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The article presents a comparison of mathematical models of steam methane reforming. The analysis is divided into two parts. The first concerns the reforming process using separate steam reformers. The second part of the article compares models of steam methane reforming processes directly inside fuel cells. Due to the fact that the steam reforming process takes place at very high temperatures, internal steam reforming can only be carried out in high temperature fuel cells. Therefore, the second part of the article deals with molten carbonate fuel cells and solid oxide fuel cells powered by methane. In the case of both of fuel cells, the methane steam reforming may take place directly on the anodes of these electrochemical devices. The mathematical models (for both external and internal reforming) were compared based on available experimental data. In this analysis of mathematical models, particular attention was paid to the causes of discrepancies between the mathematical models and the experimental data. The steam reforming process is influenced by a number of different parameters such as: temperature, ratio of the amount of water vapor to carbon contained in the fuel (steam to carbon ratio), reaction time, presence of a catalyst, type of catalyst and many others. The models presented in this article were also compared in terms of taking into account various parameters that may affect the process of steam reforming. An attempt was also made to assess the accuracy of mathematical models. Unfortunately, for most of the equations considered in this article, numerical values for inaccuracies are not given or described as acceptable or minor. • Review of mathematical models of SMR. • The kinetics models of the steam methane reforming reaction. • Description of mathematical models for the molten carbonate fuel cell (MCFC). [ABSTRACT FROM AUTHOR]

Summary: Growing installed capacity in renewable energy sources is driving demand for energy storage in the power systems. Compressed air energy storage (CAES) technology can provide a good alternative to pumped energy storage, with high reliability and good efficiency in terms of performance. The article presents three constant volume CAES systems: (i) without recuperation, (ii) with recuperation, and (iii) adiabatic. Dynamic mathematical models of these systems were built using Aspen HYSYS software. Adiabatic compressed air energy storage system with liquid thermal energy storage achieved round trip efficiency of 64.8%. [ABSTRACT FROM AUTHOR]

The article focuses on existing technologies developed to harvest and store solar irradiance as a source of primary energy in district heating systems. In the study particular attention was given to solar collector systems cooperating with seasonal heat storage solutions. Motivating this work was the search for a tool to assess achievable solar fraction ‒ the ratio of usable solar energy to total energy consumption. The outcomes of this work are: (i) a simplified dynamic model facilitating evaluation of the proposed solutions, and (ii) selection of optimal operating parameters of the proposed system. A brief review and discussion is made of the technical and legal limitations on possible investments. The ground rules of cooperation between solar based heat sources with seasonal storage systems and conventional industrial boilers and district heating network have been set out. The work touches on the physical components of the discussed systems. Commercially available solar collectors and heat exchangers are presented and their pros and cons discussed. Some in-depth analysis of seasonal heat storage solutions is provided, in particular on tank and pit thermal energy storage as well as storage solutions that use boreholes or aquifer layers. Examples are given of existing plants characterized by high solar fraction located in the EU region and outside of it. A simplified dynamic model developed in the Aspen Hysys software environment is described and the results discussed. Due to the high complexity of the primary problem, the model has been limited to a solar collector installation, seasonal heat storage system and auxiliary boiler. The results obtained from the model are discussed and future steps are presented in the last part of the article. These recommendations seek to further the development of an efficient way of analysis and commercial assessment of such systems. Image 1 • Dynamic model of solar heating plant with STES was developed. • Optimal operating parameters of the proposed system were selected. • Rules of cooperation between all components of the system have been set out. • Solar collectors and heat exchangers are presented with their pros and cons. • Results obtained from the model are discussed and future steps are presented. [ABSTRACT FROM AUTHOR]

The idea of control strategy of SOFC operating to meet demand of a public utility building was presented. The strategy was formulated with the support of Artificial Neural Network. The network was used to predict the demand for electricity. The calculations were carried out on the example of a building of the Institute of Heat Engineering Warsaw University of Technology. The control strategy is influenced by various factors depending on changes in market conditions and operating characteristics of the cell. We can define different objective functions eg: working for own needs, for maximum profit and maximum service life. The article presents a simulation of SOFC operation for demand profile of the IHE building from the selected time period. [ABSTRACT FROM AUTHOR]

