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Descripción
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| The record efficiencies achieved by multijunction (MJ) solar cells have renewed the interest in concentrator photovoltaics (CPV), as the use of high concentration is necessary to reduce the area of these expensive devices and to maximize their efficiency. The promise is a reduction of the cost of the electricity generated as compared to flat plate PV. In order to improve the efficiency of these systems, intensive research is being carried out regarding concentrator cells, optics and integration of systems. Characterization tools are also essential for the development and optimization of concentrators, from the development of the initial prototypes to the manufacturing line. However, there is a poor knowledge of appropriate characterization tools for CPV systems and their elements. Furthermore, the lack of indoor testing procedures may be a bottleneck to the large-scale production of CPV modules and a barrier to their commercial deployment. This thesis contributes to the development of instruments and methods for the indoor characterization of high-concentration PV systems and their constituent elements. Primarily, a solar simulator able to measure CPV modules has been designed and developed (probably the first in the world), which constitutes the cornerstone instrument for the indoor characterization methods developed. The key component of the illumination system of the solar simulator is a large-area collimator mirror with a long focal distance, which collimates the light coming from a small flash light source placed at its focus. An investigation of those manufacturing techniques that feature a relatively low cost and sufficient optical quality has been carried out. A mechanized aluminum mirror with 6 m of focal distance and 2 m in diameter has been developed to meet the optical requirements of the CPV solar simulator. The relevant figures of merit for the quality of the mirror have been identified: surface profile accuracy (form, waviness, roughness), collimation angle, scattering and spatial uniformity of the reflected light beam. A comprehensive range of characterization techniques have been proposed and tried out for evaluating said merit figures. The characterization of the light produced by the simulator was a subsequent research topic, as it required the development of specific measurement methods of the spectrum, spatial uniformity and angular size of the irradiance that are suitable for pulsed light sources. The characterization of the solar simulator developed was carried out using said methods and the results are presented here. According to the definitions in the norm IEC 60904 9, the solar simulator presented is classified as Class A(spectral match to AM1.5D)-B(spatial uniformity of the irradiance)-A(temporal stability). Procedures for a meaningful use of the solar simulator were then developed. A discussion on appropriate light sensors for irradiance and spectrum is presented. In order to accommodate the non-idealities of the artificial light source, the light sensor has to feature similar current sensitivity to the intensity, spectrum and angular distribution of the light as the device under test. Such a CPV reference unit can be constructed as the minimum optical-electrical unit within the module to be measured, i.e. a ?mono-module?. Component cells are proposed as the most significant sensors of the spectrum, and the latter is given through the quantity ?spectral matching ratio?. As MJ cells are most sensitive to the spectral balance of the light, a procedure for estimating the current-mismatch between their subcells under any spectrum is also described. This method is applied to a particular concentrator for its demonstration. A method that allows translating the measured performance of concentrator MJ cells into any other arbitrary conditions is presented, which enables the prediction of the energy yield under the ever-changing real-sun conditions | |
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Internacional
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Si |
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ISBN
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Tipo de Tesis
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Doctoral |
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Calificación
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Sobresaliente cum laude |
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Fecha
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