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The aim of the paper is to simulate multi-tank storage with the thermocline moving from tank to tank and compare the results against single tank storage. No analysis of this nature has previously been performed. The results lend added impetus to developing this new type of thermal energy storage, especially as heat losses through insulation have already been reduced a minimum. Dividing a seasonal thermal energy storage tank into smaller tanks reduces the negative effect of heat transfer through the thermocline. The work is a continuation of the concept already proposed in available literature of using multiple solar energy stores, but we focus mainly on developing a dynamic model of a system of this type and presenting the results of a time and thermocline dependent simulation. The study also encompassed examination of the thickness of thermal insulation of the storage tanks, with definitions of its critical size. Our study revealed that the use of multi-tank thermal energy storage reduces heat loss through the thermocline. This is illustrated mainly by changes in water temperature in the upper part of the tank, which fluctuates across a much smaller range than for a single tank. In the single tank system, the temperature drops below 60 °C, whereas for the multi-tank system it always remains above 64 °C. In addition, in the multi-tank solution the loss caused by the thermocline occurs in only one tank, leaving 3/4 of the storage system unaffected by thermocline loss. • The concept of multi tank seasonal thermal energy storage is examined. • The examination is based on the dynamic modeling. • Results are compared with the single tank thermal energy storage systems. • The examined system is more efficient due thermocline losses limitation. [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]