Microscale combined heat and power (CHP) unit based on solid oxide fuel cells (SOFC) for distributed generation was analyzed. Operation principle is provided, and the technology development in recent years is briefly discussed. System baseline for numerical analysis under steady-state operation is given. Grid-connected unit, fuelled by biogas corresponds to potential market demand in Europe, therefore has been selected for analysis. Fuel processing method for particular application is described. Results of modeling performed in ASPEN Plus engineering software with certain assumptions are presented and discussed. Due to high system electrical efficiency exceeding 40%, and overall efficiency over 80%, technology is an example of highly competitive and sustainable energy generation unit.
The article presents a zero-dimensional mathematical model of a tubular fuel cell and its verification on four experiments. Despite the fact that fuel cells are still rarely used in commercial applications, their use has become increasingly more common. Computational Flow Mechanics codes allow to predict basic parameters of a cell such as current, voltage, combustion composition, exhaust temperature, etc. Precise models are particularly important for a complex energy system, where fuel cells cooperate with gas, gas-steam cycles or ORCs and their thermodynamic parameters affect those systems. The proposed model employs extended Nernst equation to determine the fuel cell voltage and steadystate shifting reaction equilibrium to calculate the exhaust composition. Additionally, the reaction of methane reforming and the electrochemical reaction of hydrogen and oxygen have been implemented into the model. The numerical simulation results were compared with available experiment results and the differences, with the exception of the Tomlin experiment, are below 5%. It has been proven that the increase in current density lowers the electrical efficiency of SOFCs, hence fuel cells typically work at low current density, with a corresponding efficiency of 45–50% and with a low emission level (zero emissions in case of hydrogen combustion).
The article discusses the operation of solid oxide electrochemical cells (SOC) developed in the Institute of Power Engineering as prospective key components of power-to-gas systems. The fundamentals of the solid oxide cells operated as fuel cells (SOFC – solid oxide fuel cells) and electrolysers (SOEC – solid oxide fuel cells) are given. The experimental technique used for electrochemical characterization of cells is presented. The results obtained for planar cell with anodic support are given and discussed. Based on the results, the applicability of the cells in power-to-gas systems (P2G) is evaluated.
High-temperature solid oxide fuel cells (SOFCs) are considered as suitable components of future large-scale clean and efficient power generation systems. However, at its current stage of development some technical barriers exists which limit SOFC’s potential for rapid large-scale deployment. The present article aims at providing solutions to key technical barriers in SOFC technology. The focus is on the solutions addressing thermal resistance, fuel reforming, energy conversion efficiency, materials, design, and fuel utilisation issues.
Heat exchangers of different types find application in power systems based on solid oxide fuel cells (SOFC). Compact plate fin heat exchangers are typically found to perfectly fit systems with power output under 5 kWel. Micro-combined heat and power (micro-CHP) units with solid oxide fuel cells can exhibit high electrical and overall efficiencies, exceeding 85%, respectively. These values can be achieved only when high thermal integration of a system is assured. Selection and sizing of heat exchangers play a crucial role and should be done with caution. Moreover, performance of heat exchangers under variable operating conditions can strongly influence efficiency of the complete system. For that reason, it becomes important to develop high fidelity mathematical models allowing evaluation of heat exchangers under modified operating conditions, in high temperature regimes. Prediction of pressure and temperatures drops at the exit of cold and hot sides are important for system-level studies. Paper presents dedicated mathematical model used for evaluation of a plate fin heat exchanger, operating as a part of micro-CHP unit with solid oxide fuel cells.