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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Προβλήματα φωτοβολταϊκών συστημάτων συνδεδεμένων στο δίκτυο

Σελίμης, Ευστάθιος 20 October 2009 (has links)
Σκοπός της συγκεκριμένης διπλωματικής εργασίας είναι η παρουσίαση και η ανάλυση των προβλημάτων που αναπτύσσονται κατά τη σύνδεση φωτοβολταϊκών συστημάτων στο δίκτυο ηλεκτρικής ενέργειας. Επίσης, γίνεται προσομοίωση της συμπεριφοράς ενός τέτοιου συστήματος για διάφορες συνθήκες ηλιακής ακτινοβολίας και γωνίας έναυσης, ώστε να ληφθούν συμπεράσματα σχετικά με τα αρμονικά ρεύματα που προκύπτουν. Στο πρώτο κεφάλαιο γίνεται μια εισαγωγή, με αναφορά στην αστείρευτη πηγή ενέργειας, τον ήλιο. Ο άνθρωπος εκμεταλλεύεται την ηλιακή ενέργεια την οποία μετατρέπει σε ηλεκτρική μέσω των φωτοβολταϊκών κυττάρων. Στο δεύτερο κεφάλαιο παρουσιάζονται οι σημαντικότεροι λόγοι για τους οποίους η φωτοβολταϊκή τεχνολογία έγινε περισσότερο από ποτέ ανταγωνιστική. Επίσης, γίνεται μια αναλυτική περιγραφή του φωτοβολταϊκού φαινομένου. Στο τρίτο κεφάλαιο παρουσιάζονται τα συνδεδεμένα στο δίκτυο φωτοβολταϊκά συστήματα. Γίνεται μια ιστορική αναδρομή της εξελικτικής τους πορείας, ενώ τέλος παρουσιάζεται ένα τυπικό μοντέλο φωτοβολταϊκού συστήματος, συνδεδεμένου στο δίκτυο. Στο τέταρτο κεφάλαιο αρχίζει η παρουσίαση των προβλημάτων που προκύπτουν κατά τη σύνδεση φωτοβολταϊκών συστημάτων στο δίκτυο. Αρχικά, τα προβλήματα χωρίζονται σε τεχνικά και μη τεχνικά. Τα τεχνικά προβλήματα χωρίζονται με τη σειρά τους σε αυτά που προκύπτουν λόγω της επίδρασης του δικτύου στα συνδεδεμένα φ/β συστήματα και σε αυτά που προκαλούνται από την επίδραση των συνδεδεμένων φ/β συστημάτων προς το δίκτυο. Τα κυριότερα θέματα που αναλύονται αφορούν την ασφάλεια του προσωπικού και των πελατών του δικτύου, την προστασία του εξοπλισμού και των στοιχείων προστασίας και την ποιότητα ισχύος (π.χ διακυμάνσεις τάσης, αρμονική παραμόρφωση και ρεύματα προς γη). Ιδιαίτερη έμφαση δίνεται στο φαινόμενο της νησιδοποίησης, της έγχυσης συνεχούς ρεύματος και των αρμονικών ρευμάτων. Στο πέμπτο κεφάλαιο γίνεται προσομοίωση της σύνδεσης φ/β συστήματος στο δίκτυο. / The purpose of this diploma thesis is the presentation and analysis problems developed during the connection of photovoltaic systems to the electricity grid. It is a simulation of the behavior such a system for different conditions of solar radiation and firing angle, to take conclusions about the harmony flows arising. The first chapter is an introduction, with reference to the inexhaustible energy source, the sun. The man operating the solar energy which translates into electricity through photovoltaic cells. The second chapter presents the main reasons why Photovoltaic technology has become more competitive than ever. It is a detailed description of the photovoltaic effect. The third section presents the network connected to the photovoltaic systems. An historical overview of the evolutionary process, and finally shows a typical PV system model, related to network. In the fourth chapter begins the presentation of the problems that arise during the photovoltaic systems connected to the network. Initially, the problems are divided technical and non-technical. The technical problems are divided in turn into these resulting from the impact of the network connected to PV systems and to those caused by the influence of associated PV systems network. The main issues discussed related to the safety of staff and customers of the network, protecting equipment and data protection and power quality (eg, voltage fluctuations, harmonic distortion and currents to earth). Particular emphasis is given to the phenomenon of nisidopoiisis of DC injection and harmonic currents. In the fifth chapter of the Association is simulated PV system on the network.
2

Electricity across borders : regional cost sharing of grid investments, international benchmarking and the electricity demand of an ageing population

