1,430 research outputs found

    Cloaked contact grids for perovskite-silicon tandem solar modules

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    Photovoltaik (PV) spielt eine wichtige Rolle bei der Transformation des globalen Energiesystems von fossilen Brennstoffen hin zu erneuerbaren Energiequellen, die ein SchlĂŒssel zu einer nachhaltigen Zukunft des Planeten Erde ist. Eine solche Transformation wird jedoch hauptsĂ€chlich durch die wirtschaftliche WettbewerbsfĂ€higkeit einer Technologie getrieben, fĂŒr die die Stromgestehungskosten ein entscheidender Faktor sind. In den letzten Jahren sind die Preise fĂŒr Solarmodule drastisch gesunken, so dass die weitere Steigerung des Wirkungsgrades (PCE) und des Energieertrags (EY) von PV-Anlagen von zunehmender Bedeutung ist, um die wirtschaftliche WettbewerbsfĂ€higkeit der PV zu verbessern. Einer der limitierenden Faktoren moderner Solarmodule ist die Verlustleistung aufgrund inaktiver FlĂ€chen, die zur Minimierung der resistiven Verluste wĂ€hrend des Ladungstransports ĂŒber die großen Abmessungen eines Solarmoduls erforderlich sind. Optische Tarnkonzepte haben die FĂ€higkeit, Licht von inaktiven Bereichen hin zu den aktiven FlĂ€chen eines Solarmoduls zu leiten, wodurch die entsprechende Verlustleistung reduziert wird. Unter den verschiedenen optischen Tarnkonzepten sind FreiformoberflĂ€chen (FFS) als Tarnkappen eine interessante Technologie, die omnidirektionales Tarnen von inaktiven FlĂ€chen verspricht. Diese Dissertation konzentriert sich auf die Entwicklung und Herstellung von FFS mit der anvisierten Anwendung auf Perowskit/Silizium-Tandem-Solarmodulen, die ihrerseits sowohl fĂŒr die Forschung als auch fĂŒr die Industrie von höchstem Interesse sind, da die Kombination zweier Absorbermaterialien das theoretische Limit der PCE von 29 % fĂŒr Einfachsolarzellen auf 46 % fĂŒr Tandemsolarzellen erhöht. Eine detaillierte Untersuchung der optischen Verluste mittels optischer Simulation und EY-Modellierung von zwei- (2T) und vier-poligen (4T) Perowskit/Silizium-Tandemsolarmodulen in dieser Arbeit zeigt, dass Leistungsverluste durch inaktive FlĂ€chen – neben der parasitĂ€ren Absorption – einer der grĂ¶ĂŸten optischen Verlustmechanismen von Perowskit/Silizium-Tandemsolarmodulen sind. Auch wenn FFS in einem idealen Design eine perfekte Tarnung von inaktiven FlĂ€chen aufweisen, sind sie nicht mit der herkömmlichen Architektur von Solarmodulen kompatibel, da sie eine nicht planare, fĂŒr Verschmutzung anfĂ€lligere OberflĂ€che aufweisen. Um Verschmutzungen zu vermeiden, wird die Einbettung von FFS unter einer Glasabdeckung untersucht und hierfĂŒr zwei optimierte Designs von FreiformoberflĂ€chen vorgeschlagen, die unter BerĂŒcksichtigung eines geometrischen FĂŒllfaktors (GFF) von inaktiven FlĂ€chen von 4 % die Einstrahlungsleistung auf die aktive FlĂ€che theoretisch um 3.5 % erhöhen. Die FĂ€higkeit des omnidirektionalen Tarnen wird jedoch durch die vorgeschlagenen Designs beeintrĂ€chtigt, was zu einem etwas geringeren Anstieg des EY unter realistischen Einstrahlungsbedingungen von 2.4 % jĂ€hrlich fĂŒhrt. Die effektive Tarnung inaktiver FlĂ€chen verschiebt zudem den optimalen Abstand und die optimale Dicke der Frontelektrode. Unter einer zusĂ€tzlichen Optimierung der Frontkontaktierung, erhöht sich der Anstieg in EY durch den Einsatz von eingebetteten FFS weiter auf 3.1 %. Prototypen von Einfachsolarzellen aus CuInx_{\text{x}}Ga1-x_{\text{1-x}}Se2_{\text{2}} (CIGS) und kristallinem Silizium (c-Si) zeigen zwei mögliche AnsĂ€tze zur Einbettung von FFS in die vorderen Verkapselungsschichten konventioneller Solarmodule auf: (1) PrĂ€gen von FFS in das polymere Verkapselungsmaterial und Einbetten unter einer Glasabdeckung, was zu einer Erhöhung der Kurzschlussstromdichte JSCJ_{\text{SC}} eines CIGS-Solarmoduls um 4.1 % bei einem GFF inaktiver FlĂ€chen von 4.7 % fĂŒhrt, und (2) Einbetten von FFS-Cloaks direkt in das Deckglas durch Anwendung der FlĂŒssigglastechnik, die den JSCJ_{\text{SC}} von c-Si-Solarzellen um 3.8 % bei einem GFF von 4.4 % erhöht. Beide AnsĂ€tze stellen eine praktikable Option fĂŒr die Anwendung von FFS in 2T Perowskit/c-Si-Tandemsolarmodulen dar. FĂŒr 4T Perowskit/c-Si-Tandemsolarmodule ist die Abscheidung der Perowskitsolarzelle (PSC) direkt auf der Glasabdeckung vorzuziehen, da sie Frontschichten höherer optischer QualitĂ€t ermöglicht. Um eine OberflĂ€chenqualitĂ€t zu erreichen, die die Abscheidung der konformen dĂŒnnen Schichten einer PSC unterstĂŒtzt, wird die mit der FlĂŒssigglastechnik hergestellte Glasabdeckung mechanisch poliert. Die Herstellung von funktionierenden Perowskitsolarzellen ist jedoch noch nicht erfolgreich. Die optische Charakterisierung bestĂ€tigt jedoch das effiziente Tarnen von inaktiven FlĂ€chen mittels diesen Ansatzes, unterstreicht aber auch die starke AbhĂ€ngigkeit von optischen Tarnkonzepten von ihrer Ausrichtung bezĂŒglich der inaktiven FlĂ€chen. Im Hinblick auf die zukĂŒnftige Entwicklung bleiben die erfolgreiche Abscheidung von PSCs auf Glasabdeckungen, die mit der FlĂŒssigglastechnik hergestellt werden, die Verbesserung der Ausrichtung und die Aufskalierung der Technologie offene Herausforderungen

