16 results on '"Elias, Charalambos"'
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2. A comprehensive review of recent advances in materials aspects of phase change materials in thermal energy storage
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Elias, Charalambos N. and Stathopoulos, Vassilis N.
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- 2019
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3. Machine Learning Platform for Profiling and Forecasting at Microgrid Level
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Mele Enea, Elias Charalambos, and Ktena Aphrodite
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clustering algorithms ,forecasting ,machine learning algorithms ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
The shift towards distributed generation and microgrids has renewed the interest in forecasting algorithms and methods, which need to take into account the advances in information, metering and control technologies in order to address the challenges of forecasting problems. Technologies such as machine learning have been proven useful for short-term electricity load forecasting, especially for microgrids, as they can also take into account several types of historical data and can adapt to changes often encountered in small-scale systems and on a short time scale. In this paper, we present a flexible and easily customized modular toolbox, called Divinus, for electricity use profiling and forecasting in microgrids. Divinus may support a variety of machine learning algorithms for forecasting and profiling that can be used independently or combined. For demonstration purposes, we have implemented Self-Organizing Maps for profiling and k-Neighbors for forecasting. The testing of the platform was based on electricity consumption data of the Euripus campus of the National and Kapodistrian University of Athens in Evia, Greece, from January 2010 till March 2018. The tests that have been carried out so far show that the platform can be easily customized and the algorithms examined yield high accuracy and acceptable mean errors for the case of a university campus energy profile.
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- 2019
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4. Active System Management Approach for Flexibility Services to the Greek Transmission and Distribution System
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Sijakovic, Nenad, primary, Terzic, Aleksandar, additional, Fotis, Georgios, additional, Mentis, Ioannis, additional, Zafeiropoulou, Magda, additional, Maris, Theodoros I., additional, Zoulias, Emmanouil, additional, Elias, Charalambos, additional, Ristic, Vladan, additional, and Vita, Vasiliki, additional
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- 2022
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5. Microbial Fuel Cell for Wastewater Treatment as Power Plant in Smart Grids: Utopia or Reality?
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Tsekouras, George J., Deligianni, Panagiota M., Kanellos, Fotis D., Kontargyri, Vassiliki T., Kontaxis, Panagiotis A., Manousakis, Nikolaos M., and Elias, Charalambos N.
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Economics and Econometrics ,Fuel Technology ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology - Abstract
Microbial fuel cells (MFCs) have undergone great technological development in the last 20 years, but very little has been done to commercialize them. The simultaneous power production and wastewater treatment are features those greatly increase the interest in the use of MFCs. This kind of distributed power generation is renewable and friendly and can be easily integrated into a smart grid. However, there are some key issues with their commercialization: high construction costs, difficulty in developing high power structures, MFC lifespan, and maintaining a high level of efficiency. The objective of this article is to explore the possibilities of using MFCs in urban wastewater not only regarding the technical criteria of their application, but also mainly from an economic point of view, to determine the conditions through which the viability of the investment is ensured and the possibilities of their integration in a smart grid are identified. Initially, this article explores the implementation/configuration of a power plant with MFCs within an urban wastewater treatment plant on a theoretical basis. In addition, based on the corresponding physical quantities for urban wastewater treatment, the construction and operational costs are determined and the viability of the investment is examined based on classic economic criteria such as net present value, benefit–cost ratio, internal rate of return, and discounted payback period. Furthermore, sensitivity analysis is carried out, concerning both technical parameters, such as the percentage of organic matter removal, power density, sewage residence time, MFC efficiency, etc., and economical parameters, such as the reduction of construction costs due to change of materials, change of interest rate, and lifetime. The advantages and disadvantages of their use in smart grids is also analyzed. The results show that the use of MFCs for power generation cannot be utopian as long as they are integrated into the structure of a central wastewater treatment plant on the condition that the scale-up technical issues of MFCs are successfully addressed.
