Johannes Schirmer

Improving the environmental impact of civil aircraft by fuel cell technology: concepts and technological progress

Nowadays, new technologies and breakthroughs in the fields of energy efficiency, alternative fuels and added-value electronics are leading to improved, more environmentally sustainable and green thinking applications. Due to the forecasted rapid increase of volume of air traffic, future aircraft generations have to face enhanced requirements concerning productivity, environmental compatibility and higher operational availability, thus effecting technical, operational and economical aspects of in-flight and on-ground power generation systems, even if air transport is responsible for only about 2% of all anthropogenic CO2 emissions. The trend in new aircraft development is toward “more electric” architectures which is characterized by a higher proportion of electrical systems substituting hydraulically or pneumatically driven components, and, as a result, increasing the amount of electrical power. Fuel cell systems in this context represent a promising solution regarding the enhancement of the energy efficiency for both cruise and ground operations. For several years the Institute of Technical Thermodynamics of the German Aerospace Center (Deutsches Zentrum fur Luft- und Raumfahrt, DLR) in Stuttgart and Hamburg has developed fuel cell systems for aircraft applications. The activities of DLR focus on: identification of fuel cell applications in aircraft in which the properties of fuel cell systems, namely high electric efficiency, low emissions and silent operation, are capitalized for the aircraft application; design and modeling of possible and advantageous system designs; theoretical and experimental investigations regarding specific aircraft relevant operating conditions; qualification of airworthy fuel cell systems; set up and full scale testing of fuel cell systems for application in research aircraft. In cooperation with Airbus, several fuel cell applications within the aircraft for both ground and cruise operation have been identified. As a consequence, fuel cell systems capable of supporting or even replacing existing systems have been derived. In this context, the provision of inert gas for the jet fuel (kerosene) tank and electrical cabin power supply, including water regeneration, represent the most promising application fields. This paper will present the state of development and the evolution discussing the following points: modeling of different system architectures and evaluation of promising fuel cell systems; experimental evaluation of fuel cell systems under relevant conditions (low pressure, vibrations, reformate operation, etc.); fuel cell test in DLRs research aircraft ATRA (A320) including the test of an emergency system based on hydrogen and oxygen with 20 kW of electrical power. The fuel cell system was integrated into an A320 aircraft and tested up to a flight altitude of 25 000 feet under several acceleration and inclination conditions; fuel cell tests in Antares-H2—DLRs new flying test bed.

Fuel Cell Systems for Aircraft Application

Future aircraft generations have to face enhanced requirements concerning productivity, environmental compatibility and higher operational availability, thus effecting environmental, technical, operational, and economical aspects of in-flight and on-ground power generation systems. Today’s development in aircraft architecture undergoes a trend to a “more electric aircraft” which is characterised by a higher proportion of electrical systems substituting hydraulically or pneumatically driven components, and, thus, increasing the amount of electrical power. Fuel cell systems in this context represent a promising solution regarding the enhancement of the energy efficiency for both cruise and ground operations. The activities of DLR focus on identification of fuel cell applications in aircraft, design and modeling of possible system designs, experimental investigations regarding specific aircraft relevant operating conditions, qualification of airworthy fuel cell systems, and set up and full scale testing of fuel cell systems for applications in research aircrafts. In cooperation with Airbus several fuel cell applications within the aircraft for both ground and cruise operation have been identified. In consequence, fuel cell systems capable to support or even replace existing systems have been derived. In this context, the provision of inert gas for the jet fuel (kerosene) tank and electrical cabin power supply including water regeneration represent the most promising application fields.

Fuel Cells For Aircraft Applications

Although air transport is responsible for only about 2 % of all anthropogenic CO2 emissions, the rapidly increasing volume of air traffic leads to a general concern about the environmental impact of aircrafts. Future aircraft generations have to face enhanced requirements concerning productivity, environmental compatibility and higher operational availability, thus effecting technical, operational and economical aspects of in-flight and on-ground power generation systems. Today’s development in aircraft architecture undergoes a trend to a “more electric aircraft” which is characterised by a higher proportion of electrical systems substituting hydraulically or pneumatically driven components, and, thus, increasing the amount of electrical power. Fuel cell systems in this context represent a promising solution regarding the enhancement of the energy efficiency for both cruise and ground operations. For several years the Institute of Technical Thermodynamics of the German Aerospace Center (Deutsches Zentrum fur Luft- und Raumfahrt, DLR) in Stuttgart is engaged in the development of fuel cell systems for aircraft applications. In cooperation with Airbus several fuel cell applications within the aircraft for both ground and cruise operation were identified. In consequence fuel cell systems capable to support or even replace existing systems were derived. In this context, kerosene tank inertization and electrical cabin power supply including water regeneration represent the most promising application fields. The contribution will present the state of development discussing the following points: • Modeling of different system architectures and evaluation of promising fuel cell technologies (PEFC). • Experimental evaluation of fuel cell systems under relevant conditions (low-pressure, vibrations, reformate operation, etc.). • Fuel cell test in DLR`s research aircraft ATRA (A320) including the test of an emergency system based on hydrogen and oxygen with 20 Kilo Watts (kW) of electrical power and emission-free taxi ground operation with fuel cell system powering a nose wheel drive. DLR has developed the experimental motor glider Antares DLR H2 for testing of fuel cell technology under aviation conditions and for surveillance applications. The Antares DLR H2 is small, dismountable and has an experimental permit-to-fly. Thus both flight experiments and technical changes can be realized time- and cost-effectively. Equipped with fuel cell system, high power battery pack and all-electric drive train, the Antares DLR H2 is a flying test bench for fuel cells and fuel cell/battery hybrid systems. In September 2012 several long range flights have been successfully completed by this aircraft. In this context newly integrated low temperature fuel cell systems have been tested.

High Temperature Polymer Electrolyte Fuel Cell Systems for Aircraft Applications

HTPEFC as a power source for propulsion in aviation is demonstrated with the flying platform Antares DLR H2, showing a number of advantages. Methanol is selected as a hydrogen carrier and a compact modular system layout with methanol steam reforming units upstream of the liquid-cooled HT-PEFC has been established. With an appropriate dimensioning of the fuel cell system, the flight endurance is expected to be between 25 and 50 h. Power peaks during takeoff, ground operation, or critical flight situations are planned to be optionally addressed by engaging a direct fuel cell battery hybrid. Challenges and further development are discussed.

Fuel Cell Systems for Aircraft Application & Antares DLR-H2 All-Electric Flying Testbed

The Institute of Technical Thermodynamics of the German Aerospace Center (DLR e.V) has been conducting research on fuel cell systems for aircraft applications for several years. Aim of this work is the qualification of fuel cell systems for usage in aeronautical environment. In this paper two projects of the department of Electrochemical Energy Conversion are presented: Firstly the fuel cell powered nose wheel drive, which has been demonstrated successfully in July 2011. Secondly the Antares DLR-H2 – the flying test bed for fuel cell research under aeronautical conditions – which had completed initial long distance flight testing in September 2012.