    Comparisons of Current Practices of Computer Use and Training by Industry Type of Small Businesses in the Portland Area

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    The problem was to determine what are the current computer uses, and training practices for small businesses in the Portland area. Comparisons were made by industry type

    Ideal and real structures of different forms of carbon, with some remarks on their geological significance

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    Carbon is found in nature in a huge variety of allotropic forms and recent research in materials science has encouraged the development of technological materials based on nanocarbon. Carbon atoms with sp2 or sp3 hybridization can be thought of as building blocks. Following a bottom-up approach, we show how graphene and diamond molecules are built up and how their properties vary with size, reaching an upper limit with bulk graphite and diamond. Carbon atoms with sp2 hybridization give rise to an impressive number of different materials, such as carbon nanotubes, graphene nanoribbons, porous carbon and fullerene. As in any crystalline phase, the crystal structures of natural carbon allotropes (i.e. graphite and diamond) contain various types of imperfections. These so-called lattice defects are classified by their dimensions into 0D (point), 1D (line), 2D (planar) and 3D (volume) defects. Lattice defects control the physical properties of crystals and are often a fingerprint of the geological environment in which they formed and were modified. Direct observations of lattice defects are commonly accomplished by transmission electron microscopy. We present and discuss the ideal and real structures of carbon allotropes, the energetics of lattice defects and their significance in understanding geological processes and conditions

