High Power Density Design Research Articles

(Invited) Solid Oxide Cell Design for High Power Density and Reliability: Applications in Power and Fuels Production

Solid oxide fuel cells (SOFC) offer a carbon-neutral solution to power generation, fuel flexibility, and robust design suitable for stationary and air transportation applications. OxEon Energy developed an air electrode supported (AES) cell design that demonstrated 63% increase in power density compared with its heritage cell design in short stack tests.OxEon Energy team has been advancing solid oxide technology for over three decades and the stacks operate fully reversibly in fuel cell and electrolysis cell modes. The SOEC/SOFC technology builds on the success of the SOEC stack installed on NASA’s Mars Perseverance Rover as part of the MOXIE (Mars Oxygen In-situ resource utilization Experiment) mission. The MOXIE stack produced propellant grade, high-purity O2 by electrolyzing Mars atmosphere CO2. MOXIE stack used an electrolyte supported design to meet the reliability requirements for a space mission.An infiltrated air electrode cell design was developed to increase fuel cell stack specific power (kW/kg). Electrolyte thickness, the most resistive element of the SOFC, was reduced from ~250 microns to 70 microns. The fabrication process results in a bi-layer of dense scandia stabilized zirconia (ScSZ) electrolyte and a porous yttria stabilized zirconia (YSZ) matrix for air electrode infiltration. Fuel electrodes are screen printed. The reduced thickness of the electrolyte offers a compromise between improved performance over electrolyte supported design, while meeting robustness required for aerospace applications.Producing infiltrated electrodes with well-adhered and homogeneous distribution of active material is a challenge that requires multiple infiltration-calcination cycles to deposit sufficient material. Key variables are precursor chemistry to reduce the number of infiltrations and prevent interaction between electrode layers; intermediate calcination temperatures; and process development using infiltration equipment that enables volume production. OxEon partnered with National Energy Technology Laboratory (NETL) for electrode infiltration process development and PNNL for button cell and short stack validation testing.SOFC fuel flexibility was demonstrated in button cells and stacks previously; performance was nearly identical among hydrogen, ammonia, and reformed natural gas. Durability testing shows similarly stable performance in each fuel.A 10-cell AES stack was tested in SOFC mode at 800 °C in H2 and NH3 fuel feeds at 0.7 V/cell, and the same stack was operated in steam electrolysis to produce H2. SOFC testing demonstrated powder density of 0.35 W/ cm2 at 0.7 V/cell in the AES stack in ammonia feed; an electrolyte supported stack with equivalent materials measured 0.20 W/cm2 at 0.7 V. Long term testing in steam electrolysis showed stable performance at 800 °C and 1.2 V/ cell.Button cell tests show the thin electrolyte cell structure is capable of an area specific resistance (ASR) of 0.25 Ω-cm2 in H2- and NH3 fuel feeds. OxEon’s continued AES cell development is focused on improving manufacturability, infiltrated electrode stability, and implementing degradation mitigation strategies developed for electrolyte supported cell structures. Improved performance with AES cell design has critical implications for future integration in OxEon’s technology suite: SOEC systems to generate H2 and syngas from renewable energy, and Fischer-Tropsch to produce synthetic fuels.This material is based on research sponsored by Air Force Research Laboratory under agreement number FA8649-22-P-0792. The views expressed are those of the authors and do not necessarily reflect the official policy or position of the Department of the Air Force, the Department of Defense, or the U.S. government. Approved for public release; distribution is unlimited. Figure 1

Power Generation Optimization for Next-Generation Cruise Ships with MVDC Architecture: A Dynamic Modeling and Simulation Approach

The cruise industry is obliged by economic and environmental initiatives to pursue fuel-efficient solutions and lower ship exhaust emissions. The medium voltage DC (MVDC) distribution with intelligent power management has become a concept for next-generation onboard power systems as its energy-saving feature is to eliminate the frequency constraint and simultaneously optimize engine loads and speed in response to load variations. The incentive for this transition lies on one hand in the fuel efficiency consideration and the reduction of power losses from serial conversion stages. On the other hand, the DC-based technology has been conceived as high-power density design, thus significantly increasing the payload. This study investigates such potential benefits focusing exclusively on large cruise vessels. A highly representative model of the integrated power platform that incorporates all dynamic interactions from the ship hull and essential machinery typically installed on board cruise ships is proposed. The power management strategy also takes account of actual sea conditions and real-time operation requirements. The simulation results demonstrate that the optimization-based MVDC system is able to maximize the opportunity of search agents in finding optimum fuel efficiency areas throughout the scenario time. An analysis of the system structure weight and space reduction of the MVDC architecture is also performed through the utilization of more compact electrical distribution devices and very high power-dense combustion turbines.

