Solar Incidence Angle Research Articles

AI-Driven Particulate Matter Estimation Using Urban CCTV: A Comparative Analysis Under Various Experimental Conditions

Despite the high public interest in particulate matter (PM), a key determinant for indoor and outdoor activities, the current PM information provided by monitoring stations (e.g., data per administrative district) is insufficient. This study employed the closed-circuit television (CCTV) cameras densely installed within a city to explore the spatial expansion of PM information. It conducted a comparative analysis of PM estimation effects under diverse experimental conditions based on AI image recognition. It also fills a gap by providing an optimal analysis framework that comprehensively considers the combination of variables, including the sun’s position, day and night settings, and the PM distribution per class. In the deep learning model structure and process comparison experiment, the hybrid DL-ML model using ResNet152 and XGBoost showed the highest predictive power. The classification model was better than the ResNet regression model, and the hybrid DL-ML model with the post-processed XGBoost was better than the single ResNet152 model regarding AI prediction of PM. All four experiments that excluded the nighttime, added the solar incidence angle variable, applied the distribution of PM per class, and removed the outlier removal algorithm showed high predictive power. In particular, the final experiment that satisfied all conditions, including the exclusion of nighttime, addition of solar incidence angle variable, and application of outlier removal algorithm, derived predictive values that are expected to be commercialized.

Design and Implementation of a Dual-Axis Solar Tracking System with IoT-Enhanced Monitoring Using Arduino

The position of the sun varies over the day and with the seasons, making it difficult for conventional fixed solar panel systems to achieve optimum energy production. By reorienting the panels to face the sun, solar tracking systems solve this problem. This study suggests a dual-axis solar tracker system that continuously adjusts the panels to stay perpendicular to sunlight in order to maximize energy capture. The system uses sensors to monitor the sun's elevation and azimuth angles. Light sensors, motor controllers, microcontrollers, control algorithms, and an Internet of Things (IoT) monitoring system are some of the system's essential parts. The microprocessor determines the ideal angles for panel alignment based on the location of the sun as detected by the light sensors. The motor driver then adjusts the panels appropriately. The sun's position is accurately and smoothly tracked using dual-axis tracking systems, which employ sensors to detect solar position and actuators controlled by sophisticated algorithms to adjust the panels accordingly. Real-time parameter monitoring of the solar panel is done using an IoT-enabled webpage. The study's findings show that the dual-axis solar tracker system performs noticeably better in terms of energy capture efficiency than fixed installations, especially in areas with high solar incidence angles and fluctuating sunshine.

The Global Distribution of Water and Hydroxyl on the Moon as Seen by the Moon Mineralogy Mapper (M3)

The Moon Mineralogy Mapper (M3) on the Chandrayaan-1 spacecraft provided nearly global 0.5–3 μm imaging-spectroscopy data at 140 m pixel–1 in 85 spectral bands. Targeted locations were imaged at 70 m pixel–1 and higher spectral resolution. These data enable a detailed look at the mineralogy, hydroxyl, and water signatures exposed on the lunar surface. We find evidence for multiple processes, including probable solar wind implantation, excavation of hydroxyl-poor and water-poor material in cratering events, excavation of hydroxyl and water-rich materials from depth and global trends with rock type and latitude. Some water-rich areas display sharp boundaries with water-poor rocks but have a diffuse halo of hydroxyl surrounding the water-rich rocks indicating a weathering process of destruction of water, probably due to a regolith gardening process. Mapping for specific mineralogy shows evidence for absorptions near 2.2 μm, probably associated with smectites, and near 1.9 μm due to water. Lunar swirls are confirmed to be OH-poor, but we also find evidence that swirls are water-poor based on a weak 1.9 μm water band. Some swirls show enhanced pyroxene absorption. “Diurnal” signatures are found with stable minerals. Pyroxene is shown to exhibit strong band depth changes with the diurnal cycle, which directly tracks the solar incidence angle and is consistent with changing composition and/or grain size with depth. Mapping of M3 data for the presence of iron oxides (e.g., hematite and goethite) is found to be a false signature in the M3 data due to scattered light in the instrument.

