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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.
11

Performance evaluation of ground source heat pump heating systems in Stockholm

BÖRJESSON, MARCUS January 2020 (has links)
GSHP systems are common in Sweden but there are few evaluations quantifying the performance of the systems and highlighting problem that occurs during operations. The research project Annex 52 Long-term performance measurement of GSHP systems serving commercial, institutional and multifamily building part of IEA HPT TCP proves the need to systematically be able to evaluate GSHP systems. This thesis aims to expand the knowledge of how to evaluate GSHP systems and provide case studies for Annex 52. Three residential ground source heating systems used for heating has been evaluated and analyzed in this study. The evaluation has consisted of three parts. The first part analyzes the operation and stability of the GSHP systems. The second part consist of a detailed study of the performance of the GSHP systems. The seasonal performance factor has been calculated for different system boundaries based on the work done by SEPEMO. In addition, a method on how to evaluate the efficiency of the heat pumps based on the two temperature levels, source side temperature and the heat sink temperature, that the heat pump is operating at throughout a year has been developed within this thesis. This has included a method on how to normalize the temperatures based on the operation of the heat pump in order to quantify one temperature for each the two temperature levels. The third part consist of a comparison of the mean secondary fluid temperature between the calculated temperature using the software EED and the measured temperatures. This includes a comparison evaluation and sensitivity analysis on input parameters during the design of the borehole heat exchanger fields. This study has expanded the available reference cases of GSHP systems in Sweden. It also can be used as a guideline for those who will evaluate future GSHP systems. Designers of GSHP system will also benefit from the recommendations listed in this thesis regarding instrumentation and possible problems that may occur. The results show that the evaluation successfully managed to quantify the performance and operational issues that have occurred for each system. The method developed in this study was able to quantify the operation of the different systems based on the temperature levels and can be used for future GSHP evaluations of similar system type. / Bergvärmesystem är vanligt förekommande i Sverige men trots detta finns det få studier där prestandan har utvärderats och de vanligt förekommande problemen under drift har belysts. Forskningsprojektet Annex 52 Annex 52 Long-term performance measurement of GSHP systems serving commercial, institutional and multi-family building som är en del av IEA HPT TCP visar på behovet av att systematisk utvärdera bergvärmesystem. Detta examensarbete syftar till att utveckla och bidra till kunskap om hur bergvärmesystem kan utvärderas och att bidra med exempelstudier till Annex 52. Inom detta examensarbete har tre bergvärmesystem som betjänar flerbostadshus utvärderats och analyserats. Utvärderingen bestod av tre analyser. I den första analyserades driften av bergvärmesystemen och hur stabilt systemet har varit historiskt. Detta följdes av en detaljerad analys av olika nyckeltal för bergvärmesystemen. Årsverkningsgraden har beräknats för olika gränsdragningar vilka baseras på det tidigare arbetet utfört av SEPEMO. Inom detta examensarbete har även en metod tagits fram för att utvärdera verkningsgraderna för en värmepump baserat på de två temperaturnivåerna, köldbärarsidan och värmebärarsidan, som värmepumpen arbetar med under ett år. Till detta har en metod tagits fram om hur temperaturen kan normaliserats baserat på driften av värmepumparna för att kvantifiera en temperatur vardera för de två temperaturnivåerna. I den tredje utvärderingen jämfördes den beräknade medelfluidtemperaturen av köldbäraren i borrhålen med den uppmätta temperaturen. Till detta utfördes en känslighetsanalys av hur indata av dessa beräkningar påverkar resultaten.
12

Cost-effectiveness assessment of energy efficiency obligation schemes - implications for Swedish industries

