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The characteristics of concentrator photovoltaic modules based on a 120 × 120 mm Fresnel lens with secondary concentrators in the form of hollow aluminum focons with internal mirror walls are studied. The optimal sizes and configurations of secondary concentrators are determined to increase the efficiency of focusing systems of concentrator modules. The maximum value of the allowable misorientation angle was obtained, equal to ±0.75°, corresponding to a power drop to a level of 90% relative to the maximum power value of the concentrator photovoltaic module at normal beam incidence. For a module with the most efficient focon 40 mm high and side face slope angles of 17°, the maximum efficiency of the module under laboratory conditions was obtained, equal to 35.15%. Under natural conditions, the efficiency value reached 33.8%. The results obtained correspond to the level achieved for the best foreign analogues. [ABSTRACT FROM AUTHOR]

Energy needs have increased with global advancements and industrial revolutions. Electrical energy utilization shares a huge amount of energy with residential and industrial loads. Traditional energy resources are expensive and polluting, producing greenhouse gasses, which is a major environmental concern. Solar energy utilization is a cost-effective, sustainable, and green solution to meet the ongoing energy demand. Concentrator photovoltaic (CPV) systems are developed for energy conversion by providing high efficiency using multi-junction solar cells. This paper provides an overview of the recent optical developments in CPV systems and emerging technologies that are likely to shape the future of CPV systems. The objective of this article is to provide an overview of the issues that need to be resolved to improve the geometrical concentration, acceptance angle, uniformity, and optical efficiency of CPV systems. A comprehensive comparison is also presented on different types of solar concentrators. In addition, future research directions are presented to facilitate the continued growth and success of CPV systems. Furthermore, this review article gives an up-to-date and widespread overview of CPV technology, assesses its potential for various applications, and distinguishes the challenges and opportunities for future research and development. [ABSTRACT FROM AUTHOR]

Concentrated Photovoltaic (CPV) is a promising technology for higher efficiency power generation than other photovoltaic power generating technologies. However, the lack of demand and its failure in the commercial field is mainly due to its long-term reliability issues as well as its cost, which is an order of magnitude higher than the other technologies. Therefore, several measures have been taken to minimize the cost, improve the reliability as well as improve the performance of these concentrators. In this approach, Micro photovoltaic concentrators have been introduced as an outstanding alternative to shed light on all these challenges while keeping the same principle as the CPV modules. This paper presents a theoretical analysis of a micro photovoltaic concentrator system with a geometrical concentration ratio of 100x consisting of a Plano-convex lens as a primary optical element, a ball lens as a secondary optical element, and a solar cell. The aim is to present a compact module with high optical efficiency, low thermal stress, and high mechanical tolerance to keep the optimum optical alignment between the submillimeter cell and the small-sized optics.

This work deals with real conditions testing of two Fresnel lens-based optical concentrators for concentrator photovoltaic systems (CPV). Particular attention is paid to validate the performances of the secondary optical elements (SOEs), namely pyramid and cone, both made from highly transparent fused silica and mounted with a poly methyl methacrylate (PMMA) Fresnel lens as a primary optical element (POE). The effet of the focal distance of the POE on the main optical characteristics is analyzed by simulation and the corresponding results and behavior are discussed in details. Prototypes based on Fresnel lens having 75 and 100mm in diameter and pyramid- and cone-based secondary optical elements have been simulated, fabricated and tested. Optical and electrical characterization procedures are described in details. The optical efficiency, acceptance angle, spatial homogeneity of the output power and electrical performances of the fabricated CPV units are measured and are in a good agreement with simulation data. Results show that the pyramid-type concentrator gives the best optical and electrical performances. The electric efficiency achieved by the pyramid-based concentrators reaches 30% which make it able to reach the highest standards of CPV technology performances. A large acceptance angle of 1.35° is measured as one of the highest value reported in the literature for systems with pyramid as a SOE. A good agreement between simulation and experiment results has been obtained, confirming the performance expected from a CPV system having the same secondary optical element with a larger primary optical element.