    Orientation of Planar Deformation Features (PDFs) in quartz

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    Differently oriented single crystal quartz was shocked experimentally at pressures of 20 to 32 GPa and pre-shock temperatures up to 630 C. Based on this systematic investigation, we can demonstrate that the orientation of planar deformation features in quartz is not only dependent on shock pressure but also on pre-shock temperature and shock direction. Moreover, the orientation of Planar Deformation Features (PDF's) is strongly influenced by the set-up in recovery experiments. PDF's in quartz are defined as optically recognizable, planar microstructures diagnostically produced by shock compression. PDF's differ from all kinds of microstructures found in volcanic environment and therefore, their presence is a primary criterion for recognizing impact craters and ejecta layers such as the K/T boundary. Because experiments have shown a pressure dependence of the orientation of PDF's, this property is used extensively for shock wave barometry in natural impact sites. However, the unreflected application of experimental results neglects that parameters such as pre-shock temperature, shock direction, or the experimental arrangement may influence the spatial distribution of PDF's. In order to test this assumption, shock experiments on single crystal quartz at pre-shock temperatures of 20, 275, 540, and 630 C, and with shock directions (1010) and (0001) were performed. Most of the recovery experiments were carried out by using a reverberation technique, whereas in only one experiment a single shock was produced (impedance method). In the former case 0.5 mm thin discs of single crystal quartz were used, in the latter a 15 mm thick cylinder. The orientation of PDF's was measured by means of a conventional universal stage and the results are given. Effects of the experimentation technique can be derived showing the orientation of PDF's in quartz shocked at 27.5 GPa. In comparison to the well defined peaks at (1012) found in samples from reverberation experiments, the impedance matching technique causes PDF's with a broad distribution pattern and indistinct maxima. Our results have serious implications for shock-wave barometry in nature: the existing classification scheme which relates PDF orientation exclusively to shock pressure is no longer applicable. In consequence more experimental data is needed

    Implications of genotype and amino acid sup-ply on pork quality

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    An experiment was conducted to evaluate the effect of different feeding regimes and genotypes on growth performance, carcass characteristics, composition and eating quality of pork under organic framework conditions. 198 individually housed pigs of 4 genotypes were allocated to three dietary treatments. Feeding regimes differed in relation to the supply of limiting amino acids (AA). The genotypes used were Pi x (DL x DE); Du x DL, Pi x German Swabian Hall (Pi x SH) and pure SH breed. While Pi x (DL x DE) pigs showed the highest carcass yields, pigs of the genotype Du x DL achieved higher values in dlwg and in meat composition compared to the other genotypes. Performance traits were significantly influenced by the feeding regime. Lean meat percentage and area of M.l.d. were significantly lower when a diet reduced in limited amino acids compared to the control treat-ment was fed. Backfat thickness was not influenced by the feeding regime. However, intramuscular fat content clearly increased when a diet without AA supplementation was fed. The results indicate that the limited availability of high quality feedstuffs in organic farming does not impair but improve the preconditions to produce pork of high eating quality

    Evidence for silicate dissolution on Mars from the Nakhla meteorite

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    Veins containing carbonates, hydrous silicates and sulphates that occur within and between grains of augite and olivine in the Nakhla meteorite are good evidence for the former presence of liquid water in the Martian crust. Aqueous solutions gained access to grain interiors via narrow fractures, and those fractures within olivine whose walls were oriented close to (001) were preferentially widened by etching along [001]. This orientation selective dissolution may have been due to the presence within olivine of shock-formed [001](100) and [001]{110} screw dislocations. The duration of etching is likely to have been brief, possibly less than a year, and the solutions responsible were sufficiently cool and reducing that laihunite is absent and Fe liberated from the olivine was not immediately oxidised. The pores within olivine were mineralised in sequence by siderite, nanocrystalline smectite, a Fe-Mg phyllosilicate, and then gypsum, whereas only the smectite occurs within augite. The nanocrystalline smectite was deposited as sub-micrometre thick layers on etched vein walls, and solution compositions varied substantially between and sometimes during precipitation of each layer. Together with microcrystalline gypsum the Fe-Mg phyllosilicate crystallised as water briefly returned to some of the veins following desiccation fracturing of the smectite. These results show that etching of olivine enhanced the porosity and permeability of the nakhlite parent rock and that dissolution and secondary mineralization took place within the same near-static aqueous system
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