December 09, 2013

Repower or Replace: The route to cleaner diesel

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Unife's CleanER-D research initiative says there will be significant benefits from accelerating the uptake of diesel engines compliant with European Stage IIIA and IIIB emissions standards. Kevin Smith examines the project, its findings and recommendations.

JANUARY 1 2012 was a watershed moment for diesel-powered rail transport in Europe. Just three years after EU Stage IIIA emissions standards for diesel engines came into force, EU Stage IIIB emissions standards were adopted for all diesel locomotives in the 560kW category.

These new regulations followed identical requirements for vehicles with a 130-560kW rating, which were adopted in January 2011, and restricted permitted Nitric Oxide (NOx) particle emissions by 40% to 3.4g/kWh and Particulate Matter (PM) emissions by 88% to 0.02g/kWh from the previous standards.

Operators, manufacturers and infrastructure managers were aware of the change as early as 2004 when the European Commission (EC) amended the Non-Road Mobile Machinery Directive (NRMM) to include railway engines for the first time. Since then several engines have been developed to meet the new regulations. But with such a step change from one standard to another taking place in such a short period of time, cross-industry support was required to develop a strategy for effective integration into vehicles and to build in-service experience.

Step forward the CleanER-D research initiative. With a budget of e11.6m, including a e7.8m grant from the EC, the project was founded to develop, improve and integrate emissions reduction technologies for diesel locomotives to meet these standards. Led by the European Railway Industry Association (Unife), and supported by 24 industry and academic partners, CleanER-D commenced in 2009 and concluded last month following the presentation of a range of findings and recommendations to the EC, railway manufacturers, operators and infrastructure managers during a final conference in Brussels.

cleanerRailway transport accounts for less than 2.5% of NOx and 4.5% of PM emissions from transport. Indeed, NOx and PM emissions from railway vehicles fell by 35% between 1990 and 2008. This was achieved through the introduction of cleaner engine technologies, the reduction in size of diesel locomotive fleets from 16,700 in 2003 to 13,300 in 2010 with around 75% in active service (although dmu numbers have actually increased from 6900 in 2003 to 7100 in 2010), increasing network electrification, lower mileage of vehicles with older engines, and more efficient operations.

However, diesel traction still accounts for 20% of European rail traffic, and remains the primary source of traction on mainlines in Britain, Ireland, the Baltic States and Greece. The European railway industry consequently supports the EU's directive to reduce emissions further and agreed to cut total NOx and PM exhaust emissions by 37% and 46% respectively by 2030 compared with base year 2008 and total CO2 emissions by 50% compared with 1990.

Ms Judit Sándor, Unife's senior project manager and CleanER-D project director, says that the CleanER-D project is supporting the sector to achieve these goals. She says CleanER-D's research has led to projections that around 30% of locomotives and 41% of dmus will adopt Stage IIIA and Stage IIIB engines by 2020, and that NOx will fall by a further 35% and PM by 45% between 2008 and 2020, as diesel locomotive numbers fall to 9100, while the dmu fleet again increases to 11,100.

Subprojects

The initiative considered the socio-economic benefit of the transition to Stage IIIB, as well as providing a working framework for a successful transition by carrying out two demonstration subprojects to retrofit Stage IIIB engines into existing vehicles: a heavy-haul subproject (SP3) and a lightweight subproject (SP4).

Two methods of lowering exhaust emissions were identified initially for the projects. While all engines use a diesel particulate filter (DPF), some reduce NOx emissions inside the engine through Exhaust Gas Recirculation (EGR), and others use Selective Catalytic Reduction (SCR) exhaust after-treatment.

SCR requires the use of an additional consumable fluid (aqueous urea solution) and is the option preferred for dmu engines, which have to comply with a 2.0g/kWh NOx limit due to its larger NOx reduction capability. EGR is preferred for larger locomotive engines, which although not providing much scope for further emissions reductions, avoids the need for the use of a second consumable fluid and related investments in infrastructure to distribute and supply the fluid, enhancing operational flexibility. Following the cancellation of a dmu subproject involving Czech Railways (CD) and Tedom in 2012, which retrofitted 20-year-old dmus with an SCR, results were obtained only for the EGR system.

SP3 encompassed integrating a 16-cylinder 2.8MW Caterpillar C-175 engine, which meets Stage IIIB standards, into a four-axle diesel-electric Vossloh Eurolight locomotive, which was designed to use a Stage IIIA engine. The purpose of the trial was to assess the cost-effectiveness of a Stage IIIB implementation on mainline locomotives in terms of its impact on vehicle design and operations and maintenance.

Following installation of the engine which used EGR, DPF and Diesel Oxidation Catalyst (DOC) systems, initial trials were conducted at Vossloh Rail Vehicles' plant in Valencia in the first half of 2012 with the assistance of teams from the CMT Motores Térmicos department of the Polytechnic University of Valencia. These tests ensured the correct engine package was installed and performance met the desired specifications before field trials commenced in Italy in cooperation with Trenitalia Cargo. The locomotive began operations in October 2013 and remained in service up to the end of the project.

SP4 also involved a similar retrofitting programme. This time a German Rail (DB) class 225 locomotive dating from 1971 was fitted with a prototype 12V4000 engine developed by MTU, which has a 1.8MW output at 1800 rpm. The engine also utilises a cooled EGR, two-stage turbocharging with intercoolers, an enhanced low-emission combustion system, and an exhaust after-treatment system. It was tested for 14 months in the field by DB Schenker, clocking up 700 hours of service.

In addition to the class 225 tests, SP4 trialled a commercially-available DPF system on a French National Railways (SNCF) BB 69400 shunting locomotive in regular service in France. Temperature and pressure sensors onboard the shunter indicated how DPF performed in regular service and was optimised during operations for improved performance.