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- 2022
6. Applications of Energy Storage Methods in Smart Grids
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Gkaroutsou, Maria, primary, Tsampasis, Eleftherios, additional, Elias, Charalambos, additional, and Gkonis, Panagiotis, additional
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- 2022
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7. Energy Storage in Smart Electrical Grids
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Dedes, Ioannis-Christos, primary, Tsampasis, Eleftherios, additional, Elias, Charalambos, additional, and Gkonis, Panagiotis, additional
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- 2021
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8. Thermochemical Energy Storage in Solar Power Plants
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Gkaroutsou, Maria, primary, Tsampasis, Eleftherios, additional, Elias, Charalambos, additional, and Stathopoulos, Vassilis, additional
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- 2021
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9. An annual midterm energy forecasting model using fuzzy logic
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Elias, Charalambos N. and Hatziargyriou, Nikos D.
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Fuzzy algorithms -- Usage ,Fuzzy logic -- Usage ,Fuzzy systems -- Usage ,Mathematical optimization -- Analysis ,Fuzzy logic ,Business ,Electronics ,Electronics and electrical industries - Abstract
The objective of this paper is to present a new fuzzy logic method for midterm energy forecasting. The proposed method properly transforms the input variables to differences or relative differences, in order to predict energy values not included in the training set and to use a minimal number of patterns. The input variables, the number of the triangular membership functions and their base widths are simultaneously selected by an optimization process. The standard deviation is calculated analytically by mathematical expressions based on the membership functions. Results from an extensive application of the method to the Greek power system and for different categories of customers are compared to those obtained from the application of standard regression methods and artificial neural networks (ANN). Index Terms--Energy forecasting, fuzzy logic, optimization of membership functions, standard deviation.
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- 2009
10. Modelling of a Magnetostrictive Torque Sensor
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Tsiantos Vasilios, Karagiannis Vasilios, Ktena Aphrodite, Manasis Christos, Ladoukakis Onoufrios, Elias Charalambos, Hristoforou Evangelos, and Vourna Polyxeni
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Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
Existing magnetostrictive torque sensor designs typically measure the rotation of the saturation magnetization under an applied torque and their theoretical treatment revolves around the minimization of the free energy equation adapted according to the assumptions considered valid in each design. In the torque measurement design discussed in this paper, Ni-rich NiFe films have been electrodeposited on cylindrical austenitic steel rods. Contrary to existing designs, the excitation field is applied along the axial direction and is low enough to ensure that the resulting magnetization along the same direction remains in the linear region of the M(H) characteristic. Assuming homogeneous magnetization, positive magnetostriction constant λ, negligible hysteresis and demagnetizing fields, torque T may be expressed in terms of an effective uniaxial anisotropy constant Ku around 45° to the axial direction. It is shown, that for the proposed arrangement, the resulting M is the linear superposition of the effect of a torque-induced effective field and the excitation field, the applied field accounts for the vertical offset of the magnetization response and the applied torque increases the slope of the M(H) characteristic.
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- 2016
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11. Communication challenges in Smart Grid
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Tsampasis Eleftherios, Bargiotas Dimitrios, Elias Charalambos, and Sarakis Lambros
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Engineering (General). Civil engineering (General) ,TA1-2040 - Abstract
Smart grid is not a system, application, network, or single device. It is no surprise that there is no unique definition of the Smart Grid (SG): ABB says is an evolved grid system that manages electricity demand in a sustainable, reliable and economic manner, built on advanced infrastructure and tuned to facilitate the integration of all involved elements. However, the definitions from authoritative organizations follow a common theme: Smart grids utilize information and communication technologies to manage the energy distribution and optimize the transmission from suppliers to consumers and vice versa. Capacitor banks and reclosersneed the intelligent control to appropriately adapt the supply to the demand. In this paper, we discuss communication systems and the requirements they have to fulfill in the smart grid applications.
