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What are alternative propulsion technologies?
Alternative propulsion technologies are technologies used in rail systems that power trains without fossil fuels. In the railway sector, these include electric batteries and hydrogen-based propulsion systems such as fuel cells and hydrogen internal combustion engines.
Such technologies are increasingly essential as businesses and consumers look for less polluting and more eco-friendly modes of transport. Countries are actively reducing their carbon emissions by adopting these systems. The shift towards hydrogen as a clean energy source is particularly noteworthy due to its potential for significant decarbonisation.
To make the most of these alternative railway traction technologies, every stakeholder from businesses to governments to the public must have confidence in their safety, reliability and efficiency. Assessment and training services from TÜV SÜD can facilitate trust in these innovations.
Why do alternative propulsion technologies require testing, inspection and certification?
New technologies need to be integrated correctly in existing rail networks and systems to ensure safety and functionality. This can be a challenge because of the complexity of hydrogen powered trains and traction battery systems.
Furthermore, businesses in this sector need to balance the cost of new technology implementation with long-term sustainability goals. They also have to adapt to evolving legal and normative requirements and achieve regulatory compliance to enjoy global market access.
TÜV SÜD offers a comprehensive suite for the testing, inspection and certification of alternative railway traction technology services that will guide you on all of the above.
How TÜV SÜD can support you with alternative propulsion technologies?
TÜV SÜD’s global expertise and extensive experience in railway systems and alternative energy technologies deliver integrated solutions. Our holistic approach to safety assessment includes everything from early design to final implementation.
We leverage our advanced testing facilities to provide these services. Our state-of-the-art labs perform rigorous testing of high-pressure components and environmental suitability.
With our up-to-date knowledge of international standards and regulations, we can guide you on compliance with the latest requirements affecting railway traction systems.
What do our alternative propulsion technologies services include?
We provide a wide range of services to increase the safety, reliability and credibility of alternative railway traction systems.
Assessment services
- We assess, test and certify complete system concepts, designs and implementations during their development.
- We check the safety-related design concepts as well as hazard and risk analyses (e.g. FMEA, FTA, HAZOP, RAMS) to identify gaps and potentials for improvement.
- We assess the suitability of defined design measures, applied codes of practice, and verification and validation tests.
- We inspect and certify pressure gas components, tank systems, and vehicles according to international standards (high-pressure storage, liquid tanks, fuel cells etc.).
- We perform various tests in our accredited laboratories. These include:
- Material compatibility examinations (metallic and non-metallic materials)
- Pressure, leakage, and permeation testing
- Service life testing and durability examinations
- Hydraulic and pneumatic cycle testing
- Overpressure & burst testing
- Gas flow testing
- Railway suitability and environmental testing
- Refuelling Tests and Validation of Filling Protocols
- We inspect and assess railway suitability according to European and international standards for all components of innovative railway traction systems.
- We assess safety functions (sensor – logic – actuator) against performance levels (PL) or safety integrity levels (SIL) determined during risk assessments.
- We review test specifications and witness type tests, such as hydrogen tightness and hydrogen filling.
- We examine technical documentation (e.g., maintenance and servicing plans, operating manuals) and approval-relevant documentation (e.g., hazard analysis, explosion protection documents, and CE declarations of conformity).
- We assess safety management throughout the development process.
- We provide expert opinions on application of non-railway standards, derogations, and evidence of equal safety.
- We issue a declaration of no objection before commissioning, H2-filling, and / or testing.
- We provide first-hand information of new and revised standards and regulations for the duration of the project.
- We assess interfaces between vehicle, plant and railways infrastructure and hydrogen filling stations with regard to the completeness of identified hazards, suitability of defined mitigations, and safety-related application conditions.
- We assess safety-related application conditions between vehicle and component manufacturers, vehicle operators, and infrastructure managers to ensure safe product implementation and operation.
- Safe handling of hydrogen
- Materials and hydrogen
- Hydrogen related to gas supply companies
- Customer specific trainings
- Hydrogen Propulsion Systems Training Courses for Rail Vehicles
Development-accompanying and independent safety assessment according to EN 50126
Training courses designed for your needs
Frequently asked questions (FAQs)
How do hydrogen powered trains work?
Hydrogen powered trains use a hybrid configuration of hydrogen fuel cells or combustion engines, high voltage batteries, and electric traction motors.
Fuel cells convert hydrogen into electricity without combustion. In the process, hydrogen ions migrate from the anode through an electrolyte membrane to the cathode, where they react with atmospheric oxygen.
