Solid Oxide Fuel Cell System Research Articles

Digital twin model and dynamic operation for a plant-scale solid oxide fuel cell system

Large-scale solid oxide fuel cell (SOFC) systems create operational challenges owing to their size and scale. An SOFC dynamic digital twin model can help users understand the system status and determine the operating action. In this study, a dynamic digital twin of a 25 kW SOFC plant was presented as a simulator to help operators safely and stably determine the operating conditions for a real commercial SOFC plant. In the scale-up process, the data from the 1 kW SOFC pilot plant were used to analyze the reliability and electrode parameters and develop a digital twin model that matches actual conditions at the plant. The scale-up digital twin model is applied to a 25 kW SOFC system, in which the SOFC is connected with upstream reformers, downstream burners, and multiple heat exchangers. The 25 kW SOFC digital twin model was validated by steady-state data and applied to on-site operation prediction with very high accuracy. The digital twin was used as an operating reference in the field, and the results showed that it could effectively help operators determine operation strategies using simulations to safely and stably execute the process.

Exergy Analysis of a Novel Chemical Looping Hydrogen Generation System Integrated with SOFC

In this paper, a novel system integrating chemical-looping hydrogen generation (CLH) system and solid oxide fuel cell (SOFC) has been proposed. This new methane-fuelled energy system was investigated with energy balance and exergy analysis. CLH produces the hydrogen as the fuel of the SOFC, and the FeO and Fe3O4 are selected as the looping material. Waste heat from the SOFC is absorbed by the CLH and converted to chemical energy through the reduction reaction of CLH. Owing to the cascade utilization of the fuel between the CLH and SOFC, the net efficiency of this novel system can achieve 62.8% considering CO2 separation, more than 10 percentage points higher than a methane reforming fuelled SOFC system. Meanwhile, by using the CLH to produce the hydrogen, the CO2 can be recovered without an energy penalty. Through the analysis of the graphical exergy, the cascade utilization of waste heat and the high-efficiency hydrogen production is the main reason of high performance. This novel system also has the advantage of CO2 capture without energy penalty, so this combined system is an advantaged method to accomplish the efficient utilization of methane.

Overcoming the energy and environmental issues of LNG plants by using solid oxide fuel cells

A new intensification concept was proposed for the liquefied natural gas (LNG) plants. Our concept capitalizes on solid oxide fuel cells (SOFCs) and efficient pressure/heat recovery. Detailed processes were synthesized, simulated and optimized (with and without carbon capture) to demonstrate our concept. These configurations were derived from a superstructure using a new conceptual methodology. Unlike many of the published SOFC systems, our concept and processes are specific to the LNG sector. Another unique aspect of this work is our comprehensive simulation and optimization analyses. We rigorously considered the entire LNG plant to derive tangible conclusions and fill the existing gaps in the literature concerning fuel balance, LNG/helium specification, to name a few. The optimization was challenging due to the high degree of interactions between the units and the enormous numbers of variables, amongst other factors. Therefore, we developed a different optimization strategy that is of a holistic nature, capable of simplifying the analysis and is suitable for other systems. Relative to a base case, our optimum configuration was capable of boosting production by over 4%, with 25% less emissions. As for the processes that capture carbon dioxide, the LNG output could be increased by 2.5%, with over 65% reduced emissions.