Modifications to existing components and systems on the locomotives were carried out during the installation phase of each subproject. In particular the Eurolight locomotive required a 20% larger cooling plant and a new roof hatch, while the DPF replaced the unit's existing silencer. The amendments added 1.5 tonnes to the vehicle's weight so modifications had to be made in other areas in order to maintain the same power output and axleload.

It was a similar story on the class 225. Here a more efficient cooling system and a modified gearbox were installed. The unit's silencer was substituted for a DPF, and a switchboard added to the 12V4000 engine which replaced the locomotive's original MTU 12V956TB10 engine.

Both trials showed that it is feasible to retrofit existing units with configured Stage IIIB-compliant engines. CleanER-D reports that the field trials were a success, with both propulsion systems for Stage IIIB locomotives successfully proven. However, the additional weight added to the Eurolight locomotive during the retrofit in particular was a concern during development.

"When considering whether to refurbish locomotives, the technological and economic feasibility of carrying out this work has to be carefully evaluated," Sándor says. "The economic viability of the project given current constraints on budgets as well as the technical development required and their impact on a vehicle's space and weight has to be considered."

She says that CleanER-D estimates that if operators and infrastructure managers carried out a fleet-wide retrofit of Stage IIIA and Stage IIIB compliant engines, society could benefit from around e1.4bn in savings of accumulated external costs by 2020. On the other hand, it is estimated that the railway sector will have to spend e786m on additional life-cycle costs caused by the new equipment and this figure also does not take into account the cost and time to manufacturers of developing this technology.

"The process of introducing new technology into the market is a long and complex one that is not only constrained by the speed of progress in technology, but also constrained by legal frameworks, demand from operators and strategic decisions made years before the emergence of new technology," Sándor says.

"There is also a pre-tender period where OEMs invest capital and time to research and development of components for engine development as well as system integration and platform development. Against this backdrop there is about 10 years between when new legislation is introduced and when satisfactory engine and integration developments are achieved."

Recommendations

As a result of these findings, CleanER-D has issued a series of recommendations to the EC, equipment manufacturers, operators and infrastructure managers to ease the transition to Stage IIIB. At the centre of this is the understanding that renewal of the fleet is the most feasible and economic way of achieving the EU's goal of reducing emissions by 2030.

Sándor says there should be incentives for operators to renew their fleets. However, she warns that this should not handicap the rail industry.

"If it is not economic for operators to buy new freight locomotives it could result in a decline in their use and modal shift from rail to road which would have a larger environmental impact," Sándor says.

As a result CleanER-D recommends that framework conditions are created to support an increase in fleet renewal rates. It says that any future emissions reduction legislation should provide manufacturers and OEMs with sufficient time to develop viable solutions which will provide market stability. It also calls for investment in research and development projects that promote low life-cycle costs of propulsion systems and demonstration projects with energy storage systems for dmus and shunting locomotives.

Governments and public procurement authorities are similarly encouraged to require adopting Stage IIIB in any new procurement and provide incentives for introducing emissions-reducing technologies. This could include "scrappage" schemes for older, more polluting locomotives, which have proved successful in the automobile industry, and incentives to undertake repowering projects that will make them more economically viable.

Operators are similarly encouraged to identify instances during the life of a vehicle when it is possible to introduce energy efficient and emissions reducing equipment. This could be through increasing the load factor of vehicles and focusing on the life-cycle cost of emissions during any procurement process. Infrastructure managers are recommended to support efficient operation by utilising intelligent traffic management solutions on their networks.

Of course to achieve these goals the technology has to be ready as well as economically viable for rolling stock owners to buy. CleanER-D recommends that manufacturers prioritise development of solutions which can reduce emissions, fuel consumption and life-cycle costs. However, Sándor stressed that any new legislation coming into force must take the market situation into consideration. "Solutions must be affordable," she says.

Hybrid solutions are a technological advancement identified by CleanER-D as having the potential to reduce emissions and fuel consumption, particularly on regional and suburban routes operated by dmus, and shunting operations which involve regular starting and stopping.

CleaneER-D found that CO2 emissions and fuel consumption could be cut by around 20% compared with eco-driving for dmus, and as Sándor states, the benefit of using these technologies is their ability to reuse braking energy and to provide more flexibility in the overall design of the network's traction system.

However, operations and field experiences of hybrid technologies remain at an early stage with CleanER-D the first European-funded project to analyse their impact in detail. Sándor says further tests of hybrid energy management strategies in revenue service are required to gain more reliable data and experience.

Existing low-emissions technologies also have the potential to further reduce emissions. But as the subprojects demonstrated, cutting emissions levels with current technology tends to lead to heavier and bigger propulsion units which increases the weight of vehicles and potentially increases fuel consumption.

Sándor reiterates that emerging technologies could solve these issues and must be given time to evolve before they can be considered for commercial application.

In the meantime, CleanER-D has developed a life-cycle analysis tool which operators and rolling stock owners can use to evaluate the economic feasibility of the new solutions compared with their existing diesel assets. The tool is now available for operators to access through the CleanER-D website.

As for the future of CleanER-D, Sándor says there is certainly scope for further research and analysis of various emissions reductions technologies through a cross-industry initiative, which will further aid the adoption of Stage IIIB compliant engines.

"It was important to involve companies, railways and organisations across the European railway industry in a common project," Sándor says. "This joint cooperation helped to improve understanding as well as provide solutions to the technical challenges identified at the start of the project. The CleanER-D recommendations are also published at a time when they can contribute to the EC's work to revise the NRMM directive."

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