Dissertations / Theses: 'Optical concentrators'

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Pancotti, Lorenzo <1977&gt. "Optical concentrators for photovoltaic use." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/349/.

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Green, Adam. "Optical properties of luminescent solar concentrators." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/8361/.

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This thesis on luminescent solar concentrators (LSC) presents work carried out as part of the Electronic and Photonic Molecular Materials (EPMM) group of the department of physics and astronomy at the University of Sheffield. The work is presented in five experimental chapters looking at a range of research aspects from film deposition and measurement instrumentation, to exploring LSC optical properties and device performances by spectral based analytical methods. A Gauge R & R (GRR) study design is used to assess sources of variance in an absolute fluorescence quantum yield measurement system involving an integration sphere. The GRR statistics yield the total variance split into three proportions; equipment, day-to-day and manufacturing variances. The manufacturing variance, describing sample fabrication, was found to exhibit the smallest contribution to measurement uncertainty. The greatest source of variance was found to be from fluctuations in the laser intensity whose uncertainty is carried into the quantum yield determination due to not knowing the exact laser intensity at the time of measurement. The solvation phenomenon is explored as a potential way to improve LSC device yields; this occurs due to excitation induced changes to a fluorophore's dipole moment which leads to a response by the surrounding host medium resulting in shifts in fluorophore emission energy. This effect is shown to improve self-absorption efficiency by reducing the overlap of absorption and emission for particular organic fluorophores. This is expected to greatly improve energy yields but current dopant materials are too costly to employ according to the cost evaluations of this thesis. A spray coating deposition tool is considered for the deposition of thin film coatings for bi-layer LSC devices. A screening study design of experiment is constructed to ascertain the level of control and assess the tool's ability to meet thin film requirements. Despite poor control over the roughness of the thin film layer this property was found to lie close to the acceptable roughness limit in most samples. The biggest issue remains the film thickness achieved by the deposition, which was an order of magnitude too small according to Beer-Lambert absorption models. This spray-coating tool is thus unsuitable for the requirements of a bi-layer LSC. Concentration quenching is explored in the context of LSC device efficiency. Different fluorophores are seen to exhibited varied quenching decay strengths by looking at quantum yield versus fluorophore concentration. For two fluorophores, 4-(Dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM) and 2,3,6,7-Tetrahydro-9-methyl-1H,5H-quinolizino(9,1-gh)coumarin (C102), the quenching process is explored further using quantum yield and lifetime measurements to extract the quenching rate from rate equations. The form of the quenching rate as a function of molecular separation is shown to be of a monomial power law but distinct from the point-like dipole-dipole coupling of Förster resonant energy transfer (FRET). Additional quenching modes including surface-point and surface-surface interactions are considered to explain the power law form. Spectral analytical models have been constructed to model performance metrics for square-planar LSC devices. In this model the input solar irradiance is considered to be incident normal to the LSC collection face. Device thickness optimisation is explored to ensure maximisation of the absorption efficiency by the fluorophore using Beer-Lambert absorption modelling. The normalised fluorophore emission spectrum is converted to an equivalent irradiant intensity spectrum based on the amount of energy absorbed. Propagation of this energy through the LSC structure is considered in terms of the mean path length of light rays waveguided by total internal reflection and again Beer-Lambert absorption modelling. Self-absorption and host transport losses are included in some detail. Out-coupling of LSC irradiance at the harvesting edges to connected solar cells is then modelled, using c:Si and GaAs power conversion efficiency spectra, and the resultant power output performance can therefore be estimated. Comparison with real devices from literature show that the model works reasonably well compared to these single device configurations and is somewhat conservative in its estimates. Cost efficiency models based on reasonable assumptions conclude the scope of this work showing that current materials fall short of delivering competitive energy solutions by at least factor of 2 in the case of the best dye modelled here.

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Buie, Damien Charles William. "Optical considerations in solar concentrating systems." University of Sydney. Physics, 2004. http://hdl.handle.net/2123/587.

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To optimise the performance of concentrating solar power systems, a detailed knowledge of the resultant flux distribution in the imaging plane is required. To achieve this, an accurate model of the direct solar beam impinging on the concentrator is essential. This thesis presents an empirical model of the terrestrial solar distribution that has both a high-correlation to observed data and an invariance to a change in location. The model is based on the amount of circumsolar radiation in the direct beam and takes into account the small variations that are due to atmospheric scattering. A modelling framework is developed to simulate the flux distribution in the imaging plane of a generic solar concentrating system. Algorithms are developed to include the following: the spatial solar energy distribution; the systemic effect of reflecting that distribution off a non-ideal mirrored surface; the spectral energy distribution; the transmission, absorption and reflection characteristics of optical thin films; and the coordinates of the solar vector. The framework is then used to investigate the performance of anti-reflection coatings on silicon substrates and the performance of linear Fresnel systems. Combined, these algorithms and simulation tools can be applied to create comprehensive optical models of solar concentrating systems.

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Giannuzzi, Alessandra <1980&gt. "Enhancing the efficiency of solar concentrators by controlled optical aberrations." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6224/.

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The diameters of traditional dish concentrators can reach several tens of meters, the construction of monolithic mirrors being difficult at these scales: cheap flat reflecting facets mounted on a common frame generally reproduce a paraboloidal surface. When a standard imaging mirror is coupled with a PV dense array, problems arise since the solar image focused is intrinsically circular. Moreover, the corresponding irradiance distribution is bell-shaped in contrast with the requirement of having all the cells under the same illumination. Mismatch losses occur when interconnected cells experience different conditions, in particular in series connections. In this PhD Thesis, we aim at solving these issues by a multidisciplinary approach, exploiting optical concepts and applications developed specifically for astronomical use, where the improvement of the image quality is a very important issue. The strategy we propose is to boost the spot uniformity acting uniquely on the primary reflector and avoiding the big mirrors segmentation into numerous smaller elements that need to be accurately mounted and aligned. In the proposed method, the shape of the mirrors is analytically described by the Zernike polynomials and its optimization is numerically obtained to give a non-imaging optics able to produce a quasi-square spot, spatially uniform and with prescribed concentration level. The freeform primary optics leads to a substantial gain in efficiency without secondary optics. Simple electrical schemes for the receiver are also required. The concept has been investigated theoretically modeling an example of CPV dense array application, including the development of non-optical aspects as the design of the detector and of the supporting mechanics. For the method proposed and the specific CPV system described, a patent application has been filed in Italy with the number TO2014A000016. The patent has been developed thanks to the collaboration between the University of Bologna and INAF (National Institute for Astrophysics).

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Schultz, Ross Dane. "On the characterisation of diffused light and optical elements in high concentrator photovoltaic modules." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/5170.

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High Concentrated Photovoltaics (H-CPV) promise a more efficient, higher power output than traditional photovoltaic modules. This is achieved by concentrating sunlight onto a small triple junction (CTJ) InGaP/InGaAs/Ge cell (ranging from 3.14 mm2 to 1 cm2) by using precision optical systems. These systems utilise non-imaging optics to concentrate and distribute the incident solar flux uniformly onto the CTJ device receiver to achieve maximum performance and power output from an H-CPV module. However, the performance of the device can be reduced due to the partial or complete absorption of a range of wavelengths present in the solar spectrum by the optical materials that are used for concentration. An investigation to determine the current density topographies of each subcell in a CTJ cell by multiple raster scans of an optical fibre receiver of a spectrometer in the plane of the aperture of the secondary’s optical element was conducted. Results showed that the physical properties of the optical elements’ material absorbed different amounts of the spectral content with respect to the subcell photosensitive wavelength regions. The facet properties of the primary optical Fresnel lens showed that the more rounded the Fresnel facets were, the lower the concentration of sunlight incident onto the CTJ cell. The increase in facet numbers showed an increase in scattering of the incident sunlight and chromatic aberrations. Chromatic aberration created by the refractive optics showed a variation in the amount of concentration on each individual subcell as well as the difference in intensity profiles across for the different subcells. Based on these results and the development of new multi-junction devices by industry, the performance of a four and six-junction device with the optical materials was investigated by simulations. The simulations showed that the careful integration of an additional subcell in a multi-junction device could rectify current mismatch between the subcells in the device. Based on the simulations, the best performing multi-junction cell was identified as the four-junction device that showed a cell and module efficiency under operation of 42.5 % and 35.5 %, respectively. Additionally, based on the performance results observed from the H-CPV module, the development of an HCPV module that would attempt to harness the incident tracked diffuse sunlight available to a concentrator photovoltaic (CPV) module for additional energy yield was undertaken. The part of the study comprised of measurements of the solar source, design of a prototype Hybrid High Concentrator Photovoltaic (HH-CPV) module. Results showed that power generation from the H-CPV system was highly dependent on the DNI levels and fluctuates greatly with variation in the DNI. The irradiance levels within the diffuse regions of the H-CPV module showed that the baseplate and vertical sides had an average irradiance range of 140-450 and 50-225 W.m-2, respectively. Irradiance topographic raster scans revealed that the baseplate and vertical sides had a relatively uniform intensity distribution and was identified as favourable sites for diffuse cell population. Simulations of various PV technologies showed the most suitable technology for the placement within the cavity of the HH-CPV module. The developed HH-CPV module was finalized with the utilization of CIS modules to harness the diffuse irradiance. During a 3 month power monitoring of the HH-CPV system, it was determined that the major power generation for the HH-CPV module come from the CPV component, while the CIS modules showed a minor power contribution. The total energy yield for the monitoring period was 45.99, 3.89 and 1.76 kW.h for the CPV, four-vertical sides and baseplate components, respectively. The increase in energy yield of the HH-CPV module when compared to the standard H-CPV module was determined to be 12.35 % for the monitoring period. The incorporation of the CIS modules into the H-CPV module to create the HH-CPV module did increase the energy yield of the module during high DNI conditions and did offset the almost zero power generation during low DNI conditions.

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Mulder, Carlijn Lucinde. "Engineering the optical properties of luminescent solar concentrators at the molecular scale." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/71482.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 121-128).
Luminescent Solar Concentrators (LSCs) concentrate solar radiation onto photovoltaic (PV) cells using an inexpensive collector plate to absorb incoming photons and waveguide fluorescently re-emitted photons to PVs at the edge. This thesis addresses the two main energy loss mechanisms in LSCs, namely transport losses and trapping losses. We used phycobilisomes, a biological light-harvesting complex, as dyes in the LSC collector to circumvent transport losses caused by photon re-absorption. The selfassembled structure of phycobilisomes couples numerous donor chromophores to a handful of acceptor chromophores through an internal F6rster energy pathway that isolates the absorption and emission spectra. We established that energy transfer within intact phycobilisomes reduces LSC self-absorption losses by approximately (48±5)% by comparing intact and partly decoupled phycobilisome complexes. To reduce trapping losses in LSCs, we leveraged the anisotropic emission pattern of dichroic dye molecules. We aligned their dipole moments normal to the face of the waveguide by embedding them in a liquid crystal host. Vertical dye alignment increased the fraction of the power emitted below the critical angle of the waveguide, thereby raising the trapping efficiency to 81% from 66% for LSCs with unaligned dyes. The enhanced trapping efficiency was preserved for geometric gains up to 30, and an external diffuser can enhance absorption in LSCs with vertically-aligned dyes. This thesis also explores an energy harvesting strategy for portable electronics based on LSCs with dye molecules that are aligned in-plane. The purely absorptive polarizers used to enhance contrast ratios in displays can be replaced with two linearly polarized luminescent concentrators (LSCs) that channel the energy of absorbed photons to PVs at the edge of the display. We coupled up to 40% of incoming photons to the edge of a prototype LSC that also achieved a polarization selection ratio of 3. Finaly, we investigated the contribution of self-absorption and optical waveguiding to triplet exciton transport in crystalline tetracene (Tc) and rubrene (Rb). A timeresolved imaging technique that maps the triplet distribution showed that optical waveguiding dominates over diffusion and can transport energy several micrometers at the high excitation rates commonly used to probe the exciton diffusion constants in organic materials.
by Carlijn Lucinde Mulder.
Ph.D.