Reliability analysis for a multi-stack solid oxide fuel cell system subject to operation condition-dependent degradation

PurposeA reliability analysis of a solid oxide fuel cell (SOFC) system is presented for applications with strict constant power supply requirements, such as data centers. The purpose is to demonstrate the effect when moving from a module-level to a system-level in terms of reliability, also considering effects during start-up and degradation.Design/methodology/approachIn-house experimental data on a system-level are used to capture the behavior during start-up and normal operation, including drifts of the operation point due to degradation. The system is assumed to allow replacement of stacks during operation, but a minimum number of stacks in operation is needed to avoid complete shutdown. Experimental data are used in conjunction with a physics-based performance model to construct the failure probability function. A dynamic program then solves the optimization problem in terms of time and replacement requirements to minimize the total negative deviation from a given target reliability.FindingsResults show that multi-stack SOFC systems face challenges which are only revealed on a system- and not on a module-level. The main finding is that the reliability of multi-stack SOFC systems is not sufficient to serve as sole power source for critical applications such as data center.Practical implicationsThe principal methodology may be applicable to other modular systems which include multiple critical components (of the same kind). These systems comprise other electrochemical systems such as further fuel cell types.Originality/valueThe novelty of this work is the combination of mathematical modeling to solve a real-world problem, rather than assuming idealized input which lead to more benign system conditions. Furthermore, the necessity to use a mathematical model, which captures sufficient physics of the SOFC system as well as stochasticity elements of its environment, is of critical importance. Some simplifications are, however, necessary because the use of a detailed model directly in the dynamic program would have led to a combinatorial explosion of the numerical solution space.

Operation of a Solid Oxide Fuel Cell Based Power System with Ammonia as a Fuel: Experimental Test and System Design

Ammonia has strong potentialities as sustainable fuel for energy applications. NH3 is carbon free and can be synthetized from renewable energy sources (RES). In Solid Oxide Fuel Cells, NH3 reacts electrochemically thereby avoiding the production of typical combustion pollutants such as NOx. In this study, an ammonia-fueled solid oxide fuel cells (SOFC) system design is proposed and a thermodynamic model is developed to evaluate its performance. A SOFC short stack was operated with NH3 in a wide range of conditions. Experimental results are implemented in the thermodynamic model. Electrical efficiency of 52.1% based on ammonia Lower Heating Value is calculated at a net power density of 0.36 W cmFC−2. The operating conditions of the after burner and of the ammonia decomposition reactor are studied by varying the values of specific parameters. The levelized cost of energy of 0.221 $ kWh−1 was evaluated, as introduced by the International Energy Agency, for a system that operates at nominal conditions and at a reference power output of 100 kW. This supports the feasibility of ammonia-fueled SOFC systems with reference to the carbon free energy market, specifically considering the potential development of green ammonia production.

Electrical Resistance of Co-W Alloy Coated Ferritic Stainless Steels As Interconnector Parts of Solid Oxide Fuel Cells

