1,720,991 research outputs found
Komparativna analiza centralnih toplinskih sustava u Hrvatskoj i Danskoj
No full textDistrict heating systems are one of the elements that can help meet the goals set by the EU Directives for the reduction of primary energy consumption. Therefore, they are of high interest to both Croatia and Denmark. DH systems are essential for their heat production that can be produced with a wide variety of energy sources with high efficiency. Heat energy for DH can be produced by high-efficiency cogeneration or the use of renewable energy sources like geothermal heat and heat pumps. The advantage of DH systems are substantial and include secure heat energy supply, primary energy savings, and they also have greater means of regulating energy consumption. Numbers like 63% of all Danish dwellings, and 11% of households in Croatia that are heated by district heating systems, show the relevance of these systems. This thesis compares DH systems in Zagreb and Aalborg in order to see their similarities and differences from which conclusions are drawn on how to improve the systems. The method chosen for this thesis is the comparative analysis. Different parts of district heating system are analyzed point by point. In this way, the data is organized and structured so to allow clear and concise comparison. The results of the comparative analysis show that Aalborg DH system is more advanced than Zagreb DH system. This advantage is prominent in aspects of supply, demand, distribution and economic spheres. As a result of this difference, more improvement could be stated for Zagreb DH than Aalborg DH. Some of the possible improvements include lowering specific heat and water losses, which are 68%, and 36 times lower in Aalborg DH. Systematic replacements and refurbishments of the old network pipes are key to this. Supply temperature, which is correlated with heat losses, could be lower in both DH systems. Further advances in both systems must be made in heat supply. In Zagreb new CHP unit could be built and in Aalborg more excess heat from the industry should be use. Further integration of the renewable energy sources should be achieved in both systems. Technological advancements and market forces are expected to bring new technologies in heat generation in DH systems such as waste to energy plants, geothermal plants, biomass CHP, solar thermal, and heat pumps run by the electricity from wind turbines, hydroelectricity plants and photovoltaic systems.Centralni toplinski sustavi (CTS) jedan su od elemenata kojima bi se mogli postići ciljevi postavljeni u EU Direktivama, o smanjenju potrošnje primarne energije. Samim time, oni su od iznimnog interesa i za Hrvatsku i Dansku. CTS-i izuzetno su bitni radi mogućnosti proizvodnje topline sa širokim dijapazonom izvora energije, s visokom razinom efikasnosti. Toplina za CTS može se proizvesti kogeneracijom ili obnovljivim izvorima energije poput geotermalne energije i toplinskih pumpi. Prednosti CTS-a znatne su, a uključuju sigurnu opskrbu energijom, štednju primarne energije te su tu također mogućnosti reguliranja potrošnje energije. činjenice poput te da je 63% danskih kućanstva grijano CTS-om, kao i 11% hrvatskih kućanstva, govori o važnosti ovih sistema. U ovom diplomskom radu uspoređuju se CTS-i u Zagrebu i Aalborgu, kako bi se pokazale njihove sličnosti i razlike, iz kojih se mogu izvući zaključci kako poboljšati spomenute sustave. Metoda izabrana za razradu rada je komparativna analiza. Pojedini dijelovi centralnih toplinskih sustava analiziraju se dio po dio. Na ovaj način podatci se organiziraju i strukturiraju kako bi se ostvarila jasna i koncizna usporedba. Rezultati komparativne analize pokazuju da je CTS u Aalborgu znatno napredniji od sustava u Zagrebu. Prednost je znatna u području opskrbe, potražnje, distribucije i na ekonomskom polju. Kao rezultat te činjenice više poboljšanja moglo se predložiti za sustav u Zagrebu nego za sustav u Aalborgu. Neka od mogućih poboljšanja uključuju snižavanje specifičnih toplinskih gubitaka i gubitka vode, koji su 68% i 36 puta niži u Aalborgu. Za to su ključne sistemske zamijene i poboljšanja stare mreže cijevi. Temperatura polaza, koja je u korelaciji s gubitcima topline, mogla bi biti niža u oba analizirana sustava. Daljnja poboljšanja u dobavi topline nužna su u oba sustava. U Zagrebu bi se mogla izgraditi nova kogeneracijska jedinica, dok bi se u Aalborgu trebao više koristiti višak topline iz industrije te bi se također trebalo integrirati više obnovljivih izvora energije. Napredak u tehnologiji i „sile tržišta“ trebale bi donijeti nove tehnologije u proizvodnju topline u CTS-ima, poput modernih spalionica otpada, geotermalnih postrojenja, kogeneracija na biomasu, solarnih toplinskih kolektora te dizalice topline pogonjene električnom energijom iz vjetroelektrana, hidroelektrana i fotonaponskih elektrana
Reapplication model for planning, development and integration of Smart district heating systems in Smart energy system
No full textU ovom radu obrađena je tema reaplikacije pametnih centraliziranih toplinskih sustava kao dijela pametnih energetskih sustava u pametnim gradovima. Rad je napravljen u skladu s zadacima postavljenima u radnom paketu 8, projekta SmartEnCity.