This powers batteries to provide a stable power source for propulsion and the operation of auxiliaries. This includes equipment such as pressure vessels, fuel cells, and lithium-ion batteries for buffering any electrical energy generated.
The train's braking process is used for brake energy recovery (recuperation) by converting kinetic energy into electricity, which is temporarily stored in batteries and contributes to fuel efficiency.
An alternative to hydrogen fuel cells is a hydrogen combustion engine. These produce mechanical energy used for traction, or to generate electrical energy similar to that produced by conventional diesel power packs. While fuel cells used on hybrid trains require highly purified hydrogen to ensure a long operating lifetime, hydrogen combustion engines can utilise a larger range of hydrogen purities.
What are the advantages of hydrogen over an electric or diesel train?
Hydrogen fuel cells produce power with no emissions of carbon-dioxide, with water vapour the only emitted substance. Provided that the hydrogen was produced in a climate-neutral way, this results in a zero emission, zero-carbon fuel. Also, the hydrogen used to power the fuel cells is stored in pressurised tanks which offers a high specific energy density relative to the total mass than those of lithium-ion batteries used in electric hybrid trains, thereby making hydrogen powered trains ideal for traveling long distances.
Hydrogen combustion engines are based on diesel engines that have been converted into hydrogen engines, thereby eliminating all emissions in accordance with EU standards.
Another potential advantage of hydrogen rail (hydrail) over conventional railway technology is that they make the installation of additional contact wires for the expansion of existing electrified railway networks almost unnecessary.
In addition, hydrogen can be produced and stored whenever there is a high load of renewable energy on the grid. Other than electric trains, which consume energy regardless of the grid load, the use of hydrogen leads to better carbon footprint in our current energy mix.
What safety issues are associated with hydrogen trains?
Safety has always been a critical concern in the design, development and operation of trains and train equipment. However, managing safety concerns with hydrogen powered trains is much more complex than traditional railway traction technologies.
Hydrogen in air forms a flammable gas mixture that can create an explosive atmosphere when released or handled incorrectly. Because of the high operating pressures required for hydrogen rail (hydrail), there is also a burst potential. Alongside this, lithium-ion traction battery systems also present fire, smoke and explosion risks if they are improperly handled or damaged.
Any systems that store or handle these alternative fuel sources must therefore be designed to address the specific risks associated with their use. For example, onboard storage systems must be capable of safely holding hydrogen gas under high pressure.
Unfortunately, industry standards are not keeping pace with technology developments as there are currently no European and international regulations that address the use of hydrogen systems in railway vehicles. Independent safety assessments with special competence in these technologies are therefore required to fill this gap.
Why is risk management so important?
An effective hazard identification and mitigation will help you to identify and control the potential hazards in the design, commissioning and operation of the innovative technology and efficiently achieve compliance with regulatory authorities’ requirements.
Independent safety assessment in a development accompanying approach can help manufacturers expedite the development process as any safety concerns can be resolved early on, thereby reducing the likelihood of last-minute design changes and minimising delays.
Manufacturers and developers must therefore adopt a robust risk management process that fully considers all risks associated with the use of alternative fuel sources. The ultimate goal should be to identify the technical risks and reduce the probability of occurrence to an acceptable level by definition of adequate mitigation measures and safety related application conditions.
What are the steps involved in TÜV SÜD's assessment process for evaluating alternative propulsion systems in rail systems?
At TÜV SÜD, our alternative propulsion assessment for rail systems is a comprehensive process designed to evaluate the safety and indirectly the feasibility, efficiency, and environmental impact of using non-traditional propulsion technologies. Our assessment process involves several key phases, ensuring that vehicle or subsystem manufacturer can make informed decisions, in accordance with the V-model of the system development life cycle acc. to EN 50126:
- Concept and design phase – Examines the system concept and evaluates the preliminary risk analysis and the high-level measures derived from it and the safety concept as a basis for examination.
- Design and realisation phase – Includes the development-accompanying assessment of the implementation of the derived requirements, detailing of the risk analysis (FMEDA, HAZOP, explosion protection analysis, etc.) and constructive implementation.
- Validation and approval phase – Includes final review of the final hazard log and safety case, verification of the implemented safety requirements, inspection of the test object and support with functional and leak tests, and the creation of the safety assessment report.
- Operation, maintenance and performance monitoring phase - Includes review of emergency plans specific for alternative propulsion systems, verification and testing of refuelling stations and protocols, review of the practicability, ergonomics, and safety of maintenance activities on alternative propulsion systems, and assessment of safety concepts of maintenance entities and implications on maintenance infrastructures.
