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Fuel cell power trains and clustering in heavy-duty transports

Final Report Summary - FELICITAS (Fuel cell power trains and clustering in heavy-duty transports)

The FELICITAS project was focused on developing Fuel Cell (FC) technologies capable of meeting the demands of Heavy-Duty Transport for road, rail and marine applications.

FELICITAS concentrated on two FC technologies most suitable for Heavy-Duty Transport applications: Polymer Electrolyte Fuel Cells (PEFC) and Solid Oxide Fuel Cells (SOFC).

The objective defined for FELICITAS was the development of fuel cell drive trains capable to meet the demands of heavy-duty transport for road, rail and marine applications. To achieve these objectives the following parameters were chosen:
- Powerful units of more than 200kW electrical output.
- High reliability and long system durability - >10 000 hours operation time.
- High system efficiency > 60%.
- Operating with different hydrocarbon fuels as well as hydrogen.

FELICITAS focused on:
- SOFC technology - given its comparative immaturity appraisal and feasibility of the technology rather than demonstration in real applications,
- Proton Exchange Membrane (PEM) technology - began demonstration on a larger scale to be feasible for powering passenger and heavy-duty vehicles such as inner city buses, but degradation mechanisms in operation and durable system technologies were required.

The FELICITAS project comprised four subprojects, each focusing on a main topic of fuel cell system and drive train development.

Subproject I (Application Requirements and System Design) was structured into two work packages:
WP1: Specification, defining of application requirements and standardisation.
WP2: System design and simulation.

Subproject II (Mobile Hybrid SOFC) was structured into four work packages:
- Development and marinization of a 250kW SOFC unit.
- Testing of marinised 60kW sub-system and stationary power 250kW generator module.
- Fuel processing.
- SOFC power management, controller design, and simulation.

Subproject III (PEFC-Cluster) was broken into three work packages.
WP III.1 included investigations and configuration activities for fuel cell clusters. This included both the fuel cell system itself and the auxiliaries, the connection to an electrical architecture as well as safety related considerations and finally the design of such a prototype system.
WP III.2 concentrated on the test activities including investigations and preparation of a close to reality drive cycle and load profile of an inner city transit bus as well as investigations and measures taken to improve operation conditions of the fuel cell systems in a hybrid environment.
WP III.3 included the integration of the Fuel Cell Cluster into a research vehicle of the Fraunhofer Institute and test operation to verify the function of the overall system.

Subproject IV (Power Management and Hybridisation) consisted of three work packages:
- Processing of thermal energy.
- Controller design for PEFC-Clusters.
- Components for SOFCPEFC coupling.

The project had been broken down into several phases.

In the initial phase of the project the partners worked on the theoretical aspects of using the selected fuel cell technologies in heavy-duty applications. This included the definition of application requirements for different transport modes, the principal layout and design for the fuel cell modules and power trains - including on board reforming and turbo machinery for the marine SOFC, as well as system simulations at various stages in such power trains.

In the development phase, these investigations were evaluated against the available technologies and the defined requirements. Technological assessment and developments were initiated for both SOFC and PEFC technology to cover these requirements.

Finally, on the PEM side the improved system technology was integrated into a research vehicle of the Fraunhofer Institute for evaluation and testing.

The FELICITAS Subproject II focused on the issues required for the marinisation of the Rolls-Royce Fuel Cell Systems Ltd (RRFCS) 1MW Pressurised SOFC design for a 250 kW APU. The approach to marinisation was to minimise design changes to system architecture and thus additional development and product cost for a marine version of the existing stationary power Rolls-Royce Fuel Cell Systems Ltd (RRFCS) SOFC design. Extensive design changes and additional equipment would adversely affect the commercial prospects of a marinised stationary fuel cell system.

Besides pure hydrogen, the use of different hydrocarbon based fuels was a main research topic of FELICITAS and a precondition for most heavy-duty applications.

For SOFC the intelligent reuse of thermal energy generated by electrochemical reactions was the main key to achieve high system efficiency. The thermal management of the SOFC covered all measures related to:
- Heat recuperation for preheating of inlet mass flow,
- Management of heat sinks like internal fuel processing and
- Using heat by-product by gas and in some cases steam turbines.

In particular, the introduction of gas turbines offered a remarkable increase of electrical efficiency but on the other hand required also a very careful system design and management.

Subproject III was assigned to investigate the usage of PEM Fuel Cell Systems for heavy duty transport applications. The aim was a market orientated approach by using fuel cell systems developed for the automotive industry to be adopted in operation strategies for hybrid configurations for heavy-duty applications.