Introduction Over the last decade, several attempts have been made to improve a solid oxide fuel cell (SOFC) system which is one of the most promising alternative power sources due to its high efficiency and low emission. The SOFC system consists of several parts, such as electrolytes, anodes, cathodes, and interconnectors. Recently, the operation temperature of the SOFC system has been reduced to 800 °C, which makes it possible to apply ferritic stainless steels (FSSs) for the interconnector parts. However, the formation of Cr containing oxide layers over time would jeopardize the electrical conductivity of FSS interconnectors. Furthermore, the evaporation of Cr from FSS would react with neighboring components, resulting in their degradation of catalytic activity and electrical conductivity.To overcome these issues, the authors have proposed Co-W alloy electroplating on FSSs. By heat exposure in air, the Co-W coated FSS forms multilayered oxides and among them, a CoWO4 layer effectively suppresses the outward diffusion of Cr cations at high temperatures. However, our former work of the Co-W coated FSSs was conducted under the condition that the coated specimens were separated with other materials, thus for the practical application as interconnector parts, further investigation is required under the simulated condition as a practical SOFC system.In this study, several cathodic half cells were built using the Co-W coated FSSs as interconnector parts and perovskites-type conductive oxides, and the operation condition was simulated by the electricity from a constant current power source. For the cathode materials, La0.8Sr0.2MnO2.97 (LSM) and La0.8Sr0.2Co0.8Fe0.2O2.97 (LSCF) were selected due to their high electrical conductivity and high reaction activity. The results of their electrical performance and microstructural changes of the half cells are discussed. Results and discussions The cross-sections of uncoated and Co-W coated LSM specimens after 500 h exposure in air at 800 °C are shown in the following image. The formation of a CoWO4 oxide layer brought a significant influence on the Cr outward diffusion.In the uncoated samples, Cr diffuses into both LSM and LSCF specimens to form Cr containing particulate oxides such as SrCrO4 or MnCr2O4, showing the Cr-poisoning. Further, the Cr oxide layer was not continuous in the uncoated samples due to Cr evaporation. Thus, internal oxidation in the grain boundaries are observed by the BSE image.On the other hand, the Co-W coated samples exhibited in a completely different manner. Similar to our previous study, after oxidation, the five-layered structure was formed beneath the LSM and LSCF coatings. In the five layered oxides, Cr is enriched just beneath the Co-W oxide layer to form a continuous and dense Cr oxide layer. Thus, the further oxidation of the substrate is suppressed by the presence of the CoWO4 layer, due to its role as an outward diffusion blocker of Cr which accordingly protects cathodic materials against Cr poisoning. In addition, the ASR measurement proved that the addition of W in the Co coating does not significantly increase the electrical resistance of the cathodic system compared with those of other Co based coatings.It should also be noted that the LSM particles showed an intrusion effect into the oxide layer formed on the metallic surface. Co oxide reacts with Mn oxide in the LSM cathode layer to form a Co-Mn spinel which can improve the adherence between the cathode and the protective layer. This intrusion effect can also reduce the contact resistance and improve the electrical property. And this kind of Mn-Co spinels are typically used in the SOFC interconnects for their good CTE mismatch with the substrate stainless steel and high electric conductivity. Conclusions For the evaluation of Co-W alloy electroplated ferritic stainless steels, cathodic half cells were fabricated simulating the SOFC system, and the following conclusions are drawn. The CoWO4 layer effectively suppressed the outward diffusion of Cr and protected cathode materials against Cr poisoning.The ASR value by the Co-W coated specimens were almost comparative to those in Co-based alloy coatings, confirming that W addition did not significantly increase the ASR values.LSM particles showed an intrusion effect into the oxide layer formed on the metallic surface. Co oxide reacts with Mn oxide in the LSM cathode layer to form a Co-Mn spinel which can improve the adherence between the cathode and the protective layer. Figure 1

Detecting Solid Oxide Fuel Cell Stack Failure from Impedance Spectroscopy Using Machine Learning

Solid oxide fuel cells (SOFC) offer great potential for efficient use of renewably-generated storage fuels. However, commercialization of SOFCs is currently limited by a lack of long-term durability. This work explores the potential of using electrochemical impedance spectroscopy (EIS) as in-situ diagnostic of SOFC stack and system health based on machine learning. A multi-physics 2D/3D-model of SOFC, operating with humidified hydrogen or natural gas fuel, is used to simulate impedance data at various nominal operating conditions. The model is also used to simulate impedance responses under different critical failure modes, such as uneven fuel distribution that leads to high local fuel utilization, electrode delamination or deactivation. Based on impedance simulations, classification models are synthesized to recognize patterns and distinguish different degradation mechanisms. Based on these models, we believe that impedance measurements can provide better indications of SOFCs system health compared to polarization curves.

A simple model for solid oxide fuel cells

It is widely accepted that solid oxide fuel cells (SOFCs) represent a promising energy conversion approach that deliver a myriad of benefits including low environment pollution, high efficiency, and system compactness. This paper describes the construction of a basic model based on ohmic considerations, mass transfer, and kinetics that can effectively evaluate the performance of small button SOFCs. The analysis of the data indicates that there is a close alignment between the cell potential calculated using the model and previous experimental data. As such, it can be concluded that the model can be employed to optimize, evaluate, or control the design parameters within a SOFC system.