The impact of a natural phase change material (PCM) based thermal solar collector, with a compound parabolic concentrator (CPC), was investigated during summer. This paper introduces a natural PCM (beeswax) instead of commercial phase change material, which was used as an energy storage media to improve the performance parameter of the solar collector. In this study, the natural phase change material was used within the solar collector, as it was easily available in nature. The outdoor experiments were carried out where compound parabolic concentrator, made of glass, was mounted on thermal collector during the day time. The data of consecutive three months have been collected and analyzed in this paper. The system performance, such as, thermal efficiency, operating value and collected energy of the collector were tested at a set different flow rate. The date was measured and compared between the systems with and without phase change material. Based on the measured collected energy and thermal efficiency, all parameter for the collectors as functions of water flow rate was obtained. This result shows that the maximum outlet water temperature of 50⁰C and the maximum thermal efficiency of 35-40% were achieved at a water flow rate of 0.004 kg/s. The system with PCM was illustrated to have much better performances. Phase change material was more effective to improve thermal efficiency in low solar radiation. The system reaches maximum plate temperature more quickly in June than in July and August. The highest absorber plate temperature reading found in June was 90⁰C and it took the system 3.5 hours to reach the point. ΔT/H operating value was inversely proportional to thermal efficiency. Water flow rate was proportional to collected energy and maximum collected energy was 456 W. It can be highlighted that the best water flow rate was 0.004 kg/s because it gives the maximum thermal efficiency and collected energy.

After being adequately captured and concentrated, solar radiation can be conducted by optical fiber bundles/cables and directly used for illumination (lighting) or heating of confined spaces, or indirectly used by converting it in other forms of energy (e.g., for producing electricity). This article reports preliminary tests conducted on a 7-m-long optical fiber bundle/cable with an effective aperture circular area of 14 mm in diameter, specially designed and manufactured by a leading company to transmit up to 1000 Wth of unfiltered concentrated sunlight. The cable was tested in the typical receiver position at the top of a solar concentration central tower. The main purpose was the experimental determination of the transmission efficiency of the cable in function of the incidence angle using selected groups of heliostats belonging to the heliostat field. The testing methodology proved to be capable of evaluating the performance of the cable. The cable withstood the tests without revealing any type of damage. The results obtained showed that the transmissivity of the cable is higher than 50% when the incidence angle of the solar radiation is lower than 14.7°, increasing sharply to circa 95% when the incidence angle is lower than 4.5°.

In the present work, the design of a high-precision luminosity sensor (HPLS) is shown. On sunny and clear days, the design allows the sun position to be determined with 99.7% accuracy; in the presence of clouds (partly sunny or cloudy conditions), the most clear area, which represents the area with the greatest amount of direct solar radiation at the moment, is determined. In both cases (clear and cloudy sky conditions), the above is achieved through the location in real time of the maximum luminosity point (MLP) in the sky through the construction of luminosity gradients, which are obtained under the acquisition and processing of the output signals of a set of sensors constituting the HPLS. The distribution of the sensors is determined through optical and geometric analyses. The HPLS is validated through a set of experiments in which the search and signaling of the MLP were carried out on a sunny day and on days where partly sunny and cloudy conditions were present. Finally, a technical comparative analysis between the HPLS and other sensors is presented; the cost of the HPLS is $293.50 USD (obtained in a calculation performed in this work), and a cost comparison with some commercial sensors is presented as well. [ABSTRACT FROM AUTHOR]

The safety of the use of construction facilities should be a priority in today’s busy world, where it is not difficult to get involved in an accident. Most of them, due to the pace at which we live today, are caused by slips, trips, and falls. This work presents a detailed analysis of the resistance of ceramic floors to these events, taking into account the surface properties and conditions (dry/wet), which, as presented, have a significant impact on the final slip resistance values. This study also investigates the relationship between surface roughness and anti-slip properties. According to the obtained results, it can be concluded that the surface roughness is not the main determinant of slip resistance, and the final value of it is influenced by many components that should be considered together and not be neglected when designing the surface finish. Furthermore, based on experimental measurements, it can be noted that the highest slip resistance in both wet and dry conditions showed the unglazed tiles with lapatto finish and the glazed tiles without any extra finish.