Variation in Reflected Beam Shape and Pointing Accuracy Over Time and Heliostat Field Position

Heliostats are typically constructed with fixed mirror shapes, which they move to varying angles to reflect sunlight onto a receiver. While heliostat facet curvatures and canting angles are selected to maximize a chosen performance criterion, these fixed shapes inevitably cannot maintain focus throughout widely varying solar incidence angles. Further, heliostat pointing accuracy generally exhibits error due to manufacturing and installation imperfections. In this paper we present a systematic study of how reflected beam shape and pointing accuracy vary with heliostat position, time of day, and time of year. We selected nine heliostats spanning the Sandia National Laboratories National Solar Thermal Test Facility (NSTTF) heliostat field, and measured their beam shape and required pointing corrections throughout the day, for six key dates spanning a solar year. We also present ray tracing analysis to aid understanding of the observed effects. The resulting data provide insight into the nature and magnitude of heliostat focus loss at various times, and clarify the nature of the problem faced when attempting to maximize heliostat field performance, especially for high-temperature industrial applications. We conclude that fixed heliostat fields canted with an off-axis strategy will lose significant performance away from the solar noon hour to which they are tuned, and that aim point corrections can vary widely, both between independent heliostats and over time for a given heiostat. This implies that multiple measurements of each heliostat are required to determine calibration pointing corrections.

An Experimental Assessment of the Performance of Solar Panels Using Efficiency Enhancement Techniques in India's Tropical Region

<p style="text-align:justify"><span style="font-size:11pt"><span style="line-height:normal"><span style="font-family:Calibri,sans-serif"><span lang="EN-US" style="font-size:10.0pt"><span style="color:black">Due to its abundance and lack of pollution, solar energy will soon be the most popular source of electricity production. Numerous factors, including the temperature effect, solar irradiance effect, shadow effect, incident angle effect, dust accumulation on the solar cell, shunt resistance, types of solar cell materials, mechanical defects in the solar panel, spectral mismatch loss, cable loss, maintenance and cleaning cycle, load mismatching effect, etc., harm the efficiency of solar P.V. power generation systems. This study aims to quantify the impact of these factors and explore efficiency enhancement techniques to mitigate their effects. Among the various factors, solar irradiation and temperature significantly influence solar P.V. panel efficiency. This research investigates the effects of solar irradiation, incident angle, and temperature through simulations and experimental methods using two 100W solar panels. Efficiency enhancement techniques like sensor-based sun tracking and temperature cooling systems are incorporated with conventional solar P.V. power generation systems. The experimental results prove that the efficiency enhancement techniques improved the efficiency of solar panels by up to 12% compared to conventional solar panels.</span></span></span></span></span></p>

Solar radiation on naturally ventilated double skin facade in real climates: The impact of solar incidence angle

Although the angular dependence of optical properties has long been recognised in transparent glazing facades, the impact of such dependence on natural ventilation between glazing has not been widely studied, especially in building facades with high solar incident angles. To better cope with such properties with the prevailing implementation of transparent building envelopes, this study investigated the effects of high solar incidence angles for vertical building facades through theoretical and numerical methods. The theoretical model validates the features of the optical properties simulated by the numerical model, supporting the numerical model's capability of revealing the radiation reflection, absorption, and transmission when multi-reflection is present. Then, such angular impact is studied with typical seasonal data in three cities, namely Shanghai, Melbourne and Chicago. Results firstly revealed the discrepancies between considering or ignoring multi-reflection between two glazing facades at varying incidence angles. Due to the opposite variation trend in reflectivity and transmissivity over angles, there is a critical solar incidence angle at 75° when multi-reflection's impact on natural ventilation reaches its highest. After that, the influence is reduced to its minimum. Identifying this angle helped highlight the enhanced natural flow due to realistic angular-dependent reflections between transparent panes, namely, under-estimation occurs if the angular dependence is not considered in the setting of optical properties. The analysis in three cities also revealed the climatic and locational impact of the angular impacts on ventilation rates. By addressing the impact on the optical and thermal performance of transparent facades, the dynamic variation of solar conditions can be more accurately integrated into passive building designs.