Xylia, Maria January 2013 (has links)
This thesis is an investigation of whether an energy efficiency obligation scheme would be cost-effective for the Swedish industrial sector. The basic guidelines of the scheme were constructed based on the characteristics proposed in the Energy Efficiency Directive and the previously implemented schemes in other EU Member States. In order to measure the cost effectiveness of the scheme for the industries, a Cost Benefit Analysis was performed. The results of the study show that the participation of the industries in an energy efficiency obligation scheme seems to be cost effective, and the Benefit to Cost Ratios of the analysis where ranging in numbers higher than one, showing that the benefits outweigh the costs. The scheme is in general more cost effective when scenarios assuming high policy intensity for the whole economy of the country are used as input for the calculation of the BCRs, which are also affected positively when higher fuel prices scenarios are adopted. The obligation should be placed upon the distributors, since the prices of energy distribution are administratively regulated. There is opportunity of financial benefits for the Swedish industries from agreements of energy savings delivery to the distributors in order for them to fulfill their obligation. These benefits will support the cost recovery of the investments for the energy savings measures. The possibility of certificate trading in the context of the scheme is another option that can create opportunities for financial gains and stimulate further the energy market. Basing the costs inputs from other EU Member States offers an insight on how these costs could be formed in the case of Sweden, but they cannot be taken as a complete calculation of the scheme’s financial effects. As a result, this study does not offer a final conclusion on the cost-effectiveness of the scheme; it rather serves as a means of support of the final conclusion regarding the cost-effectiveness of energy efficiency obligation schemes for the Swedish industries.
13

Modélisation quantochimiques des forces de dispersion de London par la méthode des phases aléatoires (RPA) : développements méthodologiques / Quantum chemical studies of London dispersion forces by the random phase approximation (RPA) : methodological developments.

Mussard, Bastien 13 December 2013 (has links)
Dans cette thèse sont montrés des développements de l'approximation de la phase aléatoire (RPA) dans le contexte de théories à séparation de portée. On présente des travaux sur le formalisme de la RPA en général, et en particulier sur le formalisme "matrice diélectrique" qui est exploré de manière systématique. On montre un résumé d'un travail sur les équations RPA dans le contexte d'orbitales localisées, notamment des développements des orbitales virtuelles localisées que sont les "orbitales oscillantes projetées" (POO). Un programme a été écrit pour calculer des fonctions telles que le trou de d'échange, la fonction de réponse, etc... sur des grilles de l'espace réel (grilles parallélépipédiques ou de type "DFT"). On montre certaines de ces visualisations. Dans l'espace réel, on expose une adaptation de l'approximation du dénominateur effectif (EED), développée originellement dans l'espace réciproque en physique du solide. Également, les gradients analytiques des énergies de corrélation RPA dans le contexte de la séparation de portée sont dérivés. Le formalisme développé ici à l'aide d'un lagrangien permet une dérivation tout-en-un des termes courte- et longue-portée qui émergent dans les expressions du gradient, et qui montrent un parallèle intéressant. Des applications sont montrées, telles que des optimisations de géométries aux niveaux RSH-dRPA-I et RSH-SOSEX d'un ensemble de 16 petites molécules, ou encore le calcul et la visualisation des densités corrélées au niveau RSH-dRPA-I / In this thesis are shown developments in the random phase approximation (RPA) in the context of range-separated theories. We present advances in the formalism of the RPA in general, and particularly in the "dielectric matrix" formulation of RPA, which is explored in details. We show a summary of a work on the RPA equations with localized orbitals, especially developments of the virtual localized orbitals that are the "projected oscillatory orbitals" (POO). A program has been written to calculate functions such as the exchange hole, the response function, etc... on real space grid (parallelepipedic or of the "DFT" type) ; some of those visualizations are shown here. In the real space, we offer an adaptation of the effective energy denominator approximation (EED), originally developed in the reciprocal space in solid physics. The analytical gradients of the RPA correlation energies in the context of range separation has been derived. The formalism developed here with a Lagrangian allows an all-in-one derivation of the short- and long-range terms that emerge in the expressions of the gradient. These terms show interesting parallels. Geometry optimizations at the RSH-dRPA-I and RSH-SOSEX levels on a set of 16 molecules are shown, as well as calculations and visualizations of correlated densities at the RSH-dRPA-I level
14

Die Britse owerheid en die burgerlike bevolking van Heidelberg, Transvaal, gedurende die Anglo-Boereoorlog (Afrikaans)

