Thèses sur le sujet « FISICA SOLARE »
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Cavalazzi, Gianmarco. « Fisica delle celle fotovoltaiche modelli e prospettive di ricerca ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24338/.
Texte intégralAlbertazzi, Clarissa. « Studio di celle fotovoltaiche di terza generazione : celle tandem ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8942/.
Texte intégralFranceschetti, Paolo <1981>. « Energie rinnovabili e microgenerazione distribuita : serra solare ad evaporazione ». Doctoral thesis, Università Ca' Foscari Venezia, 2013. http://hdl.handle.net/10579/4658.
Texte intégralIn an International context of research focused on the development of new technologies based on energy supplied by renewable sources, the development of micro-water treatment plants is of increasing interesting. The current study fits into this perspective with the aim to provide an innovative tool for the optimization of the desalination/water purification systems, by using only the solar radiation source. In the present study, the state of art of the systems, hereafter called solar stills, was analyzed in order to understand their potential and limits from a physical and efficiency perspective. Afterwards, new prototypes were developed and tested, resulting in a significant improvement of the solar stills’ performances. Basing on results from the first test performed, the exergetic calculation of the system was carried out. . Additionally, the experimentation on different types of materials to be used for the construction of the solar stills, in association to the thermodynamic and fluid dynamic modeling processes, allowed us to reach a further development of the systems. Such improvements leaded to a higher efficiency of the solar still, compared to the state of the art. Once the system has been consolidated, a geo-spatial analysis based on both climatic conditions (geo-spatial index - GSI ) and anthropogenic conditions (socio-economic index - SEI), has been performed with the aim to identify the areas where the developed systems were more applicable.
Sotte, Marco. « Design, test and mathematical modeling of parabolic trough solar collectors ». Doctoral thesis, Università Politecnica delle Marche, 2012. http://hdl.handle.net/11566/242075.
Texte intégralSolar radiation at its origin is a high-exergy energy source: the Sun has an irradiance of about 63 MW/m2. But on the Earth’s surface solar energy flow dramatically decreases. For this reason, when high temperatures or high-exergy need to be reestablished, concentrated solar systems are adopted. Among all possible geometries, parabolic trough collectors are by far the most widespread technology. A field of usage of PTCs is in industrial process heat: this application has a dramatic potential and can be adopted at latitudes like those of central and southern europe. In this thesis the results of research project (PTC.project) for the study of PTCs in IPH and other heat demands in the temperature range from 80 to 250 °C are exposed. The design and manufacture of two prototypes are described in detail, giving complete information on geometrical characteristics, materials and manufacturing processes. Then the results of preliminary tests on the mentioned prototypes are produced, together with the characteristics of a test bench designed to determine PTCs performances with water and heat transfer oil as working fluids in a temperature range from 10 to 150 °C. Then a mathematical model, able to determine the performance of any PTC is described: the model accounts for optical and thermal losses of the collector, and also contains a routine code to calculate the solar position. In the end a simulation environment for annual analysis of the performance of a PTC applied to a specific process heat demand load is presented and the results obtained on a realistic heat demand yearly profile are described. The energetic results suggest that there could be space for this technology in the variety of renewable energies that will be needed to meet international goals in terms of energy and environment in the nearest future. But the experience acquired also suggests that investments are needed if an acceleration on the spreading of PTCs and other CSP technologies is to be realized
Zambolin, Enrico. « Theoretical and experimental study of solar thermal collector systems and components ». Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3422853.
Texte intégralI collettori solari termici maggiormente impiegati per convertire la radiazione solare in calore sono i collettori a tipologia piana e a tubi evacuati. Nelle applicazioni convenzionali essi vengono utilizzati per la produzione di acqua calda sanitaria o riscaldamento domestico in combinazione con sistemi a bassa temperatura. Prove d’efficienza termica ed ottimizzazione di questi dispositivi solari sono affrontati e discussi in questa tesi. Nuove prove sperimentali in varie condizioni sono state effettuate su collettori piani vetrati e a tubi evacuati per effettuare una nuova analisi comparativa. L’efficienza è stata misurata secondo le indicazioni della normativa europea EN 12975 ed inoltre si sono ricavate curve input-output e di efficienza media giornaliera. Questo approccio permette un confronto più ampio delle prestazioni effettive dei collettori solari considerati. Uno strumento di simulazione delle prestazioni dei collettori a geometria piana è anche proposto. Il modello numerico permette di ottenere un “collettore virtuale” e fornisce informazioni sulle prestazioni di un collettore senza costruirne un prototipo funzionale. Il modello tridimensionale stima le prestazioni di un collettore a geometria piana in condizioni stazionarie ed è stato validato confrontando le prestazioni stimate con i risultati sperimentali ottenuti su due collettori diversi. Misure di temperatura della piastra assorbente, della copertura vetrata, dei tubi dell’arpa ed analisi all’infrarosso sono stati utilizzati per investigare le dispersioni termiche e le caratteristiche ottiche della geometria considerata. Il modello è inoltre stato usato per analizzare gli effetti di alcune scelte progettuali riguardanti la geometria e i materiali dei componenti del collettore. I collettori solari a tubi evacuati sono in linea di principio più costosi dei collettori piani e sono idonei ad applicazioni a più alta temperatura (sistemi di riscaldamento, macchine ad assorbimento..). La loro geometria rende più difficile la caratterizzazione completa delle prestazioni del collettore. Una nuova procedura per caratterizzare questo tipo di collettori è stata sviluppata ed è qui descritta. Sono state eseguite prove sperimentali su un collettore a tubi evacuati, con tubi ad U, con assorbitore cilindrico, con e senza riflettori CPC (compound parabolic concentrator) esterni. I risultati sperimentali sono stati utilizzati per validare la nuova procedura e per fornire indicazioni sull’incremento dell’efficienza dovuto all’impiego dei riflettori CPC.
Maoulaoui, Khaled. « Sistemi solari stand-alone per il mantenimento della catena del freddo ». Doctoral thesis, Università Politecnica delle Marche, 2013. http://hdl.handle.net/11566/242736.
Texte intégralThe present work aims to make a comparison between different sun‘s cold technologies ―Ice maker ―; These machines could be thermally powered by (solar thermal energy adsorption or absorption) or electrically (FV- vapor Compression) The work begins with an introduction, that explains the advantages of solar Ice maker: Self-sufficiency, Health and non-toxicity, Ecological sustainability, Social and Economic factors. I mentioned at the beginning the topic of the PV and thermal solar collectors, which will be used to drive these machines, and then i illustrated in the thermodynamic cycle of the machines mentioned above. Then i studied the adsorption machine (methanol-activated charcoal) powered by a solar thermal Panel. Starting from a mathematical model and fixed and dynamic data (temperature and radiation) inserting them in a software that gives us the dynamic simulation results, then it was discussed the parametric analysis and design of all components (solar collector, condenser, evaporator, ...) The second machine was the solar absorption (water-lithium bromide) powered by solar thermal Panel. Doing the same procedure of first mathematical model input data dynamic simulationresultsparametric analysis (without studying the machine design). For the third machine the vapor compression (R-600a) powered by polycrystalline Panel and DC motor. Doing the same procedure just over mentioned. The final comparison between these three machines was done based on comparing index (Ice quantity per day/Panel surface, STR, Lowers temperatures reached ...) to find that the best machine is the solar adsorption. The next step is to go beyond dynamic simulation, and to Design/install these three machines in the same climate zone (sub-Saharan Africa) studying the effective machines run and to establish which one is the best in the same operating conditions.
Orlando, Andrea. « Multispacecraft observations of Coronal Mass Ejections ». Doctoral thesis, Università di Catania, 2012. http://hdl.handle.net/10761/990.
Texte intégralRONCHI, ALESSANDRA. « Hybrid and Nanostructured materials for low power photon upconversion based on triplet-triplet annihilation ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/370864.
Texte intégralIn my PhD project, I investigated the photophysical process of photon upconversion assisted by triplet-triplet annihilation (sTTA-UC) through spectroscopy studies in a variety of systems, profoundly different on many levels. In sTTA-UC high energy radiation is emitted from the fluorescent recombination of the excited singlet of an emitter molecule, previously populated via annihilation of the metastable triplet states of two emitters. This is a sensitized process since a sensitizer is necessary to harvest the low energy incident light and to transfer the stored energy to the emitters via Dexter energy transfer. Because its functioning relies on long-lived metastable triplets, this process can be highly efficient also under low power, noncoherent light. As such, sTTA-UC is particularly suited for solar applications as it can increase the conversion efficiency by reducing transmission losses. During my studies, I focused on addressing two crucial issues that still limit the application of upconverters in solar technologies, i.e. the limited storage ability of common organic sensitizers and the poor sTTA-UC performance in solid-state upconverters, which are intrinsically better suited than liquid solutions for technological applications. To solve the first problem, I investigated hybrid sensitizers, composed of semiconductor nanostructures decorated with conjugated organic ligands characterized by broadband absorption. CdSe nanocrystals (NCs) doped with gold cations and decorated with 9-anthracene carboxylic acid demonstrated to be efficient innovative broadband hybrid sensitizers. The doping strategy inserts into the NCs energy gap localized hole-accepting states where the holes localize on the picosecond timescale, outpacing hole transfer to the ligand HOMO. With this strategy, I achieved the UC efficiency of 12%, the record performance obtained so far for hybrid upconverters. I then discussed how the CdSe nanoplatelets surface and photophysical properties make them potential optimal light harvesters. My studies on the nanoplatelets-to-ligands energy transfer dependency on the surface ligand density revealed that the surface coverage is not homogeneous but proceeds in an island-like way promoted by π- π stacking and results in the formation of ligands aggregates on the nanoplatelets surfaces, which causes a redshift of the ligand triplet energy with critical repercussions on the sTTA-UC performance and on the emitter selection. To address the second issue, I investigated two solid-state upconverters, i.e. nanostructured glassy polymers that show similar macroscopic properties but fabricated via different approaches. They both feature liquid droplets of mean size less than 50 nm where the upconverting dyes accumulate, embedded in a rigid polymer matrix that grants excellent oxygen protection and optical quality and long-term stability. The dyes confinement allows to increase the effective local excitons density resulting in an enhanced UC efficiency at low excitation intensities, thanks to the reduced intermolecular distances and the activation of the confined sTTA-UC regime. I also introduced a new perylene derivative as emitter, specifically designed to prevent molecular aggregation to maximize its fluorescence efficiency. By employing this emitter, I achieved the record UC efficiency of 42%, which directly stems from the emitter molecular structure, as it limits the formation of aggregates, while guaranteeing excellent singlet generation efficiency upon TTA. I finally presented a perspective of the performances that can be achieved by combining the two topics considered, i.e. loading broadband sensitizers in nanostructured polymers. I highlighted that if the best trade-off between nanostructure size and energy distribution is met the maximum UC efficiency can be achieved at excitation powers orders of magnitude lower that the solar irradiance, therefore promoting the development of real-world solid-state upconverters.
Emmi, Giuseppe. « ANALISI TEORICA E SPERIMENTALE DI SISTEMI SOLARI PER LA CLIMATIZZAZIONE E LA PRODUZIONE DI ACQUA CALDA SANITARIA DI EDIFICI RESIDENZIALI ». Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3427018.