Multiobjective Optimal Controlled Variable Selection for a Gas Turbine–Solid Oxide Fuel Cell System Using a Multiagent Optimization Platform

Hybrid gas turbine–fuel cell systems have immense potential for high efficiency in electrical power generation with cleaner emissions compared with fossil-fueled power generation. A systematic cont...

Membrane processes for CO2 removal and fuel utilization enhancement for solid oxide fuel cells

Incomplete oxidation on the anode side of a solid oxide fuel cell (SOFC) leaves a considerable amount of unused fuel (e.g., H2 and CO) in the anode exhaust. In order to enhance fuel utilization, CO2-selective membranes can be employed to remove the CO2 in the anode exhaust before returning the recovered fuel to the SOFC. In this study, two membrane processes have been designed for integration with a SOFC system, one with an air sweep (SOFC-MBair) and the other with a vacuum (SOFC-MBvac), on the permeate side. The transport properties of developed membranes were applied to the processes, and techno-economic analysis (TEA) was carried out to estimate the CO2 removal cost of each process. The parameters investigated were the anode exhaust recycle percentage, stack fuel utilization of the SOFC, power output, as well as the area and transport properties of the membranes. Notably, at 100% anode exhaust recycle, the system fuel utilization can be boosted to >99% for both processes. By tuning the stack fuel utilization, a steam-to-carbon ratio above 1.5 is achievable. It was found that the SOFC-MBvac process can achieve a lower CO2 removal cost than the SOFC-MBair process. For the SOFC-MBvac process, by considering the value of the recovered fuel, the CO2 removal cost not only can be fully rebated by the recovered fuel value, but also there is a profit of about $38 per tonne of CO2 captured. Moreover, by taking into account a CO2 sale price of $40/tonne for enhanced oil recovery, a profit of about $66 per tonne of CO2 captured may be achieved. Furthermore, more cost reduction or profit is attainable by developing membranes with higher CO2 permeances. In addition, a zero-carbon electricity generation can be achieved by the SOFC-MBvac process.

A critical review on global trends in biogas scenario with its up-gradation techniques for fuel cell and future perspectives

Renewable biogas production technology is an excellent method for eradication of greenhouse gas emission and thereby reducing global warming. This review discusses extensively on global biomass potential, energy need and method of satisfying the energy demand through sustainable techniques. One of the best alternative technological developments for the conversion of waste into useful energy is anaerobic digestion to produce biogas. It is recognized as one among leading green energy to manage the environmental and meet the current energy tasks to tackle globally. Generally, biogas can be utilized for cooking, heat and electricity generation. In order to extend the scope of application, traces of carbon dioxide, hydrogen sulphide has to be removed by several upgrading technologies to produce high purity methane (90%). This study discusses on biogas up-gradation using physical and chemical absorption, membrane separation, cryogenic separation, hybrid technology etc. Among the various up-gradation techniques, hybrid technology yields methane purity of 97%. In addition, this work reviews about benefits and problems in anaerobic integrated Solid Oxide Fuel Cell (SOFC) with latest real-world achievement in SOFC. Several SOFC systems with dynamic model development were reviewed based on efficiency of power generation. SOFC generates 45% more electricity than generator with heat engine. This review extends the scope for further research in biogas upgradation and global warming mitigation potential with carbon credits.

System simulation and exergetic analysis of solid oxide fuel cell power generation system with cascade configuration