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- 2016
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12. Smart Load for a Hybrid Microgrid Testbed
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Billas, Ilias, primary, Konstantaras, John, additional, Tsambasis, Eleftherios, additional, Elias, Charalambos, additional, Ktena, Aphrodite, additional, and Manasis, Christos, additional
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- 2019
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13. Electricity use profiling and forecasting at microgrid level
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Mele, Enea, primary, Elias, Charalambos, additional, and Ktena, Aphrodite, additional
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- 2018
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14. GAMIFICATION FOR ELECTRICITY USE PROFILING.
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Ktena, Aphrodite, Elias, Charalambos, Manasis, Christos, Koutsoubis, Yannis, Mele, Enea, Constantos, Elias, Tsalkitzi, Evgenia, Tatsiopoulou, Anna, and Tatsiopoulos, Christos
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ELECTRIC power consumption ,BEHAVIOR modification ,RENEWABLE energy sources - Abstract
Copyright of B&H Electrical Engineering is the property of Sciendo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2018
15. Contribution to short-term and mid-term load and energy Forecasting based on fuzzy logic
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Elias, Charalambos N.
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Σύστημα ηλεκτρικής ενέργειας ,Midterm Energy Forecasting ,Μεσοπρόθεσμη πρόβλεψη ενέργειας ,Fuzzy Logic ,Βραχυπρόθεσμη πρόβλεψη φορτίου ,Short-term Load Forecasting ,Confidence Interval ,Ασαφής Λογική ,Διάστημα Εμπιστοσύνης ,Power system - Abstract
199 σ., Η παρούσα διατριβή έχει ως αντικείμενο τη διερεύνηση και τη μελέτη του προβλήματος της πρόβλεψης ζήτησης φορτίου και ενέργειας του συστήματος ηλεκτρικής ενέργειας σε βραχυπρόθεσμη και μεσοπρόθεσμη κλίμακα με χρήση ασαφούς λογικής. Αρχικά, πραγματοποιείται μία σύντομη εισαγωγή στην πρόβλεψη φορτίου και ενέργειας, αναδεικνύεται η σημασία τους, αναλύονται οι εφαρμογές αυτών και οι παράγοντες που επηρεάζουν τη ζήτηση της ηλεκτρικής ενέργειας. Επιπλέον, αναλύονται τα διάφορα μοντέλα πρόβλεψης φορτίου και ενέργειας, τα οποία περιέχονται στη διεθνή αρθρογραφία. Προκειμένου να καλυφθεί η ανάγκη για βραχυπρόθεσμη πρόβλεψη φορτίου, αναπτύχθηκε ένας νέος αλγόριθμος πρόβλεψης ημερήσιας καμπύλης φορτίου για το διασυνδεδεμένο σύστημα με χρήση ασαφούς λογικής, για την επόμενη και τη μεθεπόμενη ημέρα, ενώ έχει πραγματοποιηθεί και ο υπολογισμός του πρόστιμου της πρόβλεψης που αφορά τις αντίστοιχες ημέρες, σύμφωνα με τους σχετικούς κανονισμούς. Ο αλγόριθμος αυτός βελτιστοποιείται ως προς την επιλογή των εισόδων του, των χαρακτηριστικών παραμέτρων των συναρτήσεων συμμετοχής και των διαφόρων μεθόδων εξαγωγής συμπεράσματος. Επίσης, μελετήθηκε η συμπεριφορά του μοντέλου ως προς τα χρόνια εκπαίδευσης. Το μοντέλο εφαρμόστηκε, ενδεικτικά, για το έτος 2008. Για τον προσδιορισμό του διαστήματος εμπιστοσύνης, αρχικά καταγράφηκαν οι βασικές μέθοδοι προσδιορισμού τυπικών αποκλίσεων για τις μεθόδους των τεχνητών νευρωνικών δικτύων και, στη συνέχεια, τροποποιήθηκε η μέθοδος της επαναδειγματοληψίας για την εύρεση του διαστήματος εμπιστοσύνης στην περίπτωση της ασαφούς λογικής, ενώ αναπτύχθηκε και μία πρωτοποριακή μέθοδος αναλυτικού υπολογισμού της τυπικής απόκλισης, που σε συνδυασμό με τη συνάρτηση πυκνότητας πιθανότητας του σφάλματος, οδηγεί στον υπολογισμό του διαστήματος εμπιστοσύνης. Στη συνέχεια, ο προτεινόμενος αλγόριθμος πρόβλεψης τροποποιήθηκε κατάλληλα, ώστε να είναι δυνατή η εφαρμογή του και σε μη διασυνδεδεμένο σύστημα. Εκτελέστηκε, δε, για το απομονωμένο σύστημα της νήσου Αγίου Ευστράτιου. Ο αλγόριθμος υπολογίζει την ημερήσια καμπύλη της επόμενης ημέρας έχοντας ως δεδομένα ένα ελάχιστο πλήθος 100 ημερών (λόγω έλλειψης δεδομένων). Αντίστοιχα, δημιουργήθηκε ένα μοντέλο μεσοπρόθεσμης πρόβλεψης της ενέργειας