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11 pages, 447 KiB

Open AccessArticle

Phase Field Study of Cr-Oxide Growth Kinetics in the Crofer 22 APU Alloy Supported by Wagner’s Theory

by Kai Wang and Robert Spatschek

Energies 2023, 16(8), 3574; https://doi.org/10.3390/en16083574 - 20 Apr 2023

Cited by 1 | Viewed by 1569

Abstract

The Crofer 22 APU alloy is a frequently used metallic material to manufacture interconnects in solid oxide fuel cells. However, the formation and evaporation of Cr

_{2}

O

_{3}

not only increases the electrical resistance but also leads to the Cr-related degradation over [...] Read more.

The Crofer 22 APU alloy is a frequently used metallic material to manufacture interconnects in solid oxide fuel cells. However, the formation and evaporation of Cr

_{2}

O

_{3}

not only increases the electrical resistance but also leads to the Cr-related degradation over the service time. In order to investigate the growth kinetics of Cr-oxide, i.e., Cr

_{2}

O

_{3}

, the multi-phase field model coupled with reliable CALPHAD databases is employed. The phase field simulation results are benchmarked with the predictions of Wagner’s theory. Moreover, we evidence the influence of the temperature and Cr concentration on the ferritic matrix phase and the oxygen concentration at the Cr

_{2}

O

_{3}

/gas interface on the growth kinetics of Cr-oxide, paving the way for further investigations of Cr-related solid oxide fuel cell degradation processes. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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14 pages, 7308 KiB

Open AccessArticle

An Adaptive Joint Operating Parameters Optimization Approach for Active Direct Methanol Fuel Cells

by Zhengang Zhao, Dongjie Li, Xiaoping Xu and Dacheng Zhang

Energies 2023, 16(5), 2167; https://doi.org/10.3390/en16052167 - 23 Feb 2023

Cited by 2 | Viewed by 1381

Abstract

The operating parameters of the active direct methanol fuel cell (DMFC) are essential factors that affect cell performance. However, it is challenging to maintain the optimal maximum output power density due to the system’s complexity, the operating conditions variation, and the correlations between [...] Read more.

The operating parameters of the active direct methanol fuel cell (DMFC) are essential factors that affect cell performance. However, it is challenging to maintain the optimal maximum output power density due to the system’s complexity, the operating conditions variation, and the correlations between those parameters. This paper proposes an adaptive joint optimization method for fuel cell operating parameters. The methods include the adaptive numerical simulation of the operation parameters and the optimization for fuel cell performance. Based on orthogonal tests, a BP neural network is used to build a performance evaluation model that can quantify the influence of the operating parameters on fuel cell performance. The optimal combination of operating parameters for the fuel cell is obtained by a whale optimization algorithm (WOA) through the evaluation model. The experimental results show that the evaluation model could respond accurately and adaptively to the cell operating conditions under different operating conditions. The optimization algorithm improves the maximum power density of the fuel cell by 8.71%. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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20 pages, 4868 KiB

Open AccessFeature PaperArticle

Sizing and Performance Analysis of Hydrogen- and Battery-Based Powertrains, Integrated into a Passenger Train for a Regional Track, Located in Calabria (Italy)

by Petronilla Fragiacomo, Francesco Piraino, Matteo Genovese, Lorenzo Flaccomio Nardi Dei, Daria Donati, Michele Vincenzo Migliarese Caputi and Domenico Borello

Energies 2022, 15(16), 6004; https://doi.org/10.3390/en15166004 - 18 Aug 2022

Cited by 11 | Viewed by 2965

Abstract

In order to decarbonize the rail industry, the development of innovative locomotives with the ability to use multiple energy sources, constituting hybrid powertrains, plays a central role in transitioning from conventional diesel trains. In this paper, four configurations based on suitable combinations of [...] Read more.