A solid oxide fuel cell (SOFC) based power generation system with cascade configuration has been analyzed using the exergy-based analysis method. A cascade system has double SOFC stacks, where the unreacted fuel released from the primary SOFC stack is re-utilized in the secondary stack, generating additional power and maximizing fuel-use in the system. For comparison and evaluation, a simple SOFC system and an SOFC system with anode off-gas recirculation are also analyzed. In all the SOFC systems, efficiency increases with increasing fuel utilization. The simple and anode off-gas recirculation systems show 63.7% and 66.0% electrical efficiency at 85% and 90% fuel utilization, respectively. The cascade system shows 66.47% electrical efficiency at 90% fuel utilization, which is the highest electrical efficiency among the systems analyzed. Through the exergy analysis, the magnitude, location, and resources of the thermodynamic irreversibility within the SOFC systems are clearly identified, giving the quantified information why the cascade configuration has higher efficiency than the other configurations. The SOFC stack shows very high exergetic efficiency over 90%. In the cascade configuration, the released exergy from the primary SOFC stack can be exergetically-efficiently utilized in the secondary SOFC stack, contributing to a higher efficiency.

Electrochemical Modeling and Performance Assessment of H2S/Air Solid Oxide Fuel Cell

Hydrogen sulfide (H2S) is an abundantly present, corrosive, and noxious compound. Though the Claus process is effective in processing H2S, it extracts minimal energy from H2S. Solid oxide fuel cell (SOFC) can harvest the chemical energy of H2S to generate electric power. For practical implementations, the performance of H2S/air SOFCs and the potential losses in the system are determined. The present study aims to develop the complete electrochemical model of H2S/air SOFC system and to analyze its performance. The theoretical cell potential of H2S/air SOFC is determined, and the deviations from the theoretical cell potential due to polarization are studied. According to the results, H2S/air SOFC generates electric power with energetic, exergetic, and voltaic efficiencies of 59.0%, 43.0%, and 89.7%, respectively, at atmospheric pressure and a temperature of 1100 K. Further efficiencies can be achieved if the output heat is utilized for useful applications. Moreover, the SO2 formed by the electrochemical reactions in SOFC can be recovered as elemental sulfur or sulfuric acid as an additional useful commodity. In brief, this study demonstrates the performance of H2S/air SOFC to serve as a basis for the implementation of H2S/air SOFC toward eliminating the environmental impact of H2S and converting it into electric power.

Off-design performance analysis of a turbocharged solid oxide fuel cell system

The aim of this study is to analyse the off-design performance of an innovative turbocharged solid oxide fuel cell system, fed by biogas and designed to generate 30 kW during nominal operating conditions. The layout of such a plant combines the high efficiencies of the solid oxide fuel cell with a reduced-cost option for fuel cell pressurization: fuel cells are usually pressurized by a micro gas turbine, but the alternative use of a turbocharger, a mass-produced component widely used in the automotive field, could reduce significantly the capital cost of the system. This kind of layout has been rarely investigated in literature, and a detailed performance analysis of a turbocharged SOFC system would be a valuable source of information for both academia and industry. To perform this analysis, a steady-state model has been created using a modular tool developed in Matlab®-Simulink® that includes off-design models of the system components. The model has been used to compare different control strategies. The most suitable control strategy, based on wastegate and cold bypass valves, was adopted, obtaining compliance with the operative constraints and high system efficiency. Afterward, the system steady-state operation was simulated for various electric power loads and ambient temperatures. The performance analysis focused on the effect of these two variables on the system behaviour and has provided insight on the influence on the most significant system outputs, including global efficiency, temperatures and pressures. A system efficiency increase was observed at part load, with values growing from 50.8% to 57.3%. Higher values of ambient temperature resulted in a more significant pressurization of the fuel cell, affecting positively the system efficiency: from 50.5% at 0 °C to 51.0% at 30 °C. Great attention was paid to the system constraints, to verify that the plant could operate properly in all the considered conditions. The proposed control strategy was tested and proved to be effective at achieving this objective.