Seasonal Variation of Saturn's Lyα Brightness

We examine Saturn’s nonauroral (dayglow) emissions at Lyα observed by the Cassini/Ultraviolet Imaging Spectrograph (UVIS) instrument from 2003 until 2017, to constrain meridional and seasonal trends in the upper atmosphere. We separate viewing geometry effects from trends driven by atmospheric properties, by applying a multivariate regression to the observed emissions. The Lyα dayglow brightnesses depend on the incident solar flux, solar incidence angle, emission angle, and observed latitude. The emissions across latitudes and seasons show a strong dependence with solar incidence angle, typical of resonantly scattered solar flux and consistent with no internal source such as electroglow. We observe a bulge in Lyα brightnesses that shifts with the summer season from the southern to the northern hemisphere. We estimate atomic hydrogen optical depths above the methane homopause level for dayside disk observations (2004–2016) by comparing observed Lyα emissions to a radiative transfer model. We model emissions from resonantly scattered solar flux and a smaller but significant contribution by scattered photons from the interplanetary hydrogen (IPH) background. During the northern summer, inferred hydrogen optical depths steeply decrease with latitude toward the winter hemisphere from a northern hemisphere bulge, as predicted by a 2D seasonal photochemical model. The southern hemisphere mirrors this trend during its summer. However, inferred optical depths show substantially more temporal variation between 2004 and 2016 than predicted by the photochemical model. We benchmark our brightness values by comparing observed IPH Lyα emissions from Cassini/UVIS in 2006 with a model of the IPH emissions. Cassini/UVIS observations agree well with the modeled IPH background.

Comparing the quantum use efficiency of red and far-red sun-induced fluorescence at leaf and canopy under heat-drought stress

Sun-Induced chlorophyll Fluorescence (SIF) is the most promising remote sensing signal to monitor photosynthesis in space and time. However, under stress conditions its interpretation is often complicated by factors such as light absorption and plant morphological and physiological adaptations. To ultimately derive the quantum yield of fluorescence (ΦF) at the photosystem from canopy measurements, the so-called escape probability (fesc) needs to be accounted for.In this study, we aim to compare ΦF measured at leaf- and canopy-scale to evaluate the influence of stress responses on the two signals based on a potato mesocosm heat-drought experiment. First, we compared the performance of recently proposed reflectance-based approaches to estimate leaf and canopy red fesc using data-supported simulations of the radiative transfer model SCOPE. While the leaf red fesc showed a strong correlation (r2 ≥ 0.76), the canopy red fesc exhibited no relationship with the SCOPE retrieved red fesc in our experiment. We therefore propose modifications to the canopy model to address this limitation.We then used the modified models of red fesc, along with an existing model for far-red fesc to analyse the dynamics of leaf and canopy red and far-red fluorescence under increasing drought and heat stress conditions. By incorporating fesc, we obtained a closer agreement between leaf and canopy measurements. Specifically, for red fesc, the r2 of the two variables increased from 0.3 to 0.50, and for far-red fesc, from 0.36 to 0.48.When comparing the dynamics of the quantum yield of red and far-red fluorescence (ΦF,687 and ΦF,760) under increasing stress, we observed a statistically significant decrease of both leaf and canopy ΦF,687 as well as leaf ΦF,760, as drought and heat conditions intensified. Canopy ΦF,760, on the contrary, did not exhibit the same trend, since measurements under low stress conditions showed a wider spread and lower median than under high stress conditions. Finally, we analysed the sensitivity of ΦF,687 and ΦF,760 to changing solar incidence angle, by comparing the variability of the measurements without and with mesocosm rotation. Our results suggest that the variation in ΦF,760 strongly increased with changing solar incidence angle. These findings highlight the need for further research to understand the causes of discrepancies between leaf and canopy scale ΦF,760. On the contrary, the underutilised and understudied ΦF,687 showed great potential in assessing plant responses to drought and heat stress.

Analysis of Solar Radiation Differences for High-Voltage Transmission Lines on Micro-Terrain Areas

The stable operation of high-voltage transmission lines is significantly affected by atmospheric icing. Research on the physical processes of icing and de-icing of transmission lines in micro-terrain, as well as the factors affecting them, is a crucial theoretical foundation for enhancing current icing prediction capabilities and guiding the planning of transmission lines in mountainous areas. The difficulty lies in the fact that, unlike the calculation of surface radiation, the amount of radiation received by the lines is affected by a combination of terrain, environmental shading, and the orientation of the lines. Therefore, this work initially establishes a method for calculating the total amount of radiant heat received per unit length of the line throughout the day at various heights from the ground, based on the angle of solar incidence and the three-dimensional spatial position of the lines. Furthermore, a method of mapping the regional heat radiation by gridding the direction of the lines was proposed, providing the daily heat radiation and equivalent Joule heat. The proposed mapping method supports anti-icing planning for high-voltage transmission lines in micro-terrain areas.

