Dynamic Range Extension of a SPAD Imager Using Non-Uniformity Correction Techniques

The extraordinary sensitivity of single-photon avalanche diodes (SPADs) makes these devices the ideal option for vision systems aimed at low-light applications. Nevertheless, there exist large dark count rate and photon detection probability non-uniformities, which reduce the dynamic range of the detector. As a result, the capability to create image contrast is severely damaged or even lost. This paper presents the implementation of a correction algorithm to compensate for the mentioned non-uniformities and thus extend the contrast of the generated images. To demonstrate its efficiency, the proposed technique is applied to real images obtained with a fabricated SPAD image sensor. An increase of more than 3 b of contrast is obtained.Peer ReviewedPostprint (author's final draft

Early degradation of PV modules and guaranty conditions

CIEMAT PVLabDER has largely increased its demand on testing and characterizing PV plants, according to the fast growth of PV installed capacity in Spain. One of the topics in which manufacturers, promoters, and owners of the plants are more interested in, is the possible degradation of PV modules and its relationship to guarantee contracts, as it is related to subsidies. This paper presents some findings in campaigns of PV plants evaluation carried out during last years. This evaluation usually consists of visual inspection, I-V curve measurement in the fields (the whole plant or selected areas), thermal evaluation by IR imaging, and, in some cases, measurement of the I-V characteristic and thermal behaviour of selected modules in the plant, chosen by the laboratory. It must be noticed that new defects that grow when the module is into operation may appear in modules initially free of them (named as hidden manufacturing defects). Usually some of these hidden defects that only appear in normal operation are not detected in reliability tests (EN61215 or EN 61646) [4][5] due to the different operational conditions of the module in the standard tests and in the field (serial-parallel connection of many PV modules, power inverter influence, over voltage on wires, etc.

Early degradation of PV modules and guaranty conditions

CIEMAT PVLabDER has largely increased its demand on testing and characterizing PV plants, according to the fast growth of PV installed capacity in Spain. One of the topics in which manufacturers, promoters, and owners of the plants are more interested in, is the possible degradation of PV modules and its relationship to guarantee contracts, as it is related to subsidies. This paper presents some findings in campaigns of PV plants evaluation carried out during last years. This evaluation usually consists of visual inspection, I-V curve measurement in the fields (the whole plant or selected areas), thermal evaluation by IR imaging, and, in some cases, measurement of the I-V characteristic and thermal behaviour of selected modules in the plant, chosen by the laboratory. It must be noticed that new defects that grow when the module is into operation may appear in modules initially free of them (named as hidden manufacturing defects). Usually some of these hidden defects that only appear in normal operation are not detected in reliability tests (EN61215 or EN 61646) [4][5] due to the different operational conditions of the module in the standard tests and in the field (serial-parallel connection of many PV modules, power inverter influence, over voltage on wires, etc.

Influence of initial power stabilization over crystalline-Si photovoltaic modules maximum power

Measurements that suppliers offer in specification sheets are not always close to the actual power measured in independent laboratories such as CIEMAT. Independent measurements tend to be lower than those printed on the label sometimes even lower than the allowed tolerance indicated by the manufacturer on the same label. Furthermore, a potentially significant power reduction has been reported when Standard EN50380 (which requires photovoltaic (PV) modules to be exposed to more than 20 kWh/m2 of sunlight prior to taking the measurements that appear on the label) is followed. This is the initial power stabilization and this work studies the power stabilization that tends to appear in crystalline PV modules. Crystalline PV modules usually decrease in power around 1%, but decreases >4% have also been reported. These power losses are only detected after the mentioned power stabilizatio

Analysis of air mass dependence of three photovoltaic arrays

The solar spectrum, which is also could be described by air mass factor, has a significant relationship with the performance of photovoltaic modules. The air mass dependence has been investigated by a theoretical method as well as an actual case of three different photovoltaic arrays: polycrystalline silicon, amorphous silicon and cadmium telluride, at the EUIT Agrícola-UPM (Madrid, Spain, 40.4426oN, 3.7295oW). The calculating results show that: AM dependence of poly-Si array is positive because an elevating AM-value indicates a red shift and poly-Si module is more red sensitive; On the contrary, as a-Si module and CdTe module are more blue sensitive, their AM dependences are negative. Furthermore, the outdoor AM dependences of three arrays are corresponding to the calculating results although the thermal annealing effect could be superimposed on spectral effect in the case of a-Si. Keywords: PV system, spectral response, polycrystalline silicon, a-Si, CdT