Nylund, Hans January 2013 (has links)
This thesis deals with issues related to investments and regulation of high-voltage electricity grids, and to the households’ demand for electricity. The thesis consists of four self-contained papers. Papers I and II address the challenge of reaching agreements on the expansions of electricity grid infrastructure across national borders. Agreements can be problematic to reach due to regional welfare-effects from new infrastructure, which leads to questions of how investment costs should be shared and under what circumstances cooperation will be rational for all nations. This relates to both the allocation rule used, and the number of countries involved in the sharing (e.g., bilateral or regional). These issues are analysed by game theoretic methods and a numerical optimisation model of the electricity systems of six European countries. Results show that proportional sharing of investment costs in relation to benefits is the most practical solution, and that it also gives outcomes in terms of welfare and transmission capacity that are very close to the regional welfare optimum.The utilities responsible for the transmission system operation and the grid development are the national Transmission System Operators (TSO). The TSOs are monopoly utilities that operate under regulatory oversight. The absence of competition in this sector means that regulators have an important role in monitoring performance and ensuring overall efficiency. One way to do this is by frontier benchmarking methods. However, there are in general no national comparators for TSO, which means that performance needs to be measured against international comparators. Paper III applies a benchmark model to analyse the technical efficiency of 29 European TSO. Data envelopment analysis (DEA) is used to estimate efficiency scores and different approaches to account for the heterogeneity in operating environments are tested. Results show that the average technical efficiency is between 88% and 94%, depending on model and data sample. While this indicates that there are efficiency differences between the TSOs, the extension to regulation of TSOs is not straight forward since the reasons for inefficiency may be due to factors that are outside the TSO’s control.In Paper IV attention is turned towards the households’ demand for electricity. The question answered is how the ageing populations in OECD countries, and the consequential changes in population age-structures, may affect the residential demand for electricity. The implications of changing demography is analysed by a family life-cycle model, and an empirical analysis is made by specifying an econometric model of electricity demand that includes the population age-structure by four age-group variables. Results show that the oldest age-group has the largest positive effect on aggregate per capita consumption, while the other groups have lower but similar effects. The results have implications for projections of future electricity demand and for policies aimed at influencing households’ electricity demand, not the least since the share of elderly in the populations of western societies will increase by several percentage points over the coming decades. / <p>Godkänd; 2013; 20130809 (hannyl); Tillkännagivande disputation 2013-09-06 Nedanstående person kommer att disputera för avläggande av filosofie doktorsexamen. Namn: Hans Nylund Ämne: Nationalekonomi Avhandling: Electricity Across Borders: Regional Cost Sharing of Grid Investments, International Benchmarking and the Electricity Demand of an Ageing Population Opponent: Professor Andreas Stephan, Jönköping International Business School Ordförande: Professor Robert Lundmark, Luleå tekniska universitet Tid: Fredag den 27 september 2013, kl. 13.00 Plats: A109, Luleå tekniska universitet</p>
3

En applikation för kommunikation mellan fastighetsägare och hyresgäst vid åtgärder i fastighetens styrsystem

Gådin, Erik, Kylmänen, Ester, Sjöholm, Markus, Tamm, Matilda January 2019 (has links)
Utvecklingen av större städer förhindras för närvarande av kapacitetsbrist i elnätet. För dagens moderna samhälle är det inte rimligt att bygga nya fastigheter utan en garanti av tillgång till energi, både under byggnationen och det senare underhållet. Marknadsaktörer som belastar elnätet samtidigt är ett exempel på vad som leder till dessa överbelastade nät. Städernas totala energiförbrukning behöver inte nödvändigtvis justeras. Snarare måste förbrukningen under högbelastade tidpunkter flyttas till tidpunkter då belastningen är mindre, – näten måste alltså användas smartare. Detta innebär mycket ansvar för fastighetsägare som har stor inverkan på energiförbrukningen, eftersom dem har möjligheten att styra förbrukningen i sina fastigheter. Därför var syftet med projektet att låta fastighetsägarna på ett lätthanterlig och bekvämt sätt informera sina hyresgäster om förändringar som utförs i fastigheterna. Resultatet var implementation av ett tillägg till en mobilapplikation och i form av en molnbaserad databas, vilken kunde uppkopplas till fastighetens styrsystem. Vidare finns även möjlighet för fastighetsägare att ge hyresgäster förslag på vad de själva kan bidra med för att minska energianvändningen. Vår lösning kommer inte lösa hela kapacitetsbristen i elnäten, utan det är snarare en dellösning och ett steg närmre en smartare elanvändning och ett ändrat användarbeteende. En lösning som inte kräver utbyggnad av elnätet. / The development of larger cities is currently prevented by congested electricity grids. In today's modern society, it is not sensible to build new real estates without a guarantee of access to energy, both during the construction and the maintenance. Market participants who utilize the power grid simultaneously is an example of what leads to these congested grids. The cities' total energy consumption does not necessarily need be adjusted. Rather, the times of usage must be. This puts a great deal of responsibility on property owners who have a big impact on the energy consumption, because they have the power to control the consumption in their properties. Therefore, the purpose of the project was to allow the property owners in an easy-to-manage and convenient manner to inform their tenants of changes made inside the properties. The result was the implementation of an add on to a mobile application in the form of a cloud-based database, which could be connected to the database of the property's control system. Furthermore, through the application  property owners can give tenants suggestions on how they can contribute to reduce energy use. Our solution will not solve the entire capacity shortage in the  grids, but rather it is a partial solution and one step closer to a smarter electricity use and a changed user behaviour. A solution that does not require expansion of the power grid.
4