Electromagnetic design for high power density of fully superconducting synchronous motor with through-shaft type field coil for electric aircraft

Abstract The global demand for aircraft is currently increasing, paralleled by a growing emphasis on decarbonization through the replacement of fossil fuel engines with electric propulsion. In response to this trend, we have developed a superconducting motor distinguished by its high efficiency, output, and low weight. Our focus centers on two critical aspects. Firstly, we addressed the issue of the field coil’s shape. The widely used REBCO wire in high-temperature superconductivity is tape-shaped, making a racetrack coil the most straightforward method for winding the wire. However, this configuration necessitates dividing the motor shaft as it comes in contact with the field coil, raising concerns about the mechanical durability of motors. To overcome this challenge, we introduce a saddle-type coil and design a coil shape that achieves a single continuous through-axis. Utilizing the Frenet-Serre formula, we created a 3D model of the coil’s end without applying load to the wire. This method, previously employed in accelerators, enhances durability, potentially leading to increased output due to higher rotation speeds and reduces weight through part savings. Secondly, introducing a saddle coil presents challenges in forming an ideal magnetic field distribution. In a rotating-field-type motor using an iron core, the winding can be directly wound around it, resulting in multiple coils forming similar magnetic fields that can be superimposed to create one large magnetic pole. However, with a saddle coil, coils are arranged along the circumference, and the magnetic field distribution and an anticipated decrease in output. To address this, we aimed to optimize the magnetic field distribution and increase output through a parameter survey. Specifically, we conducted an analysis under fixed armature conditions (current, number of turns, and shape) in three cases. In Case1, with a fixed total number of turns for the field coil, we compared magnetic field distributions and output by varying the number and arrangement of coils. In Case2, building on the findings of Case1, we aimed to enhance output by fixing the coil arrangement and increasing the number of turns. Finally, in Case 3, we examined the change in motor size with fixed coil parameters while altering the coil arrangement and pitch.

Design of High-power Density and High-frequency Transformers for Auxiliary Power Supply System in Electric Multiple Units

Design of High-power Density and High-frequency Transformers for Auxiliary Power Supply System in Electric Multiple Units

Study on dynamic performance and optimal design for differential gear train in wind turbine gearbox

The differential gear train is a common component in wind turbine gearboxes. Investigating the dynamic performance of the gear train is crucial for improving its transmission capabilities. Unlike planetary and compound gear train, there has been relatively little research on differential gear train. Additionally, transmission efficiency is a critical performance metric for gear train, while addressing volume constraints remains a significant challenge in gear research. Currently, there is a lack of relevant research on dynamic transmission efficiency and precise volumetric modeling for differential gear train. Therefore, this paper introduces a high power density design approach for the differential gear train, utilizing the analysis of its dynamic performance. Practical application is demonstrated through two examples. In the first example, the system achieved a 26.32 % reduction in power loss, a 35.44 % decrease in volume, and a maximum root mean square reduction of 12.4 % in component vibration acceleration. In the second example, the system achieved a 19.21 % reduction in power loss, a 41.07 % decrease in volume, and a maximum root mean square reduction of 103.4 % in component vibration acceleration. This research establishes a solid foundation for improving dynamic performance, reducing energy consumption, and minimizing volume in helical differential gear train.