In order to decarbonize the rail industry, the development of innovative locomotives with the ability to use multiple energy sources, constituting hybrid powertrains, plays a central role in transitioning from conventional diesel trains. In this paper, four configurations based on suitable combinations of fuel cells and/or batteries are designed to replace or supplement a diesel/overhead line powertrain on a real passenger train (the Hitachi Blues) tested on an existing regional track, the Catanzaro Lido–Reggio Calabria line (Italy), managed by Trenitalia SpA. (Italy). The configurations (namely battery–electrified line, full-battery, fuel cell–battery–electrified line, and fuel cell–battery) are first sized with the intention of completing a round trip, then integrated on board with diesel engine replacement in mind, and finally occupy a portion of the passenger area within two locomotives. The achieved performance is thoroughly examined in terms of fuel cell efficiency (greater than 47%), hydrogen consumption (less than 72 kg), braking energy recovery (approximately 300 kWh), and battery interval SOC. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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23 pages, 4328 KiB

Open AccessArticle

Real-Time Estimation of PEMFC Parameters Using a Continuous-Discrete Extended Kalman Filter Derived from a Pseudo Two-Dimensional Model

by Yasser Diab, Francois Auger, Emmanuel Schaeffer, Stéphane Chevalier and Adib Allahham

Energies 2022, 15(7), 2337; https://doi.org/10.3390/en15072337 - 23 Mar 2022

Cited by 8 | Viewed by 2380

Abstract

Proton Exchange Membrane Fuel Cells (PEMFCs) are clean energy conversion devices that are widely used in various energy applications. In most applications, the main challenge is accurately estimating the state of health (SoH) of the PEMFCs during dynamic operating conditions. Moreover, their behavior [...] Read more.

Proton Exchange Membrane Fuel Cells (PEMFCs) are clean energy conversion devices that are widely used in various energy applications. In most applications, the main challenge is accurately estimating the state of health (SoH) of the PEMFCs during dynamic operating conditions. Moreover, their behavior is affected by numerous physical phenomena such as heat and membrane flooding. This paper proposes the design of an observer to estimate the PEMFC parameters. A state-space model is first built from 2D physical equations solved by a finite difference in a discretized space domain. The discretized dynamic model is then used to design an observer based on the continuous-discrete extended Kalman filter. The observer has been validated experimentally and is used to estimate the parameters of a PEMFC under dynamic operating conditions. For several load variations, the results obtained using the proposed observer accurately characterize the dynamic responses of PEMFC in real-time. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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13 pages, 2628 KiB

Open AccessArticle

Optimization of a Membraneless Microfluidic Fuel Cell with a Double-Bridge Flow Channel

by Ji-Hyun Oh, Tien-Dung Vuong and Kwang-Yong Kim

Energies 2022, 15(3), 973; https://doi.org/10.3390/en15030973 - 28 Jan 2022

Cited by 4 | Viewed by 2382

Abstract

In this work, a design optimization study was conducted to improve the performance of a membraneless microfluidic fuel cell with a double-bridge cross-section of the flow channel. Governing equations including Navier–Stokes, mass-transport, and Butler–Volmer equations were solved numerically to analyze the electrochemical phenomena [...] Read more.

In this work, a design optimization study was conducted to improve the performance of a membraneless microfluidic fuel cell with a double-bridge cross-section of the flow channel. Governing equations including Navier–Stokes, mass-transport, and Butler–Volmer equations were solved numerically to analyze the electrochemical phenomena and evaluate the performance of the fuel cells. Optimization was performed to maximize the peak power density using a genetic algorithm combined with a surrogate model constructed by radial basis neural network. Two sub-channel widths of the flow channel were selected as design variables for the optimization. As a result, a large increase in the inner channel width and a small decrease in the outer channel width effectively increased the peak power density of the MMFC. The optimal design increased the peak power density by 57.6% compared to the reference design. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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18 pages, 5158 KiB

Open AccessArticle

PEFC System Reactant Gas Supply Management and Anode Purging Strategy: An Experimental Approach

by Naseruddin Khan, Yousif Al-Sagheer and Robert Steinberger-Wilckens

Energies 2022, 15(1), 288; https://doi.org/10.3390/en15010288 - 1 Jan 2022

Viewed by 2327

Abstract

In this report, a 5 kW PEFC system running on dry hydrogen with an appropriately sized Balance of Plant (BoP) was used to conduct experimental studies and analyses of gas supply subsystems. The improper rating and use of BoP components has been found [...] Read more.