The performance of a South African parabolic trough solar collector (PTSC) module has been characterised using the ASHRAE 93-1986 standard. The collector is designed for component testing and development in a solar energy research programme. Low-temperature testing was performed at Mangosuthu Technikon’s STARlab facility using water as the working fluid. Both an evacuated glassshielded receiver and an unshielded receiver were tested, with which peak thermal efficiencies of 53.8% and 55.2% were obtained respectively. The glass-shielded element offered superior performance at the maximum test temperature, desensitising the receiver to wind and reducing the overall heat loss coefficient by half. The collector time constants for both receivers indicate low thermal inertia and the measured acceptance angles exceed the tracking accuracy of the PTSC, ensuring the collector operates within 2% of its optimal efficiency at all times. Off-sun thermal loss results and the behaviour of the PTSC under increased angles of incidence are described. A description of the test system components is given.

Highlights • Two schemes are reported to enlarge the acceptance angle of a side-absorption CPV. • The measured acceptance angle is enlarged twofold by one scheme of v-groove arrays. • The simulated acceptance angle is tripled by the other of parabolic-groove arrays. Abstract Conventional planar solar concentrators own the merit of compactness but usually with some issues, such as complicated fabrication, complex assembly, low efficiency, etc. Our previous work investigated a kind of planar solar concentrators, the concentrator of the side-absorption concentrated photovoltaic system (SCPV) which consists of the single concentrating element and is rather compact, feasible for fabrication and assembly, as well as efficient. Since the angular acceptance is essential for concentrating photovoltaics, this study proposes two schemes to increase the acceptance angle of a SCPV. The first scheme optimizes the v-groove array reflector at the bottom of the concentrator by means of tracing the angular subtense of the sun, while the second scheme replaces the v-groove array with the parabolic groove by investigating a sacrifice region. The design principles and the numerical evaluations of the two schemes are reported, while the experimental results and the causes of efficiency loss are systematically analysed and discussed. The simulated results show that the acceptance angles of the first and the second schemes are enlarged by factors of 2.2 and 3.1, respectively, while the theoretical optical-efficiency of concentrator are 85.5% and 94.2%, respectively. Experimentally, the acceptance angle for the first scheme was measured as ±4.4°, equivalent to an enlargement by a factor of 2.2 and agreeing with the simulation. From comparisons between modelling and experimental results, the causes of efficiency loss are thoroughly explored, and the approaches for further efficiency enhancement are presented. Moreover, since enlarging the acceptance angle of the concentrating photovoltaics eases the maintenance and reduces the expenses of the tracker, this work highlights the potential of the reported schemes for benefitting cost reduction, maintenance, compactness and weather endurance of the concentrated photovoltaic system. [ABSTRACT FROM AUTHOR]

This paper attempts to compare three methods of testing floor slip resistance and the resulting classifications. Polished, flamed, brushed, and grained granite slabs were tested. The acceptance angle values (αob) obtained through the shod ramp test, slip resistance value (SRV), and sliding friction coefficient (μ) were compared in terms of the correlation between the series, the precision of each method, and the classification results assigned to each of the three obtained indices. It was found that the evaluation of a product for slip resistance was strongly related to the test method used and the resulting classification method. This influence was particularly pronounced for low roughness slabs. This would result in risks associated with inadequate assessments, which could affect the safe use of buildings facilities.

Abstract We present toBeeView, a program that produces from a digital photograph, or a set of photographs, an approximation of the image formed at the sampling station stage in the eye of an animal. toBeeView is freely available from https://github.com/EEZA-CSIC/compound-eye-simulator. toBeeView assumes that sampling stations in the retina are distributed on a hexagonal grid. Each sampling station computes the weighted average of the color of the part of the visual scene projecting on its photoreceptors, and the hexagon of the output image associated with the sampling station is filled in this average color. Users can specify the visual angle subtended by the scene and the basic parameters determining the spatial resolution of the eye: photoreceptor spatial distribution and optic quality of the eye. The photoreceptor distribution is characterized by the vertical and horizontal interommatidial angles—which can vary along the retina. The optic quality depends on the section of the visual scene projecting onto each sampling station, determined by the acceptance angle. The output of toBeeView provides a first approximation to the amount of visual information available at the retina for subsequent processing, summarizing in an intuitive way the interaction between eye optics and receptor density. This tool can be used whenever it is important to determine the visual acuity of a species and will be particularly useful to study processes where object detection and identification is important, such as visual displays, camouflage, and mimicry.