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Wilson, Lindsay Robert. "Luminescent solar concentrators : a study of optical properties, re-absorption and device optimisation." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2336.

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This thesis presents the results of work on the optical properties and design optimisation of the luminescent solar concentrator (LSC). The optical properties of a range of uorophores were measured and it was found that the Lumogen F Rot 305 organic dye exhibited properties which make it ideal for use in LSCs, namely a wide absorption range (300-650 nm), 100% quantum yield at concentrations up to 1700 ppm, and the highest photostability of all the Lumogen F dyes, although the overlap of the absorption and emission spectra results in reabsorption (RA) losses. Despite these optimum properties, a detailed analysis showed that LSCs based on Rot 305 cannot compete with conventional glass/glass laminate modules on grounds of either cost or embodied energy. Since Rot 305 represents an optimum dye, this suggests it is unlikely that LSCs based on organic dyes will ever be competitive with conventional technologies. The only solution is the use of a uorophore with greatly reduced RA losses, for example a rare-earth (RE) complex. The RA losses of a europium-containing complex were found to be less than those of the Rot 305 dye, despite the lower quantum yield of the complex (86 %). The solar-to-electric conversion e ciencies of several LSC modules based on Rot 305 were measured. Modules with dimensions of 10 cm x 10 cm and 60 cm x 60 cm had e ciencies of 2.7% and 1.84% respectively, both measured without a back re ector. In addition, the technique of current-matching the edge cells was successfully demonstrated, resulting in a 15% increase in power output from an edge using matched cells relative to an edge using unmatched cells.

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Weatherby, Clive K. "Reducing the cost of photovoltaic energy conversion : the development of low-cost optical concentrators." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288026.

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Reusswig, Philip David. "Sensitized energy transfer for organic solar cells, optical solar concentrators, and solar pumped lasers." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93831.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-130).
The separation of chromophore absorption and excitonic processes, such as singlet exciton fission and photoluminescence, offers several advantages to the design of organic solar cells and luminescent solar concentrators (LSCs) for the end goal of achieving a lower cost solar energy generation. This thesis explores three new device architectures to overcome limited solar absorption in singlet-exciton-fission based solar cells and neodymium based LSCs. The process of singlet exciton fission is de-coupled from photon absorption, exciton diffusion, and charge transport in singlet-exciton-fission based solar cells by inserting a singlet fission material at the donor-acceptor interface of an organic solar cell. Singlet excitons generated in the singlet exciton donor are transferred to the singlet fission material through near field energy transfer. In this device structure, the singlet donor can be chosen for high photon absorption, exciton diffusion, and charge transport, and the singlet fission sensitizer can be selected for high singlet fission efficiency. We demonstrated a doubling of the external quantum efficiency from 12.8% to 27.6% in a singlet donor (TPTPA) through the introduction of thin film singlet fission sensitizer (rubrene) for high efficiency organic solar cells. To reduce the cost of electricity generated by sunlight via LSC systems, replacing the expensive high efficiency visible photovoltaic (PV) elements with cheap, high efficiency, earth abundant near-infrared PV elements made with silicon. This requires replacing within the LSC the visible emitting chromophores with near infrared emitters. Here, we present the use of a lanthanide ion, neodymium--colloidal nanocrystal energy cascade system as a promising LSC emitter scheme for the silicon spectral region. Peak optical quantum efficiencies of 43% in a Nd³+:glass based LSC are demonstrated with simulated high geometric gain performance. With cascade energy transfer, the optical quantum efficiency in the visible of a Nd³+:glass is significantly improved with peak efficiency of 28%. The enhanced solar absorption of Nd³+:glass through cascade energy transfer can be extended into the infrared with more optimal sensitizers. The idea of directly converting broad-band solar radiation into coherent and narrow-band laser radiation could enable many attractive technologies for solar energy. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-[mu]m-thick Nd³+-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 20 W-cm2 , or approximately 200 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.
by Philip David Reusswig.
Ph. D.

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Correia, Sandra Filipa Henriques. "Organic-inorganic hybrid materials for green photonics: luminescent solar concentrators." Doctoral thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/17407.

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Doutoramento em Física
Luminescent solar concentrators are inexpensive devices that aim to increase the efficiency of photovoltaic cells and promote the urban integration of photovoltaic devices, with unprecedented possibilities of energy harvesting through the façade of buildings, urban furniture or wearable fabrics. Generally, they consist of a transparent matrix coated or doped with active optical centres that absorb the incident solar radiation, which is re-emitted at a specific wavelength and transferred by total internal reflection to the edges where the photovoltaic cells are located. The main objective of this work is the production of luminescent solar concentrators whose optically active layer is based on organic-inorganic hybrid materials doped with europium ions or organic dyes, in particular, Rhodamine 6G and Rhodamine 800. Rhodamine 800, as opposed to europium ions and Rhodamine 6G which emit in the visible range, emits in the near infrared (NIR) range, which is an advantage for crystalline Si-based photovoltaic cells, whose efficiency is greater in the NIR. In this work, although the luminescent solar concentrators with planar geometry are addressed, the main focus is the use cylindrical geometry. The use of this type of geometry allows the effect of concentration to be higher relative to the planar geometry, since the ratio between the exposed area and the area of the edges is increased. The cylindrical geometry is exploited by producing luminescent solar concentrators based on polymer optical fibre (plastic) where the optically active layer is on the outside (as a coating) or inside (as a filling in the hollow core) of the optical fibre. Furthermore, the possibility of increasing the exposed area was also dealt with the production of bundles of luminescent solar concentrators in which the plastic optical fibres are placed side by side and, also, by fabricating luminescent solar concentrators with length in the metre scale.
Os concentradores solares luminescentes são dispositivos de baixo custo que têm como objetivo aumentar a eficiência de células fotovoltaicas e promover a integração de dispositivos fotovoltaicos em elementos do dia-a-dia, tornando possível a captura de energia solar, através da fachada de edifícios, mobiliário urbano ou em têxteis. Geralmente, consistem numa matriz transparente coberta ou dopada com centros óticos ativos, capazes de absorver a radiação solar incidente e reemiti-la com um comprimento de onda específico que será transportada, através de reflexão interna total, para as extremidades da matriz onde se encontra(m) a(s) célula(s) fotovoltaica(s). O principal objetivo deste trabalho consiste na produção de concentradores solares luminescentes cuja camada ótica ativa é baseada em materiais híbridos orgânicos-inorgânicos dopados com iões lantanídeos (európio, Eu3+) ou corantes orgânicos, nomeadamente, Rodamina 6G e Rodamina 800. A Rodamina 800, ao contrário dos iões de európio e da Rodamina 6G que emitem na gama do visível, emite na região espetral do infravermelho próximo (NIR), que se revela uma vantagem quando a célula fotovoltaica em uso é composta de silício cristalino, cuja gama de maior eficiência é no NIR. Neste trabalho, apesar de serem abordados concentradores solares luminescentes com geometria planar, o principal foco é a utilização da geometria cilíndrica. Este tipo de geometria permite que o efeito de concentração seja superior, relativamente à geometria planar, uma vez que a razão entre a área exposta e a área das extremidades é aumentada. A geometria cilíndrica é explorada, através da produção de concentradores solares luminescentes com base em fibra ótica polimérica (plástica) em que a camada ótica ativa se encontra no exterior (como um revestimento) ou no interior (como um preenchimento do núcleo oco). Além disso, a possibilidade de aumentar a área exposta foi, também, abordada com o fabrico de uma matriz de concentradores solares luminescentes colocados lado a lado e, também, com o fabrico de concentradores solares luminescentes na escala do metro.

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Zacharopoulos, Aggelos. "Optical design modelling and experimental characterisation of line-axis concentrators for solar photovoltaic and thermal applications." Thesis, University of Ulster, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342344.

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Selimoglu, Ozgur. "Design And Realization Of A New Concentrating Photovoltaic Solar Energy Module Based On Lossless Horizontally Staggered Light Guide." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615639/index.pdf.

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Concentrating Photovoltaic systems are good candidates for low cost and clean electricity generation from solar energy. CPV means replacing much of the expensive semiconductor photovoltaic cells with the cheaper optics. Although the idea is simple, CPV systems have several problems inherent to their system design, such as module thickness, expensive PV cells and overheating. Light guide systems are good alternatives to classical CPV systems that can clear off most of the problems of those systems. In this thesis we explore a new light-guide based solar concentrator by optical design and simulations. It is shown that this solar concentrator can reach 1000x geometric concentration, 96.5% optical efficiency with a ±
1 degree acceptance angle. As a result of simulations, effectiveness of the horizontally staggered light guide solar concentrators is proved. A practical module study is carried on to improve the knowledge related to light guide CPV systems. The concentrator geometry is fabricated as a medium concentrator system with a geometric concentration of 45x and +-2 degrees acceptance angle. With the prototype level injection molding 74% optical efficiency is achieved and can be improved with a better mold manufacturing. A cost analyses is also performed with real manufacturing parameters and it is shown that grid parity can be achieved with this kind of light guide solar concentrators.

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Coughenour, Blake Michael. "Photovoltaic concentrator optical system design| Solar energy engineering from physics to field." Thesis, The University of Arizona, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3619002.

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This dissertation describes the design, development, and field validation of a concentrator photovoltaic (CPV) solar energy system. The challenges of creating a highly efficient yet low-cost system architecture come from many sources. The solid-state physics of photovoltaic devices present fundamental limits to photoelectron conversion efficiency, while the electrical and thermal characteristics of widely available materials limit the design arena. Furthermore, the need for high solar spectral throughput, evenly concentrated sunlight, and tolerance to off-axis pointing places strict illumination requirements on the optical design. To be commercially viable, the cost associated with all components must be minimized so that when taken together, the absolute installed cost of the system in kWh is lower than any other solar energy method, and competitive with fossil fuel power generation.

The work detailed herein focuses specifically on unique optical design and illumination concepts discovered when developing a viable commercial CPV system. By designing from the ground up with the fundamental physics of photovoltaic devices and the required system tolerances in mind, a select range of optical designs are determined and modeled. Component cost analysis, assembly effort, and development time frame further influence design choices to arrive at a final optical system design.

When coupled with the collecting mirror, the final optical hardware unit placed at the focus generates more than 800W, yet is small and lightweight enough to hold in your hand. After fabrication and installation, the completed system's illumination, spectral, and thermal performance is validated with on-sun operational testing.

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Qandil, Hassan Darwish Hassan. "Investigations of the Fresnel Lens Based Solar Concentrator System through a Unique Statistical-Algorithmic Approach." Thesis, University of North Texas, 2019. https://digital.library.unt.edu/ark:/67531/metadc1609121/.

