Energy analysis of holographic lenses for solar concentration

The use of volume and phase holographic elements in the design of photovoltaic solar concentrators has become very popular as an alternative solution to refractive systems, due to their high efficiency, low cost and possibilities of building integration. Angular and chromatic selectivity of volume holograms can affect their behavior as solar concentrators. In holographic lenses, angular and chromatic selectivity varies along the lens plane. Besides, considering that the holographic materials are not sensitive to the wavelengths for which the solar cells are most efficient, the reconstruction wavelength is usually different from the recording one. As a consequence, not all points of the lens work at Bragg condition for a defined incident direction or wavelength. A software tool that calculates the direction and efficiency of solar rays at the output of a volume holographic element has been developed in this study. It allows the analysis of the total energy that reaches the solar cell, taking into account the sun movement, the solar spectrum and the sensitivity of the solar cell. The dependence of the recording wavelength on the collected energy is studied with this software. As the recording angle is different along a holographic lens, some zones of the lens could not act as a volume hologram. The efficiency at the transition zones between volume and thin behavior in lenses recorded in Bayfol HX is experimentally analyzed in order to decide if the energy of generated higher diffraction orders has to be included in the simulation

Holographic Sensor Based on Bayfol HX200 Commercial Photopolymer for Ethanol and Acetic Acid Detection

This paper presents a holographic sensor based on reflection holograms recorded in the commercial photopolymer Bayfol® HX 200. The recording geometry and index modulation of the hologram were optimised to improve accuracy for this specific application. The sensor was subjected to tests using various analytes, and it exhibited sensitivity to acetic acid and ethanol. The measurements revealed a correlation between the concentration of the analyte in contact with the sensor’s surface and the resulting wavelength shift of the diffracted light. The minimum detectable concentrations were determined to be above 0.09 mol/dm3 for acetic acid and 5% (v/v) for ethanol. Notably, the sensors demonstrated a rapid response time. Given that ethanol serves as a base for alcoholic beverages, and acetic acid is commonly found in commercial vinegar, these sensors hold promise for applications in food quality control

Ruta exportadora del producto cortinas desde Colombia al país con mejor opción de la unión Europea /

El mundo se volvió global. La necesidad de competir inicialmente en mercados domésticos, condujo, con la invención de los autómatas industriales, a economías de escala y la acumulación de excedentes de producción, que tenían que ser colocados en mercados internacionales. De esta manera, y acompañado del gran desarrollo de los medios de comunicación y transporte, surgió la oferta global y el contrabando, que despertó una demanda también global, y puso al alcance de los más pobres, bienes que antes eran imposibles poseer. El éxito o fracaso en ésta estrategia, ha hecho a unas empresas o países, más fuertes y competentes que otros, siendo el principal reto de los gobiernos y las organizaciones mundiales, asegurar que la libre competencia continúe. La automatización, sistematización, globalización, y la apertura van destruyendo poco a poco industrias, y negocios de intermediación en el manejo de bienes y servicios, y con ello, el empleo mundial. Como consecuencia de lo anterior, se producen corrientes migratorias desde los países más pobres, donde la oferta de trabajo es escasa y mal remunerada, hacia los países más ricos.Incluye bibliografí

Effect of radar rainfall time resolution on the predictive capability of a distributed hydrologic model

The performance of distributed hydrological models depends on the resolution, both spatial and temporal, of the rainfall surface data introduced. The estimation of quantitative precipitation from meteorological radar or satellite can improve hydrological model results, thanks to an indirect estimation at higher spatial and temporal resolution. In this work, composed radar data from a network of three C-band radars, with 6-minutal temporal and 2 × 2 km2 spatial resolution, provided by the Catalan Meteorological Service, is used to feed the RIBS distributed hydrological model. A Window Probability Matching Method (gage-adjustment method) is applied to four cases of heavy rainfall to improve the observed rainfall sub-estimation in both convective and stratiform Z/R relations used over Catalonia. Once the rainfall field has been adequately obtained, an advection correction, based on cross-correlation between two consecutive images, was introduced to get several time resolutions from 1 min to 30 min. Each different resolution is treated as an independent event, resulting in a probable range of input rainfall data. This ensemble of rainfall data is used, together with other sources of uncertainty, such as the initial basin state or the accuracy of discharge measurements, to calibrate the RIBS model using probabilistic methodology. A sensitivity analysis of time resolutions was implemented by comparing the various results with real values from stream-flow measurement stations

Full modeling and experimental validation of cylindrical holographic lenses recorded in Bayfol HX photopolymer and partly operating in the transition regime for solar concentration

Concentrating photovoltaics for building integration can be successfully carried out with Holographic Optical Elements (HOEs) because of their behavior analogous to refractive optical elements and their tuning ability to the spectral range that the photovoltaic (PV) cell is sensitive to. That way, concentration of spectral ranges that would cause overheating of the cell is avoided. Volume HOEs are usually chosen because they provide high efficiencies. However, their chromatic selectivity is also very high, and only a small part of the desired spectral range reaches the PV cell. A novel approach is theoretically and experimentally explored to overcome this problem: the use of HOEs operating in the transition regime, which yield lower chromatic selectivity while keeping rather high efficiencies. A model that considers the recording material’s response, by determining the index modulation reached for each spatial frequency and exposure dosage, has been developed. It has been validated with experimental measurements of three cylindrical holographic lenses with different spatial frequency ranges recorded in Bayfol HX photopolymer. Simulations of systems comprising two lenses and a mono-c Si PV cell are carried out with the standard AM 1.5D solar spectrum. Promising results are obtained when using the system with lower spatial frequencies lenses: a total current intensity equal to 3.72 times the one that would be reached without the concentrator.Generalitat de Catalunya (2017FI_B2_00127); Ministerio de Economía y Competitividad of Spain (ENE2013-48325-R, ENE2016-81040-R); Diputación General de Aragón - Fondo Social Europeo (TOL research group, T76); Universidad de Zaragoza (UZ2017-CIE-02)

Modelling HOE performance with an extended source; experimental investigation using misaligned point sources

Holographic Optical Elements (HOEs) have the potential to enable more compact, versatile and lightweight optical designs, but many challenges remain. Volume HOE’s have the advantage of high diffraction efficiency but they present both chromatic selectivity and chromatic dispersion which impact on their use with wide spectrum light sources. Single-colour LED sources have a narrow spectrum that reduces these issues and this makes them better suited for use with volume HOEs. However, the LED source size must be taken into consideration for compact volume HOE-LED systems. To investigate the design limits for compact HOE-LED systems, a theoretical and experimental study was carried out on the effects of an extended source on the HOE output for different holographic lenses, with focal lengths from 2.5-10 cm. The lenses were recorded in Bayfol HX200 material and their diffraction efficiency was characterised across the lens aperture by measuring the Bragg angular selectivity curve at each location. Offset point sources were used to experimentally study the effects of a non-point source on the HOEs and the system was also modelled using Matlab and Zemax