Development of solver with user interface for surface radiative exchange based on OpenFOAM platform

Surface radiative exchange is widely used in the fields related to industrial and environment. Accurate and rapid calculation of the surface radiant heat flux can predict and prevent accidents. In this study, a solver for surface radiative exchange based on the OpenFOAM platform is developed. The solver’s accuracy can be verified by calculating the net heat rate of the cubic cavity and the triangular-prism geometries. The solarLoad radiation model is used to study the variation of heat flux with respect to the solar incidence angle for a satellite in orbit and a human standing in a room with a window. Finally, a Graphical User Interface (GUI) based on the PyQt5 for this solver is developed to simplify the operation process and make the solver user-friendly.

Optimization of the Diameter of CdS Nanowires Embedded in a CZTS Buffer Layer under Different Solar Incidence Angles

Optimization of the Diameter of CdS Nanowires Embedded in a CZTS Buffer Layer under Different Solar Incidence Angles

Multilayer stacked ultra-wideband perfect solar absorber and thermal emitter based on SiO2-InAs-TiN nanofilm structure.

In this paper, a broadband solar absorber is constructed and simulated based on the finite difference time domain method (FDTD). The modeled structure of the absorber consists of cyclic stacking of five absorber cells with different periods on refractory metal W, where a single absorber cell is composed of a three-layer SiO2-InAs-TiN square film. Due to the Fabry-Perot resonance and the surface plasmon resonance (SPR), an absorptivity greater than 90% within a bandwidth of 2599.5 nm was achieved for the absorber. Notably, one of these bands, 2001 nm, is a high-efficiency absorption with an absorption rate greater than 99%. The average absorption efficiency reaches 99.31% at an air mass of 1.5 (AM 1.5), and the thermal radiation efficiencies are 97.35% and 97.83% at 1000 K and 1200 K, respectively. At the same time, the structure of the absorber is also polarization-independent, and when the solar incidence angle is increased to 60°, it still achieves an average absorption of 90.83% over the entire wavelength band (280 nm to 3000 nm). The novelty of our work is to provide a design idea based on a unit structure with multiple cycles, which can effectively expand the absorption bandwidth of the absorber in the visible-near-infrared wavelengths. The excellent performances make the structure widely used in the field of solar energy absorption.

A study on the model of solar radiation transfer in multi-layer glass facade with attached droplets

To obtain the optical properties of the spray cooling double skin façade (SC-DSF), a solar radiation transfer model of the multi-layer glass system with attached droplets is proposed in this study. The solar radiation is segmented into direct and diffuse radiation, and the monte carlo ray tracing method and angle discretization method are used to obtain the optical properties of the single layer glass with attached droplets. And then, the energy balance equation of the multilayer glass system is established based on the net-radiation method, and the transmittance, reflectance and absorptance of the multilayer glass system are calculated. The effectiveness of the proposed method is verified by the experimental results, which shows the numerical results are in good agreement with the experimental data. In addition, some important influence factors are analyzed and discussed, including the solar incidence angle, the droplet contact angle, the droplet coverage rate, and the average droplet diameter. It is found that there is little influence on the system transmittance when the incidence angle is smaller than 40°. However, the transmittance decreases with the increase of the incidence angle when the solar incidence angle is greater than 40°. When the droplet contact angle is small (less than 40°) or large (larger than 140°), its influence on the transmittance of the system is negligible. Subsequently, with the increase in the droplet contact angle within 40–140°, the transmittance firstly decreases and then increases. Adjusting the droplet coverage rate and droplet size is an effective measure to decrease transmittance and solar heat gain.