The paper presents a thermodynamic analysis of selected CAES and LAES systems. The LAES cycle is a combination of an air liquefaction cycle and a gas turbine power generation cycle. CAES and LAES systems are simulated using Aspen HYSYS software. CAES is modeled in a dynamic mode. A comprehensive thermodynamic analysis was conducted along with the comparison of storage volumes. The results indicate that both systems are characterized by high energy storage efficiency, equal to approximately 40% for the CAES and 55% for the LAES systems. One clear advantage of the LAES over the CAES is the significantly lower volume demanded for energy storage. For the considered LAES system,the liquid air tank volume is around 5000 m 3 , while for the CAES the cavern volume is approximately 310000 m 3 . Heat exchangers and combustion chambers are the main contributors to the total exergy destruction in the analyzed systems. [ABSTRACT FROM AUTHOR]

This paper reports the performance of a molten carbonate fuel cell (MCFC) fed directly with liquid fuels referenced against results with hydrogen fuel in experiments conducted by the research team. Alcohols have greater energy density than pure hydrogen in normal conditions and, if presented as biofuels, the MCFC can be deemed a renewable energy source. For evaluation purposes various alcohols occurring in standard conditions in the liquid state were used for electricity generation in the MCFC: methanol, ethanol, propanol, butanol and glycerol. Since these alcohols can be subjected to steam reforming when mixed with water in specific ratios, they can be delivered directly in the liquid state to the fuel cell, where hydrogen is released and used to produce electricity and heat. The alcohols were mixed with water in ratios of 1:2, 1:3, 1:4. The results were compared to the MCFC fed with pure hydrogen as a fuel. In terms of power referenced to hydrogen (100%), the maximums achieved were 78% for butanol, 80% for glycerol, 83% for propanol, 86% for ethanol and 93% for methanol in comparison to the same amount of hydrogen delivered to the fuel cell in ideal steam reforming situation. Threats such as carbon deposition on the fuel cell surface were also evaluated. • MCFC fed directly with various mixtures of alcohols and water have been studied. • The steam reforming of mixtures of alcohols and water generates energy. • Temperature and anode material provide the necessary conditions for steam reforming. • Maximum power compared to hydrogen fuel for various fuels ranges between 78 and 93%. • Carbon deposition in the anode channel of commercial units can be a problem. [ABSTRACT FROM AUTHOR]

The article shows the proposed solution of the objective function for the seasonal thermal energy storage system. In order to develop this function the technological and economic assumptions were used. In order to select the optimal system configuration mathematical models of the main elements of the system were built. Using these models, and based on the selected design point, the simulation of the entire system for randomly generated outside temperatures was made. The proposed methodology and obtained relationships can be readily used for control purposes, constituting model predicted control (MPC). [ABSTRACT FROM AUTHOR]

The objective of this paper was to study the sCO2 cycle as a waste heat recovery system for a 180 kW biogas engine. The research methodology adopted was numerical simulations through two models built in different programs: Aspen HYSYS and GT Suite. The models were used to optimize the design and thermodynamic parameters of a CO2 cycle in terms of system power, system efficiency, expander, and compressor efficiency. Depending on the objective function, the sCO2 cycle could provide additional power ranging from 27.9 to 11.3 kW. Based on the calculation performed, "Recuperated cycle at maximum power" was selected for further investigation. The off-design analysis of the system revealed the optimum operating point. The authors designed the preliminary dimensions of the turbomachinery, i.e., the rotor dimension is 16 mm, which will rotate at 100,000 rpm. [ABSTRACT FROM AUTHOR]

The research presents an overview of the possibilities of using boron-containing compounds as electrolytes for fuel cells. The main assumption here is to develop a molten carbonate fuel cell type power source, where the molten electrolyte is kept by a ceramic matrix between the electrodes. In the cases which are described in this study, attempts were made to develop electrolytes based on borates. Whereas the reported studies contain very little information on this subject, it was possible to identify several promising compounds and to extrapolate their performance to higher temperatures. Reported data on the temperature at eutectic points suggest that the operating range of such electrolytes is at a level like the molten carbonate fuel cell. The study presents a proposal for a mathematical model of a new type of fuel cell based on molten borates. The mathematical model is based on the reduced order model, supplemented with the influence of the ceramic matrix on the resulting ionic conductivity of the electrolyte layer. The model was used to determine potential performances for a few selected borates and a sensitivity analysis of selected geometric parameters was performed for the best of them. The results obtained were compared against the standard molten carbonate fuel cell. • Conductivities of various boron compounds have been investigated and compared. • Application of boron-containing compounds in fuel cells electrolyte has been analyzed. • A model of molten borate fuel cell has been developed. • Borates occurring to have higher potential than carbonates what might result in higher efficiency. [ABSTRACT FROM AUTHOR]

