Fuel Cell and Hydrogen Technologies in Aviation

This chapter is dedicated to the technology of storing hydrogen for the usage in aviation. Step by step, different methods of storing hydrogen are explained. There are physical storage systems, but as well other types like chemical, hybrid or adsorption storage. All technologies are described and where needed even in more detail. At the beginning of this chapter, the history of hydrogen storage is recapped, and the different ways of storage are compared in their capacity to store hydrogen. Thereafter, the typical design and installation of hydrogen accumulators in the aviation industry are shown and explained. At the end of the chapter, a short overview on the safety regulation for aviation hydrogen storage is given.

Hydrogen is constantly gaining attention as future energy carrier and is already considered as game changer for many applications. Since hydrogen-based mobility applications such as cars, buses, trucks, and trains have already entered the market as industrial available products, now also the maritime and aviation industries are progressing toward market introduction. The idea of liquid hydrogen as propellant for commercial aviation is not new but dates back to the 1970s when NASA in collaboration with Boeing and Lockheed conducted a very detailed study both concerning the aircraft itself as well as the necessary airport infrastructure. A historical overview of this development is given and likewise an overview of the development of the industrial liquid hydrogen technology. Furthermore, the principle of hydrogen liquefaction technology is presented, and the reason why liquid hydrogen can be considered as preferred aviation fuel is explained. Also, future trends for the further development of the liquid hydrogen technology are discussed. Long-term phase-out of kerosene with parallel phase-in of hydrogen in aviation has to be considered as a huge economical challenge. This chapter also refers to the necessary airport requirements when the hydrogen consumption at the airport has already reached a certain industrial-scale quantity and hydrogen aircraft are in regular fleet operation.”

Fuel cells (FCs) are clean and green power sources. The reported FCs in vehicle applications include three types: (1) hydrogen FCs, (2) methanol FCs, and (3) solid oxide FCs. In terms of unmanned aerial vehicle (UAV) applications, using the hydrogen FCs to achieve the power supply is the easiest and most commonly used scheme. In addition, the methanol and solid oxide FCs also have their special applications as major or auxiliary power sources in UAVs. This chapter focuses on the related technologies and crucial issues of the commonly used FCs in UAV applications. The discussions include the simplified working principles and analyses of the above three types of FCs, onboard hydrogen fuel storage styles, auxiliary or complementary power sources, topologies and power control of FC hybrid power systems, and crucial issues of current FC technologies. At last, conclusions and future breakthrough directions are given, which would be very useful for developing novel and high-performance FC power systems for UAVs.

The chapter discusses historic, current and future opportunities for hydrogen fuel cell–powered aircraft from 2021 time perspective. In particular, the notion of passenger carrying airplanes is elaborated by presenting key challenges, technological enablers as well as the certification framework development. Further, different sizing aspects and hydrogen tank placement on board and their implication on the aircraft as a whole, as researched, are discussed. The current state of the art is presented too, together with indications about passenger airplane sizing evolutions and development intents of actual forefront hydrogen fuel cell–powered aircraft. In the last part challenges related to water vapour deposition as connected to future fuel cell–powered aircraft operation are noted.

The addition of several power sources in an aircraft increases the complexity of the sizing and energy management problem while allowing a system redundancy that makes aircrafts safer. The optimization of the sizing and the energy management of hybrid electric aircraft powertrains can be accomplished using comprehensive mathematical models from the aircraft and its power sources, reducing the load of experimental activities that turn to be expensive and time-consuming. In this work, the authors apply an optimization method to obtain two optimized energy management strategies to be applied to two different types of all-electric aircraft: a general aviation powertrain and an electric vertical take-off and landing powertrain. These two aircrafts are designed to employ the same power sources configuration with a hydrogen-fueled fuel cell and a battery pack. The energy management optimization was performed to maximize the traveled distance while keeping the battery’s state of charge difference at a minimum, observing the power sources restrictions. In addition, for the second powertrain, the optimization of the power sources was performed. The analysis of the results shows that using the proposed method, the general aviation powertrain improves the traveled distance by 2.78%, reducing the equivalent energy consumption by 2.73%, and the electric vertical take-off and landing powertrain reduces the equivalent power consumption and guarantees the same battery’s state of charge at the start and at the end of the flight allowing a non-plugin operation.

The aim of this chapter is to provide insight into the necessary infrastructure, logistics, and safety aspects required to handle and operate a hydrogen-powered aircraft at an airport. Hydrogen-powered aircraft which use hydrogen in an engine either through combustion or by fuel cells operation will revolutionize the local and regional airline segment. Their commercialization will require airport ground infrastructure, as current airport infrastructure is not suitable, i.e. either non-existent, inadequate or unsuitable, for the operation of hydrogen aircraft. This chapter is dedicated to the necessary airport requirements that must be considered before hydrogen aircraft can operate commercial flights. These requirements include the necessary hydrogen logistics, which refers to obtaining, producing, distributing, or transporting hydrogen to an airport and also considers handling and other processes such as storage, purification, hydrogen liquefaction, or compression. The chapter also provides an overview of the safety aspects of handling hydrogen technology and provides valuable recommendations on how to design not only the infrastructure but also the safety measures to ensure operation with hydrogen-powered aircraft under safe conditions.

An auxiliary power unit (APU) is responsible for powering different aircraft electrical demands, mainly electrical services, when the aircraft is on the ground. Conventional APUs comprise a generator coupled to a combustion engine that partially consumes the aircraft jet fuel, which causes noise and environmental pollution. Aircraft efficiency improvements rely on substituting systems that were once mechanical, pneumatic, and hydraulic to systems in search of higher efficiency, reliability, and reduction of costs and pollutant emissions, such as in a more electric aircraft (MEA). In a fuel cell APU, the combustion engine is replaced by a fuel cell, an electrochemical device producing electrical energy with higher conversion efficiency. A fuel cell generates heat and water on board that can reduce the use of heavy on board aircraft components (e.g., water tanks) and improve passenger satisfaction. After introducing technical details of conventional APUs, this chapter presents current developments of fuel cell APUs. It focuses on the two most promising fuel cell APUs types, the APU comprising a solid oxide fuel cell (SOFC-APU) and a proton-exchange membrane fuel cell (PEMFC-APU).

In this chapter, the reader is introduced to solid oxide fuel cell (SOFC) technology, the different cell designs involved in SOFCs, the different architectures in which single cells can be made and the different system architectures currently designed with SOFCs. Further, since SOFC is a flex-fuel device, the most promising fuels to be used in SOFC systems for the most promising applications in the next decade are also discussed. Aviation or the aerospace industry is a hard to abate sector in terms of emissions, and there is ample scope for new powertrain designs, electrification architectures and much more that can be accomplished to cut down emissions. SOFCs and systems built around it are one possible choice for several applications in the aerospace industry. Hence, a complete section is dedicated to first discuss the needs of the aerospace industry and then discuss where and how SOFC-based systems can provide a suitable solution.