Parametric evaluation of solar integrated combined partial cooling supercritical CO2 cycle and Organic Rankine Cycle using low global warming potential fluids

In this study, the performance of the organic Rankine cycle combined with the partial cooling supercritical CO2 cycle as the bottoming cycle for recovering the low grade heat powered by a solar power tower was evaluated. Ecofriendly fluids were taken into consideration. To simulate the model under consideration, a computer programme was created in engineering equation solver software. The impacts of solar radiation, concentration ratio, solar incidence angle, CO2 turbine inlet temperature, heat exchanger effectiveness and main compressor inlet tempera-ture were investigated. Based on working fluid R1224yd(Z), it was determined that the com-bined cycle’s thermal efficiency, exergy efficiency, and power output improved from 35.16% to 55.43%, 37.73% to 59.42%, and 188 kW to 298.5 kW, respectively, as solar irradiation raised from 0.4 kW/m2 to 0.95 kW/m2. Lower the solar incidence angle and higher the concentration ratio can enhance the combined system’s performance. Amongst the working fluids that were taken into account, R1224yd(Z) was suggested as having superior performance.

Assessment and ANN model development of natural light transmittance of light-transmitting concrete

This study aims to reveal the potential of Light-transmitting concrete (LTC) in transmitting natural light or sunlight, and to investigate the relationship between fibre diameter, fibre spacing, solar incidence angle, surface area, and light transmittance properties. The artificial neural network model as well as explicit equations from the model were developed to predict the light transmittance of LTC. The surface area was altered by varying LTC block arrangements from one to six. It was found that light incidence angle significantly affected the light transmittance of LTC. The highest light transmittance of LTC was achieved near solar noon, but it decreased drastically as soon as the solar incidence angle exceeded the acceptance angle. The effect of the LTC surface area and solar incidence angle on light transmittance diminished with a smaller fibre diameter or larger fibre spacing. The ANN model and explicit equations developed from the network provide good accuracy in predicting light transmittance of LTC.

Comprehensive analyses of solar thermal module with booster mirror integration for adaptation to various application scenarios

Integration of a booster mirror reflector enhances the performance of evacuated tube collector within a prescribed range of solar incidence angles and reject solar rays within others. Seasonal performance adjustment makes it possible to adapt to various scenarios with different seasonal application purposes, for example, only domestic hot water, only space heating, or both. In this study, a mathematical model describing the photo-thermal conversion of this solar module was developed and validated using experimental data. The dynamic contributions of the collector and mirror planes were decomposed, and the optimal combination configurations for adaptation to three different application scenarios in four representative Chinese cities were investigated through the rotation of both planes. The three scenarios were: Scenario 1, annual performance augmentation; Scenario 2, coldest month performance augmentation; and Scenario 3, winter performance augmentation and prevention of summer overheating. It was found that optimal performance was always achieved when the collector plane was perpendicular to the mirror plane in the three scenarios. Depending on the optimal configurations, in Scenario 1 the mirror reflector contributed 30–32% heat energy, in Scenario 2 the mirror reflector contributed 41–49% heat energy during the coldest months, and in Scenario 3 the mirror reflector contributed 40–47% heat energy during the entire heating season. The objective of this study was to develop a comprehensive tool to evaluate the photo-thermal performance of this solar module and determine optimal configurations for various application scenarios.

Towards accurate stereo-video based free-surface reconstruction for wave tank experiments

Measuring accurately the shape of the free surface in medium-scale hydrodynamic testing facilities is challenging with conventional wave gauges. To overcome this problem, it is necessary to go towards higher resolution measurement systems. For this purpose, we investigate the ability of stereo-video acquisition systems to reconstruct free surface waves in laboratory conditions. This technique has been proven to give satisfactory results in open sea conditions, although it is dependent on the environmental conditions (weather, solar incidence angle). At sea, the stereo-video reconstruction algorithm makes profit of the short waves generated by the wind in order to correlate the points from the left and right images. The main challenge of adapting this technique to laboratory conditions, i.e. in absence of sun and wind, is to overcome the absence of texture on the free surface. This paper presents recent work aiming at developing a stereo-vision measurement system for laboratory conditions. Our efforts have been devoted to finding an adapted lighting system and generating a texture suitable for the reconstruction algorithm. Different lighting configurations have been tested in order to understand its impact on the reconstructions. For the texture generation, we have investigated different means of generating short surface waves (water droplets, air blowing, circulation current, underwater acoustic emissions) in different experimental facilities. Our conclusions show that it is possible to reconstruct the shape of surface gravity waves in the presence of short surface waves and that the effects of lighting and texture on the quality of the reconstruction are strongly coupled.

