficiencies and operational restrictions mean that inevitably a proportion is lost. The acceleration profile of the train (eg number of stop/start cycles, driving style) affects the amount of energy needed to overcome inertia; topography of the line affects the energy input needed due to grade resistance. All energy needed to overcome running resistance is due to friction and is disspiated, mostly as heat. An empirical expression for train resistance R on a straight level track is given by the Davis formula (UIC EVENT 2003, RSSB 2007a) as: R = A + Bv + Cv 2 Where A, B and C are constants for a given train-track system: A is the rolling resistance component independent of train speed v; B is the train resistance component dependant on train speed v; C is a coefficient dependent on train aerodynamic properties, proportional to the square of train speed. Table 2.1: Principal contributors and example values for the three Davis formula coefficients Principal contributors Example values 1 A Journal resistance; rolling rotational resistance; track resistance 2240 B Flange friction; flange impact; wave action of rail; wheel to rail rolling resistance C Head end wind pressure; skin air friction on train sides; rear air drag; air turbulence between vehicles; yaw angle of constant wind 4.41 Sources: Based on information from RSSB (2007a) and UIC EVENT (2003) 1 Notes: Figures for the Swedish X2 high-speed train in a 6-car configuration running at 200km/h (v = 55.56m/s) calculated from p20 of the EVENT final report. It can be seen from the example values given in Table 2.1 that for a train travelling at 200 km/h (55.56 m/s) the aerodynamic term (Cv 2 ) is around an order of magnitude greater than the other two terms, which are similar to each other in magnitude. From this it can be concluded that: For modern high-speed rail travel, aerodynamic resistance dominates, and; For a given train, the resistance to motion increases approximately with the square of train speed Losses in traction systems Inefficiencies in various electrical and mechanical components in the train traction system lead to energy being dissipated as heat, which in turn leads to a demand for ancillary energy for cooling. Modern electric trains draw power from overhead lines, transform to DC (if necessary) before using a traction inverter to provide 3-phase AC power to synchronous motors. State-of-the-art 16.7Hz 15kV AC systems are around 85% power efficient at full load, with 50Hz AC or DC systems reporting higher efficiencies (UIC EVENT, 2003). However it should be noted that overall power efficiency is lower at lower loads, meaning that energy efficiency over a typical load cycle will be much lower than at peak load. The inverse power train (used in regenerative braking) has approximately the same efficiency as the forward power train (Kemp 2009, Hitachi 2009). 6

15 In some cases (e.g. transformers), the most efficient components are also the heaviest, and so there is a trade-off between reducing weight and reducing traction system losses when optimising traction components. Figure 2.3: Energy conversion losses for a German ICE electric multiple unit 12% 6% Gear Motor Traction inverter 26% 40% DC link Rectifier Transformer 10% 5% 1% Auxiliaries Sources: Based on information from UIC EVENT (2003) Project report, p Comfort functions Comfort functions include lighting, heating and ventilating coaches for passenger comfort. Whilst this is mainly required during operation there is demand during stabled hours for cleaning and maintenance and to ensure a comfortable temperature when the train begins operation. Comfort function energy demand depends strongly on ambient temperature. The UIC EVENT (2003) study estimated that comfort functions account for around 20% of the energy consumption of a train on average. Since comfort function energy use is independent of train speed, a train that travels at higher speeds or spends less time idling between stations will have a lower comfort function energy use per seat-km than the same train taking more time to cover a given distance. Figure 2.4: Comfort function demands for a train in UK winter (0 C) 8% 10% Passenger area climate control Heating of secondary spaces 26% 56% Coach ventilation Lighting etc Sources: Based on information from UIC EVENT (2003) Project report, p Losses in supply system Losses occur in the electrical supply system due to resistance in catenary lines and inefficiencies at substations. However, such losses will be constant for an electrical system supplying power at a given voltage, regardless of the characteristics of the trains in the system. For this reason supply system losses are not discussed further in this section. 7