βασισμένο στις αρχές της ασαφούς λογικής. Το μοντέλο αυτό εφαρμόστηκε για την πρόβλεψη της απαιτούμενης ενέργειας για τα επόμενα τρία έτη τόσο για το σύνολο του Ελληνικού Συστήματος, όσο και για επιμέρους κατηγορίες καταναλωτών. Τα αποτελέσματα που προέκυψαν ήταν σαφέστατα καλύτερα σε σχέση με την εφαρμογή των κλασικών μεθόδων πρόβλεψης ενέργειας και ελάχιστα καλύτερα από αυτά που προκύπτουν από μοντέλα πρόβλεψης βασισμένα σε τεχνητά νευρωνικά δίκτυα. Εν κατακλείδι, καταγράφονται τα γενικά συμπεράσματα που προκύπτουν από τη δημιουργία και την εφαρμογή των μοντέλων βραχυπρόθεσμης πρόβλεψης φορτίου και μεσοπρόθεσμης πρόβλεψης ενέργειας, ενώ αναφέρονται και οι προοπτικές περαιτέρω έρευνας σε σχέση με τα παραπάνω πεδία. Στο τέλος της διατριβής, παρατίθεται μια λεπτομερής περιγραφή των βασικών στοιχείων της ασαφούς λογικής, περιγράφονται τα ασαφή σύνολα και οι βασικές πράξεις που γίνονται ανάμεσα σε αυτά, ενώ γίνεται και μία σύντομη εισαγωγή στα τεχνητά νευρωνικά δίκτυα και στον αλγόριθμο εκπαίδευσης οπίσθιας διάδοσης σφάλματος., The present thesis is focused on the investigation and the study of the problem of load and energy demand forecasting of power systems in short-term and midterm system using fuzzy logic. Firstly, a brief introduction to load and energy forecasting is made, the significance of them is distinguished and their applications, as well as the factors affecting the demand for electricity are analyzed. In addition, the various loads and energy forecasting models referred to bibliography are analyzed. In order to satisfy the demand of short-term load forecasting, a new algorithm is developed for forecasting daily load curve for the interconnected power system using fuzzy logic for the next and the one after that day while it has been performed the calculation of the provision fine with respect to corresponding days in accordance with relevant regulations. This algorithm is optimized as far as the choice of it, the characteristic parameters of the participation function as well as the various models of inference. This model was also studied in terms of behaviour towards the years of education. It is implemented for the year 2008. In order to determine the confidence interval, the basic methods for standard deviation calculations for the artificial neural networks have been recorded. After that the sampling method has been modified for case of the fuzzy logic algorithms. An innovative method for analytical calculation of the standard deviation has also been developed, which combined with the probability density function of the error leads to the calculation of the confidence interval. The respective results are compared with different criteria such as the empiric coverage, the quality interval and the relative confidence interval, where the superiority of the innovative method is proved. The proposed fuzzy logic algorithm was suitably amended in order to be applied to autonomous power systems, such as to the power system of St. Efstratiou island. The algorithm calculates the daily curve of the next day having as data a minimum number of 100 days (due to lack of data). Therefore, based on the principles of fuzzy logic a corresponding model of midterm energy forecasting was created. This model was applied to predict the energy required for the next three years for the whole Greek system and for individual categories of consumers. The results were clearly better than those obtained by conventional methods of energy forecasting and a little better than corresponding forecasting of artificial neural network models. Finally, the general conclusions arising from the creation and implementation of the short-term forecasting models and midterm energy forecasting are recorded, while prospects for further research in relation to the above fields are mentioned. At the end of the thesis there is a detailed description of the basic elements of fuzzy logic, fuzzy sets, basic operations among them and a brief introduction of artificial neural networks and back-propagation algorithm is also presented.