Texte intégralIl presente lavoro verifica l’applicazione dell’energia solare termica ai fini della climatizzazione combinata alla produzione di acqua calda sanitaria nel settore civile al fine di ridurne i consumi energetici. In particolare è stata analizzata una serie di studi derivanti da misure in opera delle prestazioni di funzionamento di un impianto solare termico installato in un’abitazione residenziale nella provincia di Treviso e da simulazioni dinamiche del sistema edificio–impianto sia per il riscaldamento che per il raffrescamento. L’obiettivo principale è verificare, o comunque prevedere, quali siano i margini di risparmio ottenibili dallo sfruttamento della tecnologia appositamente creata per l’utilizzo della radiazione solare solamente da punto di vista termico in sistemi attivi. In tale contesto infatti non verrà trattato l’aspetto relativo alla produzione elettrica fotovoltaica, che assieme ai sistemi solari termici ha avuto una grande diffusione soprattutto negli ultimi anni grazie ad incentivi di natura pubblica. Nella prima parte del lavoro si analizza quale sia lo stato attuale del mercato del solare termico nei vari Paesi europei e del mondo e quali siano le prospettive future, dal momento che l’energia solare diventerà parte integrante di tutti i sistemi energetici sia su piccola che su grande scala. Sulla base di queste considerazioni si riportano i risultati prestazionali di alcuni casi di studio. Un primo studio ha riguardato l’analisi di un sistema solare a servizio di un edificio residenziale. La prima parte dello studio ha riguardato il monitoraggio in opera per circa un anno di tutte le grandezze utili ai fini della valutazione energetica. Successivamente è stato sviluppato un modello di simulazione dinamica del sistema edificio–impianto mediante il codice di calcolo dinamico TRNSYS. La seconda parte del lavoro prosegue con la trattazione di sistemi solari dedicati al raffrescamento estivo, conosciuti anche come sistemi di solar cooling. A tal riguardo, dopo una breve descrizione delle macchine frigorifere ad assorbimento, si riporta lo studio effettuato in collaborazione con un’azienda per lo sviluppo di un prototipo di macchina solare di tipo “Plug&Play”, basata su un brevetto depositato, da utilizzarsi nell’edilizia sia residenziale che del settore terziario. In particolare sono stati affrontati problemi di natura tecnica legati ad alcune limitazioni che il prototipo ha presentato e sono stati dimensionati i componenti principali del sistema. Nonostante in questa prima fase il lavoro sia stato di natura progettuale, è stato richiesto l’ausilio di simulazioni dinamiche per poter effettuare alcuni dimensionamenti e scelte. L’ultima parte di questo progetto è dedicata alla creazione di un modello dinamico complessivo del sistema considerando utenze di tipo sia residenziale che terziario. Mediante tale modello sono state effettuate delle simulazioni accoppiando la macchina a diverse tipologie di sistemi radianti. La parte conclusiva ha riguardato un altro caso di studio sul solar cooling, differente da quello precedente; tale lavoro ha avuto come primo obiettivo lo studio di una camera termica da installare all’interno di un’azienda al fine di testare i sistemi radianti di propria produzione. Successivamente si sono effettuate delle simulazioni analizzando una tipologia di sistema radiante a soffitto accoppiato ad un sistema di solar cooling. A differenza del lavoro precedente, in questo caso sono stati valutati i fabbisogni energetici legati al riscaldamento, al raffrescamento e alla produzione di acqua calda sanitaria per quattro zone climatiche.
SANTUNIONE, GIULIA. « Sviluppo di un metodo di invecchiamento biologico accelerato delle superfici ad alta efficienza energetica ». Doctoral thesis, Università degli studi di Modena e Reggio Emilia, 2022. http://hdl.handle.net/11380/1277157.
Texte intégralBiological growth on building surfaces can be responsible of degradation of their aesthetical and functional properties. Phototrophic organisms as algae and cyanobacteria have been identified as the first ones to colonize surfaces and allow the formation of following biocenosis, where also heterotrophic bacteria and fungi are involved. Biological colonization depends mainly on climate and microclimate conditions over and all around surfaces, mainly moisture and light availability. This phenomenon is particularly damaging for solar reflective materials (cool building materials), which are characterized by the ability to reflect solar radiation in the whole wavelength spectrum and remain cooler under the sun. Cool materials represent one of the most efficient countermeasures to the urban heat island effect, which causes temperatures in urban areas to be significantly higher than in the surrounding rural areas. Several standards are nowadays available to investigate natural ageing of cool materials (ASTM G7) and accelerated ageing (ASTM D7897). Unfortunately, these standards are mostly focused onto surface soiling and they do not take into proper account the presence and growth of microorganisms. This research work was firstly aimed to develop a laboratory procedure able to reproduce biological colonization on new materials in a repeatable way, in order to quantify the loss of energy performance due to the biological growth. Another goal was to reduce the bio ageing test duration, which normally requires many years through natural exposition. The novel method was built step by step studying separately the influence of different experimental parameters on biological growth then on repeatability of the test. Several setups and environmental conditions have been tested, compared and finally evaluated according to repeatability of results. The experimental device used to expose material samples to bioageing was a bioreactor -a Temporary Immersion System (TIS); three different types of high-efficiency building materials samples, precisely white asphalt shingle (AS), single ply white membrane (WM) and white paint (WP) were tested. Materials samples have been characterized in terms of physical and chemical properties, before and after bioageing exposure. Furthermore, biological growth has been monitored, measured, and finally correlated to colonization level on surfaces. Algae and cyanobacteria growth as well as bio-colonization dynamics describes a curve which follow Avrami’s law, a model previously used to simulate algal colonization process as temporal evolution. Ancillary aspects to bioageing phenomenon were investigated in this research: scientific literature reports that the deposition of soiling on surfaces seems to provide a nutrient layer for phototrophic organisms, encouraging their growth; however, it has been also observed that the presence of atmospheric pollutants could inhibit both the size and diversity of the microbial community. Hence, algal and cyanobacteria growth on soiled surfaces was here studied and compared to growth on new ones. Moreover, metabolites profile production of some algal species after their exposure to soiling mixture was described, in order to outline the influence and effects of soiling solution as abiotic stress to algal cells metabolism. Definitely, this research offers an experimental protocol to induce accelerate bio ageing process on cool building surfaces, providing data about repeatability and strength of the method; the modularity and the application of the protocol to define bio-resistance of a surface type was finally described by Avrami’s model. The application of the protocol on different types of cool surfaces and reproducibility definition are expected as future perspectives.
MATTARELLI, Agnese. « PROGETTARE L'EFFICIENZA ENERGETICA : esperienze sul ruolo del sistema edificio, del sistema impianto e della loro gestione ». Doctoral thesis, Università degli studi di Ferrara, 2012. http://hdl.handle.net/11392/2389443.
Texte intégralLivi, Silvia Helena Becker. « A relação entre cancelamento de fluxo magnético e fulgurações solares ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 1994. http://hdl.handle.net/10183/122006.
Texte intégralFlares have been studied for a long time and continue to puzzle solar scientists. Our work is on the relationship between flares and flux cancellation. Flux cancellation is an observational phenomena discovered using series os magnetograms of the line-of-sight component. It consists of the encounter and further disappearance of magnetic flux where opposite magnetic polarities are in apparent contact with each other and maintain a high gradient of magnetic field.
Migliorini, Alessandra. « Studio fisico dei piccoli corpi del sistema solare ». Paris 7, 2007. http://www.theses.fr/2007PA077013.
Texte intégralThe topic of my PhD research is to study the surface composition of asteroids, Trans-Neptunian Objects, and planetary satellites. I analyzed and interpreted both data taken with ground-based telescopes and space instrument data. They have been analyzed with standard methods: the comparison of observed data with laboratory data, or with synthetical spectra, obtained by mixing end-members, according to the theory of light diffusion. I contributed in interpreting spectroscopical data of the icy satellites of Saturn, Phoebe, lapetus, Enceladus, Tethys and Hyperion, observed by the Cassini/CIRS spectrometer, on board the Cassini spacecraft, in the far infrared spectral range, Physical causes of the absence of features on these spectra have been studied. As a result, such satellites seem to have a very high porouse surface. Laboratory experiments have been conducted, in order to set more strict constrains on icy surfaces properties. Surfaces properties of some more small bodies of the outer Solar System, and a group of 10 E-type asteroids of the Main Belt were also derived, by analyzing ground-based telescopes data. For E-type asteroids, some interesting comparisons with meteorites were found. Moreover, I participated to an astrometrical research of Trojan asteroids of the giant planets. My PhD research has covered a wide spectral range, from visible to FIR: the whole spectral range has provided a useful contribution in the comprehension of the small bodies. Moreover, the possibility to analyze data, taken both with space instruments and ground-based telescopes has greatly enriched with new results the knowledge of our Solar System
Bouich, Amal. « Study and Characterization of Hybrid Perovskites and Copper-Indium-Gallium Selenide thin films for Tandem Solar Cells ». Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/160621.
Texte intégral[EN] The thesis work presented is part of the work in the Laboratory of New Materials for Photovoltaic Energy in the main target to use low cost techniques for elaboration of Perovskite and Copper, indium, gallium, and selenium CIGS materials for photovoltaic application. Organic-inorganic lead halides perovskites have currently and exceptionally appeared as new materials for low cost thin film solar cells specially that the efficiency of perovskite based solar cell have jumped from 3.8% to 22.7% in short time.in other hand, CIGS solar cells record 23.35% efficiency and still can be boosted. Here, we report the elaboration and characterization of CIGS as well as methylammonium lead iodide perovskites MAPbI3 and formamidinuim iodide lead iodide perovskites FAPbI3 absorbers for perovskite-based solar cells and Tandem Perovskites/ CIGS. The thin films prepared were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis, atomic force microscopy (AFM), transmission electron microscopy (TEM), Photoluminescence analysis (PL) and UV-Vis spectroscopy. The first stage was devoted for the effect of different parameters on the growth of CIGS by electrodeposition and we investigate the impact of different back contact in structural and optical proprieties. In a second stage, we report the growth of CIGS films by spray pyrolysis, we studied the effect of experimental parameter also the annealing process which is the key factor for improving the performance of solar cells,subsequently we elaborated different films constituted CdZnS/CdS/CIGS/Mo solar cells, the approach is to change the toxic ZnO by using a transparent, conductive CdZnS layer. In other hand, MAPbI3 film was investigated in order to optimize the chemical composition and to study the crystallization process also to get sight about the stability of perovskite materials to meet the requirement of their application as an active layer in perovskite solar cell. For this purpose. the MAPbI3 film surface was treated by adding diethyl ether antisolvent with different rates. during the treatment complex exchanges are appearing at the same time under the influence of quite a lot of physicochemical properties. A whole understanding of this topic is critically important for improving solar cell performance. MAPbI3 doped by the tetrabutylammonium TBA is boosting the formation of perovskite structure, leading to a higher orientation along the (110) and shows better crystallinity, large grain size, pinhole-free, which is suitable for the manufacturing of the optoelectronic devices with higher performance. Also, we have identified the impact of TBA in the photo-physical properties, we have noticed that the TBA improve the photoluminescence emission by reducing the density of trap states and the optical absorption indicates a significant shift to the lower wavelength and optical bandgap varied from 1.8 to 1.52 eV. Finally, the stability was explored for 5% TBA, it found that after 15 days the stability remained excellent in relative humidity of ~60%. These results would be helpful for realizing stable and high performance MAPbI3-based devices. Furthermore, we inspect the effect of monovalent cation substitution of Guanidinium (GA) on the structural and optical properties of FAPbI3 thin films perovskites. The ratio between the desirable a-phase and the undesirable y yellow phase is studied as a function of GA content. GA doping is shown to be efficient in the control of a/y phases ratio and then in the stabilization of the a-FaPbI3 phase. We qualitatively evaluate the impact of 10% of guanidinium on the phase composition and microstructure of films. The results show that an adequate amount of 10% GA:FaPbI3 leads to a homogeneous perovskite film with stable a phase, large grains, and free pinholes. 10% GA: FaPbI3 films demonstrate excellent stability after aging for 15 days in relative humidity of~60%.
