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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]

Development of the district heating system (DHS) is needed to achieve the Renewable Energy Directive goals. To maintain the economic profitability of DHN, the increase of intensity of heat production/consumption has to be ensured. Well, a known method is a cold production using an adsorption heat pump. However, developing a system suitable for implementation in the district heating companies is very difficult. As a solution, the authors propose a composite substation equipped with the adsorption heat pump and the heat/cold storage system based on a PCM.

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]

This paper describes the model of the novel concept liquid piston engine, which is designed to convert low-grade waste heat into electricity. The proposed dynamic oriented model is implemented in Aspen Hysys that enables simulations dynamic simulation of various working agents. The simulation results were verified with experimental data obtained from the research installation. The proposed model demonstrated relatively small discrepancies with respect to experimental research, hence it could be used as a tool for research on optimization of an innovative power plant operation, i.e. various working agents, various operating pressures.

The paper contains a comprehensive summary of the current state of research on the polymer burnout process in molten carbonate fuel cells (MCFC). Outline information discussing both MCFC fundamentals and the start-up process are given along with references to the literature. The main part of the article presents the result of an on-site experiment regarding polymer burnout performed on an MCFC stack. The outcomes are discussed and conclusions are clearly stated. [ABSTRACT FROM AUTHOR]

This paper presents models of three elements: heat exchanger, compressor and expander dedicated to supercritical CO2 cycles (Brayton). The models are built using Ebsilon software and validated against experimental data from available literature. Radial turbomachinery and thin plate heat exchangers were used to meet the demands of the relatively compact design of the S-CO2 cycle elements. It seems that there are no general relationships for the turbomachinery and real characteristics need to be used for constructing the models. [ABSTRACT FROM AUTHOR]

The paper contains a comprehensive summary of potential sCO2 cycle applications being considered for power generation. The authors give examples of different sCO2 based cycles used in combination with conventional energy sources like fossil fuels or nuclear as well as renewable energy sources like solar. The article presents sCO2 recompression cycle simulation model results and - using this example, cycle flexibility and parameters - discusses potential application of the cycle. [ABSTRACT FROM AUTHOR]

The paper presents an investigation into the three cathode layers for the Molten Carbonate Fuel Cell that were obtained by using printing techniques on various surfaces. The main differences during the manufacturing process were the substrates used when printing the layers: glass and two different sorts of paper. The cathodes were investigated at the theoretical and experimental level. To identify the influence of the substrate used we built a mathematical model of the fuel cell, in which the influence is expressed by the conductivity of the layer. The paper demonstrates the possibility of using printing techniques to manufacture Molten Carbonate Fuel Cell layers. [ABSTRACT FROM AUTHOR]

Solid Oxide Fuel Cells are regarded as a high-efficiency, low-environmental impact technology for power and heat generation. SOFCs based on proton-conducting electrolyte are one of the most attractive technologies, mainly due to their high efficiency in energy conversion and operation at the intermediate range of temperatures. The main objective of this paper is an investigation into the possibility of applying the reduced order model proposed by Milewski [1] to model proton-conducting Solid Oxide Fuel Cells. The reliability of the simulation results were verified with experimental data reported in the literature. It was shown that the reduced order model is valid for both ion-conducting SOFCs and proton-conducting SOFCs. [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]