Concentrator Photovoltaic (CPV) technology, by using efficient optical elements, small sizes and high efficiency multi-junction solar cells, can be seen as a bright energy source to produce more cost-effective electricity. The main and basic idea is to replace the use of expensive solar cells with less expensive optical elements made from different materials. This paper aims to give to the readers a rapid and concise overview of CPV and the main characteristics to be considered when designing a CPV system. It reviews the main optical configurations presented in the literature, their advantages and drawbacks, as well as the recent progress in the concentration ratio and the major performances achieved in the field. The paper considers the more recent works, their optical designs, as well as their optical and electrical performances. It also relates the major achievements on the industrial side with the major milestones in CPV developments.

The sensitivity of a PET system highly depends on the axial acceptance angle or maximum ring difference (MRD), which can be particularly high for total-body scanners due to their larger axial field of views (aFOVs). This study aims to evaluate the impact on image quality (IQ) and noise performance when MRD85 (18°), the current standard for clinical use, is increased to MRD322 (52°) for the Biograph Vision Quadra (Siemens Healthineers)., Methods: Studies with a cylindrical phantom covering the 106 cm aFOV and an IEC phantom filled with 18 F, 68 Ga and 89 Zr were performed for acquisition times from 60 to 1800 s and activity concentrations from 0.4 to 3 kBq/ml to assess uniformity, contrast recovery coefficients (CRCs) and to characterize noise by coefficient of variation (CV). Spatial resolution was compared for both MRDs by sampling a quadrant of the FOV with a point source. Further IQ, CV, liver SUV mean and SUV max were compared for a cohort of 5 patients scanned with [ 18 F]FDG (3 MBq/kg, 1 h p.i.) from 30 to 300 s., Results: CV was improved by a factor of up to 1.49 and is highest for short acquisition times, peaks at the center field of view and mitigates parabolic in axial direction with no difference to MRD85 beyond the central 80 cm. No substantial differences between the two evaluated MRDs in regards to uniformity, SUV mean or CRC for the different isotopes were observed. A degradation of the average spatial resolution of 0.9 ± 0.2 mm in the central 40 cm FOV was determined with MRD322. Depending on the acquisition time MRD322 resulted in a decrease of SUV max between 23.8% (30 s) and 9.0% (300 s)., Conclusion: Patient and phantom studies revealed that scan time could be lowered by approximately a factor of two with MRD322 while maintaining similar noise performance. The moderate degradation in spatial resolution for MRD322 is worth to exploit the full potential of the Quadra by either shorten scan times or leverage noise performance in particular for low count scenarios such as ultra-late imaging or dynamic studies with high temporal resolution., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Fabian Schmidt and Christian la Fougère have received research support from Siemens. Maurizio Conti is a full-time employee of Siemens Healthineers. All other authors have no conflicts of interest regarding this study to report., (Copyright © 2023 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

In this paper, we compare the optical and electrical performance of different Fresnel-based HCPV systems equipped with different refractive secondary optical elements (SOEs) through both optical modelling and experiments. The SOEs (designed with a thorough optical modelling): i) Dielectric-cross compound-parabolic-concentrator (DCCPC), ii) (SIngle-Lens-Optical element) SILO-Pyramid, iii) Refractive truncated pyramid (RTP) and, iv) Trumpet; are fabricated (made of PMMA) and mounted on commercially available concentrator solar cell assemblies. An indoor characterisation of all these HCPV units, under controlled conditions, using a CPV Solar Simulator “Helios 3198” is performed. The angular behaviour of the HCPV units is predicted properly, in general, although the measured optical efficiencies result in lower values than in the optical simulations. The reasons for those differences are explored through some fabrication and mounting imperfections detected, among others. The impact of changed irradiance and spectrum is analysed separately. No high dependence in the efficiency or in the acceptance angle, in terms of the maximum power point, was found due to changes in the irradiance. For changed spectral conditions, the decrease in the fill factor results in up to around 4% lower than the maximum values. Moreover, the impact of the spectrum on the acceptance angle was analysed. The results showed an increment of the power-based acceptance angle for blue-rich spectra for the HCPV units with SOEs working as light pipes. From the results of efficiency and acceptance angle, none of the SOEs produces a notably performance than the others. [ABSTRACT FROM AUTHOR]