This paper presents research on the impact of the material microstructure on the performance of Molten Carbonate Fuel Cells (MCFC). The study is motivated by the need to increase the operation time of MCFC stacks. As the MCFC stacks are mainly composed of porous materials, the paper shows the impact of the porosity on both fuel cell performance and degradation rate. The study is based on the mathematical model, validated through experiments with varying microstructure parameters, achieving an overall relative error of 8%. The study evaluated the performance of MCFC using anodes with different porosity and found that increasing anode porosity from 40% to 70% led to a nearly two-fold increase in maximum power density. However, from both the degradation test and polarization curves, the optimal level of porosity for the anode is around 55%. The porosity level at 55% ensures the highest catalytic surface of the electrodes and is a compromise between the mechanical properties of the electrode and its electrochemical properties. • New approach of 0D model of MCFC including materials microstructure influence is proposed. • The new model is prepared in MS Excel and Aspen HYSYS environments. • Experimental investigation for materials with predefined microstructire parameters was performed for model validation. • Variant analysis is presented for different porosity, tortuosity and constrictivity of MCFC anode. • An optimal scenario is suggested based on modleing results. [ABSTRACT FROM AUTHOR]

The aim of the paper is to examine the performance of molten carbonate fuel cell, which is supplied with a raw bioethanol, i.e. bioethanol which origins directly from fruit fermentation, without pre-treatment of fermentation products. The composition of raw bioethanol was precisely determined and then the impact of raw bioethanol on the degradation of molten carbonate fuel cells was examined. Steam to carbon ratio of the biofuel has been determined as 5.7 (in comparison to stoichiometry of reaction) which allowed for estimation of hydrogen production during steam reforming process taking place in the anode channel. The results in the form of current-voltage curve was obtained and compared with the same fuel cell fed with pure hydrogen, while the amount of hydrogen was defined as identical with the one after steam reforming of biofuel taking place in the nickel anode channel. Relevant literature studies were focused on the purified fuel or examination of the impact of individual components. Our study proved carbon deposition is not a problem, however solid particles contamination in fermentation product makes it impossible to use fuel cell fueled with fermentation product for longer periods, and prior to supplying fuel cell the bioethanol purification is required. A raw biofuel with its impurities did not have any impact on the anode and current collector surface from physical point of view, but Electrochemical Impedance Spectroscopy analysis shows visible increase of ohmic loses. • Homemade first generation bioethanol composition have been examined. • Manufactured bioethanol has been delivered directly to the MCFC anode without purification. • Performance of MCFC fueled with impure bioethanol has been investigated. • Effect of steam reforming for hydrogen generation and steam to carbon ratio were evaluated. • Pollution on the anode after cell operation was investigated with SEM and EIS. [ABSTRACT FROM AUTHOR]

This paper presents the results of research into improving the ionic conductivity of Molten Carbonate Fuel Cell by modifying the matrix material. So far, we have succeeded in using materials such as YSZ and SDC, but we are now trying to use powders based on Ba Na and TiO 2. These materials are characterized by their oxygen ion conductivity at elevated temperatures. A matrix of these materials was produced and used to build MCFCs. Based on the experiments carried out and the mathematical model of the fuel cell, the contribution of the oxygen ion conductivity to the total ionic conductivity was determined. • Research on oxygen ion conduction materials was performed. • BNT material has best oxygen ion conductivity parameters and was chosen for experiments. • New matrix made of BNT was manufactured. • Composite Li/K and BNT membrane was investigated under EIS and in fuel cell. • Model including ionic conductivity and tortuosity is presented and validated. [ABSTRACT FROM AUTHOR]