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This work investigates the Fresnel-lens-based solar concentrator-receiver system in a multi-perspective manner to design, test and fabricate this concentrator with high-efficiency photon and heat outputs and a minimized effect of chromatic aberrations. First, a MATLAB®-incorporated algorithm optimizes both the flat-spot and the curved lens designs via a statistical ray-tracing methodology of the incident light, considering all of its incidence parameters. The target is to maximize the solar ray intensity on the receiver's aperture, and therefore, achieve the highest possible focal flux. The algorithm outputs prismatic and dimensional geometries of the Fresnel-lens concentrator, which are simulated by COMSOL® Multiphysics to validate the design. For the second part, a novel genetically-themed hierarchical algorithm (GTHA) has been investigated to design Fresnel-lens solar concentrators that match with the distinct energy input and spatial geometry of various thermal applications. Basic heat transfer analysis of each application decides its solar energy requirement. The GTHA incorporated in MATLAB® optimizes the concentrator characteristics to secure this energy demand, balancing a minimized geometry and a maximized efficiency. Two experimental applications were selected from literature to validate the optimization process, a solar welding system for H13 steel plates and a solar Stirling engine with an aluminum-cavity receiver attached to the heater section. In each case, a flat Fresnel-lens with a spot focus was algorithmically designed to supply the desired solar heat, and then a computer simulation of the optimized lens was conducted showing great comparability to the original experimental results. Thirdly, the prismatic geometry of the Fresnel lens was further optimized through a statistical approach that incorporates laws of light refraction and trigonometry. The proposed design produces high focal irradiance that is more suitable for thermal applications. The motivation was to enhance the tolerability of a flat Fresnel-lens concentrator to tracking errors, without the use of secondary optics or sophisticated, and normally costly, meticulous tracking equipment. A comparative simulation analysis was conducted for two case studies from literature, each with a different design method. Fresnel lenses optimized by this work enhanced the concentration acceptance product (CAP) significantly, compared to that in literature. Then, this work introduced an innovative code-based, detailed, and deterministic geometrical approach, which couples the optimization of the Fresnel lens primary optical element (POE) and the dome-shaped secondary optical element (SOE). The objective was to maximize the concentration acceptance product, while using the minimum SOE and receiver geometries at a given f-number and incidence angle (also referred to as the tracking error angle). The laws of polychromatic light refraction along with trigonometry and spherical geometry were utilized to optimize the POE grooves, SOE radius, receiver size, and SOE–receiver spacing. Two literature case studies were analyzed to verify this work's optimization, and the equivalent POEs designed by this work, with optimized SOEs, showed a significant enhancement in the CAP values compared to that of literature. Lastly, four methods for prototyping the Fresnel lens were discussed and experimentally tested; 3D printing, acrylic resin casting, direct CNC machining in acrylic and hot embossing. Once tested, the methods of CNC machining and hot embossing of acrylic proved to be the most promising in terms of cost, fabrication time, and concentration effectiveness. Future work will focus on enhancing the algorithmic design and improving the quality of lens fabrication.

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Abdel-Hadi, Yasser Abdel-Fattah. "Development of optical concentrator systems for directly solar pumped laser systems." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978527569.

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Benecke, Mario Andrew. "On the optical and electrical design of low concentrator photovoltaic modules." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1013102.

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The increasing interest in non-fossil fuel based electricity generation has caused a prominent boost for the renewable energy sector, especially the field of Photovoltaics (PV) with one of the main reasons being the decrease in cost of PV electricity generation. However, over the last few years a saturation in the efficiency of solar cells have been reached leading into a renewed search for other means to further reduce the cost of electricity generation from photovoltaic sources. One of the technologies that has attracted a lot of attention is low concentration photovoltaics (LCPV). LCPV investigates an alternative strategy to replace costly semiconductor material with relatively cheap optical materials by developing a Low Concentration Photovoltaic (LCPV) module. A LCPV module is divided into three subsystems, namely, the optical, electrical and thermal subsystem. This study focussed on the design, construction and characterisation of an optical subsystem accompanied by a thorough investigation into the design of an electrical subsystem. A facetted parabolic concentrator using a vertical receiver was modelled and a first prototype was constructed having a geometric concentration factor of 6.00 X. Upon electrical characterisation of this first vertical receiver LCPV prototype a concentration of only 4.53 X (receiver 1) and 4.71 X (receiver 2) was obtained. The first vertical receiver LCPV prototype did not reach the expected concentration factor due to optical losses and misalignment of optical elements. The illumination profile obtained from the reflector element was investigated and an undesirable non-uniform illumination profile was discovered. A second vertical receiver LCPV prototype was constructed in an attempt to improve on the first prototype, this second vertical receiver prototype had a geometrical concentration factor of 5.80 X. The results indicated a much improved illumination profile, yet still containing a number of non-uniformities. The second vertical receiver LCPV module yielded an operational concentration factor of 5.34 X. From the preliminary results obtained it was discovered that under concentrated illumination there was a limitation on the maximum power that could be obtained from the receiver. Upon further investigation it was discovered that this limitation was due to the higher current levels under concentrated illumination accompanied by a high series resistance of the receiver. This lead to the construction of new PV receivers, where this limitation could be minimised. 3 cell, 4 cell, 6 cell and 8 cell string configurations were constructed and used for the electrical characterisation of the prototypes. Due to non-uniformity of the illumination profile obtained from the second LCPV prototype a third vertical receiver LCPV prototype was constructed. This vertical receiver design illustrated more uniformity in the obtained illumination distribution and had a geometrical concentration factor of 4.61 X, although under operation only 4.26 X could be obtained. It is important to note that the geometric concentration factor does not account for reflective losses of the reflective material. One of the main reasons for the difficulty in obtaining a uniform illumination profile with the vertical receiver design is that the facetted reflector element is far away from the PV receiver. This enhances the effect of the slightest misalignment of any of the optical elements. This large distance also increases the effect of lensing from each facet. These factors lead to the consideration of a second design, which would counteract these factors. A horizontal receiver LCPV module design implementing a facetted parabolic reflector was considered to counteract these effects. From a mathematical model a horizontal receiver LCPV prototype was constructed having a geometrical concentration factor 5.3 X. The optical characterisation of the illumination profile showed a much improved illumination profile, which was much more uniform than the previous illumination profiles obtained from the other LCPV prototypes. The uniformity of the illumination profile could be seen in results obtained from the electrical characterisation where the concentrator reached operational concentration factor of 5.01 X. The reliability of the third vertical receiver LCPV prototype and the horizontal receiver LCPV prototype as well as the receivers were investigated by placing each receiver under stressed operational conditions for 60 sun hours. I-V characteristics were obtained after every five sun hours to investigate any signs of degradation. After 60 sun hours none of the receiver displayed any signs of degradation or reduction in electrical performance.

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17

Mcvey, White Patrick. "A New Characterization Technique to Analyze Concentrator Photovoltaic Optical System Performance." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35816.

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Concentrator photovoltaics is a promising renewable energy technology, especially for utility or large-scale deployments. Like all new technologies, it has obstacles and setbacks to overcome. More specifically, the optics in a concentrator photovoltaics system introduce non-uniform spatial and spectral illumination on the cell, which can change under different operating conditions. This work was put together to discover a new characterization technique capable of analyzing the performance of a concentrator photovoltaics and provide insight to the field on what is happening within the system, linking modeling results seen in the literature to these experimental outcomes. The thesis is composed of three journal papers written by the candidate, who’s contributions are outlined at the beginning of each chapter. In order to study the illumination profiles on the cells, a new method to characterize the optical components had to be developed. Previous version lacked the ability to control the temperature of the lens and had low spectral resolution of the irradiance profiles. To improve, a novel indoor measurement method was developed capable of spectrally imaging concentrator photovoltaics optics and recreate outdoor operating conditions in a controllable environment. With the calibrated system, our test-bench is capable of measuring the spectral distribution with a 10μm2 resolution and characterizing the output of a system to within 3%. Exploiting this experimental technique, the individual effects of module misalignment, cell to primary distance, and lens temperature was studied for three leading technologies associated with the three generations of concentrator photovoltaics optical architectures. Focusing on Fresnel-based concentrator optics, the performance of silicone on a glass module without a secondary optic is the most sensitive to operating conditions, where lens temperature can decrease the absolute efficiency resulting in a difference of 11% in the annual energy yield. The next two generations have secondary optics but are designed slightly differently. The truncated inverted pyramid, designed independently of the primary optic, favoured higher lens temperature values and there was only a difference of 1% in the energy yield calculation. The primary and secondary optics in the 4-fold Fresnel-Kohler are designed together, due to new development tools, and showed the highest stability under the different operating conditions, demonstrating that concentrator photovoltaics is on the right track to overcoming its onset issue. As the technology matures, future designs can improve on the issues characterized within this thesis.

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Shanks, Katie May Agnes. "Identification and development of novel optics for concentrator photovoltaic applications." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/27935.

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Concentrating photovoltaic (CPV) systems are a key step in expanding the use of solar energy. Solar cells can operate at increased efficiencies under higher solar concentration and replacing solar cells with optical devices to capture light is an effective method of decreasing the cost of a system without compromising the amount of solar energy absorbed. CPV systems are however still in a stage of development where new designs, methods and materials are still being created in order to reach a low levelled cost of energy comparable to standard silicon based photovoltaic (PV) systems. This work outlines the different types of concentration photovoltaic systems, their various design advantages and limitations, and noticeable trends. Comparisons on materials, optical efficiency and optical tolerance (acceptance angle) are made in the literature review as well as during theoretical and experimental investigations. The subject of surface structure and its implications on concentrator optics has been discussed in detail while highlighting the need for enhanced considerations towards material and hence the surface quality of optics. All of the findings presented contribute to the development of higher performance CPV technologies. Specifically high and ultrahigh concentrator designs and the accompanied need for high accuracy high quality optics has been supported. A simulation method has been presented which gives attention to surface scattering which can decrease the optical efficiency by 10-40% (absolute value) depending on the material and manufacturing method. New plastic optics and support structures have been proposed and experimentally tested including the use of a conjugate refractive-reflective homogeniser (CRRH). The CRRH uses a reflective outer casing to capture any light rays which have failed total internal reflection (TIR) due to non-ideal surface topography. The CRRH was theoretically simulated and found to improve the optical efficiency of a cassegrain concentrator by a maximum of 7.75%. A prototype was built and tested where the power output increase when utilising the CRRH was a promising 4.5%. The 3D printed support structure incorporated for the CRRH however melted under focused light, which reached temperatures of 226.3°C, when tested at the Indian Institute of Technology Madras in Chennai India. The need for further research into prototyping methods and materials for novel optics was also demonstrated as well as the advantages of broadening CPV technology into the fields of biomimicry. The cabbage white butterfly was proven to concentrate light onto its thorax using its highly reflective and lightweight wings in a basking V-shape not unlike V-trough concentrators. These wings were measured to have a unique structure consisting of ellipsoidal pterin beads aligned in ladder like structures on each wing scale which itself is then tiled in a roof like pattern on the wing. Such structures of a reflective material may be the answer to lightweight materials capable of increasing the power to weight ratio of CPV technology greatly. Experimental testing of the large cabbage white wings with a silicon solar cell confirmed a 17x greater power to weight ratio in comparison to the same set up with reflective film instead of the wings. An ultrahigh design was proposed taking into account manufacturing considerations and material options. The geometrical design was of 5800x of which an optical efficiency of either ~75% with state of the art optics should produce and effective concentration of ~4300x. Relatively standard quality optics on the other hand should give an optical efficiency of ~55% and concentration ratio ~3000x. A prototype of the system is hypothesised to fall between these two predictions. Ultrahigh designs can be realised if the design process is as comprehensive as possible, considering materials, surface structure, component combinations, anti-reflective coatings, manufacturing processes and alignment methods. Most of which have been addressed in this work and the accompanied articles. Higher concentration designs have been shown to have greater advantages in terms of the environmental impact, efficiency and cost effectiveness. But these benefits can only be realised if designs take into account the aforementioned factors. Most importantly surface structure plays a big role in the performance of ultrahigh concentrator photovoltaics. One of the breakthroughs for solar concentrator technology was the discovery of PMMA and its application for Fresnel lenses. It is hence not an unusual notion that further breakthroughs in the optics for concentrator photovoltaic applications will be largely due to the development of new materials for its purpose. In order to make the necessary leaps in solar concentrator optics to efficient cost effective PV technologies, future novel designs should consider not only novel geometries but also the effect of different materials and surface structures. There is still a vast potential for what materials and hence surface structures could be utilised for solar concentrator designs especially if inspiration is taken from biological structures already proven to manipulate light.