In this report, a 5 kW PEFC system running on dry hydrogen with an appropriately sized Balance of Plant (BoP) was used to conduct experimental studies and analyses of gas supply subsystems. The improper rating and use of BoP components has been found to increase parasitic loads, which consequently has a direct effect on the polymer electrolyte fuel cell (PEFC) system efficiency. Therefore, the minimisation of parasitic loads while maintaining desired performance is crucial. Nevertheless, little has been found in the literature regarding experimental work on large stacks and BoP, with the majority of papers concentrating on modelling. A particular interest of our study was the anode side of the fuel cell. Additionally the rationale behind the use of hydrogen anode recirculation was scrutinised, and a novel anode purging strategy was developed and implemented. Through experimental modelling, the use of cathode air blower was minimised since it was found to be the biggest contributor to the parasitic loads. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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20 pages, 3590 KiB

Open AccessArticle

Dynamic Simulation and Thermoeconomic Analysis of a Hybrid Renewable System Based on PV and Fuel Cell Coupled with Hydrogen Storage

by Francesco Calise, Francesco Liberato Cappiello, Luca Cimmino, Massimo Dentice d’Accadia and Maria Vicidomini

Energies 2021, 14(22), 7657; https://doi.org/10.3390/en14227657 - 16 Nov 2021

Cited by 15 | Viewed by 2708

Abstract

The production of “green hydrogen” is currently one of the hottest topics in the field of renewable energy systems research. Hydrogen storage is also becoming more and more attractive as a flexible solution to mitigate the power fluctuations of solar energy systems. The [...] Read more.

The production of “green hydrogen” is currently one of the hottest topics in the field of renewable energy systems research. Hydrogen storage is also becoming more and more attractive as a flexible solution to mitigate the power fluctuations of solar energy systems. The most promising technology for electricity-to-hydrogen conversion, and vice versa, is the reversible solid-oxide cell (SOC). This device is still very expensive, but it exhibits excellent performance under dynamic operating conditions compared to the competing devices. This work presents the dynamic simulation of a prototypal renewable plant combining a 50 kW photovoltaic (PV) field with a 50 kW solid-oxide electrolyzer cell (SOEC) and a compressed hydrogen tank. The electricity is used to meet the energy demand of a dwelling located in the area of Campi Flegrei (Naples). The SOC efficiency is simulated by developing a mathematical model in MATLAB^®. The model also calculates the cell operating temperature as a function of the input current. Once the optimal values of the operating parameters of the SOC are calculated, the model is integrated in the transient system simulation tool (TRNSYS) for dynamic analysis. Furthermore, this work presents a parametric analysis of the hydrogen storage system (HSS). The results of the energy and environmental analyses show that the proposed system can reach a primary energy saving by 70% and an amount of saved CO₂ of 28 tons/year. Some possible future market scenarios are considered for the economic analysis. In the most realistic case, the optimal configuration shows a simple pay back lower than 10 years and a profit index of 46%. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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16 pages, 3727 KiB

Open AccessArticle

Modeling and Sizing of a Fuel Cell—Lithium-Ion Battery Direct Hybridization System for Aeronautical Application

by Thomas Jarry, Fabien Lacressonnière, Amine Jaafar, Christophe Turpin and Marion Scohy

Energies 2021, 14(22), 7655; https://doi.org/10.3390/en14227655 - 16 Nov 2021

Cited by 9 | Viewed by 2562

Abstract

Nowadays, many aircraft manufacturers are working on new airplanes to reduce the environmental footprint and therefore meet greenhouse gas reduction targets. The concept of more electric aircraft is one of the solutions to achieve this goal. For this aircraft architecture, several electrical devices [...] Read more.

Nowadays, many aircraft manufacturers are working on new airplanes to reduce the environmental footprint and therefore meet greenhouse gas reduction targets. The concept of more electric aircraft is one of the solutions to achieve this goal. For this aircraft architecture, several electrical devices are used in order to supply propulsive and non-propulsive functions. This paper focuses on the sizing of a direct hybridization system to supply a non-propulsive function in an aircraft. It is composed of a High-Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC) and a lithium-ion (Li-ion) battery. This sizing is based on a static model of each storage device. The accuracy of these models is compared with dynamic models during a simulation for an aeronautical mission. Static models are implemented in a genetic algorithm to achieve two goals: on the one hand, satisfy the mission profile, and on the other hand, minimize the mass of the system. Other criteria, such as battery and fuel cell aging estimation, are considered. The obtained results show that the direct hybridization system allows protecting the fuel cell against an accelerated aging. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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28 pages, 5263 KiB