Dynamic and steady-state analysis of steam reforming of methane to hydrogen in a reformer for electric-powered unmanned aerial vehicle

Abstract Hydrogen-fueled combustion systems are becoming popular in recent years. Methane is one of the significant hydrogen supplier in nature. Thus, in the study, the natural gas-fueled reactor-assisted solid oxide fuel-cell system is configured to provide a current to load the battery to turn the propeller of an unmanned aerial vehicle in the large-scale hydrogen-onboard system. The methane-fueled reactor has not been studied under a large-scale case in literature yet. To investigate the amount of products, this paper presents about the steam-reforming performance of natural gas in steady state and transient in the reactor. The influence of vital parameters such as steam/carbon, gas feed temperatures, the amount of heat transferred to the reactor in methane steam reforming for a plug flow reactor, and a continuous stirred tank-type reactor is investigated respectively. Methane conversion, yield of hydrogen gas and H2 gas generation for different medium conditions along the reactor are studied on by using the COMSOL Multiphysics program. The steady-state and time-dependent characteristics of the steam reforming of natural gas are focused on. The high conversion ratio of methane gas is obtained by ranking the steam/carbon ratio. The released hydrogen gas molar flow rate is increasing according to the reactor volume. The achieved power provided by produced gas of H2 is 97 hp supplying the thrust force for an unmanned aerial vehicle.

Performance of a Natural Gas Solid Oxide Fuel Cell System With and Without Carbon Capture

Abstract The fuel cell program at the United States Department of Energy (DOE) National Energy Technology Laboratory (NETL) is focused on the development of low-cost, highly efficient, and reliable fossil-fuel-based solid oxide fuel cell (SOFC) power systems that can generate environmentally friendly electric power with at least 90% carbon capture. NETL’s SOFC technology development roadmap is aligned with near-term market opportunities in the distributed generation sector to validate and advance the technology while paving the way for utility-scale natural gas (NG)- and coal-derived synthesis gas-fueled applications via progressively larger system demonstrations. The present study represents a part of a series of system evaluations being carried out at NETL to aid in prioritizing technological advances along research pathways to the realization of utility-scale SOFC systems, a transformational goal of the fuel cell program. In particular, the system performance of utility-scale NG fuel cell (NGFC) systems with and without carbon dioxide (CO2) capture is presented. The NGFC system analyzed features an external auto-thermal reformer (ATR) feeding the fuel to the SOFC system consisting of planar anode-supported SOFC with separated anode and cathode off-gas streams. In systems with CO2 capture, an air separation unit (ASU) is used to provide the oxygen for the ATR and for the combustion of unutilized fuel in the SOFC anode exhaust along with a CO2 purification unit to provide a nearly pure CO2 stream suitable for transport for usage in enhanced oil recovery (EOR) operations or for storage in underground saline formations. Remaining thermal energy in the exhaust gases is recovered in a bottoming steam Rankine cycle while supplying any process heat requirements. A reduced order model (ROM) developed at the Pacific Northwest National Laboratory (PNNL) is used to predict the SOFC performance. The ROM, while being computationally effective for system studies, provides other detailed information about the state of the stack, such as the internal temperature gradient, generally not available from simple performance models often used to represent the SOFC. Such additional information can be important in system optimization studies to preclude operation under off-design conditions that can adversely impact overall system reliability. The NGFC system performance was analyzed by varying salient system parameters, including the percent of internal (to the SOFC module) NG reformation—ranging from 0 to 100%—fuel utilization, and current density. The impact of advances in underlying SOFC technology on electrical performance was also explored.

Thermo-environmental analysis of a novel cogeneration system based on solid oxide fuel cell (SOFC) and compressed air energy storage (CAES) coupled with turbocharger

In this work, a novel integrated system based on a combination of solid oxide fuel cell (SOFC) with compressed air energy storage (CAES) and turbocharger is presented for simultaneous production of domestic hot water and power in the scale of retail buildings for peak shaving applications. The SOFC subsystem is the primary power generation unit, which is coupled with CAES and other supporting auxiliary cycles. The energy, exergy, and emissions are quantified through parametric analysis for evaluating the overall system performance. The preliminary results for the scenario analyzed indicate a power generation of 272 kW during 4 h in off-peak period, as well as a power generation of 407 kW during 7 h in peak demand periods. The round trip energy and exergy efficiencies for the integrated system are 78% and 58%, respectively. Also, the overall emissions of the proposed integrated system is reduced by 0.06 kgCO2/kWh in comparison to the standalone SOFC system. The afterburner accounts for the main source of irreversibility and exergy destruction among all components. Overall, the integrated system is superior to the standalone SOFC system from energy, exergy and emissions perspectives.

