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Recent advancements in fuel cell technology through the auspices of the Department of Energy, the National Aeronautics and Space Administration, and industry partners have set the stage for the use of solid oxide fuel cell (SOFC) power generation systems in aircraft applications. Conventional gas turbine auxiliary power units (APUs) account for 20%...
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Citations
... The increasing pressure on the aircraft manufacturer to reduce emissions, noise, and cost prompted the transition to more electrical aircraft (MEA) options [81][82][83]. This shift meant replacing the main engine/APU-driven generator with direct electric power generation systems, such as batteries, fuel cells, and supercapacitors, as standalone systems or in hybrid combinations. ...
... This shift meant replacing the main engine/APU-driven generator with direct electric power generation systems, such as batteries, fuel cells, and supercapacitors, as standalone systems or in hybrid combinations. Many researchers regard fuel cell systems as a significant contender for achieving MEAs [83][84][85][86][87][88][89], due to their numerous benefits, which include but are not limited to high efficiency, minimal to no emissions, distributed power generation, and the possibility of water reclamation [90,91]. Several fuel cell forms exist, varying in terms of their operating temperature range and electrolyte composition. ...
Conventional transportation systems are facing many challenges related to reducing fuel consumption, noise, and pollutants to satisfy rising environmental and economic criteria. These requirements have prompted many researchers and manufacturers in the transportation sector to look for cleaner, more efficient, and more sustainable alternatives. Powertrains based on fuel cell systems could partially or completely replace their conventional counterparts used in all modes of transport, starting from small ones, such as scooters, to the large mechanisms like commercial airplanes. Since hydrogen fuel cell (HFC) emit only water and heat as byproducts and have higher energy conversion efficiency in comparison with other conventional systems, it has become tempting for many scholars to explore their potential for resolving the environmental and economic concerns associated with the transportation sector. This paper thoroughly reviews the principles and applications of fuel cell systems for the main transportation schemes, including scooters, bicycles, motorcycles, cars, buses, trains, and aerial vehicles. The review showed that fuel cells would soon become the powertrain of the choice for most modes of transportation. For commercial long-rage airplanes; however, employing the fuel cells will be limited due to the replacement of the axillary power unit (APU) for the foreseeable future. Using fuel cells to propel such large airplanes would necessitate redesigning the airplane structure to accommodate the required hydrogen tanks, which could take a bit more time.
... Solid oxide fuel cell (SOFC) technology continues to rapidly mature and accelerates towards deployment across a variety of end-use applications [26][27][28][29][30][31] temperatures (600-1000 • C), which was earlier considered of no usability in the transportation sector. The initial operating temperature of an SOFC was greater than 800 • C, at which brittle electrolytes like ceramic need higher activation energy to conduct oxygen ions [32]. ...
There has been a growing demand to develop new energy conversion devices with high efficiency and very low emissions for both power and propulsion applications in response to the net zero-carbon emission targets by 2050. Among these technologies, solid oxide fuel cells (SOFCs) have received attention due to their high electrical efficiency (above 60%), fuel flexibility, low-emission, and high-grade waste heat, which makes them particularly suitable for a large number of applications for power and propulsion systems. The higher operating temperatures make SOFCs suitable candidates for integration with an additional power generation device such as an internal combustion engine (ICE) by (a) using the residual fuel of the anode off-gas in the engine, which further increases overall system efficiency to values exceeding 70%, (b) decreasing combustion inefficiencies and (c) increasing waste heat recovery. This paper reviews the published work on hybrid SOFC-ICE systems considering various configurations. It has been found that integrated SOFC-ICE systems are promising candidates over conventional engines and stand-alone SOFCs to be used in stationary power generation and heavy-duty applications (e.g., marine and locomotive propulsion systems). The discussion of the present review paper provides useful insights for future research on hybrid electrochemical-combustion processes for power and propulsion systems.
... Those projects involved major automotive and powertrain development companies like Delphi, 3,4 Nissan, 5 Volvo, 6 Weichai Power, 7 and AVL List GmbH, 6,8 along with SOFC stack manufacturers like Ceres Power 5,7,9 and Sunfire. 10 SOFC systems have also been considered for aircraft 11 and maritime applications. 12 Though most approaches target the utilization of liquid hydrocarbons, gasoline, diesel, or natural gas, there is ever-growing evidence that a distributed H 2 -infrastructure and thus a H 2 -based transportation system will be available in future. ...