Analyzing heat transfer in Axial Flux Permanent Magnet electrical machines: A literature review on the discretization methods-FVM and FDM

Axial Flux Permanent Magnet (AFPM) machines have gained significant attention due to their high power density, efficiency, and compact design. However, effective heat transfer analysis is critical for optimizing their performance and reliability. This paper presents a comprehensive literature review on the application of discretization methods, specifically the Finite Volume Method (FVM) and Finite Difference Method (FDM), in the thermal analysis of AFPM machines. The fundamentals of FVM and FDM are briefly explained, followed by an exploration of their applications in AFPM machine thermal analysis. The advantages and limitations of using these methods are discussed, and a comparison between FVM and FDM is provided. Advanced discretization techniques, such as the Finite Element Method (FEM), and coupled thermal-electromagnetic analyses are also examined. The paper highlights studies that have utilized FVM or FDM in developing optimized designs and effective thermal management strategies for AFPM machines. Lastly, potential future research directions are identified, including the development of more efficient discretization methods, the incorporation of advanced materials, and the investigation of novel cooling techniques. This review offers valuable insights into the current state of research and potential future directions in the thermal analysis of AFPM machines using discretization methods.

Thermal design and performance evaluation of GaN power stage in a 4-level totem-pole PFC

Low voltage Gallium Nitride (GaN) power devices are enabling the development of single-phase multi-level power factor correction (PFC) converters for high power density designs due to their superior figure-of-merit. However, despite their lower power losses compared to Si MOSFETs, it is still challenging to remove a few watts of power loss from small packages, which presents a barrier for using GaN in high power converters. To address this issue, this study establishes a 3-D thermal model for chip-scale package GaN devices, and analyses various heat sinking methods for a power stage of a single-phase 4-level PFC structure using the finite element method. The thermal performances of GaN devices with different layouts, board types, and thermal via patterns have been analyzed and verified experimentally on a power stage of a 4-level GaN PFC rated for 3.7 kW, where each of the six GaN devices dissipates 2.3 W.

An Accurate Power Model and High Power Density Design Method of Free-Standing Magnetic Field Energy Harvesters With H-Shaped Core

To achieve more output power of the free-standing magnetic field energy harvester (FSMFEH) with a smaller core volume, designing the core and coil parameters of FSMFEH is critical. However, the lack of an FSMFEH power model leads to the absence of a detailed design method. To address this issue, building an accurate FSMFEH output power model is required. In this work, by quantifying coil mutual inductance and internal resistance as core and coil parameters, an accurate power model of FSMFEH with all parameters is established based on the H-type core. As a result, based on the proposed model, the optimal values of the core column size, the core lamination size, the coil turns, and the wire diameter are designed. Experiment results show that the proposed model can maintain high accuracy, and the power density deviation is within 5% compared with the theoretical value. Besides, the optimized parameters designed according to the model analysis are effective for improving the power density. When the current of the busbar is 100A, the maximum power density can reach 4.182mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , and the corresponding maximum output power is 13.25mW with the optimized parameters.

Electrical Properties of Silicone Gel for WBG-Based Power Module Packaging at High Temperatures

Trends toward high power density designs and emerging wide bandgap (WBG)-based semiconductors will lead to a severe temperature rise in power electronic modules. In this regard, the insulation performance of silicone gel used for power module packaging deteriorates at high temperatures and frequencies is a concern and has not been well studied. This study focuses on the electrical properties of silicone gel at high temperatures, including its dielectric properties, volume resistivity, and breakdown strength. A Cole-Cole model was used to describe the dielectric response process. In particular, the dielectric loss density under PWM voltage was calculated, and the temperature rise of the encapsulation structure caused by the dielectric loss was observed. It was found that the high-frequency dielectric constant at 200°C decreases by 24% compared to room temperature; when the temperature is raised to 180°C, the volume resistivity drops by three orders of magnitude, and the 50 Hz AC and 10 kHz unipolar square wave breakdown strength of silicone gel is reduced by 50% and 42% compared with those at room temperature. The dielectric loss under PWM voltage increases by four orders of magnitude as the temperature increases up to 200°C but does not lead to a significant temperature rise in the encapsulation structure.

Fixed-Frequency PWM Control and Stability of Series-Stacked Buffer for 2ω-Power Decoupling

Active second-harmonic ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\omega $ </tex-math></inline-formula> ) filters have become an integral technology for single-phase power converters in high-power density designs. The series-stacked buffer (SSB) has emerged as an attractive topology among the existing solutions due to its low power, high efficiency, and compact design. However, one of the challenges in adopting SSB lies in its control, where hysteresis current control has been adopted conventionally. This results in a wide variation in the switching frequency, making the digital control implementation and filter design complex. On the other hand, fixed-frequency pulsewidth modulation (PWM) control necessitates developing a model for the systematic controller design to ensure stability and desired filtering performance. The assumption of SSB modeled as a second-harmonic current source, independent of the dc bus circuit components, fails to capture the dc bus loading effect on the SSB. In this work, a dynamic model of SSB is developed where the main dc bus and its passive elements are considered. The derived model enables a systematic approach for the controller design while ensuring the desired <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\omega $ </tex-math></inline-formula> filtering. The stability limits and parameter sensitivities of the model are studied analytically and in simulations. The analytical model is validated, and the proposed controller performance and stability limit are verified experimentally on a hardware prototype. A video demonstrating the transition from stable to unstable operation is provided.

