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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]

Preparations for the EU's post-2020 Multiannual Financial Framework have brought increased interest to the functional approach as a major paradigm of the EU policies towards cross-border areas. This approach aims to focus cross-border programmes on territories where there is a high degree of cross-border interaction. Cross-border functional areas (CBFAs) can be a potential instrument for this, fostering further reduction of cross-border barriers and enhancing flows of people, goods, materials and knowledge. However, certain aspects of this notion are rather vague. This includes both the way how to turn the rather discursive concept of the CBFA into more material-institutional practices, and how CBFAs can be identified in practice to successfully implement the EU's cohesion policy. This paper debates the concept of the CBFA and proposes understanding CBFAs as spatially specific territorial complexes, located on two (or more) sides of a state border(s) that are not defined by administrative borders, but by cross-border functional linkages, a system of cooperative relationships and the existence of governance mechanisms. The paper proposes a novel approach for CBFA's identification based on a four-level model, taking into account the selected criteria. The proposed framework enabled to identify CBFAs and potential CBFAs at the borders of Poland. [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]