[CA] L'objectiu principal d'aquesta tesi és contribuir a l'avanç de noves tècniques d'elaboració de baix cost, fent servir materials d'aliatges del tipus de coure, indi, gal·li i seleni (CIGS) i perovskites, per a aplicacions en energia solar fotovoltaica. El CIGS sembla ser adequat ja que són de baix cost de producció i s'han reportat eficiències de conversió del 23,35%. D'altra banda, les perovskites híbrides d'halurs de plom orgànics-inorgànics han aparegut com a nous materials excepcionals per cel·les solars, especialment perquè l'eficiència de les cel·les solars basades en perovskites ha augmentat del 3.8% al 22.7% en menys d'un lustre. En el present treball, reportem l'elaboració i caracterització de CIGS y de perovskitas de iodur de plom de metilamoni (MAPbI3) i de iodur de plom de formamidini (FaPbI3) per a les cèl·lules solars de CIGS i tàndem Perovskites/CIGS. En les capes de CIGS dipositades per electrodeposició es va investigar l'efecte dels diferents paràmetres sobre el procés d'electrodeposició, així com l'efecte del contacte posterior sobre les propietats estructurals i òptiques del CIGS. Ens trobem que el tipus de contacte posterior té un efecte significatiu en la posterior interpretació de pel·lícules primes CIGS. A més, vam estudiar la tècnica de polvorització de la piròlisi per produir pel·lícules de CIGS. Es va estudiar el procés de recuit, que és el factor clau per millorar el rendiment de les cèl·lules solars. Es van produir diferents pel·lícules fines formades pel nostre dispositiu CdZnS/CdS/CIGS/Mo que utilitzaven una capa conductiva CdZnS transparent per minimitzar l'alineació de la interfície. D'altra banda, es van investigar perovskites MAPbI3, amb la finalitat d'optimitzar la composició química i estudiar el procés de cristal·lització també per a conèixer l'estabilitat dels materials de perovskita. la cristal·lització s'aconsegueix alentint la solubilitat en una solució saturada mitjançant l'addició d'una quantitat diferent de l'antisolvent d'èter dietílic. Durant el tractament apareixen al mateix temps intercanvis complexos sota la influència de moltes propietats fisicoquímiques. Una comprensió completa d'aquest tema és de vital importància per a millorar el rendiment. Amb l'objectiu principal d'augmentar l'estabilitat de MAPbI3, el tetrabutilamoni (TBA) es pot incorporar a MAPbI3, impulsant la formació de l'estructura de perovskita, la qual cosa porta a una major orientació al llarg de (110). MAPbI3 dopades amb TBA presenten una millora de la cristalinitat, major grandària, la qual cosa és adequada per a la fabricació de dispositius optoelectròniques de major rendiment. A més, hem identificat l'impacte de TBA en les propietats foto físiques de MAPbI3. Hem notat que el dopatge amb TBA millora tant l'emissió de la fotoluminiscència en reduir la densitat dels estats de trampes com l'absorció òptica on apareix un canvi significatiu de la banda òptica prohibida cap a longituds d'ona més llargues que significa disminuir l'energia del gap, que va variar de 1.8 a 1.52 eV. Finalment, es va explorar l'estabilitat per les perovsquites dopades amb 5%TBA. Es va trobar que després de 15 dies l'estabilitat romania excel·lent en un humitat de 60%. A més, hem estudiat FAPbI3 com un dels materials de perovskita més atractius. Hem investigat l'efecte de la substitució de guanidini (GA) sobre les propietats estructurals i òptiques de FAPbI3. La relació entre la fase a de perovskita desitjable i la fase indesitjable y es va estudiar en funció del contingut de GA. Es mostra que el dopatge amb GA és eficaç en el control de la relació de fases a /y i després en l'estabilització de la fase a-FaPbI3. Els resultats mostren que una quantitat adequada de 10% GA condueix a una pel·lícula homogènia amb fase a estable, grans grans lliures de porus i forats. Les pel·lícules de 10% GA:FaPbI3 demostraren una excel·lent estabilitat després de l'envelliment durant 15 dies en un ambient humit (humitat relativa de 60%).
Bouich, A. (2020). Study and Characterization of Hybrid Perovskites and Copper-Indium-Gallium Selenide thin films for Tandem Solar Cells [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/160621
TESIS
Barbosa, Gerson. « Modelagem e simulação de um refrigerador solar por adsorção fisica ». [s.n.], 1993. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254521.
Texte intégralDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Descreve-se a elaboração de um modelo matemático simplificado e sua validação através da simulação em regime transiente de um ciclo real, realizado com um refrigerador solar por adsorção física utilizando um par carvão ativo / metanol. A diferença em relação aos resultados obtidos no ciclo real foi 4% para a massa ciciada de metanol, 2,2% para a temperatura máxima do coletor, e 3xl0-3 para o Coeficiente de Performance Teórico do Ciclo - CO.P.T.C. Simulações adicionais do mesmo ciclo mostraram a possibilidade de se aumentar a massa de metanol ciciada em cerca de 150%, utilizando-se de parâmetros da equação Dubinin - Astakov correspondentes a diferentes tipos e quantidades maiores de carvão ativo.
Abstract: This study describes the construction of a simple mathematical model and its validation through the simulation in transient state of a real cycle performed by a solar refrigerator based on physical adsorption using an activated carbon / methanol pair. The deviation from experimental results was 4% for the cycled mass of methanol, 2.2 % for maximum collector average temperature, and 3xl0-3 for the theoretical cycle coefficient of performance. Additional simulations of the same cycle inputting values representing different types and larger amounts of activated carbon showed the possibility of increasing the cycled methanol mass up to about 150 %.
Mestrado
Mestre em Engenharia de Alimentos
POMA, ALESSANDRO. « PHOTOACTIVE MATERIALS FOR SOLAR FUELS PRODUCTION ». Doctoral thesis, Università degli Studi di Milano, 2018. http://hdl.handle.net/2434/544066.
Texte intégralBERNARDONI, Paolo. « Performance Optimization of Luminescent Solar Concentrator Photovoltaic Systems ». Doctoral thesis, Università degli studi di Ferrara, 2016. http://hdl.handle.net/11392/2403385.
Texte intégralThe purpose of this work is the optimization of photovoltaic systems based on luminescent solar concentrators, these devices are not a new concept but, so far, a thorough analysis of the performance of LSC systems with sizes practical for building integration applications is missing. For this reason in this work the performances of LSCs based on different dyes, different sizes and various optical configurations were analysed as well as the effect of self-absorption on the output spectrum, moreover the performances of the systems with different optical configurations were analysed under some possible shading conditions in order to identify the most efficient and convenient design non only under an ideal working exposure but also in a real world scenario. The prototypes were built after an extensive work of simulation of their optical behaviour aimed at selecting the most promising designs, in particular not only the efficiency has been taken into account but also the scalability of the modules to larger or smaller sizes and the ease of assembly: important features for a design that should undergo a technology transfer from research to industrialization. The first result obtained is that the feasibility of large size LSCs (up to one square metre) well above the common laboratory size of 5×5cm have been demonstrated, moreover, it has also been shown that the performances of LSC systems can be improved, while lowering cost at the same time, by using reflective layers to get a more uniform irradiance profile on the cells. Anyway the most remarkable result obtained so far is having demonstrated that systems employing a small number of cells and a reflective film on the remaining sides of the LSC can yield a higher efficiency than a traditional design with cells placed on four sides, moreover these systems have also demonstrated a lower sensitivity to shading losses which represents a fundamental result for a technology targeted at the building integration, highlighting the progress of luminescent solar concentrators from a mere laboratory research topic to a promising industrialisable technology.
BERNAREGGI, MASSIMO. « COMPOSITE PHOTOCATALYTIC MATERIALS FOR SOLAR ENERGY CONVERSION AND ENVIRONMENTAL APPLICATIONS ». Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/613026.
Texte intégralTessarolo, Marta <1985>. « Organic Bulk Heterojunction Solar Cells : Materials Properties Device Stability And Performance ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7266/1/Tesi_PhD_Marta_Tessarolo.pdf.
Texte intégralTessarolo, Marta <1985>. « Organic Bulk Heterojunction Solar Cells : Materials Properties Device Stability And Performance ». Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amsdottorato.unibo.it/7266/.
Texte intégralDEGANI, MATTEO. « Design and Characterization of Hybrid Perovskite for New Generation Solar Cells ». Doctoral thesis, Università degli studi di Pavia, 2023. https://hdl.handle.net/11571/1471734.
Texte intégralPerovskites are semiconductors with ideal optoelectronic properties (like high absorption and high charge mobility) for photovoltaic applications and at a low cost. However, their commercial application is limited by the instability of this material. The degradation of perovskite is caused by some external factors such as oxygen and humidity. In this thesis both structures (NIP and PIN) of perovskite solar cells have been studied. To make them more stable and efficient, they have been treated with new passivation methods and with recently synthesized materials that have led to the achievement of the goal. Various characterization techniques were also used to understand the reasons for the performance improvements of these devices. This allowed obtaining a greater knowledge of the mechanisms of the improvements and consequently to closer commercialization of these perovskites.
De, Bastiani Michele. « The Stability of Third Generation Solar Cells ». Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424345.
Texte intégralNegli ultimi cinquant’anni la rapida evoluzione delle tecnologie ha gradualmente sbilanciato l’equilibrio che esiste tra la produzione e il consumo dell’energia. Le risorse tradizionali che vengono sfruttate per la produzione di energia - carbone, petrolio e gas naturali - iniziano ad essere sempre meno sufficienti per soddisfare la richiesta di energia senza rischiare di danneggiare l’ambiente che ci circonda. E’ proprio per questo motivo che le energie rinnovabili attraggono sempre più interessi e attenzioni andandosi a candidare come una potenziale soluzione al fabbisogno energetico. Tra le energie rinnovabili, il fotovoltaico si conferma come una delle tecnologie più promettenti per fornire energia a costi contenuti nel rispetto dell’ambiente. Tuttavia per poter sfruttare appieno il potenziale di questa tecnologia la fisica e i meccanismi di conversione fotovoltaica devono essere studiati nel dettaglio. Tra questi la stabilità delle celle solari ricopre uno degli aspetti fondamentali, dove per stabilità si intendono sia la durata e il tempo di vita dei dispositivi sia la stabilità dei meccanismi elettrici delle celle. In questa tesi viene studiata nel dettaglio la stabilità di due tecnologie emergenti nel settore fotovoltaico: le celle solari polimeriche e le celle solari a base di perovskiti. Nelle celle solari polimeriche capire e comprendere i meccanismi di degrado dei materiali foto attivi permette di sviluppare nuovi materiali in grado di aumentare la durata e l’efficienza delle celle. In generale, il degrado di questi dispositivi è dovuto all’interazione tra la parte ultravioletta della luce e gli agenti atmosferici, in particolare ossigeno e vapore acqueo. Gli effetti del decadimento si riscontrano da un lato nella formazione di stati elettronici che fungono da “trappole” per le cariche fotogenerate diminuendo l’efficienza generale della cella, dall’altro nella modifica chimica dei materiali che porta ad una rottura delle catene polimeriche deteriorando completamente le proprietà ottiche della cella. Studiare e comprendere questi meccanismi è la corretta strada per lo sviluppo di nuovi materiali per celle più efficienti. L’introduzione delle perovskiti ibride ha rappresentato una rivoluzione nel settore fotovoltaico. Questa tipologia di materiali offre il vantaggio sia di essere processabile da soluzioni sia quello di avere un’efficienza confrontabile a quella del silicio cristallino. Inizialmente queste perovskiti erano utilizzate come materiale fotoassorbente in celle solari simili alle dye senistized solar cells (DSSCs). Questi primi dispositivi sfruttavano uno scaffold mesoporoso di diossido di titanio per estrarre gli elettroni. Successivamente, in seguito allo sviluppo empirico delle celle, lo scaffold mesoporoso è stato rimosso in favore di una configurazione planare. Tuttavia, in entrambe le configurazioni, queste celle hanno dimostrato una naturale instabilità elettrica che si manifesta in una forma di isteresi nella determinazione della caratteristica curva corrente/voltaggio. Questo fenomeno rende ambigua la determinazione finale dell’efficienza di questi dispositivi limitandone effettivamente le possibili applicazioni. In questa tesi viene presentata un’indagine completa delle cause e delle conseguenze di questo fenomeno, mostrando una possibile soluzione a questo problema.