Open AccessFeature PaperArticle

A Compact, Self-Sustaining Fuel Cell Auxiliary Power Unit Operated on Diesel Fuel

by Remzi Can Samsun, Matthias Prawitz, Andreas Tschauder, Stefan Weiske, Joachim Pasel and Ralf Peters

Energies 2021, 14(18), 5909; https://doi.org/10.3390/en14185909 - 17 Sep 2021

Cited by 5 | Viewed by 3488

Abstract

A complete fuel cell-based auxiliary power unit in the 7.5 kW_e power class utilizing diesel fuel was developed in accordance with the power density and start-up targets defined by the U.S. Department of Energy. The system includes a highly-integrated fuel processor with [...] Read more.

A complete fuel cell-based auxiliary power unit in the 7.5 kW_e power class utilizing diesel fuel was developed in accordance with the power density and start-up targets defined by the U.S. Department of Energy. The system includes a highly-integrated fuel processor with multifunctional reactors to facilitate autothermal reforming, the water-gas shift reaction, and catalytic combustion. It was designed with the help of process analyses, on the basis of which two commercial, high-temperature PEFC stacks and balance of plant components were selected. The complete system was packaged, which resulted in a volume of 187.5 l. After achieving a stable and reproducible stack performance based on a modified break-in procedure, a maximum power of 3.3 kW_e was demonstrated in a single stack. Despite the strong deviation from design points resulting from a malfunctioning stack, all system functions could be validated. By scaling-up the performance of the functioning stack to the level of two stacks, a power density of 35 W_e l⁻¹ could be estimated, which is close to the 40 W_e l⁻¹ target. Furthermore, the start-up time could be reduced to less than 22 min, which exceeds the 30 min target. These results may bring diesel-based fuel cell auxiliary power units a step closer to use in real applications, which is supported by the demonstrated indicators. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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21 pages, 892 KiB

Open AccessArticle

Optimization Algorithms: Optimal Parameters Computation for Modeling the Polarization Curves of a PEFC Considering the Effect of the Relative Humidity

by Ángel Encalada-Dávila, Samir Echeverría, Jordy Santana-Villamar, Gabriel Cedeño and Mayken Espinoza-Andaluz

Energies 2021, 14(18), 5631; https://doi.org/10.3390/en14185631 - 7 Sep 2021

Cited by 2 | Viewed by 2728

Abstract

The development of green energy conversion devices has been promising to face climate change and global warming challenges over the last few years. Energy applications require a confident performance prediction, especially in polymer electrolyte fuel cell (PEFC), to guarantee optimal operation. Several researchers [...] Read more.

The development of green energy conversion devices has been promising to face climate change and global warming challenges over the last few years. Energy applications require a confident performance prediction, especially in polymer electrolyte fuel cell (PEFC), to guarantee optimal operation. Several researchers have employed optimization algorithms (OAs) to identify operating parameters to improve the PEFC performance. In the current study, several nature-based OAs have been performed to compute the optimal parameters used to describe the polarization curves in a PEFC. Different relative humidity (RH) values, one of the most influential variables on PEFC performance, have been considered. To develop this study, experimental data have been collected from a lab-scale fuel cell test system establishing different RH percentages, from 18 to 100%. OAs like neural network algorithm (NNA), improved grey-wolf optimizer (I-GWO), ant lion optimizer (ALO), bird swarm algorithm (BSA), and multi-verse optimization (MVO) were evaluated and compared using statistical parameters as training error and time. Results gave enough information to conclude that NNA had better performance and showed better results over other highlighted OAs. Finally, it was found that sparsity and noise are more present at lower relative humidity values. At low RH, a PEFC operates under critical conditions, affecting the fitting on OAs. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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21 pages, 5468 KiB

Open AccessArticle

Mass Transport Limitations of Water Evaporation in Polymer Electrolyte Fuel Cell Gas Diffusion Layers

by Adrian Mularczyk, Andreas Michalski, Michael Striednig, Robert Herrendörfer, Thomas J. Schmidt, Felix N. Büchi and Jens Eller

Energies 2021, 14(10), 2967; https://doi.org/10.3390/en14102967 - 20 May 2021

Cited by 9 | Viewed by 3273

Abstract

Facilitating the proper handling of water is one of the main challenges to overcome when trying to improve fuel cell performance. Specifically, enhanced removal of liquid water from the porous gas diffusion layers (GDLs) holds a lot of potential, but has proven to [...] Read more.