Comparison of support vector regression and random forest algorithms for estimating the SOFC output voltage by considering hydrogen flow rates

Solid Oxide Fuel Cell (SOFC) are complex systems in which gas-phase mass transport, heat transfer, ionic conduction, chemical reactions and electrical conduction take place simultaneously. Therefore, reliable simulation tools are needed to control and optimize their operation. Machine Learning (ML) can quickly estimate and generalize the relationship between the input values and the output values in a process. ML algorithms are used in various applications such as modelling, simulation, optimization, control, signal processing, pattern recognition, up to systems like power, production and renewable energy systems. Many methods help the successful design of algorithms for SOFC systems. However, a few researchers have studied and compared regression algorithms.This paper includes an in-depth study to compare the two efficient ML algorithms – namely Random Forest (RF) and Support Vector Regression (SVR). These algorithms are used to predict the performance of a SOFC cell. The algorithms were generated by the experimental data which are measured by using the different temperatures and hydrogen flow rates. Additionally, the effect of the amount of pure hydrogen and the total amount of hydrogen in the content of the fuel mixtures, which fed to the anode side of the SOFC, on the experimental voltage were compared. The experimental data set used for developing the model consists of 1272 records regarding the SOFC operated under different operating conditions. 1122 records of the experimental data set are used for training the regression algorithms mentioned above. Accordingly, the algorithms are tested and then, the experimental data are compared to the results generated by the algorithms to validate prediction performances. The model predicts the cell performance (output voltage) in approximately 0.52 s with the mean absolute percentage errors 1.97% for the RF algorithm and as low as 0.92% for the SVR algorithm. In this article, the SVR algorithm is identified as the most promising model. The process parameters effects on the variation of the output voltage of the SOFC can be examined when the developed models are proven reliability and precision after test with unknown data.

System simulation and exergetic evaluation of hybrid propulsion system for crude oil tanker: A hybrid of solid-oxide fuel cell and gas engine

This study investigates a hybrid electrical propulsion system of gas engines and a solid-oxide fuel cell (SOFC), quantifying the CO2 emission and proposing a way to further reduce CO2 emissions. The indirect-coupling and direct-coupling configurations are proposed and analyzed from the perspectives of energy and exergy. In the indirect-coupling configuration, the engine and fuel cell system are only integrated electrically without the transfer of any heat or material stream. In the direct-coupling configuration, the unused remaining fuel, which is released from the fuel cell, is transported to the gas engine, and the unused surplus steam, which is produced from the engine exhaust, is provided with the reforming section of the fuel cell system. An Aframax-class crude oil tanker is selected as an application; detailed information of its operational mode is used to quantify the CO2 emission of crude oil delivery. Results reveal that the indirect-coupling hybrid system reduces CO2 emission by a maximum of 9% when a 5-MW SOFC system is integrated with 4.7-MW gas engines. For the direct-coupling configuration, a further reduction of 16% in CO2 emission is achieved. Results of the exergy analysis show that the gas engines and SOFC are the primary contributors to the exergy destruction, and contribute to thermodynamic inefficiencies. By implementing the direct-coupling configuration, the exergy destruction of the overall system can be reduced by 32% by utilizing the unused fuel and steam in a more effective way.

Transient simulation of failures during start‐up and power cut of a solid oxide fuel cell system using multiphysics modeling

Transient simulation of failures during start‐up and power cut of a solid oxide fuel cell system using multiphysics modeling