... While solid oxide cell technologies based on electrolytesupported cells for stationary applications were developed, both the anode-supported cell (ASC) and metal-supported cell (MSC) configurations are considered to be more suitable for mobile and high power density applications. 2,11,25 Both cell types have in common a very thin electrolyte layer that is applied at the cell's core, which greatly reduces ohmic losses and thus provides an opportunity to lower the operation temperature. However, the mechanical support is made from a porous metal layer in the case of the MSC, typically formed by the same material as the metallic interconnector, while it is a ceramic layer in the case of an ASC. ...
A sustainable, interconnected, and smart energy network in which hydrogen plays a major role cannot be dismissed as a utopia anymore. There are vast international and industrial ambitions to reach the envisioned system transformation, and the decarbonization of the mobility sector is a central pillar comprising a huge economic share. Solid oxide fuel cells (SOFCs) are one of the most promising technologies in the brigade of clean energy devices and have potentially wide applicability for transportation, due to their high efficiencies and impurity tolerance. To uncover future pathways to boost the cell’s performance, we propose a detailed multiscale modeling methodology to evaluate the direct impact of cell materials and morphologies on commercial-scale system performance. After acquiring intrinsic electrokinetics decoupled from mass and charge transport of different anode and cathode materials via a half-cell model, a full cell model is employed to identify the most promising electrode combination. Subsequently, a scale-up to the system level is performed by coupling a 3-D kW-stack model to the balance of plant components while focusing on morphological optimization of the membrane electrode assembly (MEA). On optimally tailoring the MEA, model results demonstrate that an advanced cell design comprising a Ni fiber-CGO matrix structured anode and a LSCF-infiltrated CGO cathode could reach a stack power density of 1.85 kW L–1 and a net system efficiency of 52.2% for operation at <700 °C, with manageable stack temperature gradients of <14 K cm–1. The model-optimized power density is substantially higher than those of commercial stacks and surpasses industrial targets for SOFC-based range extenders. Thus, with further cell and stack development targeting the performance limiting processes elucidated in the paper, commercial SOFCs could, alongside range extenders, also act as prime movers in larger scale transport applications such as trucks, trains, and ships.
... [40] designed a hybrid Fuel Cell/battery-based design for 767 as a replacement to APU. In Ref. [41], the key benefits of using SOFC-based APU are evaluated by simulating the performance of the fuel cell using proprietary library modules. The study employs a twin-engine aircraft designed for short-range missions. ...
The Auxiliary Power Unit (APU) is an integral part of an aircraft, providing electrical and pneumatic power to various on-board sub-systems. APU failure results in delay or cancellation of a flight, accompanied by the imposition of hefty fines from the regional authorities. Such inadvertent situations can be avoided by continuously monitoring the health of the system and reporting any incipient fault to the MRO (Maintenance Repair and Overhaul) organization. Generally, enablers for such health monitoring techniques are embedded during a product's design. However, a situation may arise where only the critical components are regularly monitored, and their status presented to the operator. In such cases, efforts can be made during service to incorporate additional health monitoring features using the already installed sensing mechanisms supplemented by maintenance data or by instrumenting the system with appropriate sensors. Due to the inherently critical nature of aircraft systems, it is necessary that instrumentation does not interfere with a system's performance and does not pose any safety concerns. One such method is to install non-intrusive vibroacoustic sensors such that the system integrity is maintained while maximizing system fault diagnostic knowledge. To start such an approach, an in-depth literature survey is necessary as this has not been previously reported in a consolidated manner. Therefore, this paper concentrates on auxiliary power units, their failure modes, maintenance strategies, fault diagnostic methodologies, and their acoustic signature. The recent trend in APU design and requirements, and the need for innovative fault diagnostics techniques and acoustic measurements for future aircraft, have also been summarized. Finally, the paper will highlight the shortcomings found during the survey, the challenges, and prospects, of utilizing sound as a source of diagnostics for aircraft auxiliary power units.