Facilitating the proper handling of water is one of the main challenges to overcome when trying to improve fuel cell performance. Specifically, enhanced removal of liquid water from the porous gas diffusion layers (GDLs) holds a lot of potential, but has proven to be non-trivial. A main contributor to this removal process is the gaseous transport of water following evaporation inside the GDL or catalyst layer domain. Vapor transport is desired over liquid removal, as the liquid water takes up pore space otherwise available for reactant gas supply to the catalytically active sites and opens up the possibility to remove the waste heat of the cell by evaporative cooling concepts. To better understand evaporative water removal from fuel cells and facilitate the evaporative cooling concept developed at the Paul Scherrer Institute, the effect of gas speed (0.5–10 m/s), temperature (30–60 °C), and evaporation domain (0.8–10 mm) on the evaporation rate of water from a GDL (TGP-H-120, 10 wt% PTFE) has been investigated using an ex situ approach, combined with X-ray tomographic microscopy. An along-the-channel model showed good agreement with the measured values and was used to extrapolate the differential approach to larger domains and to investigate parameter variations that were not covered experimentally. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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27 pages, 9639 KiB

Open AccessArticle

Development of a Flexible Framework Multi-Design Optimization Scheme for a Hand Launched Fuel Cell-Powered UAV

by Zaid O. Alrayes and Mohamed Gadalla

Energies 2021, 14(10), 2951; https://doi.org/10.3390/en14102951 - 20 May 2021

Cited by 3 | Viewed by 2477

Abstract

This paper presents different methods for the design of a hand-launchable, fixed wing, fuel cell-powered unmanned aerial vehicle (UAV) to maximize flight endurance during steady level flight missions. The proposed design methods include the development of physical models for different propulsion system components. [...] Read more.

This paper presents different methods for the design of a hand-launchable, fixed wing, fuel cell-powered unmanned aerial vehicle (UAV) to maximize flight endurance during steady level flight missions. The proposed design methods include the development of physical models for different propulsion system components. The performance characteristics of the aircraft are modeled through empirical contributing analyses in which each analysis corresponds to an aircraft subsystem. The contributing analyses are collected to form a design structure matrix which is included into a multi-disciplinary analysis to solve for the design variables over a defined design space. The optimal solution is found using a comprehensive optimization tool developed for long endurance flight missions. Optimization results showed a significant improvement in UAV flight endurance that reached up to 475 min with take-off ratio equals to 59 min/kg. Wind tunnel and bench-top tests and HiL simulation tests are performed to validate the results obtained from the optimization tools. Validated optimization results showed an increase of the overall UAV flight endurance by 19.4% compared to classical approaches in design methods. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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19 pages, 9096 KiB

Open AccessArticle

Cooling Design for PEM Fuel-Cell Stacks Employing Air and Metal Foam: Simulation and Experiment

by Ali A. Hmad and Nihad Dukhan

Energies 2021, 14(9), 2687; https://doi.org/10.3390/en14092687 - 7 May 2021

Cited by 9 | Viewed by 3350

Abstract

A new study investigating the cooling efficacy of air flow inside open-cell metal foam embedded in aluminum models of fuel-cell stacks is described. A model based on a commercial stack was simulated and tested experimentally. This stack has three proton exchange membrane (PEM) [...] Read more.

