Search results for "IRRADIANCE"
showing 10 items of 152 documents
Increasing efficiency of photovoltaic systems under non-homogeneous solar irradiation using improved Dynamic Programming methods
2017
Abstract The paper presents a complete technique, based on the combination of algorithms, devoted to minimize losses and increase efficiency of Total Cross Tied (TCT) connected photovoltaic (PV) systems under non-homogeneous solar irradiation, based on irradiance equalization criterion. Irradiance equalization is achieved by changing the connections of the solar panels adaptively by a dynamic switching matrix so that total solar radiation on parallel circuits is the most equalized. In this paper, the authors introduce two algorithms. The first one is SmartChoice (SC) algorithm, which is combined with Dynamic Programming (DP) in order to create a hybrid method and obtain better results as co…
A hierarchical architecture for increasing efficiency of large photovoltaic plants under non-homogeneous solar irradiation
2019
Abstract Under non-homogeneous solar irradiation, photovoltaic (PV) panels receive different solar irradiance, resulting in a decrease in efficiency of the PV generation system. There are a few technical options to fix this issue that goes under the name of mismatch. One of these is the reconfiguration of the PV generation system, namely changing the connections of the PV panels from the initial configuration to the optimal one. Such technique has been widely considered for small systems, due to the excessive number of required switches. In this paper, the authors propose a new method for increasing the efficiency of large PV systems under non-homogeneous solar irradiation using Series-Para…
Measurements of total ozone amount over Badajoz (Southwestern Spain) by means of a GUV multiband radiometer
2012
This paper presents the first measurements of total ozone amount performed at the radiometric station of Badajoz (Spain) by means of a multichannel radiometer GUV-2511. The retrieval of total ozone amount from GUV measurements of solar ultraviolet irradiance is performed with the support of look-up tables calculated using the SBDART radiation transfer code. This methodology is based on the different absorption by ozone suffered by the radiation at two certain near wavelengths. In this case the pair 305, 340 nm was chosen because of its better performance than the pair 305, 320 nm. The look-up table contains the ratio between irradiances at the mentioned wavelengths calculated under differen…
Emulation of Leaf, Canopy and Atmosphere Radiative Transfer Models for Fast Global Sensitivity Analysis
2016
Physically-based radiative transfer models (RTMs) help understand the interactions of radiation with vegetation and atmosphere. However, advanced RTMs can be computationally burdensome, which makes them impractical in many real applications, especially when many state conditions and model couplings need to be studied. To overcome this problem, it is proposed to substitute RTMs through surrogate meta-models also named emulators. Emulators approximate the functioning of RTMs through statistical learning regression methods, and can open many new applications because of their computational efficiency and outstanding accuracy. Emulators allow fast global sensitivity analysis (GSA) studies on adv…
Characterization of Thin Film Cig(S,Se)2 Submodules Using Solar Simulator and Laser Beam Induced Current Techniques
2015
In this work, the electrical and optical characterization of CIG(S,Se)2 sub-modules using both a solar simulator equipment and the Laser Beam Induced Current (LBIC) technique is presented. By using the solar simulator and a proper set-up, the electrical parameters of the modules at varying irradiance and temperatures are determined. In addition, the LBIC measurements are carried out to analyze the 2D photocurrent uniformity of the modules at two different wavelengths. Dispersion values of extracted parameters can be very useful for practically tuning the modelling stage at device/module level.
The parameterisation of the atmospheric aerosol optical depth using the Ångström power law
1998
Abstract We have analysed the ability of the Angstrom power law to model the spectral aerosol optical depth, τaλ, for the 400–670 nm band, obtained from spectral direct irradiance measurements at normal incidence. The spectra were registered at ground level in Valencia, Spain, using a Li-cor 1800 spectroradiometer. The results obtained showed that the fitting method that introduces lower errors in the determination of the Angstrom power law coefficients is to adjust directly the spectral experimental data. In this way the errors obtained for the turbidity coefficient, β, were about 0.004 and for the wavelength exponent, α, 0.07. The correlation coefficient was always greater than 0.95. Thes…
Sensitivity of UVER enhancement to broken liquid water clouds: A Monte Carlo approach
2016
The study uses a Monte Carlo radiative transfer model to examine the sensitivity of the UV erythemal radiation (UVER) enhancement to broken liquid water clouds of the cumulus and stratocumulus type. The model uses monochromatic radiation at 310 nm corresponding approximately to the peak of the product between irradiance and the erythemal curve. All scattering, absorption, extinction coefficients, and spectral albedos are tuned to this wavelength. In order of importance, fractional cloud cover, the area of individual cloud patches, and cloud thickness exert a strong influence on the enhancement, with smaller contributions from cloud optical depth, cloud base height, and solar zenith angle. I…
Centre-to-limb variation of photospheric facular radiance and image resolution
2005
Abstract We study the effect of the angular resolution on the determination of the angular properties of the facular radiance. We analyze photospheric intensity in the continuum, around the Ni 676.8 nm line, and longitudinal magnetic field along the line of sight, measured by the MDI instrument aboard SOHO with two spatial resolutions, 4″ and 1.2″ (2″ and 0.6″ pixels, respectively). The effect of the limited photometric sensitivity of the instrument and the limited information on the angular structure of the magnetic field tubes are considered. Our study of the high-resolution data shows that intensity contrast of magnetic features between 80 and 600 Gauss increases from centre to limb up t…
Zero axial irradiance by annular screens with angular variation
1992
For optical alignment, it may be convenient to use a three-dimensional diffraction pattern with zero irradiance along the optical axis. This pattern is created here by using annular screens in the form of a phase daisy, a daisy flower, or a pie, with an even number of slices of an equal central angle and with every other slice with a phase retardation of 180 degrees . We recognize this form of angular variation as a particular solution of a wider set of functions that are able to produce zero axial irradiance.
All-incoherent dispersion-compensated optical correlator
2007
We report on a simple, spatially incoherent, wavelength-independent imaging system that, in contrast to the conventional case, exhibits a dispersion-compensated point-spread function. Our hybrid (diffractive-refractive) three-lens imaging configuration thus acts as an all-incoherent dispersion-compensated optical irradiance correlator. So the optical arrangement is well adapted to processing color information (both spatially and temporally incoherent) under natural illumination.