Reversible Fuel Cell Aircraft Propulsion for Onboard Hydrogen Refilling

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Solution Overview

Problem

Existing aircraft propulsion systems face challenges with high voltage electrical conductors generating heat, requiring large diameters or cooling, and the need for hydrogen refilling at airports due to limited availability.

Innovation Solution

A reversible fuel cell system with a nacelle, electric motor, and reversible pump allows hydrogen tank filling via electrolysis of water, using a supply line and temporary water tank, and includes a heat exchanger and thermally insulating layer to manage temperatures and reduce conductor needs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If high voltage electrical conductors are used to supply current from the generator to the motor, then the electrical power transmission is improved, but the temperature in the conductors increases requiring large diameter or cooling

Engineering Contradiction:

Improveelectrical power transmissionVSAvoidconductor temperature

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

The patent extracts the hydrogen storage function from the propulsion system by using external tanks, thereby reducing the thermal load and complexity within the nacelle. This allows for better thermal management of the high-voltage conductors by separating the heat-generating components.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent introduces liquid hydrogen as an intermediary energy carrier between the fuel cell and the motor. The liquid hydrogen is stored in external tanks and fed to the fuel cell, which generates electricity with lower voltage requirements, thereby reducing the thermal load on electrical conductors.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If hydrogen lines are installed to guide hydrogen to the fuel cell, then the fuel cell operation is improved, but the system complexity increases due to tank filling requirements

Engineering Contradiction:

Improvefuel cell operationVSAvoidhydrogen refilling system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-storing hydrogen in external tanks before operation. The hydrogen is liquefied and stored in insulated tanks, ready for immediate use by the fuel cell, eliminating the need for complex on-site refilling systems during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The propulsion system is designed to be self-sufficient with onboard hydrogen storage tanks that can supply the fuel cell for the entire flight duration. This self-service capability eliminates the need for external hydrogen refilling infrastructure at airports.

Inventive Principle:

Principle #25Self-service

3Reliability

If long electrical conductors are used between the generator and motor, then the electrical connection is improved, but the conductor diameter must be large or cooling must be added

Engineering Contradiction:

Improveelectrical connectionVSAvoidconductor size and cooling system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical electrical generation system with a chemical energy conversion system. The fuel cell converts chemical energy from hydrogen directly into electrical energy, eliminating the need for long electrical conductors and associated cooling systems between generator and motor.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enables efficient hydrogen tank refilling during stopovers and reduces electrical conductor requirements, improving system efficiency and safety by utilizing on-site water electrolysis and air circulation for cooling.

Implementation Method 1

allows the hydrogen tank to be filled from an electrolysis of water in the fuel cell

Methodology Applied

Scientific EffectElectrolysis: Electrolysis

Implementation Method 2

the propulsion system includes a heat exchanger arranged to ensure heat exchange between the electric motor and the hydrogen in the supply pipe

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Implementation Method 3

and includes a heat exchanger and thermally insulating layer to manage temperatures and reduce conductor needs

Methodology Applied

Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentEP4455015B1Propulsion system for an aircraft, said propulsion system comprising a reversible fuel cell

Publication Date: 2026.01.28 AIRBUS (SAS)

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AI summary

The invention relates to a propulsion system (150) comprising an electric motor (108) whose output drives a propeller (110), and a reversible fuel cell (250) having a cathode and an anode connected to the electric motor (108), a supply line (256) connecting the fuel cell to the hydrogen tank (254), a feed line (257) connecting the fuel cell to the temporary water tank (257a), and a pump (258) arranged on the supply line between the hydrogen tank and the fuel cell, and wherein the pump is reversible to alternately pump hydrogen from the hydrogen tank to the fuel cell or from the fuel cell to the hydrogen tank. Such a system allows, by means of the fuel cell, the hydrogen tank to be filled during port calls.