Almeida, Waldenio Gambi de. « Avaliação de um modelo fisico estimador de irradiancia solar baseado em satelites geoestacionarios ». reponame:Repositório Institucional da UFSC, 1998. http://repositorio.ufsc.br/xmlui/handle/123456789/77621.
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Silveira, Júnior Vivaldo 1962. « Montagem e teste de desempenho de um refrigerador solar por absorção fisica com produção de gelo ». [s.n.], 1990. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254518.
Texte intégralDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Este trabalho descreve com detalhes a, construção, montagem, instrumentação, e testes de estanqueidade do protótipo experimental de um refrigerador solar por adsorção física, que usa o par carvão ativado / metanol. São analisados quatro testes de desempenho do equipamento. Os dados experimentais utilizados foram: energia solar incidente, temperatura e pressão do reator, temperaturas ambiente, do gabinete e da água estocada no reservatório. Este protótipo produziu 3.0 kg de gelo num ciclo de 24 horas com um Coeficiente de performance solar de 0.042, usando um coletor solar plano multitubular contendo 9.9 kg de adsorvente. Os parâmetros (Wo e D) da equação de Dubinin Raduskevich foram calculados com os dados experimentais para o par carvão ativado (Deion) e metanol. A faixa ótima da temperatura máxima do coletor foi estimada entre 90 e 100° C . Este conhecimento será útil para futuros estudos de otimização do sistema
Abstract: This study details the construction, instrumentation, and leak tests of an experimental prototype of a solar refrigerator by physical adsorption, using an activated carbon / methanol pair. Four performance tests of the equipment are analyzed. The experimental data utilized are solar energy temperature and pression of the reator, ambient temperature, temperature of the gabinet and temperature of water stornaged. The prototype produced 3,0 kg of ice in a 24 h cycle with a C.O.P.solar of 0,042 using a multipipe ftat-plate solar colletor containing 9,9 kg of adsorvent. The Dubinin-Raduskevich's equation parameters (Wo and D) are calculated with the experimental data for activated carbon (Deian) / methanol pair. The optimum temperature range for the colletor was predicted between 90 and 100°C. This knowledge will be useful to future studies to optimize the system
Mestrado
Mestre em Engenharia de Alimentos
Rial, Lesaga Samuel. « Temporal evolution of MHD waves in solar coronal arcades ». Doctoral thesis, Universitat de les Illes Balears, 2019. http://hdl.handle.net/10803/671489.
Texte intégral[spa] En esta tesis estudiaremos las oscilaciones verticales de una arcada potencial en la aproximaci on 0 de un plasma, cuando diferentes per les de densidad son considerados. Por un lado nos vamos a centrar en la evoluci on temporal de este problema para as analizar la otra cara de la moneda de las oscilaciones magnetohidrodin amicas, la cual tradicionalmente se ha estudiado mediante el an alisis de modos normales. Vamos a estudiar la propagaci on, la conversi on energ etica y la atenuaci on de ondas generadas mediante un impulso inicial, as como las escalas espaciales y temporales generadas, para de esta manera obtener una imagen lo m as completa posible. Para el estudio de la atenuaci on, vamos a examinar dos mecanismos f sicos que podr an estar involucrados en la r apida atenuaci on de la oscilaciones verticales observadas en bucles coronales, que son la emisi on de energ a mediante \wave tunneling" y absorci on resonante. En este trabajo, siempre que sea posible, se van a comparar los resultados de las simulaciones temporales con las propiedades conocidas que han de poseer los modos normales. Esto nos va a servir como un m etodo de comprobaci on de nuestros resultados adem as de ayudarnos a entender como ambas visiones est an relacionadas entre si.Por otro lado lado vamos a investigar el uso de una nueva t ecnica para obtener los modos normales de un sistema cuando el m etodo est andard es dif cil de llevar a cabo. Este m etodo lo vamos aplicar a un modelo de bucle coronal recto y vamos a obtener los modos normales del sistema con el grado de precisi on que deseemos mediante el uso de un criterio de convergencia.
[cat] En aquesta tesi estudiarem les oscil lacions verticals d'una arcada potencial en l'aproximaci o 0 d'un plasma quan diferents per ls de densitat s on considerats. Per un costat ens centrarem en l'evoluci o temporal d'aquest problema per tal d'analitzar l'altra cara de la moneda de les oscil lacions magnetohidrodin amiques, la qual tradicionalment s'ha estudiat mitjan cant l'an alisi de modes normals. Estudiarem la propagaci o, la conversi o energ etica i l'atenuaci o de les ones generades mitjan cant un pols inicial, aix com les escales espacials i temporals generades, per tal de ser capa cos d'obtenir una imatge el m es completa possible. Per a l'estudi de l'atenuaci o, examinarem dos mecanismes f sics que podrien estar involucrats en la r apida atenuaci o de les oscil lacions verticals observades en els bucles coronals, que s on l'emissi o d'energia mitjan cant \Wave tunneling" i l'absorci o ressonant. En aquest treball, sempre que sigui possible, compararem els resultats de les nostres simulacions temporals amb les propietats conegudes que han de tenir els modes normals. Aix o ens servir a com a m etode de comprovaci o dels nostres resultats aix com per entendre com les dues visions estan relacionades entre si. Per altre costat investigarem l' us d'una nova t ecnica per obtenir els modes normals d'un sistema quan el m etode est andard es dif cil de dur a terme. Aquest m etode l'aplicarem a un model de bucle coronal recte i obtindrem els modes normals del sistema amb el grau de precisi o que desitgem mitjan cant un criteri de converg encia.º
MUSA, Maria Luisa. « Modellazione dei sistemi di accumulo termico per impianti solari ». Doctoral thesis, Università degli studi di Ferrara, 2011. http://hdl.handle.net/11392/2388759.
Texte intégralMARTUCCI, MATTEO. « Study of low energy protons produced during Solar Particle Events with the PAMELA experiment ». Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2014. http://hdl.handle.net/2108/202097.
Texte intégralBarichello, Jessica <1990>. « From dye sensitized to perovskite solar cells : processes and materials for the forthcoming era of photovoltaic technology ». Doctoral thesis, Università Ca' Foscari Venezia, 2018. http://hdl.handle.net/10579/15021.
Texte intégralMirabelli, Alessandro James. « Highly efficient monolithic Perovskite/Silicon bifacial tandem solar cells ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20369/.
Texte intégralLegnani, Giacomo. « Evoluzione delle celle solari al silicio ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7795/.
Texte intégralBenini, Gabriella. « Studio di celle solari innovative basate su "multiple electron-hole generation" ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8936/.
Texte intégralPereira, Denis Rafael de Oliveira. « Construção e caracterização de célula solar tipo barreira Schottky CdTe/Al ». Universidade Federal de Viçosa, 2011. http://locus.ufv.br/handle/123456789/4249.
Texte intégralConselho Nacional de Desenvolvimento Científico e Tecnológico
In this work the techniques of hot wall epitaxy (HWE) and molecular beam epitaxy (MBE) on thin films of CdTe (cadmium telluride) were used in order to manufacture a prototype solar cell type Schottky barrier. The films were produced by evaporation of a solid alloy of CdTe, varying two parameters of deposition: the growth time and substrate temperature. In the manufacture the Schottky Barrier solar cells Al-CdTe, the CdTe film was grown on glass substrate coated with a layer of TO (tin oxide doped with fluorine - SnO2:F) and an evaporation system was used in the deposition of Al contacts. The films were characterized by several techniques including profilometry to measure the thickness, atomic force microscopy (AFM) for determining surface morphology and x-ray diffraction for crystalline properties. The prototypes of the solar cell were characterized by electrical measurements (IxV curve) with and without illumination. The results show a strong influence of substrate temperature and thickness on the properties of solar cells. It was observed that the increase of substrate temperature favors the increase of grain and the growth of films with better quality, resulting in devices with better features. In addition, thinner layers of CdTe cells also produce a higher short circuit current when illuminated. Although the cells produced showed very low efficiency, we believe that it is possible to improve manufacturing processes, achieving better efficiency.
Neste trabalho utilizou-se as técnicas de epitaxia por paredes quentes (HWE) e epitaxia por feixe molecular (MBE) na fabricação de filmes finos de CdTe (telureto de cádmio) com o objetivo de fabricar um protótipo de célula solar tipo barreira Schottky. Os filmes foram obtidos por evaporação de uma liga sólida de CdTe, fazendo-se variar dois parâmetros de deposição: o tempo de crescimento e a temperatura do substrato. Na fabricação das células solares tipo Barreira Schottky Al-CdTe, o filme de CdTe foi crescido sobre o substrato de vidro recoberto com uma camada de TO (óxido de estanho dopado com Flúor – SnO2:F) e uma metalizadora foi utilizada na deposição dos contatos de Al. Os filmes foram caracterizados por diversas técnicas, incluindo a perfilometria para medida da espessura, a microscopia de força atômica (AFM) para determinação das propriedades morfológicas e difração de raios-x para determinação das propriedades cristalinas. Os protótipos da célula solar foram caracterizados através de medidas elétricas da curva IxV com e sem iluminação. Os resultados obtidos mostram uma forte influência da temperatura do substrato e da espessura nas propriedades das células solares construídas. Observou-se que o aumento da temperatura do substrato favorece o aumento do grão e o crescimento de filmes com melhor qualidade resultando em dispositivos com melhores características. Além disso, camadas mais finas de CdTe também produzem células que apresentam maior corrente de curto-circuito, quando iluminadas. Apesar das células fabricadas apresentarem eficiência muita baixa, acreditamos que existe a possibilidade de melhorar os processos de fabricação, conseguindo melhorar a eficiência.
Batista, Leonardo Fabr?cio Gomes. « N?o-extensividade no contexto da atividade magn?tica solar : o problema da assimetria hemisf?rica ». Universidade Federal do Rio Grande do Norte, 2014. http://repositorio.ufrn.br/handle/123456789/19958.
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Indicadores de atividade solar, tais como; n?umero de manchas solares, ?area das manchas e flares sobre a fotosfera do Sol n?ao s?ao distribu??dos de forma sim?etrica entre os hemisf?erios norte e sul. Este comportamento ?e tamb?em conhecido como Assimetria NorteSul dos diferentes ??ndices solares. Dentre as diferentes conclus?oes obtidas por diversos autores, pode-se apontar que a assimetria N-S ?e um fen?omeno sistem?atico e real, e n?ao devido `a variabilidades aleat?orias. No presente trabalho, as distribui?c?oes de probabilidade dos dados provenientes do sat?elite Marshall Space Flight Centre (MSFC) da NASA s?ao investigadas usando uma ferramenta estat??stica originada da bem conhecida Mec?anica Estat??stica N?ao-Extensiva proposta por C. Tsallis em 1988. Nesse contexto, apresenta-se resultados e discuss?oes com suas implica?c?oes f??sicas, confrontando o modelo te?orico com as observa?c?oes realizadas. Os resultados obtidos revelam que existe uma forte depend?encia entre o par?ametro entr?opico n?ao-extensivo q e a variabilidade de longo-termo presente nos dados de ?areas de manchas solares. Dentre os resultados mais importantes, destaca-se a assimetria do ??ndice q, a qual revela o dom??nio predominante do hemisf?erio norte em rela?c?ao ao sul. Esse comportamento foi discutido e confirmado por v?arios autores, por?em em nenhum momento estes atribu??ram tal comportamento `a uma propriedade estat??stica do modelo por eles empregado. Com isso, conclui-se que tal par?ametro pode ser considerado como uma medida eficiente para diagnosticar varia?c?oes de longo-termo do d??namo solar. Finalmente, a referida disserta?c?ao abre um novo caminho para investigar s?eries temporais em Astrof??sica pela ?otica da n?ao-extensividade.