Pretorius, Willem Jacobus 01 July 2008 (has links)
Op 23 Junie 1900 het die Britse troepe Heidelberg beset. Die rustige bestaan het vir spanning onder die burgerlikes en agterdog teenoor die Britse militêre owerheid plek gemaak. Inwoners soos ds. A.J. Louw, wat geweier het om die Eed van Neutraliteit te teken, is onverwyld uit die dorp verban. Vroue soos Issie Kriegler en Cassie O’Reilly, wat met hulle uitgesprokenheid die gramskap van die Britte ontketen het, is saam met hulle gesinne na die konsentrasiekamp by Merebank in Natal gestuur. Aangesien die beëindiging van die oorlog vir die Britse owerheid belangrik was, het distrikskommissaris J.M. Vallentin Heidelbergse wapenneerlêers gebruik om die burgers tot oorgawe te oorreed en voorstelle vir die bereiking van vrede aan die hand te doen. As deel van die verskroeide aarde-beleid is Boerevroue en kinders wat sonder heenkome was, na die blanke konsentrasiekamp op Heidelberg geneem, waar hulle getalle mettertyd tot ongeveer 2 000 aangegroei het. Die Heidelbergse kampowerhede het die aankomelinge van tente voorsien terwyl higiëniese maatreëls en mediese dienste vir liggaamlike welsyn ingestel is. Siektes het uitgebreek. Die pogings van die Britse medici om die sterftesyfer met Westerse medikasie en voorskrifte vir beter voeding aan kinders te verlaag, het allesbehalwe seepglad verloop onder meer vanweë die Boerevroue se wantroue in hulle. Voor die Anglo-Boereoorlog was die gemeentelike lewe besonder aktief. Met die Britse oorname het eredienste, bediening van die doop en katkisasie in die susterskerke op Heidelberg op 'n gereelde grondslag voortgegaan. Godsdiensoefening in die konsentrasiekamp is ook nie agterweë gelaat nie. Fasiliteite is vir die gemeentelike aktiwiteite van die drie susterskerke beskikbaar gestel. Ook het die Britse kerke op Heidelberg, die St. Ninian’s Anglican Church en die Wesleyan Methodist Church, ‘n bloeitydperk beleef, terwyl die Berlynse Sendinggenootskap sy werksaamhede gestaak het. Teen 1902 is die kampinwoners toegelaat om dienste in hulle gemeentes op die dorp by te woon. Onderwys het met die Britse besetting ‘n nuwe tydvak betree. Die kampskool het saam met die skoolgeldheffende skole en die “free schools” op die dorp daartoe bygedra om die grondslag vir ‘n Britse onderwysstelsel in Transvaal te lê. Ingevoerde Britse onderwysers het nuwe wêrelde vir die kampkinders ontsluit, wat hulle tot verdere intellektuele ontwikkeling sou aanspoor. Die kampskole, waarby ook volwassenes gebaat het, was ‘n ligpunt in die bestaan van die konsentrasiekampe. Tot onlangs was min oor die swart konsentrasiekampe in die Heidelbergdistrik bekend. Toestande in hierdie kampe het na hulle oorname deur die Departement van Naturellevlugtelinge in Junie 1901 verbeter. Swartes is deur die leër en privaat huishoudings in diens geneem. Sommige was selfversorgend deurdat hulle mielies en ander gewasse produseer het. Die swart kamp op Heidelberg se sterftesyfer was laag. Dit is waarskynlik aan die goeie werk van die mediese offisier, ene Stewart, te danke. Hervestiging van blanke en swart kampinwoners het na afloop van die oorlog in Mei 1902 gevolg. Met Britse hulp en danksy rantsoene wat aan hulle uitgereik is, kon hulle huiswaarts keer. Dit blyk dat Heidelberg se blanke konsentrasiekamp relatief goed bestuur is en vanweë sy lae sterftesyfer onder die beter kampe tel. / Thesis (DPhil (History))--University of Pretoria, 2008. / Historical and Heritage Studies / unrestricted
15

Optimización teórico-experimental de sondas de calor para intercambio geotérmico (SGE) según condiciones hidrogeológicas, características geométricas y propiedades de sus materiales