Temporary Variables for Predicting Electricity Consumption Through Data Mining

Silva, Jesús, Senior Naveda, Alexa, Hernández Palma, Hugo, Niebles Núẽz, William, Niebles Núẽz, Leonardo 07 January 2020 (has links)
In the new global and local scenario, the advent of intelligent distribution networks or Smart Grids allows real-time collection of data on the operating status of the electricity grid. Based on this availability of data, it is feasible and convenient to predict consumption in the short term, from a few hours to a week. The hypothesis of the study is that the method used to present time variables to a prediction system of electricity consumption affects the results.
5

Price policy estimation for Demand Response of heat-pump-based loads / Prissättningspolicy för uppskattning av eferfrågeflexibilitet med värmepumsbaserade laster

Gil Simancas, Carlos Eduardo January 2023 (has links)
The electricity grids have become a key player in the society. An increased usage of electricity is both a result from the more electrified society, but also as a main solver in reaching the climate goals by reducing emissions. This thesis work explores some of the new features for the electricity grid from integration of electrification from renewable energy resources (RES) and from strategies for energy optimization related to the loads and specifically from thermal heat pumps. These strategies lie in the field of demand response, which takes advantage of the flexibility of loads in terms of willingness to switch or decrease their consumption at a particular moment of the day. This research proposes a three-step framework to harness the flexibility of Thermo-Statically controlled loads (TCLs) based on a simulated grey-box building model that uses historical outside temperature and prices data and learns the thermal parameters such as Thermal Resistance, Thermal Capacitance, but also price responsiveness (pth ) through a Differential Evolution (DE) based optimization algorithm. The price responsiveness is used to provide further insight into the flexibility of the loads and is employed in the last step to propose a price policy estimation algorithm also based on DE that minimizes the gap between supply and demand while preserving supplier and customer profitability. The proposed approach has proven to be accurate for a large number of parameters but also effective with reduced training data (prediction errors around 2.5% on the power average and standard deviation), as well as to be successful in providing a Day-Ahead Real-Time Price policy that maximizes supplier and customer utility. The price policy provides a lower total price for the customer compared with a tariff without demand response (reduction up to 53.63 %), reduces the gap between RES-based energy sources and heating demand, and respects grid technical constraints. / Elnätet har blivit en nyckelaktör i samhället. En ökad elanvändning är både ett resultat av det mer elektrifierade samhället, men också som en huvudlösare för att nå klimatmålen genom att minska utsläpp. Detta examensarbete undersöker några av de nya funktionerna för elnätet från integration av elektrifiering från förnybara energiresurser (RES) och från strategier för energioptimering relaterade till ellaster och specifikt från termiska värmepumpar. Dessa strategier ligger inom området för efterfrågerespons, som drar fördel av lasternas flexibilitet när det gäller viljan att byta eller minska sin konsumtion vid en viss tidpunkt på dagen. Den här forskningen föreslår ett ramverk i tre steg för att utnyttja flexibiliteten hos termostatiskt kontrollerade laster (TCL) baserat på en simulerad gråbox-byggnadsmodell som använder historisk utomhustemperatur och prisdata och lär sig de termiska parametrarna som termisk motstånd, termisk kapacitans , men också priskänslighet (pth) genom en Differential Evolution (DE) baserad optimeringsalgoritm. Priskänsligheten används för att ge ytterligare insikt om lasternas flexibilitet och används i det sista steget för att föreslå en prispolitisk uppskattningsalgoritm också baserad på DE som minimerar klyftan mellan utbud och efterfrågan samtidigt som leverantörs- och kundlönsamheten bevaras. Det föreslagna tillvägagångssättet har visat sig vara korrekt för ett stort antal parametrar men också effektivt med reducerad träningsdata (förutsägelsefel runt 2,5% på effektmedelvärde och standardavvikelse), samt vara framgångsrik i att tillhandahålla en Day-Ahead Real -Tidsprispolicy som maximerar leverantörs- och kundnyttan. Prispolicyn ger ett lägre totalpris för kunden jämfört med en tariff utan efterfrågerespons (reduktion upp till 53, 63 %), minskar gapet mellan RES-baserade energikällor och värmebehov samt följer nättekniska begränsningar.

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