16 2.1.2 Principal measures to reduce energy consumption in electric rail Measures to reduce energy consumption in electric rail can be grouped into two categories: technical measures where hardware is modified to reduce its consumption in given operating conditions, and operational measures where the operating conditions are modified to reduce the energy consumption of hardware. These measures are summarised in Table 2.4, and the most significant are discussed in more detail below. None of the studies reviewed or interviews conducted as part of this research pointed to any measures, technical or operational, which only applied to one of high-speed or conventional rail services. The rolling stock manufacturers interviewed affirmed that the main technical measures planned to reduce energy consumption in new rolling stock are common to both high-speed and conventional rail, and the magnitude of benefit achieved by each measure was broadly similar. Table 2.2 shows the elasticities 1 for three key efficiency measures on overall train energy consumption: improving the efficiency of the traction system, reducing train mass and reducing train running resistance (friction and drag). The effect of regenerative braking on the elasticities is also shown. It can be seen that the elasticities are very similar for high speed and intercity trains; the likely differences for elasticities with regard to train mass and running resistance are discussed in and respectively. Similar levels of significance for the different types of measure can also be seen in the simulated impacts for the Japanese high-speed Shinkansen trains in Table 2.3 (WCHSR, 2008). It is important to note that considering elasticities alone can be deceptive. In considering how to target effort, the relative ease (and cost) of making improvements and the total remaining potential for improvements also needs to be taken into account. For example, it may be that it is easier or more cost effective to make significant reductions in train mass than to improve traction efficiency. Furthermore, it is important to also take account of potentially counter-balancing effects of different options. For example, high-efficiency transformers tend to be heavier, offsetting electrical efficiencies gained. The consensus amongst the rolling stock manufacturers interviewed was that high-speed trains will always consume more energy per seat-km than conventional trains with the same technological refinements, and that the current proportional difference in direct energy consumption is unlikely to change significantly in the next years. Table 2.2 Elasticities for efficiency measures on total energy consumption for current electric trains Elasticities with regard to: Train type Traction Efficiency Train Mass Running Resistance High speed without regenerative braking High speed with regenerative braking Intercity without regenerative braking Intercity with regenerative traking Notes: Reproduced from UIC EVENT Project report, Table 2. Table 2.3 Modelled impacts of efficiency measures on energy consumption for Japanese Shinkansen HSR Measures Level of measure Impact on energy consumption Impact for 1% change Reducing vehicle weight 1 ton/car decrease -1% -0.4% Reducing air friction 10% decrease -6% -0.6% Efficiency of main electrical circuit 1% increase -4.0% -4.0% Notes: Based on figures on effects estimated by simulation for Shinkansen vehicles with regenerating brake, 515 km from Tokyo to Osaka (WCHSR, 2008) 1 Elasticity is defined as the level of influence an energy efficiency measure has on total energy consumption; for example, if for a certain train the elasticity with regard to reducing train mass is 0.17, reducing the train mass by 10% will reduce overall energy consumption by 0.1 x 0.17 = 1.7%. 8

17 Table 2.4: Type of measure Techical Operational Summary of measures to reduce energy consumption from trains Measure Mass reduction Aerodynamics and friction Reducing traction system losses Regenerative braking Improved space utilisation Improved comfort function efficiency Increase load factor Efficient driving strategies Typical effect on energy consumption See elasticities in Table 2.2; WCHSR (2008) report a 1 ton/car decrease in weight on Shinkansen reduces energy consumption/co 2 emissions by 1% (Table 2.3). See elasticities in Table 2.2; WCHSR (2008) report a 10% reduction in air drag on Shinkansen reduces energy consumption/co 2 emissions by 6% (Table 2.3). See elasticities in Table 2.2; 1% reduction in energy use of a traction component reduces overall energy use by 1%, more if regenerative braking is employed as efficiency of both traction and regenerative braking systems are improved. Kemp (2009) has estimated 5-7% energy savings on intercity services; UIC EVENT (2003) implies trains that employ regenerative braking use 8-9% less energy than trains that do not. TGV duplex achieves almost 30% reduction in energy per seat-km over single-storey TGV. Reducing passenger climate control energy consumption by 10% would reduce overall train energy use by around 1% 2. UIC EVENT (2003) states increasing the load factor has the biggest potential of any measure to reduce energy on a passenger-km basis. RSSB (2007a) estimate a potential for up to 7.5% of overall traction energy use. Typical Elasticity N/A N/A N/A Applicability for HSR vs CR Broadly similar effects to both types of train; slightly more benefit to services with more frequent stops. More significant at higher speeds as proportion of energy demand due to aerodynamic drag is greater. The potential for reducing energy consumption is the same for both train types. A prerequesite on any modern electric train. More benefit to services with more frequent stops. Equally applicable to both types of train; some strategies (double-deck, wide body) incompatible with UK infrastructure. Trains that travel more km per day will have proportionally lower comfort function energy demand per