Summary: This article shows the teaching processes of artificial neural networks that are used to model the molten carbonate fuel cell (MCFC). Researchers model MCFCs to address a variety of issues across a range of complexities, from simply gauging the effect of temperature through to a complete model with 14 input parameters. The architecture of the model is a triple layer network with one hidden layer containing three neurons. The activation function used for the hidden layer was a hyperbolic tangent, with the last layer being based on linear function. We produced various network configurations, mostly networks containing one hidden layer. Models map the work of a real fuel cell with an average error in the range of 2.4% to 4.6%. The model we created guided the optimization of the thermal‐flow and construction parameters of the MCFC. Commercially available software was used to build the model and optimize the operating parameters. The selected objective functions were the efficiency of electricity production and the power density obtained from the cell's surface. The results obtained serve as pointers for possible changes in fuel cell operation and could lead to some structural changes being made. [ABSTRACT FROM AUTHOR]

Within this study, the electrochemically inert, molten carbonate fuel cell (MCFC) γ -LiAlO 2 matrix is replaced by oxygen ion conducting ceramics, typical for solid oxide fuel cell (SOFC) application. Such solution leads to synergistic ion transport both by molten carbonate mix (CO 3 2- ) and yttria-stabilized zirconia (YSZ) or samaria-doped ceria (SDC) matrix (O 2- ). Single unit cell tests confirm that application of hybrid ionic membrane increases the performance (power density) of the MCFC over pure γ -LiAlO 2 for a wide range of operating temperatures (600 °C–750 °C). Cell power density with SDC and YSZ matrices is 2% and 13% higher, respectively, compared to the γ -LiAlO 2 at typical 650 °C operating temperature of MCFC. [ABSTRACT FROM AUTHOR]

The paper aims to examine the possibility of improving the manufacturing process for MCFC cathodes. using noble, semi-precious, and rare earth metals sourced from waste electric and electronic equipment (WEEE). As MCFC components are not particularly sensitive to ceramic and metal impurities. The addition of noble metals recovered from WEEE as catalysts are economically justifiable. The reported experimental research revealed the positive impact of MCFC cathode fabricated with 20% recycled electronic scrap. Especially the cell with powder marked as 4/1 enjoyed much better performance operating at 550 °C than the reference cell. During the operation at a temperature of 650 °C, the cell with powder marked as 4/1 has almost the same performance as the reference cell, i.e., 1.01 V OCV and power density of 0.13 A/cm2. The cell with cathode with 4/2 powder has the worst performance – current density of 0.09 A/cm2 and OCV of 0.97 V. [Display omitted] • Rare earth elements separated by positive charge contains less cerium than separated by negative charge. • The maximum current densities and Open Circuit Values are similar as reference case for maximum gas flows. • The maximum current densities and Oper Circuit Voltages are better with additives for lower operational temperature. [ABSTRACT FROM AUTHOR]

This article deals with a thermal energy storage system in the form of a water tank with a thermocline. The well-known thermocline phenomenon is modeled using computational fluid dynamics (CFD). However, the reservoir model proposed in this article is zero-dimensional. This is due to the fact that the aim of this article is to build a mathematical model that will be more useful in mathematical models of complex energy systems in which a hot water tank is one of many elements of the system. In such a zero-dimensional mathematical model, the hot water tank will be modeled using equations describing heat transfer, and the thermocline itself will be treated as a heat transfer surface with known dimensions and heat transfer coefficient. A novelty of this paper is that it addresses heat loss across the thermocline as defined in this manner. A CFD model of a thermal storage tank is created, validated with available experimental data, and used to obtain the heat transfer coefficient U. The resulting value is then analyzed quantitatively and qualitatively and the changes in the thickness of the thermocline are accounted for in the equation. The results from this groundbreaking work can be used to analyze heat storage in the form of thermocline water tanks at the level of system modeling, e.g., for the purpose of configuring the structure of other devices and control systems. [ABSTRACT FROM AUTHOR]