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Johansson, Christian. "Optimal Allocation of Smart Meters to Real or Virtual Data Concentrators." Thesis, KTH, Skolan för elektro- och systemteknik (EES), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-169281.

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The Smart Grid is the new, modernized, electrical distribution grid. It allows for many applications such as automation, reliability and efficiency of electrical distribution. A key feature of the smart grid is the AMI (Advanced Metering Infrastructure) which is the system that measures, collects and analyzes energy use.When designing an LV/MV AMI smart grid, one can use several different media types, two of those are PLC (Power Line Communication) and GPRS (General Packet Radio Service). Choosing one over another may have differences in both communication performance and overall economic cost.This thesis describes a method to optimally assign the smart meter communication devices in an AMI network to either the secondary substation via the power lines (PLC) or towards the head-end via GPRS. When assigned to the secondary substation, the data collected from the smart meters will be managed by a Data Concentrator or forwarded by a Gateway towards the head-end where a Virtual Data Concentrator would be located. As an alternative to PLC communication, GPRS can be used to wirelessly communicate between smart meters and the virtual data concentrator.The method proposed uses MatLab to read the users input data, such as smart meter and power line link locations. The read data then gets compiled into a network topology consisting of smart meter nodes and power line links between them. For easier comparisons, the network is then clustered into groups. The clustering is done using two methods, one fore PLC and another for GPRS.The cluster data will then be compared with the packet loss ratio data acquired from either simulations or other sources, stored in a repository. The comparisons, along with various constraints set by the user, will then determine if the communication is fit for use.If deemed fit for use, each type of communication have their CAPEX and OPEX costs calculated, based on the users input. This thesis will use data acquired from DSOs (Distribution System Operators) to analyze the costs of four network locations and determine the cheapest assignments for each one for various settings.
Smart Grids, eller smarta elnät, är framtidens moderna elektriska distributionsnät. Smarta elnät tillåter många tillämpningar som automatisering, tillförlitlighet och effektiv elektrisk distribution. En nyckelegenskap hos de smarta näten är funktionen AMI (Advanced Metering Infrastructure), ett system som samlar ihop, mäter och analyserar energiförbrukning.När man designar ett låg- eller mellanspännings AMI elnät kan man utnyttja ett flertal mediatyper, två av dem är PLC (Power Line Communication) eller GPRS (General Packet Radio Service). Att välja den ena framför den andra kan leda till olikheter både när det gäller kommunikationsprestanda och den ekonomiska kostnaden.Detta examensarbete beskriver en metod för att på ett optimalt sätt tilldela smarta elmätare i ett AMI elnätverk till antingen det sekundära ställverket via de elektriska ledningarna (PLC) eller till huvudcentralen (head-end) trådlöst via GPRS. När mätarna tilldelas det sekundära ställverket samlas data från dem ihop av antingen en Data Concentrator (DC) eller en Gateway (GW) . En Gateway skickar därefter datan vidare till huvudcentralen där en Virtual Data Concentrator (VDC) finns. Alternativt utnyttjas GPRS för att trådlöst kommunicera mellan de smarta elmätarna och VDC.Metoden som föreslås utnyttjar MATLAB för att avläsa användarens indata, som till exempel positioner till de smarta elmtarna och de elektriska elledningarna som länkar dem med det sekundära ställverket. Den avlästa indatan används till att bilda en elnätverkstopologi bestående av smarta elmätare och elledningarna. För att enklare jämföra de skapade topologierna med simulerade generella topologier, grupperas nätverket i kluster. Klustermetoden skiljer sig mellan PLC och GPRS.Klusterdatan används sedan för att jämföra packet loss ratio erhållen från antingen simuleringar eller från andra källor. Jämförelserna avgör sedan huruvida kommunikationen med sagd mediatyp upprätthåller användarens kommunikationskrav.Om kommunikationsmöjligheterna för topologin anses vara tillräcklig, kommer varje kommunikationstyp att få sin kostnad uträknad utifrån CAPEX och OPEX. I detta examensarbete utnyttjas kostnader och topologidata erhållen från DSO’s (Distribution System Operators) för att analysera kostnaderna för fyra elnätverk och avgöra de billigaste tilldelningarna för vardera utifrån olika insättningar.

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20

Childs, G. N. "Effects of high carrier concentrations on some optical properties of semiconductors." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6717/.

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Many semiconductor devices, such as heterostructure lasers and silicon bipolar transistors, require large concentrations of free carriers in the conduction and/or valence band of an active region. Under these conditions the band gap of the material is reduced by the many-body interactions of the carrier gas. The band gap narrowing results from a lowering of the conduction and raising of the valence band edge energies and is evaluated for a range of carrier concentrations. (10(^17) - 10(^22) cm_^-3)) in p-type Si and P- and n-type GaAs, Ga(_0.47) In(_0.53) As and Ga(_0.28) In(_0.72) As(_0.6) P(_0.4) at T = OK. A plasmon-pole approximation for the carrier gas dielectric function is used in the calculations. For all these materials, the largest energy shift occurs in the band containing the free carriers. For comparison the band edge shifts in all four materials are evaluated at finite temperature (300 K). The band gap narrowing at finite and zero temperatures differ notably only for low carrier concentrations (p < 5 x 10(^19) cm (^-3) in p-type Si) where the thermal excitation of the carriers reduces their screening effect so producing smaller band gap reduction. High hole concentrations also lead to increased optical losses in semi-conductor lasers due to intervalence band absorption (IVBA) transitions. These losses, which are considered to be partially responsible for the temperature dependence of threshold current densities in some semiconductor lasers, are evaluated in bulk laser materials using a pseudopotential band structure model. The temperature dependencies of the IVBA coefficients in GaAs, Ga(_0.47) In(_0.53) As and Ga(_0.28) In(_0.72) As(_0.6) P(_0.4) are shown to be either small or the coefficients themselves are negligible. Intervalence band absorption is also calculated for a 100/200 A GaAs/Ga(_0.7) al(_0.3) As quantum well laser structure for which the electronic band structure is determined using a variational k^-p approach. The wavelength dependence of the IVBA coefficients differs notably from corresponding results derived using simpler effective mass and pseudopotential models. In particular the k.p model gives significant contributions to the total loss, from certain 'forbidden' transitions.

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21

Pončík, Vlastimil. "Vyhodnocení vlastností fotovoltaických článků s optickými koncentrátory." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219233.

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This work deals about the photovoltaic systems, especially with concentration of the sunlight in use of concentrators that are placed direct on the panel. Concentrated photovoltaics systems employ sunlight concentrated onto photovoltaic surfaces for the purpose of more efficient electrical power production. A photovoltaic cell with concentrator includes difractive optical elements that concentrate light on a photovoltaic chip Flat polycarbonate optical element has difractive gratings on its surface.

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22

Huang, Jin 1969. "Optimal determination of global tropospheric OH concentrations using multiple trace gases." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/59645.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 2000.
"February 2000."
Includes bibliographical references (leaves 159-163).
The hydroxyl radical (OH) plays a decisive role in tropospheric chemistry. Reactions with OH provide the dominant path of removal for a variety of greenhouse gases and trace species that contribute to the destruction of the ozone layer. Accurate determination of global tropospheric OH concentrations [OH] is therefore a very important issue. Previous research at the global scale has focused on scaling model-calculated OH concentration fields using a single so-called titrating species, either CH3CC13 or 14 CO, and the data usually come from one measurement network. Therefore, the estimation of [OH] relies heavily on the accuracy of the emission estimates and absolute calibration of the observed mixing ratios of that single species. The goal of this thesis is to reduce the dependence of estimating [OH) fields on a single species and thus to improve our knowledge of global OH concentrations and trends. To achieve this goal, we developed a multiple titrating gases scheme which combines all the possible available surface measurements of CH3CC13, CHF2C1 (HCFC-22), CH2FCF3 (HFC-134a), CH3CFC12 (HCFC-141b) and CH3CF 2C1 (HCFC- 142b) from both AGAGE (Advanced Global Atmospheric Gases Experiment) and CMDL/NOAH (Nitrous Oxide And Halocompounds) networks. The optimal estimation of the global OH concentration and its trend is accomplished through a Kalman filtering procedure by minimizing the weighted difference between the predicted mixing ratios from atmospheric chemical-transport models and, for the first time, all the measurements of the various titrating gases simultaneously. A two dimensional land-ocean-resolving (LO) statisticaldynamical model and a 12-box model are used to predict the concentrations of the titrating gases. These two models are computationally efficient, and suitable for repetitive runs and long term integrations. The eddy-diffusive transports in the 12-box model and the 2D-LO model are tuned optimally by using the Kalman filtering and CFC-11 and CFC-12 data before the estimations of OH are carried out. Three different techniques (content method, trend method, and time-varying OH method) are used to perform the Kalman filtering. These three methods optimally fit different features of the measurements and have different sources of errors. Errors in the measurements, industrial emission estimates, and chemical-transport models are included in great detail for the OH estimation problem. The random measurement errors and mismatch errors are included in the noise matrix in the Kalman filter. For other random errors from the emission estimates and chemical-transport models, we use the Q-inclusion method which specifies the random model errors explicitly in the state error matrix Q inside the Kalman filtering. For systematic errors in the calibration, model, and emissions, we use the brute-force method which repeats the entire inverse method many times using different possible values of the measurement sensitivity matrix in the Kalman filtering. Using multiple gases, both CMDL and AGAGE data, two chemical-transport models, and selected content and trend results, our best estimate of the global mean tropospheric OH concentrations is 9.4+2.7/1.7 x 105 radicals cm-3, and our best estimate of the linear OH trend is -0.5±tL1.0% per year over the 1978-1998 time period. Methyl chloroform data give the heaviest weight to the overall estimations. This is because there are more CH3CC13 measurements than for any other titrating gases, and the industrial emission estimates of this gas are the most accurate. The derived OH estimations agree statistically with previous studies taking into account the fact that the negative OH trend derived here relies heavily on the 1993-1998 CH3CCl3 data. For example, a global mean OH concentration of (9.7 ± 0.6) x 105 radicals cm- 3 and an OH trend of 0.0 ± 0.2% per year over the 1978-1993 are reported in Prinn et al. (1995). As far as the major sources of error in the OH estimations are concerned, we find that, using individual gases separately, the uncertainties in absolute calibrations, rate constants, and industrial emissions estimates are important sources of error for all five titrating gases. The measurement errors and the initial a priori guesses in the Kalman filter are also important sources of error for the three newer titrating gases (HCFC-141b, HCFC-142b, and HFC-134a) because of their very low mole fractions as well as the short measurement records for these gases. Combining multiple OH titrating gases together, we find that errors in industrial emissions contribute the most to the uncertainty in the OH estimation problem. We also find that incorporating random model errors (other than mismatch errors) using the Q-inclusion method generates satisfactory agreement for best guess estimates with the approach in which Q = 0 in the Kalman filter. However the Q-inclusion method provides an estimate of the effect of random model error. Newer titrating gases generally yield OH estimates comparable to those from CH3CCl3 but with larger uncertainties. One of the exceptions is using HCFC-142b data with the content method, which yields a physically impossible negative OH concentration because of the underestimates of emissions for this gas. However, the trend method using HCFC-142b data still delivers reasonable OH estimations, because the trend method is not sensitive to systematic errors. The measurements of the newer OH titrating gases can be used effectively with appropriate techniques to ultimately replace the use of CH3CC13 (which is disappearing from the atmosphere), provided estimates of their emissions are improved. This is particularly true for HCFC-142b. In addition to the OH estimations, a time-varying adaptive-Kalman filter is also utilized in this thesis to deduce monthly emissions of HCFC-141b and HCFC-142b. We find that the current industrial estimates of HCFC-142b need to be at least doubled, and the emissions of HCFC-141b need to be increased by 20 to 30% to achieve the best agreement with observations.
by Jin Huang.
Ph.D.

