VSB-TUO Repository

Communities in DSpace

Select a community to browse its collections.

Now showing 1 - 10 out of 11 results

Recent Submissions

Electric vehicle charging by use of renewable energy technologies: A comprehensive and updated review
(Elsevier, 2024) Nazari, Mohammad Alhuyi; Blažek, Vojtěch; Prokop, Lukáš; Mišák, Stanislav; Prabaharan, Natarajan
The majority of the vehicles in the world consuming fossil fuels that causes emissions of harmful greenhouse gases. In order to mitigate the emissions regarding the transport sector, Electric Vehicles (EVs) have attracted attentions. One of the main concerns in the development of EVs is supply of required power for the charging stations. Renewable energy systems would be clean and attractive options for supply of required power of charging stations. In recent years, several studies have investigated applications of renewable energy systems for charging stations of EV and analyzed different aspects of these technologies. This article reviews the research works on the design, optimization and performance investigation of charging stations coupled with renewable energy systems. Studies on EV charging systems powered by stand-alone or hybrid renewable energy systems are considered in the present article. According to the reviewed works, significant potential of renewable energy systems for supply of charging stations can be concluded. Different factors such as the applied technology and components, meteorological data of the installation site and operating condition influence the performance of these systems. Furthermore, it can be concluded that control design system can influence various aspects of EV charging technologies powered by renewable energy systems such as share of renewables in the grid -connected configurations and performance reliability. Challenges and opportunities associated with the development of these systems are provided in the current works and some recommendations are highlighted for the forthcoming studies and projects.
Load monitoring and appliance recognition using an inexpensive, low-frequency, data-to-image, neural network, and network mobility approach for domestic IoT systems
(IEEE, 2024) Fazio, Peppino; Mehić, Miralem; Vozňák, Miroslav
With the low integration costs and quick development cycle of all-IP-based 5G+ technologies, it is not surprising that the proliferation of IP devices for residential or industrial purposes is ubiquitous. Energy scheduling/management and automated device recognition are popular research areas in the engineering community, and much time and work have been invested in producing the systems required for smart city networks. However, most proposed approaches involve expensive and invasive equipment that produces huge volumes of data (high-frequency complexity) for analysis by supervised learning algorithms. In contrast to other studies in the literature, we propose an approach based on encoding consumption data into vehicular mobility and imaging systems to apply a simple convolutional neural network to recognize certain scenarios (devices powered on) in real time and based on the nonintrusive load monitoring paradigm. Our idea is based on a very cheap device and can be adapted at a very low cost for any real scenario. We have also created our own data set, taken from a real domestic environment, contrary to most existing works based on synthetic data. The results of the study's simulation demonstrate the effectiveness of this innovative and low-cost approach and its scalability in function of the number of considered appliances.
Reformer + Membrane separator plant for decarbonized hydrogen production from Biogas/Biomethane: An experimental study combined to energy efficiency and exergy analyses
(Elsevier, 2024) Ruales, Henry Bryan Trujillo; Spadafora, Alex; Fiore, Piergiuseppe; Vereš, Ján; Caravella, Alessio; Iulianelli, Adolfo
Nowadays, the world energy production is still based on the exploitation of fossil fuels, mainly oil, coal, and natural gas, responsible for large greenhouse emissions in the environment. According to the measures proposed by the European Green Deal to meet the carbon neutrality by 2050, the decarbonisation of the global energy production processes represents a top priority. Hydrogen represents a carbon-free energy carrier, useful to drive the society toward a decarbonized-economy. The novelty of this work is represented by the experimental generation of clean hydrogen by a two stages plant constituted of a biogas/biomethane steam reformer and a Pd-Ag membrane separator, meanwhile applying on this simple case the methodology of the exergy analysis, identifying the main losses and suggesting improvements. Hence, it deals with the exergy analysis of the whole system with the process intensification operated by the membrane separator adopted instead of using several stages to separate/purify hydrogen - as conventionally done