A new three-stage gearbox concept for high reduction ratios: Use of a nested-cycloidal architecture to increase the power density

Increasing the Gear Ratio (GR) while decreasing the gearbox dimension is a contradiction that mechanical designers are challenged to solve. The increasing importance of fine-tuning high power density designs has led to the development of innovative solutions involving cycloidal and hypocycloidal gears. However, when the required GR increases and the number of the stages raises, the gearbox architecture plays a key role in minimizing the overall dimensions. In the present paper, an innovative gearbox architecture is presented. The new design combines three cycloidal and hypocycloidal gearing stages to achieve a higher GR with respect to a traditional two-stage cycloidal gearbox with the same overall dimension. This architecture is called Nested since it involves stages with internal and external gears arranged one inside the other. A comparison of the proposed solution with the more compact two-stage cycloidal architecture (Wolfrom) is shown. The GRs as a function of the total number of meshing features are discussed as well as the torques acting on each component. Eventually, a design solution is illustrated.

Design of high power density double‐stator permanent magnet synchronous motor

AbstractCompared with the traditional permanent magnet synchronous motor (PMSM), the double‐stator permanent magnet synchronous motor (DS‐PMSM) can utilise the internal space adequately and has high power density. In this study, the design method of this kind of motor will be researched. Different rotor magnetic circuit topologies are analysed while keeping the outer diameter of outer stator unchanged, and the rotor magnetic circuit topologies with higher power density are selected. Furthermore, the effects of pole‐arc coefficient and stator split ratio on the power density of the motor are analysed, so a high power density DS‐PMSM can be designed. On this basis, a kind of magnetic pole structure with unequal pole‐arc coefficient is proposed to solve the problem of large torque ripple in DS‐PMSM. Finally, the DS‐PMSM is investigated by the FEA, compared with the traditional single stator PMSM, the average torque of the DS‐PMSM is increased by 62.2%, and the torque ripple is only 3.2%.

Electrochemical Characterizations of Ternary MnO2/Cus/Rgo Materials for Supercapacitor Applications

Supercapacitors are considered as a new class of energy storage device because of their high power density, environmentally friendliness, long cycleability, and flexible design capabilities. MnO2 and CuS have been found to be promising for supercapacitor applications because of their low cost, abundance in nature, and are environmentally friendly. Besides this, reduced graphene oxide emerged as most promising carbon materials for energy storage applications because of its high specific surface area, good electrical conductivity, and ability to attach metal oxide withoutany agglomeration. Recently, it has been reported that ternary nanocomposites have superior electrochemical performances because of their synergistic effect, which help to enhance the charge movement within the electrode material. We already reported that the specific capacitance of CuS and MnO2 as 158 F/g and 300 F/g at current densities of 0.5 A/g, respectively [1,2]. In this work we have synthesized MnO2/CuS/rGO ternary nanocomposite by hydrothermal method. The physical characterization of the synthesized materials was carried out using X-Ray diffraction, scanning electron microscopy, differential scanning calorimetry(DSC), and thermogravimetric analysis (TGA). All electrochemical measurements were conducted in standard three-electrode configuration, using a platinum wire, Ag/AgCl, and MnO2/CuS/rGO as a counter, reference, and working electrode, respectively. The results related to physical characterization, specific capacitance, cycleability, and energy density will be presented.Reference: Rahul Singhal, David Thorne, Peter K. LeMaire, Xavier Martinez, Chen Zhao, Ram K. Gupta, David Uhl, Ellen Scanley, Christine C. Broadbridgeand Rakesh K. Sharma, AIP Advances 10, (2020) 035307; https://doi.org/10.1063/1.5132713. Rahul Singhal, Justin Fagnoni, David Thorne, Peter K. LeMaire, Xavier Martinez, Chen Zhao, Ram K. Gupta, David Uhl, Ellen Scanley, Christine C. Broadbridge, Mani Manivannan, MRS Advances, 4 (13) 777-782 (2019), https://doi.org/10.1557/adv.2019.86