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- 2012
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16. Seriously, Electricity is no Game: Play Safe.
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Ktena, Aphrodite, Mele, Enea, Tsalkitzi, Eugenia, Manasis, Christos, Elias, Charalambos, Constantos, Elias, Koutsoubis, Yannis, Tatsiopoulos, Christos, and Tatsiopoulou, Anna
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GAMIFICATION ,ELECTRIC power distribution grids ,RENEWABLE energy sources ,ENERGY demand management ,ELECTRIC power conservation - Abstract
Over the last two decades we are witnessing an accelerating paradigm shift in electricity grids and markets. The power grid, enabled by technologies such as renewable energy sources (RES), microgeneration, telemetering and telecontrol, is moving towards demand side management, under the pressure for energy saving and low carbon economy on the one hand and electricity market deregulation on the other. Demand side management requires the user to be an active agent interacting in real time with the grid and the markets rather than a passive consumer whose only interaction with the gird is paying the bill and reporting faults. Under this light, the majority of electricity users could be considered as technologically illiterate, lacking fundamental knowledge and skills, which hinders the uptake of technologies and distorts related policies. Smartege has been designed and developed as a gamified application to educate electricity users, regardless of their profile, and modify the way they perceive their relationship with the electricity grid. To that end, persuasive modeling, gamification and cognitive learning have been used in a synergistic way. The expected learning outcomes of the user are to know, understand, apply basics of electricity use and generation towards efficient energy management as well as to analyse, evaluate and create energy efficient scenarios. Existing applications, such as Electric Box, Energy Quest, Ollie's World, Electrocity, Power Matrix, Energy Ville, et. al., focus mostly on children's and teenagers' conditioning towards a more overall 'green' attitude; address only one type of user's interaction with the electricity grid; or, are designed to promote commercial products and processes. Smartege on the other hand is a game of roles, simulation, strategy, quizzes and learning. The game uses an engaging graphical user interface that emulates the basic daily functions and activities of an electricity user in a house and an office building, in real time. Using gamification mechanics, the user is guided to understand the energy profile of appliances and equipment operating in the virtual buildings with respect to user-defined set points, to evaluate the effect of his/her actions and habits on them, to analyse the costs and benefits associated with energy upgrading or saving tactics. The user is gradually allowed to 'produce' electricity in the quest for net Zero Energy Buildings. The user's knowledge base is improving through various content forms, such as tips, information, reading material, quizzes, exercises. The user is triggered at appropriate times with engaging messages and is motivated by counters, reputation points, leaderboards and badges. Special emphasis is given in the game's social dimension, employing social media, promoting user's interaction and information exchange for gaining points. Finally, at advanced levels, by purchasing appropriate hardware, the user can emulate, monitor and control the electricity use and production of a real installation. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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