after the reforming stage (two water gas shift reactors, high and low temperature, followed by a pressure swing adsorption stage) - with the objective of recovering decarbonized hydrogen coming from the biogas/biomethane steam reformer, meeting the European targets indicated by the Clean Hydrogen Alliance. This approach allowed to understand the amount of irreversibilities present in such a system as well as how the thermal efficiency may be influenced by a number of parameters, constituting globally a baseline for the scaling up of this process technology from lab to bench/pilot scale. The best results of this work highlight that the utilization of biomethane in the feed stream to generate hydrogen resulted to be a better choice than biogas in terms of thermal efficiency (based on the lower heating value) of the whole system, equal to 73 % at 773 K, while the highest percentage of exergy destruction was concentrated in the condensation stage, with values varying between 76 % and 93 %, depending on the feed stream typology. The two stages system was able to meet the "decarbonized hydrogen production target 2027", with a hydrogen recovery of 90 % and a purity of 99.9999 %. Last but not least, the overall exergy destroyed efficiency of the overall system in the two analyzed cases was 92 % (biomethane feed stream) and 88 % (biogas feed stream), respectively.
Pit lake slope stability under water level variations
(MDPI, 2024) Steiakakis, Emmanouil; Syllignakis, Georgios; Galetakis, Michail; Vavadakis, Dionysios; Renaud, Vincent; Al Heib, Marwan; Burda, Jan
This paper presents the results of a geotechnical investigation regarding the slope stability in a pit lake, emphasizing the impact of water level variations. Advanced analysis techniques were utilized for this study. The research was performed by using fully coupled flow-deformation analyses. For the fully coupled approach, Bishop's effective-stress equation was used, and for the description of soil hydraulic behavior, the Van Genuchten's model was applied. The analysis of slope stability associated with reservoir water level changes revealed that the slope tended to become unstable as the water level decreased; the stability factor was negatively related to the rate of water level reduction. Concerning the water level fluctuations, the analyses revealed that the soil mass seemed to become less stable as the rate of water level change increased. Under a specific range of rates of water level variation, the safety factor became higher as the number of fluctuations increased. Additionally, the simulation results concerning the water level rising indicate that the pressure due to the external water level acts on the slope surface with a positive impact on the stability factor. The results obtained reflect the effects under a specific site condition, but they can be used as a reference for evaluating slope stability in a pit lake design.
Influence of the chemical composition of leachates on the results of ecotoxicity tests for different slag types
(Elsevier, 2024) Pavlovský, Jiří; Seidlerová, Jana; Pěgřimočová, Zuzana; Vontorová, Jiřina; Motyka, Oldřich; Michalska, Monika; Smutná, Kateřina; Roupcová, Petra; Novák, Vlastimil; Matějka, Vlastimil; Vlček, Jozef
In this study, four ecotoxicological tests on Vibrio fischeri bacteria, Sinapis alba L. (white mustard), Daphnia magna S. (daphnia's) and earthworms were performed for three types of aqueous slag (ladle, blast furnace and converter) leachates with two-grain sizes (<4 mm, <10 mm). Concentrations of toxic elements and concentrations of Cr(VI), Ca, Na, Al, and other ions were determined. The raw slags were analyzed using X-ray fluorescence spectroscopy (XRFS), and major substances were determined by X-ray powder diffraction (XRD). The aqueous slag leachates passed ecotoxicological tests and met the required criteria, showing no toxicity to Vibrio fischeri and complying with white mustard test criteria. According to the results of the ecotoxicity tests with daphnia, the blast furnace slag samples were not ecotoxic, while two other slag samples were found to be entirely compliant. Characterization of the slags showed that the effect of element/ion leachability and slag grain size is essential. Biplot principal component analysis (PCA) showed that grain size does not significantly affect the separation of individuals on the plane. A positive correlation on toxicity was found with pH, conductivity, calcium content, dissolved content, salinity and fluoride concentration, whereas a negative correlation was found with magnesium concentration, dissolved organic carbon and potassium concentration. The effective concentration at 50% inhibition (EC50) value for Vibrio fischeri correlated with the first dimension of bivariate assessment. In summary, it was found that the investigated slags can be effectively reused as they comply with regulations and do not endanger the environment.