A new study investigating the cooling efficacy of air flow inside open-cell metal foam embedded in aluminum models of fuel-cell stacks is described. A model based on a commercial stack was simulated and tested experimentally. This stack has three proton exchange membrane (PEM) fuel cells, each having an active area of 100 cm², with a total output power of 500 W. The state-of-the-art cooling of this stack employs water in serpentine flow channels. The new design of the current investigation replaces these channels with metal foam and replaces the actual fuel cells with aluminum plates. The constant heat flux on these plates is equivalent to the maximum heat dissipation of the stack. Forced air is employed as the coolant. The aluminum foam used had an open-pore size of 0.65 mm and an after-compression porosity of 60%. Local temperatures in the stack and pumping power were calculated for various air-flow velocities in the range of 0.2–1.5 m/s by numerical simulation and were determined by experiments. This range of air speed corresponds to the Reynolds number based on the hydraulic diameter in the range of 87.6–700.4. Internal and external cells of the stack were investigated. In the simulations, and the thermal energy equations were solved invoking the local thermal non-equilibrium model—a more realistic treatment for airflow in a metal foam. Good agreement between the simulation and experiment was obtained for the local temperatures. As for the pumping power predicted by simulation and obtained experimentally, there was an average difference of about 18.3%. This difference has been attributed to the poor correlation used by the CFD package (ANSYS) for pressure drop in a metal foam. This study points to the viability of employing metal foam for cooling of fuel-cell systems. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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23 pages, 7665 KiB

Open AccessArticle

Enhancing the Specific Power of a PEM Fuel Cell Powered UAV with a Novel Bean-Shaped Flow Field

by Somayeh Toghyani, Seyed Ali Atyabi and Xin Gao

Energies 2021, 14(9), 2494; https://doi.org/10.3390/en14092494 - 27 Apr 2021

Cited by 16 | Viewed by 3700

Abstract

One of the marketing challenges of unmanned aerial vehicles (UAVs) for various applications is enhancing flight durability. Due to the superior characteristics of proton exchange membrane fuel cells (PEMFCs), they have the potential to reach a longer flight time and higher payload. In [...] Read more.

One of the marketing challenges of unmanned aerial vehicles (UAVs) for various applications is enhancing flight durability. Due to the superior characteristics of proton exchange membrane fuel cells (PEMFCs), they have the potential to reach a longer flight time and higher payload. In this regard, a numerical assessment of a UAV air-cooled PEMFC is carried out using a three-dimensional (3-D), multiphase, and non-isothermal model on three flow fields, i.e., unblocked bean-shaped, blocked bean-shaped, and parallel. Then, the results of single-cell modeling are generalized to the PEMFC stack to provide the power of 2.5 kW for a UAV. The obtained results indicate that the strategy of rising air stoichiometry for cooling performs well in the unblocked bean-shaped design, and the maximum temperature along the channel length reaches 331.5 K at the air stoichiometric of 30. Further, it is found that the best performance of a 2.5 kW PEMFC stack is attained by the bean-shaped design without blockage, of which its volume and mass power density are 1.1 kW L⁻¹ and 0.2 kW kg⁻¹, respectively. It is 9.4% lighter and 6.9% more compact than the parallel flow field. Therefore, the unblocked bean-shaped design can be a good option for aerial applications. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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17 pages, 4527 KiB

Open AccessArticle

Resistance Separation of Polymer Electrolyte Membrane Fuel Cell by Polarization Curve and Electrochemical Impedance Spectroscopy

by Jaehyeon Choi, Jaebong Sim, Hwanyeong Oh and Kyoungdoug Min

Energies 2021, 14(5), 1491; https://doi.org/10.3390/en14051491 - 9 Mar 2021

Cited by 18 | Viewed by 3978

Abstract

The separation of resistances during their measurement is important because it helps to identify contributors in polymer electrolyte membrane (PEM) fuel cell performance. The major methodologies for separating the resistances are electrochemical impedance spectroscopy (EIS) and polarization curves. In addition, an equivalent circuit [...] Read more.

The separation of resistances during their measurement is important because it helps to identify contributors in polymer electrolyte membrane (PEM) fuel cell performance. The major methodologies for separating the resistances are electrochemical impedance spectroscopy (EIS) and polarization curves. In addition, an equivalent circuit was selected for EIS analysis. Although the equivalent circuit of PEM fuel cells has been extensively studied, less attention has been paid to the separation of resistances, including protonic resistance in the cathode catalyst layer (CCL). In this study, polarization curve and EIS analyses were conducted to separate resistances considering the charge transfer resistance, mass transport resistance, high frequency resistance, and protonic resistance in the CCL. A general solution was mathematically derived using the recursion formula. Consequently, resistances were separated and analyzed with respect to variations in relative humidity in the entire current density region. In the case of ohmic resistance, high frequency resistance was almost constant in the main operating load range (0.038–0.050 Ω cm²), while protonic resistance in the CCL exhibited sensitivity (0.025–0.082 Ω cm²) owing to oxygen diffusion and water content. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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16 pages, 4346 KiB