... Later, Rajashekara et al. [9] studied the fuel cell gas turbine hybrid system as an alternative of aircraft auxiliary power unit, considered the influence of different working height and air source on the system, and showed that the hybrid system has a greater competitive advantage in the size range of 100 kW-10 MW. Braun et al. [10] compared advanced gas turbine APU and fuel cell hybrid system APU which will be used in the short-range aircraft in terms of fuel consumption, pollutant emission and overall efficiency. It shows that although the power density of hybrid system APU system is lower, it is possible to reduce the fuel consumption and emission reduction of aircraft. ...
Developing aviation power generation methods with high efficiency is one of the important issues that need to be solved in aviation field, especially for More/All Electric aircraft. In this paper, the advanced solid oxide fuel cell gas turbine hybrid power generation system based on aviation kerosene is studied. And the performance of three configurations of hybrid system without/with SOFC exhaust recirculation are compared and evaluated, which are a basic hybrid system without exhaust recirculation (BHS), an anode exhaust recirculation hybrid system (ARHS), and an anode and cathode exhaust recirculation hybrid system (ACRHS). The results show that the power generation efficiency of the BHS is 59.3%, while the two hybrid systems with exhaust recirculation increase to around 70%: the efficiency of ARHS is 70.9%, and ACRHS is 69.7%. But the ACRHS shows greater potential in increasing the SOFC cathode inlet temperature. And the specific work of the hybrid system with exhaust recirculation can reach more than 760 kW (kg air)⁻¹. In addition, the parameters such as pressure ratio, temperature ratio and fuel utilization have important influence on the performance. Due to the advantages of high power generation efficiency and specific work, hybrid system is a competitive power generation system in aviation field.
... The traditional APU systems have very low efficiencies of at best 40% at cruising altitudes and 20% at sea level [6]. In addition, these aircraft APUs are a major source of pollutants like NO x which is especially dangerous due to its tendency to cause acid rain [10,11]. Solid Oxide Fuel Cells (SOFCs) are one of the promising ventures for improving APUs due to their capability of reduced NO x emissions [12] and relatively uncomplicated functioning. ...
... Total Syngas available in exhaust (9) h fc ¼ Electrical Power generated by FFC Total Chemical energy of the syngas utilized (10) h ov ¼ Electrical power generated by fuel cell Chemical energy from the hydrocarbon fuel (11) Both CO and H 2 from the fuel-rich combustion products are used as fuel in the FFC for electrochemical oxidation generating electrical power. The fuel cell reactions are shown in Eq. (12) and Eq. ...
Owing to several unsuccessful attempts of integrating dual chambered solid oxide fuel cell stack with the auxiliary power unit (APU) gas turbine, a novel concept for integration of flame-assisted fuel cells (FFC) with the gas turbine of an APU is presented in this paper. A complete analytical model of the FFC integrated hybrid system is presented. The FFC gas turbine hybrid system is predicted to be up to 30% more efficient at sea level and 16% more efficient at cruising altitudes compared to standard gas turbine cycle. A FFC is characterized experimentally with model combustion exhaust for fuel-rich combustion of JP-5. The fuel cell displayed 75% fuel utilization at the operating voltage of 0.5 V, which is higher than previous studies in this field. The analytically predicted reversible voltage shows good agreement with the open circuit voltage of the FFC experimental results. Analysis of temperature entropy and pressure volume diagrams of the proposed system shows that as the equivalence ratio increases the portion of the total FFC gas turbine hybrid power generated by gas turbine decreases. The breakeven distance and the complexity of the proposed FFC gas turbine hybrid is significantly lower than previous studies.
... Several devices can be used to generate power, such as the auxiliary power unit (APU) [6], the gas generator [7] and the air-turbo [8]. The APU is normally used in subsonic vehicles, which faces severe aerodynamic drag [9] and thermal protection problem [10] with the increasing flight Mach number. Even though the gas generated by gas generator has strong power generation capability, it still requires extra oxidant and propellant. ...