Evaluación del uso de paneles solares como elemento de sombreo en invernaderos

El objetivo principal de este trabajo experimental, es evaluar el uso de paneles solares como opción de elemento de sombreo en viveros, tanto de gran escala como de pequeña superficie. Esta opción podría elegirse tanto en el caso de no disponer de red de suministro eléctrico cercano así como en el caso de preferir no depender de una fuente de energía eléctrica exterior. Como hecho novedoso, se ha elegido paneles solares flexibles de capa fina y poco peso, que serían situados en la cubierta del invernadero. Dicha elección permite que los paneles se adapten a la forma de la cubierta, sea cual fuere

Thim Films Modules Characterization Under Standard Test Conditions

Photovoltaic modules based on the relatively new thin film technology are gaining importance in the photovoltaic market. Some of these modules are made of silicon, consisting of layers of amorphous silicon or microcrystalline silicon. Other thin film PV modules are made of CIS, Cadmium Telluride (CdTe) or less frequently organic compounds. The materials used in thin film technologies pose problems in terms of measuring how much power is generated under standard test conditions (STC). This is due to the fact that the modules´ power rates could vary depending both on the amount of time they have been exposed to the sun and on their history of sunlight exposure. So it is necessary to know the previous periods of sunlight exposure in order to know the current state of the module. It is necessary to determine an easily accomplishable testing method that ensures the repeatability of the measurements of the power generated. This is essential because in order to have a reliable sample of the PV module population of a large PV plant, a huge number of modules must be measured. This paper shows different tests performed on different commercial thin film PV modules in order to find the best way to obtain measurements. A correlation was tested between sun exposure and power measured. A method for obtaining indoor measurements of these technologies that takes periods of sunlight exposure into account is proposed. Additionally, temperature and irradiance coefficients were also determined for different technologies in order to obtain accurate measurements

Estudio comparativo de la eficiencia de tres tipos de tratamiento basados en compostaje respecto a los parámetros físico-químicos como indicadores de calidad del suelo para recuperar suelos degradados por el uso de agroquímicos en lateral 7, Uchumayo s/n 2021

La presente investigación tiene como finalidad proponer alternativas agroecológicas para recuperar suelos degradados por el uso de agroquímicos. La investigación constó de una metodología científico hipotética deductiva. Además, presentó un alcance explicativo. De igual manera, la investigación presentó un diseño experimental. La investigación se desarrolló en tres fases: la primera fase abarcó la elaboración de los tres tipos de compost en las ollas composteras; la segunda fase constó de la delimitación del área de estudio para poder agregar los diferentes compost al suelo degradado; en la última fase se realizó la toma de las respectivas muestras que abarca el testigo y los diferentes tratamientos con el testigo, lo cual permitió determinar el nivel de eficiencia de tres tipos de tratamiento basados en compostaje respecto a los parámetros físico-químicos evaluados en el presente estudio. Finalmente, mediante los resultados y la estadística descriptiva se identificó que el tratamiento 2 (compost a base de estiércol de conejo), presenta un mejor nivel de eficiencia para recuperar suelos degradados por el uso de agroquímicos, los indicadores evaluados donde resaltan son: potasio disponible con 2482,9233 mg/kg, fósforo disponible con 183,7467 mg/kg, pH de 8,7233 y conductividad eléctrica de 2,1167 dS/m. El único indicador donde no resalta comparado con los otros tratamientos respecto al testigo es el tratamiento 3 que es el compost a base de estiércol de vaca que da como resultado 18,1767 g/100g de materia orgánica

Practical issues for testing thin film PV modules at standard test conditions.

Thin film photovoltaic (TF) modules have gained importance in the photovoltaic (PV) market. New PV plants increasingly use TF technologies. In order to have a reliable sample of a PV module population, a huge number of modules must be measured. There is a big variety of materials used in TF technology. Some of these modules are made of amorphous or microcrystalline silicon. Other are made of CIS or CdTe. Not all these materials respond the same under standard test conditions (STC) of power measurement. Power rates of the modules may vary depending on both the extent and the history of sunlight exposure. Thus, it is necessary a testing method adapted to each TF technology. This test must guarantee repeatability of measurements of generated power. This paper shows responses of different commercial TF PV modules to sunlight exposure. Several test procedures were performed in order to find the best methodology to obtain measurements of TF PV modules at STC in the easiest way. A methodology for indoor measurements adapted to these technologies is described