Solar activity indicators, each as sunspot numbers, sunspot area and flares, over the Sun?s photosphere are not considered to be symmetric between the northern and southern hemispheres of the Sun. This behavior is also known as the North-South Asymmetry of the different solar indices. Among the different conclusions obtained by several authors, we can point that the N-S asymmetry is a real and systematic phenomenon and is not due to random variability. In the present work, the probability distributions from the Marshall Space Flight Centre (MSFC) database are investigated using a statistical tool arises from well-known Non-Extensive Statistical Mechanics proposed by C. Tsallis in 1988. We present our results and discuss their physical implications with the help of theoretical model and observations. We obtained that there is a strong dependence between the nonextensive entropic parameter q and long-term solar variability presents in the sunspot area data. Among the most important results, we highlight that the asymmetry index q reveals the dominance of the North against the South. This behavior has been discussed and confirmed by several authors, but in no time they have given such behavior to a statistical model property. Thus, we conclude that this parameter can be considered as an effective measure for diagnosing long-term variations of solar dynamo. Finally, our dissertation opens a new approach for investigating time series in astrophysics from the perspective of non-extensivity.
Baig, Faisal. « Numerical analysis for efficiency enhancement of thin film solar cells ». Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/118801.
Texte intégral[CAT] Des de fa una dècada s'està investigant intensament la forma de millorar l'eficiència de conversió d'energia (PCE) de les cèl·lules solars de silici (Si) i reduir els seus preus. No obstant això, tot i les millores obtingudes, la fabricació de cèl·lules solars de Si segueix sent costosa i pot rebaixar-se usant materials en forma de capa fina. Per això la recerca de materials absorbents alternatius, no tòxics, abundants en la naturalesa i amb bons rendiments de conversió s'ha intensificat en els últims anys. Entre els diferents materials absorbents, el sulfur d'estany (SnS), amb una banda prohibida de 1.3 eV propera a l'òptima, és un candidat adequat per a la conversió fotovoltaica. Però per a cèl·lules experimentals de SnS el rendiment assolit fins ara és de 4.6%, que és molt menor que el PCE per a dispositius de silici, mentre que entre altres cèl·lules híbrides (orgàniques-no orgàniques) com la perovskita de metilamonio de plom i iode ( MAPbI3) es demostra que és un candidat adequat amb PCE que arriba a un valor del 23%. A part de l'estabilitat, un dels problemes per a la comercialització de cèl·lules de MAPbI3 és la naturalesa tòxica del plom (Pb). Per aquest motiu, s'ha utilitzat l'anàlisi numèrica per revisar els paràmetres de disseny de les cèl·lules solars de perovskita híbrida substituint l'absorbent MAPbI3 per MASnI3 i estudiar l'efecte de la resta de paràmetres de disseny en el rendiment d'estes cèl·lules solars. Hi ha diversos programaris de simulació disponibles que s'utilitzen per a l'anàlisi numèric de cèl·lules solars. En aquest treball hem fem servir un programari anomenat "A Solar Cell Capacitance Simulator" (SCAPS), està disponible de forma gratuïta i és molt popular entre la comunitat científica i tecnològica. Per aconseguir un disseny efectiu per a una cèl·lula solar eficient, es va proposar una aproximació numèrica basada en la millora de la PCE d'una cèl·lula solar experimental. Això es va fer reproduint els resultats per a la cèl·lula solar dissenyada experimentalment en un entorn SCAPS amb estructura p-SnS / n-CdS amb una eficiència de conversió de l'1,5%. Després de reproduir els resultats experimentals, el rendiment del dispositiu es va optimitzar ajustant el gruix de la capa absorbent y de la capa tampó, el temps de vida dels portadors minoritaris, la concentració del dopatge en les capes absorbent, tampó i en la capa finestra. Mitjançant l'optimització gradual dels paràmetres del dispositiu, es va assolir un valor de 14.01% en PCE de cèl·lules solars dissenyades experimentalment en SCAPS amb arquitectura p-SnS / n-CdS / n-ZnO. A partir de l'anàlisi, es va trobar que la PCE d'una cèl·lula solar depèn en gran mesura de la concentració de dopatge de la capa absorbent, el gruix de la capa absorbent i els defectes de la interfície. D'altra banda, es va realitzar una anàlisi per determinar l'efecte de la recombinació de la interfície en el rendiment de les cèl·lules solars i com es pot controlar. Per realitzar aquesta tasca, es va realitzar una anàlisi per a la selecció de la capa tampó adequada per a la cèl·lula solar de perovskita de metilamoni d'estany i iode (MASnI3) i es va trobar que el PCE de la cèl·lula solar també depèn de l'alineació de la banda entre l'absorbidor i la capa de tampó.
[EN] A decade of extensive research has been conducted to enhance the power conversion efficiency (PCE) of silicon (Si) solar cells and to cut their prices short. But still, the fabrication of Si solar cells are costly. So, to reduce the fabrication cost of the solar cell search for alternate earth abundant and non-toxic absorber materials is thriving. Among different absorber materials tin sulfide (SnS) is found to be a suitable candidate for the non-organic solar cell with a band gap of 1.3 eV. But the PCE achieved for SnS is 4.6% that is far less from the PCE of (Si), whereas among other organic non-organic solar cells like methylammonium lead halide perovskite ({\rm MAPbI}_3) is proven to be a suitable candidate with PCE reaching to a value of 23%. The problem with the commercialization of {\rm MAPbI}_3 is due to the toxic nature of lead (Pb). So, in dealing with these issues of solar cell numerical analysis can play a key role as numerical analysis allows flexibility in the design of realistic problem and experimentation with different hypotheses can easily be performed. Complete set of device characteristic can often be easily generated by consuming less amount of time and effort. Because of this reason numerical analysis was used to revisit solar cells design parameters and the effect of solar cell physical parameters on solar cell performance. There are various simulation software's available that are used for solar cell numerical analysis. Here in this work, we used Solar cell capacitance simulator (SCAPS) software, it is freely available and is most popular among the research community. To achieve effective design for efficient solar cell a numerical guide was proposed based on which PCE of an experimental designed solar cell can be enhanced. This was done by reproducing results for the experimentally designed solar cell in SCAPS environment with structure p-SnS/n-CdS having a conversion efficiency of 1.5%. After reproduction of experimental results device performance was optimized by varying thickness of (absorber layer, buffer layer), minority carrier lifetime, doping concentration (absorber, buffer), and adding window layer. By stepwise optimization of device parameters, PCE of an experimental designed solar cell in SCAPS with architecture p-SnS/n-CdS/n-ZnO was reached to a value of 14.01%. From the analysis, it was found that PCE of a solar cell is highly depended upon doping concentration of the absorber layer, the thickness of the absorber layer and interface defects. Based on the results evaluated an analysis was performed for tin based organic non-organic methylammonium tin halide perovskite solar cell ({\rm MASnI}_3) to find the effect of interface recombination on solar cell performance and how it can be governed. The reason for this transition from SnS to {\rm MASnI}_3 was because {\rm MASnI}_3 can be fabricated simply by spin-coating methylammonium iodide (MAI) over SnS layer. To perform this task analysis was performed for the selection of suitable buffer layer for Pb free methylammonium tin halide perovskite solar cell ({\rm MASnI}_3) and it was found that PCE of the solar cell is also depended upon band alignment between absorber and buffer layer. Based on the results a new structure was proposed for Pb free perovskite solar cell (Back\ contact/{\rm MASnBr}_3/{\rm MASnI}_3/CdZnS/FTO) with PCE of 18.71% for absorber thickness of 500 nm and acceptor doping concentration of 1x10^{16}\ {\rm cm}^3. The results achieved in this thesis will provide an imperative guideline for researchers to design efficient solar cells.
Baig, F. (2019). Numerical analysis for efficiency enhancement of thin film solar cells [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/118801
TESIS
Dugaria, Simone. « Advanced surface and volumetric receivers to convert concentrated solar radiation ». Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3423148.
Texte intégralLa presente tesi è il risultato del lavoro svolto durante i tre anni di dottorato. presso il Dipartimento di Ingegneria Industriale dell'Università degli Studi di Padova. La conversione dell'energia solare in calore a media temperatura (tra 80 °C e 250 °C) ha recentemente riscontrato un rinnovato interesse per le applicazioni di riscaldamento e raffreddamento in settori industriali, commerciali, residenziali e dei servizi. I collettori solari termici a concentrazione per media temperatura ben si prestano per l’impiego in molte applicazioni commerciali e industriali, come per la produzione di calore di processo industriale, il solar-cooling e la desalinizzazione dell'acqua di mare. Si prevede un significativo sviluppo tecnologico per questa tipologia di collettori, a condizione che la conversione dell'energia solare diventi più efficiente ed economica. La corretta progettazione del ricevitore, considerato il cuore di ogni collettore a concentrazione, è essenziale per il futuro incremento dell'efficienza di conversione di questa tecnologia. In questo contesto, questa tesi riporta i risultati dell'applicazione di due innovativi ricevitori in un prototipo di concentratore parabolico asimmetrico installato nel Laboratorio di conversione dell'energia solare del Dipartimento di Ingegneria Industriale dell'Università degli Studi di Padova. Nel Capitolo 1 è presentato lo studio di diverse procedure per la stima dell'irradianza normale diretta, che è la risorsa solare utilizzata dai concentratori solari. Lo studio include una valutazione indiretta da misurazioni di irradianza orizzontale globale e diffusa insieme all'uso di modelli semi-fisici/empirici. Viene fornita un'analisi dettagliata della strumentazione e del metodo di misurazione utilizzati nonché dell'espressione dell'incertezza sperimentale. Nel Capitolo 2, le prestazioni ottiche del concentratore parabolico asimmetrico sono caratterizzate sperimentalmente. Un modello statistico di ray-tracing del concentratore per l'analisi delle prestazioni ottiche in diverse condizioni di lavoro è stato convalidato ed utilizzato per ottimizzare la geometria dei ricevitori proposti. Nel Capitolo 3, un innovativo ricevitore superficiale in alluminio e prodotto con la tecnologia bar-and-plate e un turbolatore al suo interno è stato testato nel collettore parabolico asimmetrico in regime di deflusso monofase e bifase con acqua e con un fluido alogenato a basso GWP. Un modello numerico per prevedere le prestazioni di tale ricevitore è stato sviluppato e validato sulla base dei dati sperimentali acquisiti. Nel Capitolo 4, questo modello è stato impiegato per valutare le prestazioni di un impianto ORC di piccola taglia alimentato da energia solare attraverso il suddetto collettore solare a concentrazione. L’analisi ha compreso la vaporizzazione diretta di un fluido alogenato a basso GWP e l’utilizzo un circuito solare intermedio per riscaldare acqua pressurizzata ed evaporare lo stesso fluido alogenato in uno scambiatore di calore. Infine, nel Capitolo 5 è stato proposto l’impiego di un nuovo ricevitore volumetrico ad assorbimento diretto per studiare la capacità di assorbimento della radiazione solare concentrata di un nanofluido. Il nanofluido è una sospensione di nano-corni di carbonio a parete singola in acqua distillata ed è il risultato di un progetto di collaborazione con la sede di Padova del Consiglio Nazionale della Ricerca. Attraverso lo sviluppo di un modello CFD tridimensionale, il ricevitore volumetrico è stato progettato per essere installato nella regione di fuoco del concentratore parabolico asimmetrico. La capacità del nanofluido di assorbire la radiazione solare a concentrata e non concentrata è stata studiata sperimentalmente. Al fine di indagare sulla stabilità nel tempo del nanofluido, delle prove sono state condotte in diverse condizioni, con e senza circolazione.