Onboard power generation for hypersonic vehicles is an important and urgent requirement. The capability of existing gaseous hydrocarbon fuel driven thermal power generation (TPG) is poor at low Mach speed range. To improve the TPG capability, two potential power generation improvement methods have been proposed in this study, namely: 1) the partial mass flow TPG improvement method and 2) the catalytic steam reformed hydrocarbon fuel TPG improvement method. The characteristics of the two TPG improvement methods are studied using an analytical model. The results show that the former can improve power generation capability with less fuel mass flow and the maximum output power improvement ratio can be as high as 14 at low heat flux condition, while the latter helps to generate power at a much lower fuel temperature, which could be as low as 710 K, although it requires extra water steam. Therefore, both methods are useful and the appropriate method should be selected according to the working conditions of scramjet. If the Mach number is rather low and scramjet cannot take extra water, it is better to use the partial mass flow TPG improvement method. Otherwise, the catalytic steam reformed hydrocarbon fuel TPG improvement method is more suitable.
... Rajashekara [5] et al. revealed that the efficiency of the hybrid system is 60.6% for sea level and 73.7% for high altitude. Braun [6] et al. showed that fuel burn (5%~7%) and emission (up to 70%) reductions for aircraft are possible by optimizing the hybrid systems. ...
The high-speed flight can be achieved by high-performance aero-engines. A traditional turbojet engine with steam injection is hardly operated at Mach 3.5–5 owing to the low specific impulse. The performance of turbine-less jet engines is outstanding. No turbines exist in the engine and compressors are powered by fuel cells. Therefore, the limitation of the highest combustion temperature caused by turbines disappears. In addition, fuel cell exhaust can still be used to burn and expand to output propulsion power. In this paper, the turbine-less jet engines integrated with a SOFC and steam injection are proposed to achieve high-speed flight. In order to analyze the performance of the engine, the thermodynamic model is built. Effects of thermodynamic parameters such as water-air ratio are studied. The main results are as follows: the performance of the turbine-less engine is significantly improved by integrating with steam injection. The augment of specific impulse and specific thrust of the engine is 13.13% and 51% respectively compared with the pre-cooling turbojet engine at the water-air ratio of 0.013. The specific impulse of the engine is 1.15 times that of the pre-cooling turbojet engine at Mach 4. Meanwhile, the specific thrust is increased by 26%.
... A lot of research has been done on SOFC APU modeling but most of them are steady state and feasibility study. [4][5][6][7][8]. In [13] the steady-state performance analysis and the exergetic analysis of a Jet-A fueled hybrid SOFC/GT system with a power output of 250 is analyzed. ...
... In [13] the steady-state performance analysis and the exergetic analysis of a Jet-A fueled hybrid SOFC/GT system with a power output of 250 is analyzed. In [4] the performance of various hybrid SOFC-APU system architectures is compared against an advanced gas turbinebased APU system. In addition to the merits of different system architectures, optimal SOFC system parameter selection is discussed. ...
... The main principles of SOFC modeling in the present model are mass and energy conservation. The continuity equations determined through the ideal gas assumption include the inlet and outlet flow rates and effective partial pressures of the component in channels due to the reactions: v RT 4 dP dt = (n 6 , − n6 7 , ) ...
The analysis of fuel cells can be divided into two areas, steady state modelling, and dynamic modelling. Our prior paper [1] focused on the steady-state performance of anode-supported jet fuel external reforming planar solid oxide fuel cell stack model for aircraft Auxiliary Power Unit (APU) application. The aim of the current paper is to evaluate the transient behavior of this solid oxide fuel cell system to sudden electric load changes. The present model solves transient mass, energy, and electrochemical equations for a solid oxide fuel cell (SOFC) and calculates time responses of output parameters of the system by a step change of the electric current. In this model, some important capacitive elements in the fuel cell process are modelled. The focus of this study is on application to "more-electric" airplanes and the regional jet used as a case study. SOFC system heat-up stage and the output voltage response to a sudden load change at small, medium and large timescales are presented in this paper. Results indicate that the electric characteristics be adapted to new conditions of SOFC sooner than the state parameters.
... In addition, SOFC can integrate with a gas turbine for a ground electric generation. At present, researchers mainly focus on distribution generation [13][14][15][16][17][18] and APU [19][20][21][22][23][24] of the hybrid systems. ...
... Ananda [9] et al. put in forward SOFC gas turbine hybrid systems fueled by hydrogen for HALE UAVs. Ananda [21] et al. ...