The article provides an overview of knowledge on how to model fuel cells using software which is oriented to system modeling. The overview covers several types of fuel cell such as SOFC, MCFC and PEMFC. Fuel cells were modeled using mainly three types of software, i.e. Aspen Hysys, Aspen Plus and Matlab. Based on our literature review, we decided to use Aspen Hysys to create a proton conducting SOFC model. Model construction is based on a reduced order approach that we published earlier. We used available experimental data to verify the model we created on. The results generated by the model and the experimental data were then subjected to an error analysis. Only two of all the articles found contained a set of information that was fit for the purpose of validating the model. The model maps the work of the proton conducting SOFC with high accuracy, i.e., an error of 0.01 V. • The methodology for model implementation in available software is reported. • The model represents an alternative approach for voltage prediction of a H + SOFC. • A validation process for the models implemented in Aspen Hysys/Excel is presented. [ABSTRACT FROM AUTHOR]

It is proposed that dual conductive electrolytes have the potential to improve properties of MCFC by using oxygen ion conductors as matrix material, creating what is termed composite electrolyte. In this work we present the results of testing a novel type of electrolyte of molten carbonate fuel cell which consists of Yttria Stabilized Zirconia impregnated by Lithium/Potassium carbonates. Polarization curves were obtained for temperatures between 500 °C and 800 °C. Without very accurate measurements it is not easy to determine the additional electric charge provided by oxygen ions (O=). We made an attempt to build a mathematical model which takes into account both conductivities and, based on the model, estimated the ratio of electric charge provided by oxygen ions and carbonate ions. • We investigated double conducting electrolytes for Molten Carbonate Fuel Cell. • The investigation was done by both experimental and modeling methods. • We found small infuence done by ionic conductor. • The infunece is so small, that the results are not so evident. [ABSTRACT FROM AUTHOR]

Molten Carbonate Fuel Cells (MCFC) offer several advantages that are accelerating the research and development effort. Recent advances include improved materials, new fabrication techniques and new designs, flow configurations and applications. Nevertheless, several factors are holding back large scale implementation of fuel cells, especially in distributed energy generation, a major one being their long response time to changing parameters. Whereas alternative mathematical models of the molten carbonate fuel cell stack have been developed over the last decade, there are no reported analyses of regarding the application of models for emergency scenarios such as fuel cell malfunctions. This paper presents the 0D model of MCFC, calibrated to the appropriate available experimental data. This study investigates a generic molten fuel cell stack with nominal power output of 1 kWel. As daily, weekly and monthly variations in the electrical power load are expected, there is a need to develop numerical tools to predict the unit's performance with high accuracy. Hence, a fully physical dynamic model of an MCFC stack was developed and implemented in Aspen HYSYS 10 modeling software to enable predictive analysis of the dynamic response. The model is used to simulate a number of few malfunctions with 5. 66% broken cells in the stack. Losses of performance are obtained, manifested by rising operating temperature and falling power output. Moreover, a number of emergency operation scenarios were investigated, such as sudden loss of electric load, fuel and oxidiant supply. The presented model exhibits high accuracy and accounts for thermal and electrochemical processes and parameters. The paper presents the methodology used in the study to analyze the sensitivity of key scenarios such as load changes and emergencies. Further functionality of the model, which was validated using real operating data, is discussed. • Dynamic model of a Molten Carbonate Fuel Cell 1 kW stackis proposed. • The model was calibrated to the appropriate available experimental data. • The load changes and emergency situations were examined. [ABSTRACT FROM AUTHOR]

Molten carbonate fuel cells (MCFCs) are promising high temperature power generating devices. However, unlike solid oxide fuel cells (SOFCs) they utilize a liquid electrolyte which must be immobilized in a porous matrix. In this paper, a slurry composition for lithium aluminate ( γ -LiAlO 2 ) matrix was developed and green matrices were subsequently formed by the tape casting method. In order to achieve the desired structure of the matrix (pore size, porosity) γ -LiAlO 2 powder was milled in a planetary ball mill for 18 h with a solvent, dispersant and defoamer. After this step, other ingredients were added, including a binder and plasticizer to obtain optimal rheology of the slurry. Cell tests confirmed optimal performance of the matrix compared to the third party reference γ -LiAlO 2 matrices. Burned out matrix was characterized by scanning electron microscopy (SEM) and laser diffraction in order to determine the γ -LiAlO 2 powder particle size and morphology. The results show that high-energy milling enabled a fine pore structure and high specific surface area of the matrix to be obtained in a relatively short time, compared to conventional fabrication routes. The matrix structure obtained within this study is suitable for high performance operation of MCFC. [ABSTRACT FROM AUTHOR]