Tusnski, Daneele Saraçol. « Modelagem de processos nucleares de alta energia em explosões solares utilizando o pacote FLUKA ». Universidade Presbiteriana Mackenzie, 2018. http://tede.mackenzie.br/jspui/handle/tede/3695.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Fundo Mackenzie de Pesquisa
The emission of 𝛾-rays in solar flares is produced by interactions of primary electrons and ions accelerated to high energies with nuclei in the ambient solar atmosphere. The analysis of the 𝛾-ray spectra observed during solar flares provides important diagnostics on the mechanisms of primary particle acceleration and on the structure and evolution of the ambient plasma. In this work we investigate the high energy nuclear processes that occur in solar flares using FLUKA, a package of general purpose integrated routines for Monte Carlo calculations of particle transport and interactions in matter. Our main aim is to validate FLUKA as an effective tool for the modeling of nuclear processes in the context of solar flares. In order to accomplish that, we have performed simulations of the 𝛾-ray spectrum considering realistic models for the ambient solar atmosphere and beams of accelerated ions (protons, 𝛼-particles and heavier nuclei) with different energy and angular distributions. From the results obtained in the simulations with FLUKA, we have built templates for the nuclear de-excitation lines emission spectrum and for the full 𝛾-ray emission spectrum, which were incorporated to the program OSPEX for the fitting of spectra from observed events. Using these templates in combination with standard-functions avaiable in the programa OSPEX we have obtained statistically reasonable fittings for the 𝛾-ray spectra of the July 23, 2002 and June 12, 2010 solar flares, similar to the fittings obtained with templates built from nuclear de-excitation lines emission spectra calculated with the code developed by Murphy et al. (2009). To the best of our knowledge, the fittings carried out with the FLUKA templates for the full 𝛾-ray emission spectrum can be regarded as the first attempt to use a single code to implement a self-consistent treatment of the several spectral components in the energy range from ∼ 100’s keV to ∼ 100’s MeV.
A emissão de raios-𝛾 em explosões solares é produzida por interações de elétrons e íons primários acelerados a altas energias com núcleos na atmosfera solar ambiente. A análise dos espectros de raios-𝛾 observados durante as explosões solares fornece diagnósticos importantes sobre os mecanismos de aceleração das partículas primárias e sobre a estrutura e evolução do plasma ambiente. Neste trabalho investigamos os processos nucleares de alta energia que ocorrem em explosões solares utilizando o FLUKA, um pacote de rotinas integradas de uso geral para o cálculo Monte Carlo do transporte e das interações de partículas na matéria. Nosso principal objetivo é validar o FLUKA como ferramenta efetiva para a modelagem de processos nucleares no contexto de explosões solares. Para tanto, realizamos simulações do espectro de raios-𝛾 considerando modelos realísticos para a atmosfera solar ambiente e feixes de íons acelerados (prótons, partículas-𝛼 e núcleos mais pesados) com diferentes distribuições energéticas e angulares. A partir dos resultados obtidos nas simulações com o FLUKA, construímos templates para o espectro de emissão de linhas de desexcitação nuclear e para o espectro completo de emissão de raios-𝛾, os quais foram incorporados ao programa OSPEX para o ajuste de espectros de eventos observados. Utilizando esses templates em combinação com funções-padrão disponíveis no programa OSPEX obtivemos ajustes estatisticamente razoáveis para os espectros de raios-𝛾 das explosões solares de 23 de julho de 2002 e 12 de junho de 2010, semelhantes aos ajustes obtidos com templates construídos a partir de espectros de emissão de linhas de desexcitação nuclear calculados com o código desenvolvido por Murphy et al. (2009). Até onde sabemos, os ajustes realizados com os templates FLUKA para o espectro completo de emissão de raios-𝛾 podem ser considerados como a primeira tentativa de utilizar um único código para implementar um tratamento auto-consistente das várias componentes espectrais na faixa de energia de ∼ 100’s keV a ∼ 100’s MeV.
Libraro, Sofia. « Advanced characterization of fired passivating contacts for silicon solar cells ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19294/.
Texte intégralSilva, Francys Anthony da. « Evolu??o da atividade cromosf?rica, abund?ncia de l?tio e rota??o das estrelas an?logas e g?meas solares ». Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/16646.
Texte intégralConselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
The study of solar-type stars also includes the familiar solar analogs and twins. These objects have been one of the major research subjects in astrophysics nowadays. A direct comparison of solar activity with chromospheric activity indices for a set of stars very similar to the Sun (twins and analogs) provides an excellent opportunity to study the evolution of stellar activity on timescales of the order of the lifetime on the main sequence. This work deals with the relationship between the abundance of lithium, chromospheric activity, X-ray emission and rotation period in terms of stellar ages. We explore the influence of stellar evolution in the global properties of the stars and the aspects linked to its coronal, chromospheric and magnetic activity. Our main objective is to probe the law of decay of each of these parameters based on a sample of stars classified as well-connected as analogs stars and solar twins.
O estudo das estrelas do tipo solar inclui tamb?m as conhecidas estrelas an?logas e g?meas. Estes objetos tem sido um dos principais objetos de pesquisa da astrof?sica atual. A compara??o direta da atividade solar com os ?ndices de atividade cromosf?rica para um conjunto de estrelas muito semelhantes ao Sol (g?meas e an?logas) fornece uma ?tima oportunidade de estudar a evolu??o da atividade estelar em escalas de tempo da ordem do tempo de vida de uma estrela na sequ?ncia principal. Neste trabalho trataremos das rela??es existentes entre a abund?ncia de l?tio, atividade cromosf?rica, emiss?o de raio-X e per?odo de rota??o em termos das idades estelares. Sondaremos a influ?ncia da evolu??o estelar nas propriedades globais das estrelas e nos aspectos ligados a sua atividade coronal, cromosf?rica e magn?tica. Nosso objetivo principal ? de sondar a lei de decaimento de cada um destes par?metros com base em uma amostra de estrelas bem relacionadas e classificadas como estrelas an?logas e g?meas solares
Mehret, Leandro Cesar. « ESTUDO DOS MODOS P NO LIMBO SOLAR ». UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2015. http://tede2.uepg.br/jspui/handle/prefix/844.
Texte intégralCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
Helioseismology aims to study the oscillations observed on the surface of the Sun. These oscillations are acoustic and stationary waves called p modes, and penetrate the solar interior and provide information about the internal structure. Because these waves have small amplitudes, they can be dealed with small perturbations in a model in hydrostatic equilibrium. Acoustic waves can be represented by spherical harmonics, characterized by l degree, m order and n order (nodes on radial direction). The p modes are waves whose restoration force are pressure, and g modes are waves whose restoration force are gravity. The data analyzed in this study were obtained from the Helioseismic and Magnetic Imager (HMI) that integrates the SDO mission (Solar Dynamics Observatory). Filtergrams are narrow band wavelength filters very close to some absorption line of the Sun. From the filtergrams obtained by the HMI, a processing pipeline generates the arrays and, describing the limb brightness and displacement as a function of central angle around the limb, respectively. Through a computer program developed in IDL (Interactive Data Language), used to calculate the Fourier transform of the arrays and we obtained the modes, and compared the results of the transform with frequencies of oscillation modes obtained by other authors (in the literature) using data obtained by MDI (Michelson Doppler Imager) and GONG (Global Oscillation Network Group), in order to find the characteristic frequencies of the modes. From this analysis, we obtained the relation between amplitude and frequency for the modes, it has been found that the behavior of the full width at half maximum as a function of the frequency confirm some results found in the literature, it was found larger amplitudes for low frequencies, confirming the theoretical prediction of Toutain’s model (1998) and we found the arise of degeneracy of the modes for different m values. It was also found that the noise presence in data is significant, and probably is the main source of error.
A Heliosismologia tem por objetivo o estudo das oscilações observadas na superfície do Sol. Estas oscilações são ondas acústicas estacionárias chamadas modos p, que penetram no interior solar e trazem informações sobre a estrutura interna. Por causa da sua pequena amplitude, essas oscilações podem ser tratadas com pequenas perturbações em um modelo em equilibrio hidrostático. As ondas acústicas podem ser representadas por meio de harmônicos esféricos, caracterizados pelo grau l, ordem m e ordem n (nós na direção radial). Os modos p são ondas cuja força restauradora é a pressão, enquanto os modos g são ondas cuja força restauradora é a gravidade. Os dados analisados neste trabalho foram obtidos a partir do Helioseismic and Magnetic Imager (HMI) que integra a missão SDO (Solar Dynamics observatory). Filtrogramas são filtros de banda de comprimento de onda bem estreito próximos de uma determinada linha de absorção do Sol. A partir dos filtrogramas obtidos pelo HMI, um pipeline de processamento de dados gera os vetores e , que descrevem o brilho e o deslocamento em função do ângulo central em torno do limbo, respectivamente. Através de um programa computacional desenvolvido em linguagem IDL (Interactive Data Language), calculou-se a transformada de Fourier dos vetores e obtendo-se os modos, e comparou-se o resultado da transformada com frequências dos modos de oscilação obtidos por outros autores (na literatura) usando dados obtidos pelo MDI (Michelson Doppler Imager) e pelo GONG (Global Oscillation Network Group) para encontrar as frequências características dos modos. Com resultados desta análise, obteve-se a relação entre a amplitude e a frequência para os modos, verificou-se que o comportamento da largura à meia altura em função da frequência confirma alguns resultados encontrados na literatura, constatou-se a existência de amplitudes maiores para baixas frequências, confirmando-se a previsão teórica do modelo de Toutain (1998) e verificou-se o levantamento da degenerescência dos modos para diferentes valores de m. Também constatou-se que a presença de ruído nos dados foi significativa, constituindo provavelmente a principal fonte de erro.
Khattak, Yousaf Hameed. « Modeling of High Power Conversion Efficiency Thin Film Solar Cells ». Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/118802.