seat-km. Equally applicable to both types of train; high-speed trains typically have higher load factors than intercity services. Equally applicable to both types of train. Not an issue for consideration in this study. Notes: (a) Typical elasticities assume trains are fitted with regenerative braking systems. Estimates are derived from UIC EVENT (2003) Mass reduction All of the rolling stock manufacturers interviewed cited mass reduction as the most significant measure to reduce energy consumption of future models. Reducing train mass will reduce train energy use in several ways. Primarily it reduces the energy needed to overcome inertial and grade resistance; though theoretically recoverable by regenerative braking, inefficiencies in the traction system mean that in reality only a proportion can be returned to the catenery in this way. The total regenerative braking cycle, where energy is drawn from the catenary, put into train motion through the motors and then converted back through the inverse drive train, has a typical maximum efficiency of (0.85 x 0.85 = 0.72) (UIC EVENT 2003, Kemp 2009). In some cases (and more likely for heavier trains or trains travelling at higher speed) the braking force needed is greater than that available using regenerative 2 Calculation based on UIC EVENT 2003 figures 9

18 braking, meaning additional dissipative braking is used, further reducing the cycle efficiency. Reducing the train mass reduces the use of the comparitively inefficient regenerative braking cycle. Additionally, mass reduction will reduce frictional running resistance. Mass reduction is typically achieved through reducing the weight of specific components (e.g. carbodies, bodies, bogies etc.) or through a system-based approach to lightweighting (e.g. the articulated train design favoured by Alstom, which reduced the number of bogies by around 20% by placing them between cars). Mass reduction will benefit services with less homogenous velocity profiles (more accellerating and decelerating) most (i.e. those that accelerate and decelerate more often). Figure 2.5: Typical breakdown of components in electric multiple unit trains by weight 15% 21% Carbodies Powered bogies, motors and drives 17% Trailer bogies Propulsion equipment 10% 15% 22% Interior Miscellaneous (heating, batteries etc) Sources: Based on information from UIC EVENT (2003) Aerodynamics and friction As previously mentioned, at speeds above 200km/h aerodynamic drag dominates resistance to train motion. Figure 2.6 shows a breakdown of a train s drag by component; it shows that for a long train (as high-speed and intercity train sets typically are), surface friction and drag around the bogies dominate aerodynamic drag. The main strategies to reduce drag are streamlining the nose and tail profile of the train, reducing flow separation around the bogies, pantograph and train body by streamlining, and reducing the skin friction on the train roof and sides. More effort has gone into reducing the drag of high-speed trains as at higher speeds aerodynamic drag is more significant, but the same principles apply to conventional trains. Interviewees suggested that improvements to medium and high speed train aerodynamics are incremental and that developments in the next years are unlikely to radically alter the contribution of drag to energy demand, particularly in the UK where regulation prevents some radical aerodynamic train shapes (Hitachi 2009, Kemp 2009). Figure 2.6: Typical breakdown of components contribution to drag in electric trains 27.0% 7.5% 4.0% 8.0% 3.5% 4.5% 45.5% Front Tail Bogies and wheels Pantographs Ventilation etc Underfloor equipment Surface friction on side and roof Sources: Based on information from UIC EVENT (2003) 10

19 Reducing traction system losses New model specifications from the major rolling stock manufacturers report improved efficiency in the traction system, both by improvements in the major components (for example permanent magnet motors, medium frequency transformers) and improvements in the energy management control software for the system as a whole. The fundamental technologies are the same for both high-speed and conventional rail rolling stock and consequently forecast percentage energy savings are also similar Reducing energy consumption for comfort functions The principal component of comfort function energy use is air heating and cooling (UIC EVENT 2003). Energy demand in air temperature control can be reduced either by reducing heat transmission through improved coach insulation, or reducing fresh air intake through CO 2 monitoring (fresh air intake dependant on number of passengers rather than number of seats). In addition, energy can be supplied from waste heat rejected from traction equipment (particularly in electric multiple units, EMUs) if the requirement is for heat. It is thought that there is significant scope for energy savings in this area (Kemp, 2009), but there is no anticipated difference in reduction of comfort function energy use between high-speed and conventional trains Energy consumption of current and future rolling stock In making comparisons between conventional and high-speed rail the previous sections have discussed the theoretical background to energy consumption and the potential impacts of different energy saving measures that might be