Badenes Badenes, Borja 01 February 2021 (has links)
[ES] Uno de los mayores retos para el mercado de bombas de calor geotérmicas es el alto coste asociado a la perforación de los intercambiadores de calor geotérmicos. Conseguir unos intercambiadores de calor geotérmicos más eficientes reduciría dicho coste, ya que sería necesaria una menor longitud de intercambiador para obtener las mismas temperaturas de trabajo en él (misma eficiencia de la bomba de calor). La eficiencia térmica de un intercambiador de calor geotérmico está caracterizada por su resistencia térmica. Dicha resistencia térmica depende de una serie de elementos entre los que se encuentran: propiedades y caudal del fluido que recorre el intercambiador de calor, diámetro de la perforación geotérmica, geometría y materiales de la tubería del intercambiador de calor y las propiedades del material de relleno de la perforación (grouting). Cuanto mayor sea la resistencia térmica del intercambiador de calor, menor será el calor transferido entre el fluido caloportador y el terreno, traduciéndose en una necesidad mayor de longitud de intercambiador enterrado. Por lo tanto, es necesario una reducción de este parámetro al mínimo posible. En consecuencia, el objetivo principal de esta tesis doctoral consiste en, a partir de un modelo analítico comprensivo de cuantificación del impacto de los parámetros anteriores, realizar un estudio detallado para analizar su influencia combinada en la resistencia térmica del intercambiador geotérmico, pero también examinando dicho efecto en otros planos, como costes económicos de ejecución del intercambiador y de explotación (consumo eléctrico de la bomba de calor y costes de bombeo asociados). / [CA] Un dels majors reptes per al mercat de bombes de calor geotèrmiques és l'alt cost associat a la perforació dels bescanviadors de calor geotèrmics. Aconseguir uns bescanviadors de calor geotèrmics més eficients reduiria aquest cost, ja que seria necessària una menor longitud de bescanviador per a obtenir les mateixes temperatures de treball en ell (mateixa eficiència de la bomba de calor). L'eficiència tèrmica d'un bescanviador de calor geotèrmic està caracteritzada per la seva resistència tèrmica. Aquesta resistència tèrmica depèn d'una sèrie d'elements entre els quals es troben: propietats i cabal del fluid que recorre el bescanviador de calor, diàmetre de la perforació geotèrmica, geometria i materials de la canonada del bescanviador de calor i les propietats del material de farciment de la perforació (grouting). Com més gran sigui la resistència tèrmica del bescanviador de calor, menor serà la calor transferida entre el fluid termòfor i el terreny, traduint-se en una necessitat major de longitud de bescanviador enterrat. Per tant, és necessari una reducció d'aquest paràmetre al mínim possible. En conseqüència, l'objectiu principal d'aquesta Tesi Doctoral consisteix en, a partir d'un model analític comprensiu de quantificació de l'impacte dels paràmetres anteriors, realitzar un estudi detallat per a analitzar la seva influència combinada en la resistència tèrmica del bescanviador geotèrmic, però també examinant aquest efecte en altres plans, com a costos econòmics d'execució del bescanviador i d'explotació (consum elèctric de la bomba de calor i costos de bombament). / [EN] One of the biggest challenges for the ground source heat pump market is the high cost associated with drilling geothermal borehole heat exchangers. Achieving more efficient geothermal heat exchangers would reduce this cost, since a shorter exchanger length would be required to obtain the same working temperatures in it (same efficiency of the heat pump). The thermal efficiency of a geothermal heat exchanger is characterized by its borehole thermal resistance. This borehole thermal resistance depends on a number of parameters, mainly: properties and flow rate of the working fluid that flows through the borehole heat exchanger, diameter of the geothermal borehole, geometry and materials of the heat exchanger pipe and the properties of the borehole grouting material. The higher thermal resistance of the heat exchanger, the less heat is transferred between the heat carrier fluid and the ground, resulting in an increased requirement for the length of the buried heat exchanger. Consequently, it is essential to reduce this parameter to the minimum possible. Therefore, the main objective of this Ph. Doctoral Thesis is to carry out, based on a comprehensive analytical model of quantification of the impact of the above mentioned parameters, a detailed study to analyze their combined influence on the thermal resistance of the geothermal borehole, but also exploring this effect in other less researched areas, such as economic costs of running the exchanger and operating it (electricity consumption of the heat pump and associated pumping costs). / This research has received funding from the European Union’s Horizon 2020 Research and Innovation program under grant agreement No [657982], [727583] and [792355]. / Badenes Badenes, B. (2020). Optimización teórico-experimental de sondas de calor para intercambio geotérmico (SGE) según condiciones hidrogeológicas, características geométricas y propiedades de sus materiales [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/160477 / TESIS

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