Iskanje po katalogu digitalne knjižnice

Opis: Nowadays, traditional sources are mostly used for energy production, such as fossil and nuclear fuels. Such energy sources have a negative impact on the environment. As a result, trends in energy production are increasingly focused on renewable energy sources. These energy sources are available everywhere and their environmental impact is minimal. Nonetheless, these energy sources cannot be exploited with the same efficiency during the day (the Sun is not present the whole day, in winter, the sunlight days are shorter, the wind is not constant, etc.) or during different periods of the year. The variable amount of energy, produced from these sources and the integration with energy distribution systems, must not be overlooked. This is especially important in power plants, where it is necessary to ensure high energy reserves at excess load, which can be achieved by incorporating an improved energy storage system and higher efficiency of produced electricity. This process contributes to a significant reduction in costs. Direct energy storage systems, described in this master's thesis, are used in applications that require many fast charging and discharging cycles instead of a long-term energy storage in cars, buses, trains and lifts, where they are used for regenerative braking, short-term energy storage or as a primary source of electricity. Supercapacitors are electrochemical double-layer capacitors with low energy density and high power density. They have low series resistance, so they have the ability to emit high current, allowing them to charge quickly and a long lifespan. The goal of the thesis is to determine experimental parameters of supercapacitors and to compare them with theoretical parameters and batteries. With the simulation method of charge and discharge we have proven, that differences in results exists.
Ključne besede: storage, supercapacitor, application, modelling
Objavljeno: 02.03.2020; Ogledov: 1004; Prenosov: 112
Celotno besedilo (3,97 MB)

Opis: In the last years, energy efficiency has become an important issue for the EU and Slovenia, who both strive for more sustainable use of energy in buildings. As an innovative approach to such matter, green walls are vertical structures that can serve both as a façade or an insulation layer as well as an aesthetic design for building application. This thesis contains calculated annual heat (transmission) losses through different wall assemblies with and without a constructed green wall in front of them. The goal is to compare values of heat losses between those wall assemblies and the explanation of such results which will determine if green walls present a viable energy-efficient structure for buildings.
Ključne besede: energy efficiency, green wall, heat losses, modelling
Objavljeno: 18.11.2019; Ogledov: 855; Prenosov: 81
Celotno besedilo (3,83 MB)

Ključne besede: simulation modelling, evolutionary computation, cyber-physical system, heuristic kalman algorithm, human resource management
Objavljeno: 06.06.2019; Ogledov: 694; Prenosov: 233
Celotno besedilo (1,41 MB)

Opis: Due to the complexity of geosynthetic-soil interactions, the simple interface constitutive models embedded in the geosynthetic elements of general computing software cannot satisfy the requirements for a numerical simulation of different geosynthetic-soil interface behaviours. Based on the direct shear test results of a composite geomembrane (CGM) and polyurethane (PUR) mixed crushed stones interface, a nonlinear elastic, perfectly plastic model was used to describe the interface behaviours. The method of incorporating an interface constitutive model into the Geogrid element of a fast Lagrange analysis of continua in three dimensions (FLAC3D) procedure was presented in detail through a user-defined program in the FISH environment. Then the incorporated model of the Geogrid element was used to simulate the direct tests of the CGM-PUR mixed crushed stones interface. The results of the numerical tests confirmed the validity and reliability of the incorporated model. The method and program flowchart for implementing the nonlinear elastic, perfectly plastic interface constitutive model into the Geogrid element can provide a reference for users who want to simulate other geosynthetic-soil interface behaviours with FLAC3D.
Ključne besede: geosynthetic-soil interface, constitutive model, numerical modelling, FLAC3D, geogrid element
Objavljeno: 14.06.2018; Ogledov: 643; Prenosov: 41
Celotno besedilo (269,05 KB)
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Opis: The focus of this work is to provide a numerical formulation for coupled thermo-hydro-mechanical processes in unsaturated expansive clays, especially in compacted bentonite, with a multiphase fluid flow. The model is characterized by the presence of a deformable solid matrix filled with two fluid phases (liquid water and air). In the proposed model, both pore-water and air transfers are assumed to be governed by the generalized Darcy’s law. Fully coupled, nonlinear partial differential equations are established and then solved by using a Galerkin weighted residual approach in the space domain and an implicit integrating scheme in the time domain. The model has been validated against an experimental test from the literature, which involves bentonite under laboratory conditions. The calculated relative errors between the experimental and numerical results are 3% for the temperature and 7% for the stresses. Consequently, the developed numerical model predicts satisfactory results, when compared to the experimental test measures. The model is applicable to two-dimensional problems with various initial and boundary conditions; non linear soil parameters can be easily included in this model.
Ključne besede: thermo-hydro-mechanical process, unsaturated bentonite, finite element, numerical modelling, expansive clays
Objavljeno: 13.06.2018; Ogledov: 433; Prenosov: 33
Celotno besedilo (389,48 KB)
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