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23

Schmälzlin, Elmar, Joost T. van Dongen, Ingo Klimant, Bettina Marmodée, Martin Steup, Joachim Fishahn, Peter Geigenberger, and Hans-Gerd Löhmannsröben. "An optical multifrequency phase-modulation method using microbeads for measuring intracellular oxygen concentrations in plants." Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2007/1223/.

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A technique has been developed to measure absolute intracellular oxygen concentrations in green plants. Oxygen-sensitive phosphorescent microbeads were injected into the cells and an optical multifrequency phase-modulation technique was used to discriminate the sensor signal from the strong autofluorescence of the plant tissue. The method was established using photosynthesis-competent cells of the giant algae Chara corallina L., and was validated by application to various cell types of other plant species.

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24

Šumić, Mersiha. "Thermal Performance of a Solarus CPC-Thermal Collector." Thesis, Högskolan Dalarna, Energi och miljöteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:du-14526.

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The aim of this master thesis is an investigation of the thermal performance of a thermal compound parabolic concentrating (CPC) collector from Solarus. The collector consists of two troughs with absorbers which are coated with different types of paint with unknown properties. The lower and upper trough of the collector have been tested individually. In order to accomplish the performance of the two collectors, a thorough literature study in the fields of CPC technology, various test methods, test standards for solar thermal collectors as well as the latest articles relating on the subject were carried out. In addition, the set‐up of the thermal test rig was part of the thesis as well. The thermal performance was tested according to the steady state test method as described in the European standard 12975‐2. Furthermore, the thermal performance of a conventional flat plate collector was carried out for verification of the test method. The CPC‐Thermal collector from Solarus was tested in 2013 and the results showed four times higher values of the heat loss coefficient UL (8.4 W/m²K) than what has been reported for a commercial collector from Solarus. This value was assumed to be too large and it was assumed that the large value was a result of the test method used that time. Therefore, another aim was the comparison of the results achieved in this work with the results from the tests performed in 2013. The results of the thermal performance showed that the optical efficiency of the lower trough of the CPC‐T collector is 77±5% and the corresponding heat loss coefficient UL 4.84±0.20 W/m²K. The upper trough achieved an optical efficiency of 75±6 % and a heat loss coefficient UL of 6.45±0.27 W/m²K. The results of the heat loss coefficients are valid for temperature intervals between 20°C and 80°C. The different absorber paintings have a significant impact on the results, the lower trough performs overall better. The results achieved in this thesis show lower heat loss coefficients UL and higher optical efficiencies compared to the results from 2013.

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25

Canavarro, Diogo. "Advances in the design of solar concentrators for thermal applications." Doctoral thesis, Universidade de Évora, 2014. http://hdl.handle.net/10174/14557.

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This thesis presents advances in the design of solar concentrators. Based on the study of the Compact Linear Fresnel Re ector Concentrator "Etendue-Matched" (CLFREM), this thesis developed optical solutions based on the Simultaneous Multiple Surface method (SMS) and new approaches of analysis of the characterizing parameters of a solar concentrator. This thesis is organized into ve sections. In the rst section (Chapters 1 and 2) an introduction to the topics addressed in this work is presented together with a revision of the underlying basic optics. In the second section (Chapters 3, 4, and 5) a study of the concentrator CLFR-EM is presented. In the third section (Chapters 6 and 7) a XX SMS concentrator for continuum primaries is developed and presented. In the fourth section (Chapter 8) the application of the concept XX SMS for Fresnel primaries is explained and shown. Finally, in the fth section (Chapters 9 and 10) prospects for future developments and conclusions concerning this work are presented; Avan cos no desenho de concentradores solares para aplicações termicas Resumo: Esta tese apresenta desenvolvimentos na an álise de concentradores solares térmicos. Partindo do estudo realizado sobre o concentrador Compact Linear Fresnel Re ector "Etendue-Matched" (CLFR-EM), esta tese propoem solucoes opticas baseadas no método de Simultaneous Multiple Surface (SMS) e novas abordagens a análise dos parâmetros caracterizadores de um concentrador solar. A tese está organizada em cinco secções. Na primeira secção (Cap itulos 1 e 2) e realizada uma introdução aos temas abordados neste trabalho e uma revisão dos conceitos básicos de optica. Na segunda sec ção (Capitulos 3, 4 e 5) e apresentado um estudo do concentrador CLFREM. Na terceira secção(Capitulos 6 e 7) e apresentado um concentrador XX SMS para primários continuos para concentração máxima e receptores xos. Na quarta secção(Capitulo 8) mostra-se a aplicação do conceito XX SMS a prim arios Fresnel. Por ultimo, na quinta secção(Capitulos 9 e 10) são apresentadas perspectivas para desenvolvimentos futuros e realizadas conclusões sobre este trabalho.

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26

Ying, Xiaomin. "Statistical ray-tracing analysis of the linear Fresnel mirror solar concentrator." Virtual Press, 1993. http://liblink.bsu.edu/uhtbin/catkey/897508.

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The Monte Carlo-type statistical ray-tracing method was used to investigate the performance of the line-focusing Fresnel mirror solar concentrator. An optical model of the line-focusing Fresnel mirror concentrator using the statistical ray-tracing approach was developed. Many rays of sunlight from the solar disk were selected at random and traced through the concentrator in this model. This optical model permits calculation of the local and geometric concentration ratios. The latter requires an energyloss analysis. Small sun-tracking errors of the diurnal or transverse type were included in the model.Based on the optical model and the Monte Carlo-type statistical ray-tracing method, a computer program was written implementing the model and computations using Pascal. To facilitate performance comparisons, a baseline concentrator design was adopted. To study the effects of imperfect tracking, performance data were generated for small tracking errors up to approximately two and one-half degrees. The selected mirror configuration permitted comparisons between the statistical approach and previous applications of the "extreme ray" analysis for an imperfectly tracking mirror concentrator.Simulation results demonstrated that the concentration characteristics are highly sensitive to the tracking error. The geometric concentration ratio dramatically decreases when the tracking error increases, which is the same as the "extreme ray" analysis. Results of some typical numerical calculations are presented graphically and discussed.
Department of Physics and Astronomy

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27

Zhan, Yong. "Analysis of tracking error effects for the Fresnel mirror solar concentrator." Virtual Press, 1989. http://liblink.bsu.edu/uhtbin/catkey/560271.

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The solar concentration performance of a tracking, flat-base, line-focusing Fresnel mirror was investigated in this study. The Fresnel mirror consists of flat mirror strips situated on a base and oriented at appropriate angles to focus incident light to a desired line. Simple optical ray tracing and energy conservation were used to develop a mathematical model of the concentrator assuming small or zero diurnal tracking errors. The model analyzed the concentrator design and provided detailed expressions for the geometric evaluation of the concentrated sunlight rays in the focal plane above the mirror. The local concentration ratio and the geometric concentration ratio were introduced to describe the intensity profile in the focal plane and the average concentration of sunlight on a target absorber. Included in the model were losses of incident sunlight due to imperfect reflection, nonreflecting portions of the base, and blockage by adjacent mirror strips when imperfect tracking occurs.Based on the analytical model and using the Ada high level language, a computer program was written to simulate the concentrator. To facilitate performance comparisons, a baseline concentrator design was adopted. To study the effects of imperfect tracking, performance data were generated for small tracking errors up to approximately two and one-half degrees. The effects of design variations were studied by varying the concentrator focal length, strip width, and base width.Simulation results demonstrated that the concentration characteristics were highly sensitive to tracking error. Intensity profile shifts relative to the target caused the highest losses in intercepted sunlight.Design decisions were found to dramatically affect the concentration character- istics. For the baseline concentrator under perfect tracking conditions, an optimum focal length was identified. Except for the disadvantage of added costs, decreased strip widths was found to be a way to increase both the maximum and average concentration ratio for the absorber. Using smaller strip widths might, however, critically affect the energy intercepted by the target under imperfect tracking. Increasing the concentrator base width increased the total amount of power in the focal plane, with a higher maximum concentration ratio and additional tailing of the intensity profile.
Department of Physics and Astronomy

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Morfeldt, Johannes. "Optically Selective Surfaces in low concentrating PV/T systems." Thesis, Örebro University, School of Science and Technology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-7396.

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One of the traditional approaches to reduce costs of solar energy is to use inexpensive reflectors to focus the light onto highly efficient solar cells. Several research projects have resulted in designs, where the excess heat is used as solar thermal energy.

Unlike a solar thermal system, which has a selective surface to reduce the radiant heat loss, a CPV/T (Concentrating PhotoVoltaic/Thermal) system uses a receiver covered with solar cells with high thermal emittance.

This project analyzes whether the heat loss from the receiver can be reduced by covering parts of the receiver surface, not already covered with solar cells, with an optically selective coating. Comparing different methods of applying such a coating and the long-term stability of low cost alternatives are also part of the objectives of this project.

To calculate the heat loss reductions of the optically selective surface coating a mathematical model was developed, which takes the thermal emittances and the solar absorptances of the different surfaces into account. Furthermore, a full-size experiment was constructed to verify the theoretical predictions.

The coating results in a heat loss reduction of approximately 20 % in such a CPV/T system and one of the companies involved in the study is already changing their design to make use of the results.

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Golshani, Fariborz. "Boron doping of diamond powder by enhanced diffusion and forced diffusion : diffusion concentrations, mechanical, chemical and optical properties /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9842530.

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Rumburg, Brian Paul. "Differential optical absorption spectroscopy (DOAS) measurements of atmospheric ammonia in the mid-ultraviolet from a dairy concentrations, emissions, and modeling /." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Spring2006/b%5Frumburg%5F031006.pdf.

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Hancock, Harmony Alise. "One Step Closer to Non-Invasive: Quantifying Coral Zooxanthellae Pigment Concentrations Using Bio-Optics." NSUWorks, 2012. http://nsuworks.nova.edu/occ_stuetd/189.

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Due to the invasive nature of quantification techniques, baseline pigment data for coral-dwelling zooxanthellae are not known. In an attempt to develop a model for non-invasive estimation of zooxanthellae pigment concentrations from corals, field samples were taken from Porites rus and P. lutea in Apra Harbor, Guam. In-situ reflectance spectra (R400-R800) from 22 coral colonies were collected. “Coral truthing” was accomplished by extracting corresponding tissue core samples. Subsequent analysis to quantify the concentrations of 6 zooxanthellae pigments (µg cm-2) was performed using HPLC. Trials of multiple linear regressions were attempted (EJ Hochberg) and found inappropriate, despite previous success. The multivariate calibration technique partial least squares regression (PLS-R) is an excellent tool in the case of co-linear variables. Thus, PLS-R was attempted for chlorophyll c2 and peridinin after demonstration of co-linearity. This may be an appropriate approach for development of bio-optical models to estimate zooxanthellae pigment concentrations. Further, the dinoflagellate diagnostic pigment peridinin may be of great value for reef-scale remote sensing of changes in coral status in the future.

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Parikh, Bhairavi Rajiv. "The design and development of a direct and continuous sensor for the measurement of inhaled nitric oxide concentrations." Link to electronic version, 2000. http://www.wpi.edu/Pubs/ETD/Available/etd-0830100-001359/.