Najprije je proveden sažeti pregled projekata pametnih gradova i pametnih centraliziranih toplinskih sustava kako bi se odredili važni podaci iz projekata u tijeku. Dobiveni podaci će služiti kao vrijedan doprinos u SmartEnCity projektu.
Opisom pametnih centraliziranih toplinskih sustava su definirane njihove glavne karakteristike. Opis je dan uz pomoć sveobuhvatnog pregleda postojeće literature.
Kako bi se pametni centralizirani toplinski sustav kopirao, tj. replicirao iz jednog grada u drugi, potrebno je odrediti važne aspekte za replikaciju. Glavni aspekti koji su definirani i objašnjeni su: geografski, financijski, tehnički i aspekt vlasništva.
Nakon definiranja važnih aspekata za replikaciju, definirani su i opisani važni koraci metodologije za replikaciju pametnih centraliziranih toplinskih sustava, te je izrađen dijagram toka replikacije dajući grafički prikaz metodologije, korak po korak.
Konačno, definirana su i opisana četiri alata za korištenje u svrhu replikacije aktivnosti u gradu Sønderborg. Također, predložen je i sadržaj plana djelovanja za individualnu replikaciju u gradu Sønderborg.This thesis deals with replicating smart district heating systems as a part of smart energy systems in smart cities. The thesis was done done with inspiration from the Workpackage 8 of SmartEnCity EU research project and the municipality of Sønderborg, Denmark.
First, a brief review of smart cities and smart district heating projects was carried out in order to define important lessons learned from ongoing demonstration activities to serve as a valuable input in SmartEnCity project.
Description of smart district heating systems, defining their main characteristics was given by means of comprehensive review of existing literature. In order to replicate a smart district heating system from one city to another, it is necessary to define important aspects for replication. Main aspects that were defined and explained are geographical, financial, technical and ownership aspects.
After defining important aspects for replication, important steps of methodology for replication of smart district heating systems are defined and described and the replication flowchart is drafted giving a step-by-step graphical representation of the methodology.
Finally, four tools to be used in replication activities in the city of Sønderborg were defined and described and also the content for individual replication in the city of Sønderborg was proposed
The role of large scale heat pumps in future energy systems
No full textOvaj diplomski rad predstavlja procjenu uloge dizalica topline velikih instaliranih snaga u budućem energetskom sustavu.
U uvodu je opisana analiza trenutnog danskog energetskog sustava s posebnim naglaskom na sektore električne te toplinske energije. Također je objašnjen tehnološki koncept dizalica topline velikih instaliranih snaga.
Poslije uvoda slijedi analiza dvaju modela koji se koriste za modeliranje energetskih sustava, EnergyPLAN-a i TIMES-a (MARKAL-a), kako bi se ukazalo na prednosti i nedostatke oba modela. Glavni zaključak analize je da EnergyPLAN-u ima prednost prilikom modeliranja energetskih sustava sa visokim udjelom intermitentnih izvora energije.