12-kV 1-kA Breaking Capable Modular Power Electronic Interrupter With Staged Turn-off Strategy for Medium-Voltage DC Hybrid Circuit Breaker

The dc circuit breaker plays an important protection role in the dc distribution systems. Hybrid dc circuit breaker (HCB) offers low conduction losses and reasonably fast response times. In this article, a high power density, modular, and scalable power electronic interrupter (PEI) design is introduced for medium-voltage (MV) HCB platforms. Following this concept, the single low-voltage module is first investigated in terms of the high pulse current ratio and the voltage clamping circuit. After the comparison and test among different devices, a compact module with 1.7-kV discrete IGBTs are selected as main switches. While the voltage clamping circuit is carefully designed to guarantee no tail current bump and sufficient turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> voltage margin. Next the whole system with series modules is optimized on the aspects of the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> strategy, power supply structure, and layout of modules. An improved staged turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> scheme is proposed, which can not only reduce the peak current and total metal oxide varistor (MOV) energy, but also help balance the MOV energy distribution. A 12-kV and 1-kV breaking capable PEI was demonstrated based on the proposed PEI design, achieving a peak power density of 7.4 kW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , much higher than the IGBT module-based solution. The breaking capability and effectiveness of the modular PEI is demonstrated in a 6-kV MVDC HCB device.

Copper Pipes as Medium Frequency Transformer Windings

Owing to increasing power demand, new technologies, such as solid-state transformers, are progressively researched and improved. Thereby, galvanic isolation and voltage adaptation are achieved by medium frequency transformers. To reach high power density designs, transformer windings can be realized by means of copper pipes, allowing for efficient liquid cooling. This paper provides insight to many relevant aspects for the use of hollow copper conductors as windings. This includes electrical and thermal modeling, as well as considerations regarding mechanical implementations. Additionally, the winding concept is investigated based on a 1 MW medium frequency transformer prototype.

Rational design of high power density “Blue Energy Harvester” pressure retarded osmosis (PRO) membranes using artificial intelligence-based modeling and optimization

The challenge in harvesting Salinity Gradient Power (SGP) through pressure retarded osmosis (PRO) requires design of high power density (PD) membranes and optimized process for operation. Recent studies show that for a feasible PRO operation the minimum net PD should be around 50 W/m2. In this study, a data-driven approach has been adopted for designing optimum membranes as well as operating conditions. 200 papers, from last decade, were extensively reviewed and 34 experimental research articles were shortlisted for possible data mining, to predict water flux (WF) and PD. Comprehensive screened/pre-processed data related to both membrane and process (16 inputs) was obtained from 18 articles amounting to 339 data points. Two artificial neural network (ANN) models were explored (i) Levenberg-Marquardt (ANN-LM), and (ii) Bayesian Regularization (ANN-BR) along with a combination of three different activation functions i.e., hyperbolic tangent sigmoid transfer function (Tan-Sigmoid), logarithmic sigmoid transfer function (Log-Sigmoid) in the input and output layers. Out of the six resulting combinations, the best performing combination was found to be Tan-Sigmoid activation function in both layers with ANN-BR model having an R2 value of 0.97 for WF and 0.98 for PD. Membrane properties like the type of membrane, thickness, and water permeability coefficient were found to be the major contributing factors for the prediction of WF while for PD, operating conditions such as applied pressure were found to play the major contributing factor (10–16 %). Optimization results yield a maximum WF of 147 LMH and PD of 87 W/m2. These results were compared with the solution diffusion (S-D) model.