Texte intégral[CAT] L'energia solar fotovoltaica ha emergit com una font d'energia nova i sostenible, que és ecològica i rendible si la producció és a gran escala. En l'escenari actual, els dispositius fotovoltaics econòmics i de gran eficiència de conversió estan ben posicionats per a la generació d'electricitat neta i sostenible. Les cèl·lules solars basades en silici dominen aquest mercat des de fa molts anys. Per a la fabricació i producció de cèl·lules solars basades en silici, es requereixen tècniques de fabricació sofisticades que fan que el panell solar sigui costós. Per altra banda estan les cel·les solars de capa fina, que estan guanyant importància a causa de l'intensificació de les capacitats de fabricació. La tecnologia de capa fina és una de les tecnologies més rentables i eficients per a la fabricació de cel solars, i és un tema d'intensa investigació en la fotovoltaica industrial. La tecnologia de capa fina és més econòmica que altres tecnologies perquè els dispositius utilitzen menys material i estan basats en diversos tipus de materials semiconductors que absorbeixen la llum. Entre aquests materials, les cèl·lules solars de kesterita que utilitzen CZTS, CZTSe i les seves aleacions CZTSSe poden convertir-se en el reemplaçament òptim als absorbents de calcopirita. Aquests materials presenten unes característiques òptiques i elèctriques sobresalientes i tenen un gap òptic directe amb una banda prohibida que oscil·la entre 1,4eV i 1,5eV i un coeficient d'absorció, \alpha>{10}^4{cm}^{-1}. Aquestes característiques han propiciat que les Les kesteritas estan sent molt investigades per la comunitat fotovoltaica de capes primes. D'acord amb el límit de Shockley-Queisser, l'eficiència de conversió per a una cel·la solar basada en CZTS és d'aproximadament 28%. Aquesta eficiència és teòricament possible a través de l'ajust de la banda prohibida, però tot i així, encara no s'ha pogut assolir experimentalment, probablement a causa de la incomprensió del funcionament dels dispositius. Per a una millor comprensió de les característiques i funcionament dels dispositius, la modelització numèrica pot jugar un paper important al permetre estudiar diferents estructures de sistemes que poden estalviar temps i costos a la comunitat científica-tècnica. En aquest treball, s'ha dut a terme una modelització numèrica per estimar i analitzar l'efecte de paràmetres físics com l'espessor i la concentració de dopatge de la capa absorbent, la capa tampó i la capa finestra, a més d'estudiar l'efecte de la temperatura i l'efecte de la potència d'il·luminació del sol en el rendiment del dispositiu. L'anàlisi numèrica dels dispositius es va realitzar amb el programari de simulació denominat "Solar Cell Capacitance Simulator" (SCAPS-1D). Per això es va analitzar una estructura senzilla p-n-n^+ utilitzant molibdé com contacte posterior i FTO com a finestra òptica i contacte frontal i seguint la seqüència de materials Mo/CZTS/CdS/ZnO/FTO. A través de l'anàlisi, es va estudiar el rendiment de les cel·les solars amb la variació en l'espessor de l'absorbent per trobar l'espessor òptim de la capa absorbent. També es va estudiar l'efecte de la concentració del dopatge i de la funció de treball del metall. Després de la visualització d'una estructura de dispositiu bàsic en SCAPS-1D, es model una cel·la solar experimental basada en CZTS. Els resultats de les cel·les solars CZTS dissenyats experimentalment es simularen per primera vegada en l'entorn SCAPS-1D. Els resultats simulats de SCAPS-1D es van comparar amb els resultats experimentals. Després de l'optimització dels paràmetres de la celda, es va incrementar l'eficiència de conversió d'un dispositiu optimitzat i, a partir del modelatge, es va descobrir que el rendiment del dispositiu es millora a l'augmentar la vida útil dels minoritaris, cosa que es aconsegueix amb la incorporació d'un camp elèctric a la superfície del con
[EN] The solar cell has emerged as a newer and a relatively sustainable energy source, that is eco-friendly and cost-effective if the production is on a larger scale. In the current scenario, the economic and high-power conversion efficiency photovoltaic devices without degradation of materials are designed for the generation of electricity. The silicon-based solar cells dominated the market for many years. For the manufacturing and production of silicon-based solar cells, sophisticated fabrication techniques are required that make the solar panel costly. Due to intensification in manufacturing capabilities, thin film solar cells are gaining significance. Thin film technology is one of the most cost-effective and efficient technologies for the manufacturing of solar cells, and it is an excellent subject of intense research in the photovoltaic industry. Thin film technology is economical than other technologies because devices have relatively less material and are based on various types of light absorbing semiconductor materials. Among these materials, kesterite solar cells utilizing CZTS, CZTSe and their alloys CZTSSe are emerging as the most auspicious replacement for the chalcopyrite absorbers. The outstanding electrical and optical features having direct optical band gap ranges among 1.4eV to 1.5eV and large absorption coefficient \alpha\ >{10}^4{cm}^{-1} of CZTS have made it very interesting in the thin film community. According to the Shockley-Queisser limit, the optimum conversion efficiency of around 28\ % is theoretically possible from a CZTS based solar cell by tuning the band gap, but still, it is not experimentally possible to achieve 28% conversion efficiency from a solar cell due to lack of understanding of device characteristics. For a better understanding of device characteristics, numerical modeling can play a significant role by modeling different device structures that can save time and cost of the research community. In this work, numerical modeling was carried out for estimating and analyzing the effect of physical parameters such as thickness and doping concentration of absorber, buffer and window layers, temperature effect and effect of illumination power of the sun on device performance. Device modeling had performed on the dedicated simulation software "Solar Cell Capacitance Simulator" (SCAPS-1D). To achieve this task first, a simple {p-n-n}^+ structure for Mo/CZTS/CdS/ZnO/FTO had been analyzed with molybdenum as back contact and FTO as a front contact. Through analysis, it had been found that solar cell performance was affected by variation in absorber thickness, doping concentration, and metal work function. After visualization of a basic device structure in SCAPS-1D, CZTS based experimental solar cell had been modeled. Experimentally designed CZTS solar cell results were first simulated in SCAPS-1D environment. The SCAPS-1D simulated results were then compared with experimental results. After optimization of cell parameters, the conversion efficiency of an optimized device was increased and from modeling, it had been found that device performance was improved by improving minority carrier lifetime and integration of back surface field at the back contact. Based on the results presented, it was found that recombination in a solar cell can greatly affect the performance of a solar cell. Therefore, a new structure (Back\ contact/CFTS/ZnS/Zn(O,S)/FTO) was modeled and analyzed in which interface recombination is reduced by optimizing the band gap of Zn(O,S) layer. Based on different device structure modeling, it was found that solar cell with structure CFTS/ZnS/Zn(O,S)/FTO can exhibit an efficiency of 26.11% with optimized physical parameters like absorber thickness layer of 4\mu m and acceptor concentration density of 2\times{10}^{18}\ {cm}^{-3}. The proposed results will give a valuable guideline for the feasible fabrication and designing of high-power conversion efficiency solar cells.
Khattak, YH. (2019). Modeling of High Power Conversion Efficiency Thin Film Solar Cells [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/118802
TESIS
Redorici, Lisa. « Efficiency limits for silicon/perovskite tandem solar cells : a theoretical model ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9531/.
Texte intégralSCACCABAROZZI, ANDREA. « GaAs/AlGaAs quantum dot intermediate band solar cells ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2013. http://hdl.handle.net/10281/40117.
Texte intégralMenezes, Fabian Marcel. « Raio solar em frequências subterahertz e sua relação com a atividade solar ». Universidade Presbiteriana Mackenzie, 2017. http://tede.mackenzie.br/jspui/handle/tede/3472.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The Sun emits radiation at several wavelengths of the electromagnetic spectrum. In the optical band, the solar radius is 696,000 km and this is what defines the photosphere, the visible surface of the Sun. However, as the altitude increases, the dominant electromagnetic radiation is produced at other frequencies, causing the solar radius to change as function of wavelength. We measure the solar radius at the subterahertz frequencies of 0,212 and 0,405 THz – i.e., the altitude where these emissions are generated – and also analyse the radius variation over the 11-year solar activity cycle. These measurements enable a better understanding of the solar atmosphere and the radius dependence on the solar cycle, is a good indicator of the changes that occur in the atmospheric structure. For this, we used radio maps of the solar disk for the period between 1999 and 2016, reconstructed from daily scans made by the Solar Submillimeter-wave Telescope (SST), installed at El Leoncito Astronomical Complex (CASLEO), at Argentinean Andes. At both frequencies our measurements yield a radius of 966,′′5 with dispersion of ±2,′′8 for 0,212 THz and ±2,′′7 for 0,405 THz. This implies a height of 5.0 ± 2.0 × 106 m above the photosphere. Furthermore, we also observed strong anti-correlation between radius variation and solar activity at both frequencies.
Na banda visível, seu raio é de 696.000 km e isto é o que define a fotosfera, a superfície visível do Sol. Contudo, à medida que a altitude aumenta, a radiação eletromagnética dominante é produzida em outras frequências, fazendo com que o raio solar mude em função do comprimento de onda. Nosso objetivo é medir o raio solar em frequências de subterahertz de 0,212 e 0,405 THz, isto é, a altitude onde são geradas estas emissões e, além disso, a variação do raio ao longo do ciclo de atividade solar de 11 anos. A importância desta pesquisa é a possibilidade de se compreender mais sobre atmosfera solar e qual a dependência do raio com o ciclo solar, o que pode ser um bom indicador das mudanças que ocorrem nesta estrutura. Para isso, utilizamos mapas em rádio do disco solar de 1999 a 2016 que foram reconstruídos a partir de varreduras diárias feitas pelo Telescópio Solar para Ondas Submilimétricas (SST), instalado no Complexo Astronômico El Leoncito (CASLEO), nos Andes argentinos. O valor de raio obtido para ambas as frequências é 966,′′5 com dispersão de ±2,′′8 para 0,212 THz e ±2,′′7 para 0,405 THz, o que significa uma altitude de 5, 0 ± 2, 0 × 106 m. Além disso, observou-se uma forte anti-correlação entre a variação temporal do raio e a atividade solar em ambas as frequências.
SCILLETTA, CLAUDIA. « Carbon nanotubes for solar energy conversion ». Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2009. http://hdl.handle.net/2108/1039.
Texte intégralIt has been demonstrated that nanotechnology and nanomaterials could offer valid solutions to improve the conversion efficiency by exploiting effects induced at mesoscopic scales. In this research field, the activity on carbon nanotubes CNTs as building blocks for solar energy conversion devices is developing. The work presented in this thesis has been devoted to investigate the physical mechanisms underlying the photoresponse generation of multiwall carbon nanotubes (MWCNTs) when exploited in electrochemical cells and solid-state devices. A large part of the activity has consisted of the development of suitable strategies for the controlled growth of MWCNTs. MWCNTs have been synthesised by thermal CVD varying the experimental growth parameters. By using morphological and structural characterization techniques, it has been possible to fix the proper synthesis parameters to obtain controlled MWCNTs structures on specific substrates. Experiments of photochemical current generation by MWCNTs grown on SiO2/Si substrates have been performed as well as solid-state photoconductivity measurements. They have confirmed the capability of MWCNTs to generate a current of electrons under light irradiation, despite their close similarity to metallic graphite. EELS spectra show a shoulder at energies 2-4 eV, below the typical plasmon π -π* peak for HOPG. That can be associated, similarly to SWCNTs, to the presence of van Hove singularities in electronic density of states. These transitions allow the generation upon illumination of an exciton. The electrolyte inside the chemical cell and/or the presence of localized Schottky junctions between different MWCNTs separates the charges. The solid-state photoconductivity results have been compared with those obtained in photochemical experiments, and with other described in literature. On the basis of theoretical calculations of DOS for a specific four-wall carbon nanotube (4WCNT), it is possible to affirm that MWCNTs are able to locally create p-n and/or Schottky junctions with the silicon substrate underneath, giving rise to an extended depletion layer. This implies a modification of the feature in the expected photocurrent spectrum of MWCNTs. MWCNTs have been decorated by Cu nanoparticles and their photoresponse has been studied and compared with that of bare nanotubes. The quantum efficiency of the hybrid system increases over the entire spectrum and two models have been proposed to explain these results. Finally, a first measurement of the performance of a MWCNTs/SiO2/Si device as PV cell has been performed by using a solar simulator. The I-V characteristic under illumination is not the expected well-shaped curve of a PV cell, but it demonstrates that the MWCNT solid-state device can operate as an active power supply element under solar illumination.
Torelli, Daniele. « Studio delle proprieta ottiche di film di silicon oxynitrides (sion) per applicazioni fotovoltaiche ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/6282/.
Texte intégralBOSCHETTI, MICOL. « Water decontamination from organic micropollutants via photocatalytic solar systems based on WO3 photoanodes ». Doctoral thesis, Università degli studi di Ferrara, 2020. http://hdl.handle.net/11392/2488195.