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Razon, Anat. "Dynamic model of a three layer photovoltaic panel and the optimal use of spill-over light in a concentrator photovoltaic system /." [Sedek Boker, Israel] : Ben-Gurion University of the Negev, 2009. http://aranne5.lib.ad.bgu.ac.il/others/RazonAnat.pdf.

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Farges, Olivier. "Conception optimale de centrales solaires à concentration : application aux centrales à tour et aux installations "beam down"." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2014. http://www.theses.fr/2014EMAC0006/document.

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Depuis les années quarante, la consommation énergétique mondiale n'a cessé d'augmenter. Cette énergie étant majoritairement d'origine fossile, il en résulte une augmentation globale de température terrestre. De ce fait, il est devenu urgent de réduire les émissions de gaz à effet de serre pour stopper le changement climatique. Dans ce contexte, le développement de la production d'électricité à partir d'énergie solaire concentrée par voie thermodynamique est une solution prometteuse. Les efforts de recherche visent à rendre cette technologie plus efficace et plus compétitive économiquement. Dans ce but, ce manuscrit présente une méthode de conception optimale pour les centrales solaires à récepteur central. Elle tire parti des méthodes développées depuis de nombreuses années par le groupe de recherche StaRWest, regroupant notamment des chercheurs des laboratoires RAPSODEE (Albi), LAPLACE (Toulouse) et PROMES (Odeillo). Couplant des algorithmes de Monte Carlo à hautes performances et des algorithmes stochastiques d'optimisation, le code de calcul implémentant cette méthode permet la conception et l'optimisation d'installations solaires. Il est utilisé pour mettre en évidence les potentialités d'un type de centrales à récepteur central peu répandu : les centrales à réflecteur secondaire, également appelées centrales de type "beam down"
Since the early 40's, world energy consumption has grown steadly. While this energy mainly came from fossil fuel, its use has included an increase in temperatures. It has become urgent to reduce greenhouse gas emissions to halt climate change. In this context, the development of concentrated solar power (CSP) is a promising solution. The scientific community related to this topic has to focus on efficiency enhancement and economic competitiveness of CSP technologies. To this end, this thesis aims at providing an optimal design method applied to central receiver power plants. It takes advantage of methods developed over many years by the research group StaRWest. Both RAPSODEE (Albi), LAPLACE (Toulouse) and PROMES (Odeillo) researchers take an active part in this group. Coupling high performance Monte Carlo algorithms and stochastic optimization methods, the code we developed allows an optimal design of concentrated solar systems. This code is used to highlight the potential of an uncommon type of central receiver plants: reflective towers, also called "beam down" central receiver systems

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Ritou, Arnaud. "Développement, fabrication et caractérisation de modules photovoltaïques à concentration à ultra haut rendement à base de micro-concentrateurs." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY059/document.

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Les modules photovoltaïques à concentration (CPV) ont tendance à se miniaturiser. D’une part, la distance focale plus courte des optiques de concentration permet de réduire le besoin en matériaux pour l’assemblage du module ; et d’autre part, le rendement des modules est sensiblement meilleurs que ceux des modules CPV de taille normale. L’étude de chaque élément de la chaine de pertes dans la littérature des micro-concentrateurs a permis de confirmer cette tendance. Cette thèse aborde les problématiques de coût et de rendement à travers la conception optique d’un concentrateur à deux étages de lentilles, sa fabrication puis une étude approfondie de ses performances.La méthode de conception, développée à partir de lois d’optique géométrique et non-imageante, définit le profil des lentilles à λ=589nm en premiers lieux. Ensuite, une simulation par tracé de rayons permet d’optimiser ces lentilles pour l’ensemble du spectre solaire puis d’étudier l’impact de leur désalignement lors de la mise en module. Les limites des déplacements des éléments du module ainsi déterminées conditionnent la précision de sa fabrication. Dans notre cas, l’alignement est réalisé automatiquement par un jeu de repères mécaniques lors du moulage simultané des optiques primaires (POE) et des optiques secondaires (SOE). Contrairement aux procédés habituels, ce procédé de moulage innovant permet d’assembler un module en seulement trois étapes au lieu de cinq.Pour caractériser les micro-concentrateurs réalisés, une méthode de mesure du rapport module à cellule (CTM) est développée. Pour cela, le rendement des cellules est mesuré en simulateur solaire avant et après leur mise en module. Les cellules multi-jonctions mises en œuvre étant sensibles aux variations spectrales et spatiales de l’éclairement, la validation préalable de ces mesures est primordiale. En complément du CTM qui quantifie la somme des pertes introduites lors de la mise en module, d’autres mesures sont développées pour comprendre la chaine de perte plus en détails.Le dispositif étudié au cours de cette thèse utilise des cellules triple-jonction de 0,6 x 0,6mm² avec une concentration de 1000X et atteint un rendement de 29%. Le CTM est de 70% et l’analyse de la chaine de perte montre que le procédé inventé n’impacte pas ou peu les performances du module. De plus, la détermination de la chaine de perte montre que les pertes par réflexion et par absorption sont prédominantes, au même titre que les pertes dues à la diffusion des lentilles ainsi que les pertes dues aux non-uniformités d’éclairement sur la cellule
The actual trend of CPV is the micro-scaling of modules. A bibliographic study shows that shorter focal length of optics implies less material consumption in manufacturing and an enhanced efficiency of the modules. In this thesis, a double stage refractive micro-concentrator is designed, manufactured and characterized. First, the optical design of the concentrator is based on non-imaging technics. Thus, the profile of the lenses is generated for a single wavelength. Then, a ray tracing simulator is used to optimize the lens profile for the overall solar spectrum and study the concentrator element misalignment effect on the performances.Secondly, a three steps self-assembly process is developed instead of the usual five steps one. Both POE and SOE lenses of our device are molded simultaneously and a mechanical guidance system in the mold ensures the alignment of the micro-concentrator elements (POE, SOE and Cell).Finally, the performances measurements of the manufactured modules are managed in solar simulators in which the lightening condition are previously studied and validated. Comparing the bare cells efficiency with the module efficiency, the cell-to-module ratio (CTM) represents the overall losses in the module. Further experiments are managed to quantify each loss of the module. The manufactured and characterized micro-concentrator is a 1000X concentrating ratio with 0.6 x 0.6mm² triple junction cells. It efficiency is 29% with a 70% CTM. Finally, the loss chain study reveals that the three steps self-assembly process is reliable

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Gast, Mathias [Verfasser], Michael [Akademischer Betreuer] Huber, and Bernhard [Akademischer Betreuer] Lüscher. "Mast cell activation by supra-optimal antigen concentrations - a promising condition to identify novel regulators of FcεRI signaling / Mathias Gast ; Michael Huber, Bernhard Lüscher." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1221697536/34.

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Gailiūnas, Paulius. "Fotovoltinio modulio su koncentratoriumi projektavimas ir tyrimas." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130617_184708-47299.

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Baigiamajame magistro darbe suprojektuotos ir pagamintos dviejų rūšių šviesos koncentratorinės sistemos: jungtinė parabolinė ir sistema su Frenelio lęšiu. Atlikta saulės elementų efektyvumo analizė, išnagrinėtos šviesą koncentruojančių sistemų rūšys bei aptarti jų optiniai parametrai. Frenelio lęšis ir koncentratorinių sistemų laikančiosios konstrukcijos pagamintos vakuuminio formavimo būdu, ieškant pigesnės gamybos technologijos. Baigiamajame darbe atlikti optinio pralaidumo ir lūžio rodiklio, matomos šviesos bangų ilgių ruože, tyrimai bei saulės elementų, esančių šviesos koncentratorinėse sistemose,voltamperinių ir voltvatinių charakteristikų tyrimai. Iš tyrimų rezultatų nustatyti šviesos koncentravimo laipsniai. Darbe diskutuojama apie pigių optinių sistemų galimus pritaikymus ir jų tobulinimo būdus. Išnagrinėjus teorinę ir praktinę dalis, pateiktos išvados ir pasiūlymai. Darbą sudaro 8 dalys: įvadas, saulės elementų efektyvumo ribos, saulės šviesos koncentratoriai ir jų panaudojimas fotoelektrinėse sistemose, eksperimentinių tyrimų metodika, prototipų gamyba, eksperimentiniai tyrimai, išvados, literatūros sąrašas. Darbo apimtis – 82 p. teksto be priedų, 95 pav., 13 lent., 22 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai.
Concentrated PV systems (compound parabolic and Fresnel CPV) have been designed and investigated. The efficiency of solar cells and the types of light concentrated systems have been analyzed and their optical parameters have been discussed. Fresnel lens and the CPV system holding structure have been fabricated by means of vacuum forming machine in this way making the technology of production less expensive. Optical transmittance and refractive index of Fresnel lens were measured in the range of visible light wavelengths. Current-voltage and voltage-power characteristics of solar cells built inside the CPV systems were investigated, based on results the degree of light concentration by Fresnel lens and compound parabolic CPV has been determined. Some discussions regarding possible applications of concentrated PV systems containing the Fresnel lens as well as possible ways of CPV design improvements are given in current work. After analysed theoretical and practical parts, conclusions and suggestions are proposed. Thesis structure: introduction, theoretical and experimental parts, results of experiments, conclusions and references. Thesis consist of: 82 p. text without appendixes, 95 pictures, 13 tables, 22 bibliographical entries. Appendixes included.

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Potier, Bruno. "Détermination des champs des températures et des concentrations dans une flamme de charbon pulvérisé de taille semi-industrielle : application au four pilote 1 mw du cerchar." Orléans, 1986. http://www.theses.fr/1986ORLE0012.

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Développement d'une méthode optique de mesure des températures, basée sur l'émission et l'absorption du rayonnement thermique dans le proche infrarouge, et permettant de déterminer la température en un point. Parallèlement aux champs des températures cette méthode permet d'accéder aux champs de concentrations relatives en particules et en dioxyde de carbone et fournir des renseignements sur les valeurs in situ de plusieurs paramètres nécessaires à la modélisation des transferts thermiques.

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Lin, Qinglong. "Etude, modélisation dynamique et développement d'un capteur solaire thermique à concentration de nouvelle génération." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10099.

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Ce travail a pour objet de développer une nouvelle technologie de l’énergie solaire à concentration. Il porte sur la présentation du concept, la réalisation prototypique et l’étude optique et énergétique d’un nouveau concentrateur solaire QingSun™. Ce concentrateur a une forme de parallélépipède rectangulaire et comporte des lentilles de Fresnel linéaires, des parois tapissées de miroir et d’un récepteur solaire mobile entraîné par un système de suivi à l’intérieur du caisson de concentration. Un modèle optique et un modèle énergétique ont été élaborés et validés avec une série d’expériences. Ils ont permis d’étudier le fonctionnement et les performances énergétiques du concentrateur. Une étude de l’influence paramétrique de l’inclinaison et l’orientation a été effectuée et a montré que l’inclinaison a plus d’influence que l’orientation sur les performances. Enfin, les performances énergétiques optimales du concentrateur ont été estimées
This work is for the purpose to develop a new solar concentrating technology. It covers the presentation of the concept, the prototype realization and the optical and energy study of a new solar concentrator QingSun™. This concentrator has a shape of rectangular parallelepiped and includes linear Fresnel lenses, mirror-lined walls and a mobile solar receptor controlled by a tracking system inside the casing. An optical model and an energy model were developed and validated with a series of experiments. The both models permitted us to examine the function and the energy performance of the concentrator. A parametric study of the influence of the tilt and the orientation was performed and showed that the tilt had more influence than the orientation. Finally, the optimal energy performance of this concentrator was estimated

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Ko, Gaelle Kafira. "Etude et modélisation dynamique d'un concentrateur à miroir linéaire de Fresnel." Thesis, Perpignan, 2019. http://www.theses.fr/2019PERP0018/document.