A crucial point in the FELICITAS project was the utilisation of energy storage devices in the fuel cell drive train in order to obtain the degrees of freedom necessary to achieve the main objectives of the project.

Among the variety of proposed energy management strategies for hybrid fuel cell drives, optimal predictive control strategies were considered to be the most powerful ones. The main advantages were the capability of including information about the future traction power demand (which acts as a disturbance to the hybrid drive control system) into the calculation of the power flow within the drive system and the explicit consideration of the constraints inherent to the system, e.g. limited capacity of the storage unit and limited fuel cell power.

Merging the advantages of SOFC and PEFC technologies was the most visionary research within FELICITAS and was dealt with direct coupling of SOFC and PEFC systems. This approach could be described as a special reforming technology for PEFC stacks and was considered in Subproject IV.

The aim of work package IV.3 was the study of the serial coupling of a SOFC and a PEFC. The coupling could combine the advantages of each technology and lead to a better overall efficiency of the system compared to a single technology. The SOFC was used both as a generator of electricity and a contribution of the remaining carbon monoxide oxidation in the reformation of diesel. Five objectives had to be fulfilled:
- First, the development of an efficient Diesel reformer with a relevant method considering the heavy-duty transport application.
- Second, the development of a micro-reactor for the purification of the SOFC downstream to supply the PEFC. The CO content had to be as low as possible otherwise the performances of the PEFC decreased with time in a cumulative way. The CO had then to be removed from the electrode catalyst to recover the performances. The used technology was the impregnation of a large surface area on micro-structured metal plates for impregnation with catalytically active substances.
- Third, the development of component models with a macroscopic approach in order to be able to implement them in the simulation of the global system.
- Fourth, tests of the components in operating conditions as closed as possible from the ones in the system.
- Fifth, the simulation of the global system to quantify its performances.

Not all the objectives of FELICITAS were achieved due to technical complexity, an unforeseen incident as well as resource and timing issues.

The main objective defined for FELICITAS was the development of fuel cell drive trains capable of meeting the demands of heavy-duty transport for road, rail and marine applications.

In summary:
- The hybrid PEFC clusters were well suited to public transport applications such as buses, light rail or trams in city / town operations.
- The Rolls-Royce hybrid SOFC design would require substantive modification before it could be successfully used in a marine environment.
- Neither hybrid SOFC nor PEFC clusters technologies developed within FELICITAS met the requirements defined for FC systems in heavy rail or tram applications.
- Neither hybrid SOFC nor PEFC clusters technologies developed within FELICITAS met the requirements defined for a FC based main propulsion of heavy-duty trucks.
- Low power SOFC technology in combination with new reformer techniques developed in FELICITAS was well placed for highly efficient APUs in heavy trucks.

The FELICITAS Project achieved the following outcomes:
- A much improved and detailed understanding of the impact of the marine environment, operation and application on a Rolls-Royce SOFC technology, notably a yacht, was achieved.
- Testing of Rolls-Royce SOFC materials and components in marine relevant conditions was successfully undertaken, and the results have substantially increased the appreciation of the marinization challenges for fuel cells.
- Testing of cathode materials and other materials was achieved and results fed back into the knowledge base.
- The Rolls-Royce stack concept and system showed a high mechanical integrity in marine motion conditions.
- A high system efficiency (> 60 %) of hybrid SOFC configurations were verified by detailed simulations and partly by experiments.
- High advanced reformer technologies especially for Diesel and Liquefied Petroleum Gas (LPG) were developed and tested.
- By means of the hybrid PEFC cluster concepts developed in FELICITAS, powerful units of more than 200 kW electrical output are feasible.
- The functionality and the advantages of hybrid PEFC clusters were demonstrated in first test runs of the Fraunhofer AutoTram test vehicle.
- A remarkable increase (doubling) of lifetime could be reached for single PEFC systems in hybrid configurations.
- By means of partial redundant PEFC cluster configurations a system durability of more than 10 000 hours operation time seems to be feasible.
- Degradation processes which influence the durability of PEFC systems can be observed in operation using the in-situ diagnostic modules developed in FELICITAS.
- An improved reliability of PEFC systems was also achieved by means of a high advanced predictive energy management system which avoids operation modes with increased degradation potential.
- To raise the reliability of hybrid SOFC systems a hybridisation concept using high power energy storages was developed.
- A high system efficiency (> 60%) can be reached for PEFC systems by means of kinetic energy recuperation only. This however, limits the Heavy-Duty applications on buses or trams in city/town operation.