Texte intégralNell'ambito del trattamento delle acque è emersa la necessità di sviluppare nuovi materiali e processi al fine di consentire un'efficiente rimozione di contaminanti emergenti, quali droghe e antibiotici, attualmente presenti nei bacini idrici, sfruttando un approccio sostenibile. I metodi di fotocatalisi e di fotoelettrocatalisi innescati da luce solare sono tra i processi di ossidazione avanzata più efficaci per la decontaminazione delle acque. Tali metodi sono basati sull'interazione in acqua di luce solare con ossidi semiconduttori; questa interazione genera specie chimiche altamente reattive, capaci di ossidare i microinquinanti organici, quindi purificando l'acqua. In questo lavoro sono presentati due dispositivi solari, ossia un concentratore solare e un reattore autonomo modulare, il cui principio di funzionamento si basa sui processi di fotocatalisi e fotoelettrocatalisi. Come materiale attivo integrato all'interno dei dispositivi solari è stato studiato il triossido di tungsteno nanostrutturato. In particolare, diverse tecniche di realizzazione (solvotermale, anodizzazione elettrochimica, e sol-gel) sono state caratterizzate sfruttando substrati in vetro e metallo. Gli elettrodi basati su WO3 hanno raggiunto fotocorrenti di 1-5 mA/cm2, consistenti con quelle riportate in letteratura, e un'attivazione nella parte visibile dello spettro solare fino a 470 nm. I test di fotodegradazione, effettuati su alcuni specifici medicinali, hanno mostrato notevoli risultati, con un abbattimento pressoché totale di alcuni inquinanti, e una diminuzione di oltre il 60% del COD (Domanda Chimica di Ossigeno) in 1 ora. Entrambi i dispositivi solari possono essere ampliati in un prossimo futuro a scopi industriali per il trattamento terziario delle acque, sfruttando un processo sostenibile, senza costi energetici aggiuntivi e con una possibile produzione di idrogeno come valore aggiunto al processo di decontaminazione.
Maggiorano, Anna. « Solar radiation penetration in biogeochemical model of the coastal ocean. Numerical experiments ». Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13542/.
Texte intégralPrivitera, Alberto. « DEVELOPMENT AND CHARACTERIZATION OF NANOSTRUCTURED MATERIALS FOR ORGANIC AND HYBRID SOLAR CELLS ». Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426793.
Texte intégralNegli ultimi anni, a causa della frenetica evoluzione delle moderne tecnologie, si è andata a creare una divergenza sempre più allarmante tra la produzione e il consumo di energia. Le risorse tradizionali di energia, infatti, non sono più sufficienti a soddisfare la sempre crescente domanda energetica senza il drastico effetto di rovinare l’ambiente che ci circonda. Il fotovoltaico rappresenta una tecnologia promettente per affrontare il problema energetico mondiale. La ricerca scientifica focalizzata su questo argomento fondamentale ha dato luogo a risultati molto interessanti e le celle solari organiche ne sono una dimostrazione. Uno dei principali motivi dello sviluppo e del crescente interesse in questa nuova tecnologia è legato alla sua ecosostenibilità e al basso costo di produzione dei moduli solari che solitamente avviene su substrati (polimerici) flessibili. Inoltre, dal momento che questa tecnologia si basa sulla produzione di celle solari trasparenti e flessibili numerose applicazioni innovative sono già previste. Nonostante ciò, prima che il forovoltaico organico prevalga sulle celle solari al silicio che già da anni si sono affermate nella scena mondiale, due problemi principali devono essere affrontati: la bassa efficienza e la scarsa stabilità dei moduli fotovoltaici organici. Per far fronte a questi problemi la migliore alternativa è focalizzare gli sforzi della ricerca sia sullo sviluppo di nuovi materiali sia sulla loro caratterizzazione fotofisica e morfologica. Recentemente, l’applicazione di nanostrutture all’interno degli strati attivi delle celle solari organiche ha dimostrato di essere un’idea efficace per promuovere l’efficienza delle celle solari. Infatti è risaputo che la miniaturizzazione a livello nanometrico dei materiali apre la strada a numerose possibilità per controllare e incrementare le loro proprietà ottiche ed elettriche. In questo lavoro di tesi, le potenzialità delle nanostrutture vengono prese in considerazione. In particolare, l’attenzione di questa tesi è indirizzata allo sviluppo e alla caratterizzazione fotofisica di nuovi materiali nanostrutturati fotoattivi ibridi. Tre differenti famiglie di nanostrutture, i Quantum Dots colloidali, i Carbon Dots e le nanoparticelle di perovskite ibrida organica/inorganica, sono state incorporate all’interno di materiali fotovoltaici organici. Lo studio dettagliato delle interazioni fotofisiche e morfologiche tra le nanostrutture e i materiali organici ha permesso di considerare questi materiali nanocompositi come materiali promettenti per il fotovoltaico di nuova generazione. La prima parte del lavoro si focalizza sullo studio di uno strato fotoattivo costituito dal derivato fullerenico PCBM e dai Quantum Dots (QDs) core-shell di CdSe/CdS funzionalizzati con tre leganti differenti (l’oleilammina, l’ottadecantiolo e il propantiolo). Il primo obiettivo è stato dimostrare che la presenza dei QDs non solo influenza la morfologia degli strati fotoattivi delle celle solari, come spesso è riportato in letteratura, ma anche la loro fotofisica. Il secondo obiettivo è stato chiarire il ruolo fondamentale dei leganti dei QDs nel processo di trasferimento elettronico, processo essenziale nelle celle solari organiche. Attraverso l’uso combinato di tecniche di risonanza magnetica elettronica di stato stazionario, risolte nel tempo e impulsate, il ruolo fotofisico dei QDs nelle celle solari organiche è stato chiarito in grande dettaglio. Inoltre, è stata dimostrata la possibilità di controllare opportunamente il processo di trasferimento elettronico attraverso la scelta accurata dei leganti dei QDs. La seconda parte del lavoro mira a promuovere l’applicazione dei Carbon Dots (CDs) come materiale elettron-donatore nelle celle solari organiche. I CDs hanno dimostrato di essere una buona alternativa ai QDs colloidali grazie alla loro bassa tossicità e biocompatibilità e alle loro peculiari proprietà fotofisiche. Nonostante ciò, la loro scarsa solubilità in solventi organici e le loro deboli proprietà elettron-donatrici hanno ostacolato sinora la loro applicazione nel campo fotovoltaico. Per far fronte a queste criticità, è stata portata a termine la sintesi e la caratterizzazione fotofisica di CDs contenenti atomi di azoto e funzionalizzati con due diversi gruppi tiofenici. Lo scopo della funzionalizzazione è stato incrementare le proprietà elettron-donatrici dei CDs e migliorare la loro solubilità in solventi organici. L’aumento di solubilità ha permesso di studiare la loro interazione fotofisica con il PCBM sia in soluzione che in film. Tramite l’utilizzo della voltammetria ciclica, della spettroscopia ottica e della spettroscopia EPR, sono state dimostrate le buone proprietà di trasferimento elettronico fotoindotto in questi materiali e il processo di trasferimento elettronico è stato studiato in dettaglio. Infine, l’ultima parte di questo lavoro di tesi si concentra sulle nanoparticelle di perovskite ibrida organica/inorganica. Le perovskiti ibride sono a tutti gli effetti il miglior candidato nella corsa per sostituire le convenzionali celle solari al silicio. Negli ultimi cinque anni le perovskiti ibride massive hanno stabilito record straordinari di efficienza fotovoltaica. Nonostante ciò, l’utilizzo delle nanoparticelle di perovskite nelle celle solari organiche non è stato ancora studiato a fondo. Per ovviare a ciò, nell’ultima parte di questo lavoro è stata portata a termine la sintesi delle nanoparticelle di perovskite ed è stata studiata la loro interazione sia con il PCBM che con il polimero semiconduttore P3HT. Dopo aver confermato l’avvenuta sintesi mediante spettroscopia ottica, diffrazione a raggi X e spettroscopia di fotoemissione a raggi X, è stato analizzato il processo di trasferimento elettronico fotoindotto tra le nanoparticelle di perovskite e il PCBM. In particolare, grazie all’utilizzo di nanoparticelle funzionalizzate con due diversi leganti (ottilammina ed oleilammina), il ruolo fondamentale della lunghezza dei leganti nel processo di trasferimento elettronico è stato evidenziato. Successivamente, l’attenzione è stata rivolta al nanocomposito di nanoparticelle di perovskite e P3HT. In questo caso, è stato osservato che la presenza delle nanoparticelle di perovskite svolge un triplice effetto sulle proprietà del polimero: (1) un incremento nella dimensione dei domini cristallini, (2) un drogaggio di tipo p, e (3) un aumento dell’ordine intercatena nella fase polimerica. I risultati di questo lavoro di tesi evidenziano la rilevanza delle nanostrutture nei materiali fotovoltaici organici sottolineando il loro effetto positivo non solo sulla morfologia, ma anche su tutti i principali processi fotofisici che hanno luogo nelle celle solari. Inoltre, viene dimostrata l’importante funzione dell’ingegnerizzazione superficiale di queste nanostrutture al fine di favorire il processo di conversione dell’energia solare. Tutti questi risultati hanno lo scopo di promuovere la progettazione, lo sviluppo e l’efficienza delle celle solari di nuova generazione.
ZAFFALON, MATTEO LUCA. « Advanced Spectroscopic Investigations of Colloidal Semiconductor Nanostructures for Photon Management and Radiation Detection Schemes ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/366215.
Texte intégralDuring my PhD I investigated excitonic recombination mechanisms in colloidal semiconductor nanocrystals (NCs), promoting the development of new paradigms for the manipulation of optical and scintillation properties. Thanks to the wide range of spectroscopic techniques and the valuable collaborations undertaken, my conclusions have been published in prestigious scientific journals, contributing to the advancement of the community of nanomaterials scientists. My research mainly dealt with two topics of current technological importance: i) the origin of photoluminescence in NC of Cd-free ternary I-III-VI2 chalcogenides such as CuInS2 and AgInS2 ii) the use of perovskite nanostructures in detection schemes and/or energy conversion of ionizing radiation. Specifically, the use of complementary spectroscopic techniques in a controlled temperature regime has validated the presence of intrinsic sublevels, with different parity, in the valence band of the stoichiometric CuInS2 NCs responsible for the optical properties of this class of NC. My results, supported by Monte Carlo ray-tracing simulations, led to the fabrication of a luminescent solar concentrator - with record efficiency - based on CuInS2 NCs with optimal size. The study was then extended to AgInS2 NCs, a less investigates material so far, but very promising for bioimaging applications thanks to the absence of toxic elements. Then, I investigated the detection of ionizing radiation through high atomic number nanostructures such as lead halide perovskites (LHP), and in particular CsPbBr3. Through the detailed study of photo- and radio-luminescence properties, I highlighted the effects of the interaction between band edge exciton and shallow/deep defect states in CsPbBr3 nanostructures with different dimensionality. This fundamental study offered a platform to develop novel synthetic strategies to passivate trap sites on NC surfaces that led to a 500% enhancement of scintillation yield. The stability of CsPbBr3 NCs was finally verified in terms of radiation hardness, up to extreme gamma doses of 1 MGy. Furthermore, to extend their application to radiation detection with waveguiding devices, I studied the sensitization of an organic dye coupled to CsPbBr3 NCs, creating the first example of a plastic scintillator with wide Stokes-shift and fast luminescence based on LHP. To overcome the limitations imposed by the presence of Pb in LHPs, I finally explored the optical and scintillation properties of new emerging classes of green double perovskites. The information gathered encourages the continuation of this line of research, indicating surface passivation as the most promising strategy for achieving performance similar to the Pb-based counterparts.
BASILICO, DAVIDE. « FIRST INDICATION OF SOLAR NEUTRINOS FROM THE CNO CYCLE REACTIONS WITH THE BOREXINO EXPERIMENT ». Doctoral thesis, Università degli Studi di Milano, 2020. http://hdl.handle.net/2434/709966.
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