High Concentrator Photovoltaic (HCPV) modules (with concentrations higher than 300 times) have increased their conversion efficiency records up to more than 43% in the last years. This represents the maximum conversion efficiency by any type of photovoltaic (PV) module. Moreover, HCPV modules still have a theoretical potential for a significant efficiency growth. This work analyses the current status of efficiency records of HCPV modules and their evolution in the last 20 years, as well as the most efficient commercial HCPV modules, these last with up to around 34% efficiency nowadays. It is found that the efficiency growth of HCPV modules in the last years is considerably greater than that of other PV technologies like crystalline silicon (c-Si) or Thin Film. The values of efficiency, acceptance angle, geometrical concentration and power of current HCPV modules are gathered. Current efficiency values are typically centred in the range between 27% and 33%, whereas the current average of acceptance angle values is ± 0.9°. Regarding the geometrical concentration of the efficiency record HCPV modules, it is typically lower than 400× whereas current commercial HCPV modules work in the range of 500–1000×. Moreover, a total of 24 commercial HCPV modules were characterised indoors at the CPV solar simulator at the University of Jaén in order to compare the datasheets with the experimental data. The measurement results, including the efficiency and acceptance angle characteristics, are presented and compared with datasheet values. [ABSTRACT FROM AUTHOR]

We report analytically an electro-optically tuned non-critical phase-matched second harmonic generation of a diode pumped solid-state laser in LiNbO 3 crystal at room temperature (25 °C).The direction of propagation of fundamental wave of 1064 nm is on x-y plane, making an angle of θ = 90° with z-axis and ϕ = 33° with x-axis of the crystal. By applying an electric field of −7.87 kV/mm along z-axis of the crystal, ordinary and extra ordinary refractive indices of fundamental wave and second harmonic wave are matched to each other respectively. The calculated angular acceptance is 55.7 mrad mm 1/2 . [ABSTRACT FROM AUTHOR]

In determination of the extinction coefficient for light-scattering materials from transmission experiments, a problem arises, which is connected with unwanted contribution from the scattered light to readings of the detector of a spectrophotometer. In this paper, the problem is discussed for the case of nanostructured nonabsorbing glass-ceramics. For the detector of the spectrophotometer Shimadzu UV 3600, the acceptance angle was determined to be about 6°. The methods are proposed for determination of the critical value of optical density, exceeding of which leads to an appreciable measurement error associated with falling the scattered light into a detector. The methods are based on study of the spectral behavior of the optical density or extinction coefficient. If the acceptance angle of the detector is about 6° and the refractive index of the nanostructured material exceeds 1.6, the critical value of optical density was experimentally found to be approximately 2. [ABSTRACT FROM AUTHOR]

Introduction: In iodine-131 (I-131) imaging, the image quality is degraded by scatter and penetration in a collimator. In this work, we assessed the penetrated and the scattered photon fractions in the photopeak energy window using Monte Carlo Simulation code. Materials and Methods: The Siemens Medical System equipped with high-energy collimator was simulated. We evaluated the acceptance angle values on geometric, penetration, and scatter components in a separate file. Binary images in a data file are obtained and each one of them was imported in software ImageJ. Full-width at half-maximum (FWHM) and sensitivity were calculated and compared. Results: The simulation data show that for the acceptance angle value equal to 4.845°, the geometric, scatter, and penetration components were 93.20%, 4.13%, and 2.67%, respectively. Moreover, the resolution is improved (FWHM = 7.21 mm, full width at tenth maximum = 12.36 mm) for a point source at 12 cm from the detector. Conclusion: The small acceptance angle has a major impact on the image quality in I-131 single photon emission computed tomography. [ABSTRACT FROM AUTHOR]