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Parmi les technologies de solaire thermodynamique, la technologie du linéaire de Fresnel semble la plus adaptée aux régions d’Afrique Sub saharienne. Cela en raison de la simplicité de la technologie. C’est dans cette optique qu’un collecteur de type linéaire de Fresnel d’une superficie de 7,5 m² de miroirs a été construit au laboratoire énergies renouvelables et efficacité énergétique (LabEREE). La construction du collecteur s’est faite en utilisant en priorité les matériaux disponibles localement afinde rendre la technologie plus accessible aux populations locales et de réduire les coûts de fabrication. Des tests sont effectués sur le collecteur afin de déterminer ses rendements optiques, thermiques et globaux. Dans un premier temps, une revue bibliographie des différents collecteurs de type linéaire de Fresnel nous a permis d’identifier les variantes, de cette technologie, les plus adaptées au contexte dela région . Un modèle thermique et un modèle optique ont été mis en place comme outils de dimensionnement et d’optimisation du collecteur. Les résultats expérimentaux obtenus ont été utilisés pour valider les différents modèles mis en place. Le rendement global du collecteur obtenu expérimentalement est de 21% et il a un facteur de concentration local de 6
Among the different technologies of concentrated solar power plant, the linear Fresnel, thanks to its simplicity, appears the most adapted to rural area of Sub Sahara region. A linear Fresnel collector of 7.5 m² has been built in “laboratoire énergies renouvelables et efficacité énergétique (LabEREE)”. The collector have been designed using material available locally by local man power. This reduces the total cost of the technology and makes it affordable for local population. The collector has been characterized in order to find optical, thermal and global efficiencies. In first time, a review on different linear Fresnel collector allows finding the technology that is most adapted to the Sub-Saharan region. An optical and thermal model of the collector has been done as a tool for designing and optimisation. The experimental results enable to validate the different models done. The collector has an effective concentration factor of 6 and a global efficiency of 21%

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Pujol, Nadal Ramon. "Comportamiento Óptico y Térmico de un Concentrador Solar Lineal con reflector estacionario y Foco Móvil." Doctoral thesis, Universitat de les Illes Balears, 2012. http://hdl.handle.net/10803/84115.

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El concentrador solar Fixed Mirror Solar Concentrator (FMSC) apareció en los años 70 con la finalidad de reducir costes en la producción de energía termoeléctrica. Este diseño consiste en un concentrador de reflector estacionario y foco móvil, presenta buena integrabilidad en cubiertas, y es capaz de alcanzar temperaturas entre 100 y 200ºC manteniendo una eficiencia aceptable. En esta tesis se expone una metodología para determinar el comportamiento del FMSC. Se ha desarrollado una herramienta de cálculo basada en el método de ray-tracing, que simula el trazado de los rayos solares en el sistema óptico. Con esta herramienta se ha analizado el comportamiento óptico y térmico del FMSC, y de la versión con espejos curvos Curved Slats Fixed Mirror Solar Concentrator (CSFMSC). Se ha realizado un análisis paramétrico para conocer la influencia de los distintos parámetros en el modificador de ángulo (IAM), y para obtener los diseños óptimos a una temperatura de 200ºC para tres climas en diferentes latitudes. Se han comparado los valores teóricos obtenidos mediante ray-tracing con dos prototipos ensayados, obteniendo un buen ajuste en ambos casos. Los ensayos han sido utilizados para determinar la curva de rendimiento de uno de los prototipos. Se ha hecho uso del método propuesto en la norma EN-12975-2:2006, combinado con valores de IAM obtenidos mediante ray-tracing. Se prueba que esta combinación puede ser útil para obtener la curva de rendimiento de colectores complejos con un modelo biaxial para el IAM.
The Fixed Mirror Solar Concentrator (FMSC) appeared during the 70s with the aim of reducing costs in the production of electricity in solar thermal power plants. This design consists of a concentrator with fixed reflector and moving receiver, has a very good integrability into building roofs and can reach temperatures between 100 and 200ºC with an acceptable efficiency. In this Thesis a methodology is presented for the determination of the behaviour of the FMSC. A simulation tool based on the forward ray-tracing method has been developed. The optical and thermal behaviour of the FMSC and its curved mirror variation called the Curved Slats Fixed Mirror Solar Concentrator (CSFMSC), have been analyzed with this tool. A parametric analysis has been carried out in order to determine the influence of the different parameters on the Incidence Angle Modifier (IAM) and to determine the optimal designs at a temperature of 200ºC for three different climates at different latitudes. The theoretical values obtained from the ray-tracing code have been compared with two experimental prototypes. The experimental and numerical results obtained show a good fit. The efficiency curve of one of the prototypes has been determined from the experimental tests. The methodology proposed in the norm EN-12975-2:2006 has been used in combination with IAM values obtained by ray-tracing. It has been shown that this combination can be effectively used to obtain the efficiency curve of complex collectors with a bi-axial IAM model.

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Wu, Jyun-Hao, and 吳俊灝. "Luminescent Solar Concentrators Using Subwavelength-Structured Optical Discs." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/87856536876887067074.

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碩士
國立中興大學
機械工程學系所
98
The purpose of this study is to use the subwavelength structure of optical discs and anti-reflection coating to improve the optical waveguide effect of the luminescent solar concentrator (LSC). It can be widely applied to transparent materials, such as the building-integrated photovoltaic (BIPV). Through the vector diffraction theory and simulation by the grating software, we analyzed the influence of the period and depth of the subwavelength-structured surface on the optical waveguide effect, for achieving more efficient use of incident light. The subwavelength-structured surface allows the incident light to be diffracted into high order diffraction beams. It will give rise to an increase of the optical waveguide effect of the whole system if the diffraction angle is greater than the critical angle of total internal reflection. However, different wavelengths of incident light will cause different diffraction angles. In considering the absorption and emission spectrum of luminescent material, we selected the appropriate period and depth of the structure that will increase the internal optical waveguide effect of the whole system. According to the experimental results, we have found that the LSC with the structured surface can increase the optical waveguide effect of the substrate edge within 1~5% corresponding to different wavelengths. In the end of the study, the surface of the LSC was coated with the anti-reflection film, which is suitable in the range of absorption spectrum of the luminescent layer. The reflectivity of the substrate surface presents a reduction of 4~5%, that enhances the efficiency of the luminescent emission and increases the optical waveguide effect of the substrate edge. The experimental result shows that antireflection coating on the surface of an optical substrate can further enhance the optical waveguide effect by 0.5%.

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Carlos, Carlota Pereira de Almeida. "Advanced optical spectroscopy of new materials for luminescent solar concentrators." Master's thesis, 2019. http://hdl.handle.net/10773/29191.

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The transition from the current energy matrix towards an environmentally friendly and a ordable energy sources is a crucial challenge of the 21st century. Fully energetically sustainable architecture is a strategic focus in this e ort, through the realisation of so-called net-zero energy buildings. This implies an increase in the use of renewable resources, such as the wind, tides and the sun. Hence, new technologies that integrate solar-harvesting devices into existing and newly constructed buildings are of growing relevance. Luminescent solar concentrators consist of a transparent matrix doped or coated with active optical centres that absorb the incident solar radiation, which is reemitted at a speci c wavelength and transferred by total internal re ection to the edges, where photovoltaic cells are located. This con guration enables photovoltaic devices to be embedded in building facades or windows, allowing them to be transformed into energy harvesting units. Challenges for the luminescent species in luminescent solar concentrators include the use of sustainable, natural-based organic molecules. In this scope, semitransparent amine-functionalized organic{inorganic hybrids (ureasils) incorporating two di erent natural-based organic dyes, chlorophyll and enhanced uorescent protein (eGFP), were synthesised and processed as thin lms and monoliths. The natural dyes' and organic-inorganic hybrid's excited state dynamics were studied and characterised { the absorption bands of chlorophyll a and eGFP were identi ed, as well as their characteristic emission in the red/NIR (600-750 nm) and visible (450-600 nm) spectral regions, respectively. The emission properties were further quanti ed through absolute emission quantum yield measurements, with the maximum values measured for the eGFP-doped di-ureasil hybrid (0:33 0:03) being two times higher than the maximum value found for the chlorophyll-doped hybrid samples (0:15 0:02). Fluorescent lifetime analysis was also performed resorting to two di erent techniques: time-correlated single photon counting and spectrally-resolved streak imaging, yielding uorescent emission lifetimes of 5 ns for chlorophyll and 2-3 ns for enhanced green uorescent protein, in solution and when incorporated into the hybrid hosts. Further analysis was carried out by tting a two exponential decay model to the uorescent decay curves of the for the green uorescent protein samples, considering that two distinct electronic states are responsible for the absorption around 488 nm and the emission at 510 nm. Based on the intriguing photoluminescent features of the dye-based samples, two prototypes of luminescent solar concentrators were fabricated and optically characterised. In particular, a liquid planar luminescent solar concentrator based on a glass container lled with eGFP dispersed in an aqueous solution and a eGFPdoped di-ureasil hybrid bulk planar luminescent solar concentrator. The devices were coupled to a silicon-based commercial PV device, revealing maximum optical conversion e ciencies of 2:99 0:01% (liquid) and 3:70 0:06% (bulk), illustrating the potential of this approach for the development of nature-based luminescent solar concentrators, meeting the requirements of reliable, sustainable and competitive energy systems.
A transição da matriz energética atual para fontes de energia competitivas de baixo impacto ambiental é uma problemática central no século XXI. A arquitetura energeticamente sustentável é um ponto estratégico nesse esforço, através da realização dos chamados edifícios de energia zero. Por defenição, estes edifícios fazem uso de sistemas de produção de energia renovável local, como por exemplo a fotovoltaica, para satisfazer as suas necessidades energéticas. Assim, novas tecnologias que integrem dispositivos de coleção de energia solar em edifícios existentes ou recémconstruídos são de crescente relevância. Os concentradores solares luminescentes são dispositivos compostos por uma matriz transparente com centros óticos ativos incorporados. Estes absorbem a radiação incidente, que é posteriormente reemitida com um comprimento de onda específico e transportada por reflexão interna total até à célula fotovoltaica localizada nas extremidades da matriz. Esta configuração permite a produção de dispositivos fotovoltaicos incorporados em fachadas de edifícios e janelas, permitindo que estes sejam transformados em unidades de produção de energia. Atualmente, um dos desafios na áreas dos concentradores solares luminescentes é a incorporação de moléculas orgânicas naturais como centros óticos. Neste âmbito, foram fabricados e processados híbridos orgânico-inorgânicos semitransparentes, denominados por ureiasils, modificados por dois corantes orgânicos naturais, clorofila e proteína verde fluorescente (eGFP). A dinâmica entre os estados excitados dos corantes naturais e da matriz híbrida foi estudada e caracterizada - foram identifícadas as bandas de absorção da clorofila a e da eGFP, assim como a sua emissão característica no vermelho/infravermelho próximo (600-750 nm) e na região do visível (450-600 nm), respetivamente. As propriedades de emissão foram quantificadas através de medidas de rendimento quântico absoluto, registando-se um valor máximo para o híbrido com eGFP incorporada (0,33+/-0,03) duas vezes superior ao encontrado para as matrizes híbridas dopadas com clorofila (0,15+/-0,02). Foram também analisados os tempos de vida dos emissão dos estados excitados das várias amostras, tendo sido encontrados valores ~5 ns para a clorofila e ~2-3 ns para a eGFP, em solução ou quando incorporadas nas matrizes híbridas. Procedeu-se ainda a uma análise mais aprofundada no caso das amostras com eGFP, através da aplicação de um modelo bi-exponencial às curvas de decaimento, uma vez que o modelo eletrónico da mesma indica a presença de dois estados excitados distintos responsáveis pela absorção em torno dos 488 nm e emissão a 510 nm. Devido às características fotoluminescentes interessantes das amostras à base de corantes naturais para aplicações em concentradores solares luminescentes, foram fabricados e caracterizados dois protótipos com geometria planar { um concentrador solar luminescente baseado num recipiente de vidro cheio com eGFP em solução aquosa, e um outro concentrador que consistia num monolito da matriz híbrida dopada com eGFP. Os dispositivos foram acoplados a uma célula fotovoltaica comercial de silício, revelando eficiências óticas de conversão máximas de 2; 99+/-0; 01% e 3; 70+/-0; 06%, respetivamente, ilustrando o potencial desta abordagem para o desenvolvimento de sistemas energéticos sustentáveis e competitivos.
Mestrado em Engenharia Física

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44

Frias, Ana Rita da Silva Rocha. "High performance luminescent solar concentrators for flexible waveguiding photovoltaics." Doctoral thesis, 2019. http://hdl.handle.net/10773/29231.