Numerical Simulation of the Lunar Polar Environment: Implications for Rover Exploration Challenge

The lunar polar regions are key areas for future exploration due to the long-term continuous illumination and persistently shadowed regions that can cold trap abundant water and other volatiles. However, the complex terrain, dynamic lighting, and solar wind-induced electric-field environment present multiple challenges for polar investigation and sampling missions. China’s Chang’E-7 (CE-7) will explore the Moon’s south polar region in 2026. One of the scientific goals is to drill samples in a wide area with a rover for in situ analysis. This study analyzes the engineering constraints of the polar illumination condition, slopes, and electric field for landing and sampling-site selection. Then, we create a 3D model of CE-7’s lunar rover in three operating environments by employing the Spacecraft Plasma Interaction Software, with the rover sampling (i) on a flat surface, (ii) in a shadow, and (iii) near a meter-scale crater under different solar altitude angles. The results show that the rover can be charged to different potentials under the combined effects of solar wind incident angles and surrounding terrains. We find that a favorable traversing and/or sampling site of the rover for future polar exploration is in the upwind direction of a bulge (positively elevated terrains, such as the lander or boulders) or crater, which will cause a minimum charging effect on the rover. Our results have important implications for minimizing the risk of charging effects and guiding the lunar polar region exploration.

A thermal similarity model of a curved double-skin façade

Curved double-skin façades (CDSFs) have been widely used as building envelopes that combine the advantages of aesthetic and energy-saving. However, because of its complex structure and airflow, it is difficult to be precisely reduced in experiments and has been barely studied in the existing literature. Hence, a thermal similarity mathematical model for the CDSF is developed and validated by using methods combining CFD and experiments. The validation results show a good similarity between the reduced-scale model and the full-scale model. On this basis, the influence of dimensionless numbers, boundary conditions, size and appearance on the similarity are analyzed. The results show that the similarity improves with the increment of the Reynolds number until it reaches the self-similarity region. And the Grashof number shows a significant impact on the similarity when the Richardson number >1. So, it is necessary to ensure that the Richardson number <1 when the similarity of the Grashof number cannot be guaranteed. Moreover, solar radiation intensities between 200 W/m2 and 400 W/m2 and solar incident angles between 45° and 60° show the best similarity between the reduced-scale model and full-scale model. The scale of the model has a significant effect on the similarity and is recommended between 1/20 and 1/50 for large buildings with CDSFs. Besides, a smaller ellipse aspect ratio shows a better similarity between the two models. Therefore, a scaled CDSF model with ellipse aspect ratios less than 1 exhibits better validity compared to models with the ratio larger than 1.

Investigation of thermal performance of a parabolic trough solar collector using different heat transfer fluids

ABSTRACT Parabolic trough solar collectors (PTSCs) are the most versatile and reliable solar collectors that could achieve higher temperatures, making them employed over diversified areas like industrial and domestic applications. Understanding the working principle of PTSC as well as enhancing their performance and efficiency for better reliability is highly relevant at present, as we are in dire need of a shift toward reliable renewable sources of energy. A non-tracking, feasible, and locally scalable simple PTSC with moderate performance and temperature output has been used in this experiment. The receiver is a significant part of the collector system, carrying the heat transfer fluid (HTF), and determines the performance and output of the PTSC to a great extent. In this study, two receiver configurations, one being an evacuated tube and another a simple copper tube with a glass cover, are employed, and a comparative analysis is performed. Two different blends of water and thermal oils as HTF are also employed, and their influence on the performance of the PTSC under both receiver configurations is evaluated. Initially, water is used as the HTF, and gradually, 0.5% of Hytherm 600 thermal oil is blended in every hour, and the results are monitored. Similarly, Therminol 55 is also blended with water at a similar rate as the HTF and output readings are observed. The experimental results confirmed that the evacuated tube configuration yielded the best overall system efficiency of 55.4% in the case of both HTFs. Comparing the performance of different oil and water blend as HTF, Hytherm 600 exhibits better performance than Therminol 55, up to 32% higher efficiency in evacuated tube configuration. The best efficiency of the system was exhibited during the noon when the solar incidence angle was close to zero and the optical efficiency reached up to 71.6%.