U sljedećem poglavlju je prikazana analiza investicije u električni kotao te dizalice topline velike instalirane snage koristeći metodu usrednjenih troškova toplinske energije (eng. levelized cost of heating energy). Također je analizirana i elastičnost potražnje za električnom energijom na Nordpool burzi električne energije. Analizom se pokušalo utvrditi hoće li povećana potražnja za električnom energijom uslijed pogona dizalica topline dovesti do porasta cijena električne energije.
Naposljetku, nekoliko različitih scenarija razvijeno je u EnergyPLAN-u s različitim instaliranim snagama vjetroelektrana, optimalnim kapacitetima dizalica topline velikih instaliranih snaga te sezonskim spremnicima topline u obliku jame (eng. pit thermal energy storage). U radu je pokazano da za svaku instaliranu snagu vjetroelektrana u energetskom sustavu postoji određena optimalna snaga dizalica topline, koja će smanjiti ukupne troškove energetskog sustava, CO2 emisija i kritičnog viška u proizvodnji električne energije (CEEP). Dodatne uštede u troškovima energetskog sustava ostvarive su dodavanjem velikih sezonskih spremnika topline u sustav s već optimalno instaliranom snagom dizalica topline.In this thesis, several tasks were performed in order to evaluate the role of large scale heat pumps in the near term future energy systems.
Firstly, the analysis of the Danish current energy system was carried out with the special emphasize on the electricity and district heating sector. Moreover, a technical concept of the large scale heat pumps was provided.
Secondly, the analysis of EnergyPLAN and TIMES (MARKAL) modelling tools was performed in order to detect pros and cons of each of the models. EnergyPLAN was chosen as the favourable modelling tool for the assessment of the energy systems with high share of intermittent energy sources.
Thirdly, for the purpose of economic evaluation of investments in electric boilers and large scale heat pumps, a levelized cost of heating energy (LCOH) was calculated.
Furthermore, price elasticity of electricity demand on Nordpool’s El-spot market was calculated in order to assess possible shift in demand due to possible increased usage of electricity by heat pumps.
Lastly, several different scenarios in EnergyPLAN were developed with different wind penetration levels, large scale heat pumps capacity and pit thermal energy storage (PTES). It was shown that for each wind penetration level, a certain amount of large scale heat pumps is optimal, which reduces the total system costs, CO2 emissions and critical excess in electricity production (CEEP). Moreover, adding large scale seasonal thermal energy storage to the system with implemented optimal level of heat pumps capacity will decrease total system costs even more
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Danmark skal investere massivt i energisektoren for at nå klimamål - men ikke i atomkraft
No full textÆngstelsen for de hastigt stigende energipriser må ikke få os til at gå i panik og lede efter løsninger, der ikke er realistiske, for den faktuelle sandhed er, at snakken om dansk atomkraft er varm luft, og bliver ved med at være de
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Progress and results from the 4DH research centre [Elektronisk resurs]
No full textWith lower and more flexible distribution temperatures, fourth generation district heating systems can utilize renewable energy sources, while meeting the requirements of low-energy buildings and energy conservation measures in the existing building stock. 4DH is an international strategic research centre located at Aalborg University, which develops 4th generation district heating technologies and systems (4GDH). This technology is fundamental to the implementation of the Danish objective of being fossil fuel-free by 2050 and the European 2020 goals. The research centre is working between 2012 and 2017, with The Danish Council for Strategic Research as main financier and the participating 31 Danish and international companies and universities as co-financiers. Thirteen PhD student projects constitute a vital part of the research centre. In 4GDH systems, synergies are created between three areas of district heating and cooling, which also sum up the work of the 4DH Centre: Grids and components; Production and system integration, and Planning and implementation. This paper presents an overview of the progress and results achieved after more than two years of work. This includes the basic definition paper, the two Heat Roadmap Europe pre-studies, annual conferences, additional demonstration projects, initiated European project proposals, an international PhD course based on the new international textbook, PhD student seminars, all PhD student subjects, and a list of major papers and articles written so far within the research centre.</p
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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