Design of high power density for RV reducer

Rotate vector (RV) reducer is widely used in precision transmission field. In this paper, the high power density is introduced into the design of RV reducer. Firstly, analysis of relevant motion relations for RV reducer is given, which provides a theoretical basis for the later calculation of efficiency and volume. Secondly, meshing efficiency model of spur gear pair and cycloidal pin-gear pair is deduced. Based on the virtual power theory, a calculation method of transmission efficiency for RV reducer is introduced. Meshing efficiency of single pair of gears obtained by calculation is adopted in the model of transmission efficiency instead of the previous fix value. At the same time, the volume model of spur gear and cycloidal gear is given, and the volume model of RV reducer is built. Finally, minimum power loss and minimum volume are taken as objective functions, the optimal variables, constraints condition and optimization method are determined, and then the design of high power density for RV reducer is implemented. Three examples are provided to illustrate the proposed method. The results show that the power loss of RV reducer are reduced by 16.97%, 12.78%, 11.12%, respectively, and the volume of RV reducer are reduced by 20.62% 21.2% 28.32%, respectively.

Lean-burn characteristics of a turbocharged opposed rotary piston engine fuelled with hydrogen at low engine speed conditions

Opposed rotary piston (ORP) engines have high power density and compact designs which meet the requirements of power sources of hybrid vehicles. Hydrogen applications to ORP engines can effectively decrease greenhouse gas emissions; however, hydrogen combustion in ORP engines around stoichiometric ratio generated large quantities of nitrogen oxides (NOx), especially for low engine speed conditions. Lean-burn as an effective method to decrease NOx emissions was adopted in this research. A 3D numerical simulation method was used to explore the effect of equivalence ratio (≤1) on combustion and NOx emission characteristics of this ORP engine fuelled with hydrogen. The results indicated that peak in-cylinder pressure increased with equivalence ratio for 1000 revolutions per minute (RPM); however, the value over the equivalence ratio of 0.9 was the maximum among 2000 RPM scenarios. The effect of equivalence ratio on heat release rates was greatly dependent on the engine speeds. Start of combustion over 1000 RPM engine speed was advanced with the increase of equivalence ratio; and it was the earliest over the equivalence ratio of 0.9 at 2000 RPM conditions. During the exhaust stroke, in-cylinder pressure of free discharge was much higher than atmosphere pressure, which significantly increased the pumping losses of exhaust stroke. Accumulated NOx emissions over the equivalence ratio of 0.9 reached the maximum value for given engine speeds; and the NOx emissions were almost zero for severe lean-burn (<0.7) conditions. Engine power output decreased with the drop of equivalence ratio for 1000 and 2000 RPM engine speeds; indicated thermal efficiency over the equivalence ratio of 0.9 was the maximum at 2000 RPM engine speed.

Recent Advances in High-Performance Microbatteries: Construction, Application, and Perspective.

High-performance miniaturized energy storage devices have developed rapidly in recent years. Different from conventional energy storage devices, microbatteries assume the main responsibility for micropower supply, functionalization, and characterization platforms. Evolving from the essential goals for battery design of high power density, high energy density, and long lifetime, further practical demands for microbatteries (MBs) have been raised for the microfabrication technique and device design. Numerous studies have generally focused on specific aspects of the microelectrode structures or certain microfabrication techniques, while the connection from techniques to functional applications is rarely involved. This Review generally fills such blanks from an application-oriented perspective. First, some basic micromachining techniques with different compatible features are summarized. Afterward, device designs including diversified battery reaction types, configuration, and assembly are highlighted, as well as microbatteries serving powering resources or further complicated functional systems. Finally, through providing the overall design concept based on requirements in application, this Review offers innovative insights for further development of microbatteries.

80 Hours operation of a tubular solid oxide fuel cell using propane/air

High power density and simple design are vital for these fuel cell-based portable power generation devices. This study provides an 8.6 g tubular SOFC with embedded a catalytic partial oxidation reformer, which is fabricated and operated for more than 100 h using propane/air. Nickel-iron nanosheets, as catalysts for reforming, supported on α-Al2O3 foam ceramic are synthesized by hydrothermal treatment. Testing for 80 h gives a power degradation of about 20% compared with the initial value. It is mainly attributed to sulfur-poisoning of nickel near anode/electrolyte interface according to transmission electron microscope (TEM) analysis. From TEM/energy dispersive spectroscopy line-scan results across the anode/electrolyte interface, sulfur as either aggregate at the nickel/yttria-stabilized zirconia grain boundaries or on the nickel grain surface, and no obvious carbon phase is founded. The maximum power density is 0.67 W cm−2 at 700 °C using propane/air (12 vol% propane), about 5% higher than the same cell using 20 vol% hydrogen.