Open AccessArticle

Study of Long-Term Stability of Ni-Zr_0.92Y_0.08O_2-δ|Zr_0.92Y_0.08O_2-δ|Ce_0.9Gd_0.1O_2-δ |Pr_0.6Sr_0.4CoO_3-δ at SOFC and SOEC Mode

by Freddy Kukk, Priit Möller, Rait Kanarbik and Gunnar Nurk

Energies 2021, 14(4), 824; https://doi.org/10.3390/en14040824 - 4 Feb 2021

Cited by 13 | Viewed by 3642

Abstract

Long term stability is one of the decisive properties of solid oxide fuel cell (SOFC) as well as solid oxide electrolysis cell (SOEC) materials from the commercialization perspective. To improve the understanding about degradation mechanisms solid oxide cells with different electrode compositions should [...] Read more.

Long term stability is one of the decisive properties of solid oxide fuel cell (SOFC) as well as solid oxide electrolysis cell (SOEC) materials from the commercialization perspective. To improve the understanding about degradation mechanisms solid oxide cells with different electrode compositions should be studied. In this work, Ni-Zr_0.92Y_0.08O_2-δ (Ni-YSZ)| Zr_0.92Y_0.08O_2-δ (YSZ)|Ce_0.9Gd_0.1O_2-δ (GDC)|Pr_0.6Sr_0.4CoO_3-δ (PSC) cells are tested in the SOFC regime for 17,820 h at 650 °C, and in the SOEC regime for 860 h at 800 °C. The SOFC experiment showed a degradation speed of 2.4% per 1000 h at first but decreased to 1.1% per 1000 h later. The electrolysis test was performed for 860 h at 800 °C. The degradation speed was 16.3% per 1000 h. In the end of the stability tests, an electrode activity mapping was carried out using a novel ¹⁸O tracing approach. Average Ni grain sizes were measured and correlated with the results of the oxygen isotope maps. Results indicate that Ni coarsening is dependent on solid oxide cell activity. Strontium, chromium and silicon concentrations were also analyzed using the ToF-SIMS method and compared to the electrode activity map, but significant correlation was not observed. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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Review

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24 pages, 6067 KiB

Open AccessReview

Recent Research Progress in Hybrid Photovoltaic–Regenerative Hydrogen Fuel Cell Microgrid Systems

by Alexandros Arsalis, George E. Georghiou and Panos Papanastasiou

Energies 2022, 15(10), 3512; https://doi.org/10.3390/en15103512 - 11 May 2022

Cited by 21 | Viewed by 4134

Abstract

Hybrid photovoltaic–regenerative hydrogen fuel cell (PV-RHFC) microgrid systems are considered to have a high future potential in the effort to increase the renewable energy share in the form of solar PV technology with hydrogen generation, storage, and reutilization. The current study provides a [...] Read more.

Hybrid photovoltaic–regenerative hydrogen fuel cell (PV-RHFC) microgrid systems are considered to have a high future potential in the effort to increase the renewable energy share in the form of solar PV technology with hydrogen generation, storage, and reutilization. The current study provides a comprehensive review of the recent research progress of hybrid PV-RHFC microgrid systems to extract conclusions on their characteristics and future prospects. The different components that can be integrated (PV modules, electrolyzer and fuel cell stacks, energy storage units, power electronics, and controllers) are analyzed in terms of available technology options. The main modeling and optimization methods, and control strategies are discussed. Additionally, various application options are provided, which differentiate in terms of scale, purpose, and further integration with other power generating and energy storage technologies. Finally, critical analysis and discussion of hybrid PV-RHFC microgrid systems were conducted based on their current status. Overall, the commercialization of hybrid PV-RHFC microgrid systems requires a significant drop in the RHFC subsystem capital cost. In addition, it will be necessary to produce complete hybrid PV-RHFC microgrid systems with integrated energy management control capabilities to avoid operational issues and ensure flexibility and reliability of the energy flow in relation to supply, storage, and demand. Full article

(This article belongs to the Special Issue Design, Modeling, and Optimization of Novel Fuel Cell Systems)

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