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Fuel CelL HYdrogen System for AircraFt Emergency operation

Periodic Reporting for period 2 - FLHYSAFE (Fuel CelL HYdrogen System for AircraFt Emergency operation)

Reporting period: 2019-07-01 to 2020-12-31

Today, all aircraft and equipment manufacturers are embarked in the current trend towards “More Electric Aircraft” (MEA), in which the traditional hydraulic and pneumatic systems are replaced by electrically driven systems offering higher performance and reliability, combined with lower operating costs and also allowing to meet the increasing demand to reduce fuel consumption and Green House Gas emissions while optimising aircraft performances. To this regard, fuel cell systems are considered as one of the best options for efficient power generation systems.
The main objective of FLHYSAFE is thus to demonstrate that a cost-efficient modular fuel cell system can replace the most critical safety systems and be used as an Emergency Power Unit aboard a commercial airplane providing enhanced safety functionalities. Also, the project has the ambition to virtually demonstrate that the system is able to be integrated, respecting both installation volumes and maintenance constraints, by using current aircraft designs.
In order to shift from demonstrator levels (achieved in other projects), to the ready-to-certify product level, it is necessary to optimise the different components of the fuel cell system to reduce its weight, increase its lifetime, ensure its reliability, certify its safety and make its costs compatible with market requirements.
FLHYSAFE proposes fuel cell technologies using Proton Exchange Membrane fuel cell stacks, more integrated power converters and use of next generation aircrafts opportunities.
FLHYSAFE has three specific objectives:
1.Design a modular Fuel Cell based Emergency Power Unit with a power range from 15kw to 60kw;
2.Develop and validate the FC system based EPU at TRL5-6;
3.Prepare the roadmap for exploitation.
First, a substantial work was performed at the system level to obtain a mature and realistic EPU architecture. This work, based on several working documents – such as e.g. the usual Ram-Air Turbine technical specification, the project Environmental Test plan, the safety analysis –, allowed the consortium to choose between two high level architectures: an initially planned H2/air architecture linked to previous Fuel Cell projects or the finally chosen innovative H2/O2 architecture taking profit of next generations aircrafts like Airbus ZEROe program, which encourages fuel cell engineers to use new aircraft interfaces for cooling and fuel supply. It makes commercial fuel cell systems much simpler that positively impacts their reliability and hence makes the technology more attractive for the market.
Then, at subsystem level, progress were made in designing and developing a fuel cell sub-system adapted to airborne applications. The low temperature proton exchange membrane (LTPEM) fuel cell stack technology previously developed by Zodiac and CEA was transferred to Safran. Assembly tooling adapted to Fuel Cell stacks (short-stack and stack alpha) were designed and manufactured. Tests on short-stack fed with O2 instead of Air were performed to mitigate risks associated to oxydant choice and to optimize stack sizing.
INTA conducted a start/stop study by applying HYCARUS start-up and shutdown protocol for 466 cycles, allowing to conduct a mathematical analysis of the stack degradation (stack power evolution as a function of the number of start and stop cycles).
CEA developed a 0D FC model, which will be implemented to simulate the EPU system activity. This model translates stack behaviour under various operating conditions. A good fitting with experimental results was achieved.
The architecture of the electrical and power management subsystem has been also been finalised.
CEA designed the integrated converter and its different parts (electronics, mechanics and thermics). The electronic boards, inductors and mechanical parts were manufactured and received. The four electronic boards were tested individually. They are tested together on a prototype version (air cooling) to easily adjust the hardware and the software. Finally, the assembly of the integrated version (liquid cooling) was successfully tested.
Transverse activities have also been carried out: a virtual reality tool allowing to design and optimise maintenance instructions has been developed (it is now awaiting the EPU CAD model to get to next steps). Furthermore, dissemination activities have been reinforced, notably on social media platforms: Twitter ( and LinkedIn ( accounts were set up and are regularly fed.
Thanks to the hybridisation of the fuel cell stack with a secondary power source, a battery or a supercapacitor, the system will be able to start-up within 8 seconds as required for an EPU. Furthermore, the FC-based EPU will offer an operating time of more than 3 hours with full power availability all along, independently from the aircraft speed, and until it is stopped and safe on the ground. This functionality will be an important breakthrough and will increase safety during the most critical phase of an emergency landing. A FC-based EPU, contrary to a RAT, can be located in many different locations of the aircraft as it does not require to unfold or to directly interact with the exterior environment. Thus, the developed system will be generic and possible to integrate into different zones of next generation aircrafts. This modularity will allow to address various power demands according to the different single aisle aircraft needs with a common system architecture and common equipment sizing and development.
FLHYSAFE expects to strongly contribute to this market objective. For the adoption of the technology, if FCH technologies fly with measurable results in terms of emission reductions, noise reduction, safety, efficiency and cost, with significant applications such as an EPU, the demonstration will also be crucial to convince adoption in less demanding sectors.
Furthermore, fuel cells are also a promising solution for generating electrical power on aircraft, providing solution to minimise the environmental impact and ways of producing decentralised energy. FLHYSAFE has fixed its environmental impact objectives according to the use of a life-cycle assessment methodology to assess potential environmental impacts associated with all the stages of the FC system life cycle. A general analysis will be refined in the project and evaluated according to measures obtained when performing tests. If the first application (EPU) has limited saving possibilities when replacing the RAT, the other applications targeted by the FLHYSAFE partners – cabin/hotel loads and APU – have much important capabilities.
Finally, one of the most key objectives of the development roadmap of the aeronautic industry for 2020 to 2050 is the reduction of emissions with a focus on electrical power supply obtained from renewable energies. FC are outlined as one of the technologies to deliver on-board electrical energy and in particular an e-APU independent of the aircraft engines. In particular, FLHYSAFE will be a major contributor to the topic Sustainable energy regarding Fully on-board electrical energy by 2035 as part of the ACARE SRIA Challenge 3 – Protecting the environment and the energy supply according to the following development path.
FC © Safran Power Units – Remi Deligeon
Start/stop test on short stack at INTA test bench
Fuel Cell
Integrated converter