applied. However, it is important not only to factor in these considerations, but also the more practical market limitations on what new train types will actually be available to be put into service at the 2025 timeframe. Compared to the road transport sector, the rail industry is relatively small and trains have much longer service lives. As such, there are relatively few train manufacturing companies and train model platforms available. Also as a result of this there are relatively much longer development cycles for new platforms and much lower frequencies of platform replacement. This makes it easier to foresee with greater certainty the likely characteristics and performance of different types of electric trains in the timeframe we are interested in. The train manufacturers consulted as part of this work have confirmed that the conventional and high-speed rail platforms they are currently marketing will essentially be the ones that would be supplied for the 2025 timeframe. Although it is likely there will be some smaller incremental improvements in the efficiency of the currently available platforms, major improvements are unlikely. The following Table 2.5 provides a summary of the characteristics of different conventional and highspeed rail rolling stock, based on information from ATOC (2009) and DfT (2009a). The data on energy consumption presented in this table and in Figure 2.7 are approximate figures based on a combination of in-service measurements and modelled data. In real applications the actual achieved energy consumption will vary significantly depending on the particular characteristics of a given service. Factors that can significantly affect the actual performance will include elements such as: Service distance and number of intermediate stops; Line gradients; Service speeds; Variations in service speed along the route (e.g. due to major curves, junctions, etc.), It can be seen from the table and figure that similar levels of improvements (15-20% reduction in kwh/seat-km) have been achieved for conventional and high-speed rail rolling stock between the 1990 timeframe and the most recent models (excluding the Japanese Shinkansen). In addition, in Figure 2.8 shows a much less pronounced increase in energy consumption than has previously been suggested. For the purposes of comparisons in this study we have taken the proposed Hitachi Super Express (HSE) for the UK Intercity Express Programme (IEP) and Alstom AGV as representative of the likely performance of rolling stock in the 2025 timeframe for conventional and high-speed rail respectively. In this case, the relative increase in the energy consumption per seat-km of the AGV and the HSE compared to equivalent current designs is around 18%, which is also consistent with the trend line in Figure

20 The AGV is a train prototype rolling stock design from Alstom intended as the successor to France s current TGV high-speed trains, with a commercial service speed up to 360 km/h (220 mph). The AGV will have distributed traction with motors under the floors of the passenger carriages, instead of the current TGV configuration with separate power cars at either end of the train. This arrangement is used on many regular-speed multiple-unit trains and also high-speed trains such as the Siemens Velaro and Japan's Shinkansen trains (Wikipedia, 2009) built by Hitachi. Not having separate, dedicated power cars creates additional space that enables the AGV to provide higher seating density compared to current models. This design feature is also employed in the Hitachi Super Express (HSE) trains. Alstom offer the AGV in configurations from seven to fourteen carriages, with a total of seats (depending on internal layout and number of carriages). The AGV weighs less than its rivals which reduces its power consumption, and it consumes significantly less energy than previous TGV designs. Other design elements implemented to reduce the energy consumption of the AGV include articulation and permanent magnet motors. Both of these elements contributed to a reduction in the number of bogies, leading to further weight and aerodynamic benefits. It can be seen from Table 2.5 that both the HSE and the AGV have similar seating capacities at similar train lengths. However, the AGV has shorter vehicles and therefore a larger number in each train unit for a similar capacity. Table 2.5: Train Characteristics of current and future rolling stock used for conventional and high-speed rail Class 91 IC225 Conventional Rail Class 390 Pendolino Hitachi Super Express Class 373 Eurostar TGV Reseau High Speed Rail AVE TGV S103 Duplex Velaro Shinkan -sen 700 Series Alstom AGV Year Future Future Max Speed, km/h Service Speed,km/h * Seating Capacity Length (m) Vehicles per unit Tare mass (tonnes) Mass per vehicle (tonnes) Mass per train metre (tonnes) Mass per seat (tonnes) Energy consumption * (kwh/seat-km) Sources: Figures for the Class 91 IC225 and Hitachi Super Express were supplied by DfT (2009a) based on public information on the IEP. All other figures are based on figures from ATOC (2009), produced for Greengauge 21. Notes: * The energy consumption figures are based on the service speed. Here the service speed represents the typical maximum speed of the train in service, usually dictated by the limits of the line infrastructure. 12