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The mismatch between the AM1.5G spectrum and photovoltaic cell absorption is one of the critical factors limiting their performance. To overcome it, several approaches have been proposed. Among them, emphasis is given to luminescent down-shifting layers, additive devices that are able to enhance performance under typical operation conditions, and to luminescent solar concentrators, a complementary technology to PV cells for use in urban environments. Luminescent down-shifting layers are coatings that are directly deposited on the surface of photovoltaic cells, and absorb the incident radiation that is not absorbed by photovoltaic cells, subsequently re-emitting it at a specific wavelength and refracting/reflecting it towards the photovoltaic cell. Luminescent solar concentrators are devices comprising a transparent matrix incorporating optically active centres that absorb the incident radiation, which is then re-emitted at a specific wavelength and transferred by total internal reflection to photovoltaic cells located at the edges of the matrix. This configuration enables photovoltaic devices to be embedded in building facades or windows, allowing them to be transformed into energy harvesting units, contributing for the development of zero-energy buildings. This thesis aimed to produce and characterize transparent organic- inorganic hybrids with controlled thickness and refractive index using poly(methyl methacrylate), di- and triureasils incorporating different lanthanide ions, namely Tb3+, Eu3+, Y b3+ and Nd3+, and the fol- lowing organic dyes: Rhodamine 6G and Rhodamine 800, silicon 2,3- naphthalocyaninebis(trihexylsilyloxide), chlorophyll and R- phycoerythrin molecules with emission tuned from the visible to NIR spectral regions. LSCs with planar and cylindrical geometry are studied. The use of the cylindrical geometry allows the effect of concentration to be higher when compared with the planar geometry, since the ratio between the exposed area and the area of the edges is increased. The cylindrical geometry concentrators are produced from plastic optical fibres with hollow cores, where the optically active layer was injected. The exposed area was further optimised through the production of bundles of LSCs, in which optical fibres with different cladding geometries were placed side by side. Finally, the attractive properties of natural-based dye molecules for the production of luminescent solar concentrators, which have been poorly explored, are also studied through the incorporation of chlorophyll and R- phycoerythrin as optically active centres. Key experimental results were also validated using Monte-Carlo ray-tracing simulations.
O desfasamento entre o espetro AM1.5G e o espetro de absorção das células fotovoltaicas é um fator crítico que limita o desempenho das mesmas. De forma a ultrapassar isto, diversas aproximações têm sido propostas. Entre elas, têm sido enfatizadas as camadas luminescentes por desvio descendente de energia, dispositivos capazes de melhorar o desempenho em condições de operação específicas, e os concentradores solares luminescentes, considerados uma tecnologia complementar a das células fotovoltaicas para utilização em ambientes urbanos. As camadas luminescentes por desvio descendente de energia são revestimentos diretamente depositados no topo de células fotovoltaicas capazes de absorver a radiação incidente complementar à que as células fotovoltaicas absorvem e subsequentemente reemitem-na com um comprimento de onda específico que é refratado/refletido até à célula fotovoltaica. Os concentradores solares são dispositivos compostos por uma matriz transparente incorporando centros óticos ativos que absorbem a radiação incidente, que é posteriormente reemitida com um comprimento de onda específico e transportada por reflexão interna total até à célula fotovoltaica localizada nas extremidades da matriz. Esta configuração permite a produção de dispositivos fotovoltaicos embebidos em fachadas de edifícios e janelas, permitindo que estes sejam transformados em unidades de produção de energia, contribuindo para o desenvolvimento de edifícios de energia zero. O principal objetivo deste trabalho consiste no fabrico e caracterização de híbridos orgânicos-inorgânicos com espessura e índice de refração controlados utilizando polimetil-metacrilato, di- e tri-ureasil incorporando diferentes iões lantanídeos, nomeadamente Tb3+, Eu3+, Yb3+ and Nd3+, e corantes orgânicos como Rodamina 6G, Rodamina 800, Silício 2,3-naftalocianina bis(trietil siloxano), clorofila e R-ficoeritrina cuja emissão varia entre o visível e o infravermelho próximo. Concentradores solares luminescentes com geometria planares e cilíndrica foram estudados. A geometria cilíndrica permite que o efeito de concentração seja superior, quando comparado com a geometria planar, uma vez que a razão entre a área exposta e a área das extremidades aumenta. A geometria cilíndrica é explorada, através da produção de concentradores solares luminescentes em fibra ótica de plástico onde a camada ótica ativa se encontra no interior da fibra, como um preenchimento do núcleo oco. A possibilidade de aumentar a área exposta foi, também, abordada através do fabrico de uma matriz de concentradores solares luminescentes colocados lado a lado com diferentes geometrias da bainha. Para além disso, as propriedades óticas dos corantes orgânicos naturais, que têm sido pouco exploradas na literatura, foram alvo de estudo através da incorporação de moléculas de clorofila e de R-ficoeritrina como centros óticos em concentradores solares luminescentes. Os resultados experimentais mais relevantes foram validados através de simulações baseadas no método de Monte-Carlo.
Programa Doutoral em Física

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45

Chiang, Hung-wei, and 江鴻偉. "Analysis and comparison of equal optical path type and pyramid type secondary optical elements applied in solar concentrators." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/94641035529121724867.

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碩士
國立中央大學
光機電工程研究所
101
Based on the design methods for secondary optical elements, this thesis utilizes the equal optical path to build the solar concentrator and the optical simulation software to analyze the optical efficiency, acceptance angle and irradiance. The primary purpose is to improve the acceptance angle of solar concentrator, reduce the energy loss caused by sun angle deviations, distribute the energy evenly and finally promote the benefit of power generation. In this paper, four types of secondary optical elements are compared, including kaleidoscope with equal optical path design, kaleidoscope with flat top surface, specular pyramid and the compound solar concentrator via the simultaneous multiple surfaces design method. This study simulates the initial design and carries out the advanced design, so as to analyze and compare the optical properties. This thesis also analyzes the impacts of the broad band and assembly errors on the optical performance of the type of kaleidoscope with equal optical path design.

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Chiang, Chung-Sheng, and 江宗昇. "The Fabrication of Optical Holographic Photovoltaic Concentrator." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/96496769844758136709.

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博士
國防大學理工學院
國防科學研究所
100
The energy crisis and global warming are issues and to-be-solved problems of world concern. Looking for sustainable energy is one of today's important issues. Photovoltaic (solar) energy conversion will provide a crucial part of future sustainable energy needs. The main issue the solar industry facing currently is how to reduce the cost of power generating system. The next-generation photovoltaics should aim not only at high efficiency but also low-cost per unit area. Various approaches include replacing expensive semiconductor material with low cost solar collectors and concentrators and the use of high efficiency smaller area photovoltaic devices. This study proposes the idea and underlying theory of optical holography and its applications in solar energy concentrations without the help of tracking system. Two improved devices of converting solar energy into electricity have been constructed. The first device consists of a hologram pairs with a holographic diffraction and a holographic optical element will concentrating the solar spectrum onto solar cells. The second ones consists of lenticular lens array and a hologram paired with a holographic collimation device and a holographic solar concentrator can concentrate the solar spectrum onto solar cells.

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47

Chen, Zhi-Wei, and 陳志維. "Study of Optical Homogenizer in Solar Concentrator System." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/83367785635467026171.

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碩士
國立高雄應用科技大學
電機工程系博碩士班
96
In this study, we propose a new optical homogenizer used in solar concentrator system. With the combination of a Fresnel lens and the proposed optical homogenizer, the efficiency of a high concentrator solar system can be enhanced more than 5 percent than the accustomed one. We design three kinds of optical homogeneizer to compare their performace with each other in the thesis. By means of computer simulation and the optical measurement of the homogenizer sample, we can make sure that the high light uniformity in the central region of solar cell can be removed, and the efficiency of the solar cell is increased.

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Lin, Hung-Yen, and 林宏彥. "THE OPTICAL DESIGN OF COMBO SOLAR CONCENTRATOR LENS." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/75644338267922181737.

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碩士
元智大學
光電工程研究所
97
Considering cost of solar cell, it is necessary to reduce outlay of material of solar cell and improve conversion efficiency of solar cell. Solar concentrator by way of optical design can concentrate large area sunlight on the small area solar cell to obtain two goals as mentioned. In this study, we utilize TIR zone, Fresnel zone and aspherical zone onto constitute the combo solar concentrator lens. The characteristic of TIR can help us to make great bending angles for decreasing the depth of optical system and smearing sunlight on the solar cell. The characteristics of Fresnel lens and aspherical lens are thin in lens thickness and small bending angle. The advantages of each zone can combine into one optical system to attain the major key points: high concentration ratio, wide acceptance angle, illuminance uniformity and compactness.

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LIN, CHING-HONG, and 林錦宏. "Design and Simulation of Optical Components for Solar Concentrator." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/37062553927190824060.

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碩士
中華大學
機械工程學系碩士班
99
Concentrator photovoltaic (CPV) systems use large area optical components to collect direct sunlight and transfer the energy onto small, high-efficiency photovoltaic (PV) cells. CPV systems have potential to reduce the system cost and keep higher conversion efficiencies. High concentration systems need incorporate mechanical tracking to maintain alignment with the sun to achieve a higher optical efficiency. It is essential to consider how the misalignment and acceptance angle influence the optical efficiencies and how to improve it. This research utilizes secondary optical elements such as hollow reflective truncated pyramid, truncated pyramid lens and spherical dome lens, to improve acceptance angle induced problems in Fresnel concentrator solar power system. The results show that the optical efficiency was improved when the open angle of truncated pyramid is very close to the incident convergent lights from the sun. The optical efficiency was significantly enhanced for the CPV system with secondary optical elements. The optical efficiency of over 59 % can be achieved even under 1.1 degree of acceptance angle.

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50

Wu, Yen-Ya, and 吳彥亞. "Optical Design of Solar Cell Concentrator Using Free-form Surface." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/m4ms5r.

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碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
103
The proposed research provided a new designed concentrator to improve the light distribution on the solar cell. Note that a free-from (FF) construction method is proposed to design this new reflector. The skew ray tracing method is used to establish the FF construction method and then obtain the actual FF reflector surface. The effectiveness of the proposed FF reflectors is investigated by means of ZEMAX simulations. It is shown that the proposed FF concentrators yield a significant improvement in the irradiance uniformity compared to that achieved using other conventional concentrators.

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Dissertations / Theses on the topic 'Optical concentrators'

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