Solar Azimuth Research Articles

Solar Elevation Angle and Solar Culmination Determination using Celestial Observation; A Case Study Of Hadejia Jigawa State, Nigeria

The world typically depends on renewable resources because of its zero-emission. The most important and available resource is solar energy, which is found almost accessible in each and every location of the world. Solar energy is among the abundant renewable resources and is the alternative most fundamental sources of energy. It is mandatory to determine the solar azimuth angle, solar altitude angle together with the understanding of solar culmination relatively to the time and collection device location. This work was conducted in Hadejia Jigawa state of northern Nigeria. The main objective of this study was to identify the maximum and minimum solar elevation angle (SEA), solar azimuth angle (SAA), solar culmination (SC) and questions of time (EOT) of the study area. Keisan online calculator was used as a method to track the sun path/position and corresponding data such as solar altitude and azimuth angle, culmination and equations of time. Keisan calculator can be used trace sun specific location for any spatial location of the earth. The results shows 178 0 SAA, maximum SC 12:34:02, maximum SEA 850 and maximum EOT 16.323 respectively. The findings of this paper will help decision-makers and engineers understand the peak sun angle, sun path/position and also use for solar harvesting technology in the study, especially during solar panels installation.

Research on Analysis Method of Shading and Blocking of LFR Field

Shading and blocking problem is the main element restricting efficiency of a LFR system. The traditional analysis methods often need to build the models by using SolTrace, which results in the low efficiency. According to characteristics of single axis tracking of the LFR field, a plane right-angle coordinate system was established, and coordinate equations of reflectors at any time were deduced. Lengths of shading and blocking were got by tracking sun rays which fell on the reflectors and reflected the receiver passing through the adjacent reflector endpoints at any time. Offset caused by the solar azimuth in the shading and blocking area was got by geometrical optics. And then, the shading and blocking efficiency could be calculated. For the Puerto Errado 1 solar thermal plant, the shading and blocking efficiencies on vernal equinox hardly changed; on summer solstice, they were smaller at sunrise and sunset, and gradually stable and close to the value of spring equinox with the increase of solar altitude angle; they were smaller on winter solstice and the change with time were larger. The results of the calculations were good agreement with the simulation dates of SolTrace, and validity of the method was proved.

A MODEL SIMULATION OF THE SOLAR ENERGY IMPINGING ON THE GIZA PYRAMIDS

A simulation model of the solar energy impinging on stone blocks is made to ascertain theimpact of solar radiation on the walls of the Pyramids of Giza, Egypt. The model considers thesolar radiation hitting the upper surface, and the vertical sides of stone blocks on the four walls.The calculation concerns: the solar height and azimuth; the daily total amount of solar radiation;the instantaneous values of the flux of solar radiation. The results are reported and discussed,pointing out the main features of the daily and seasonal cycles, as well as the impact on thevarious exposures.

Seasonal and Diurnal Change of NDVI from UAV Imagery in Clear Day Condition

Recent advanced UAV (Unmanned Aerial Vehicle) technology supply new opportunities for estimating crop condition using high resolution imagery. The objective of this study was to analyze the change of vegetation index in UAV imagery according to sun altitude. This study was conducted using a fixed-wing UAV, called Ebee, with Cannon S110 camera from November 2017 to September 2018 in the grass experiment of National Institute of Agricultural Sciences on a clear day. As a result, the NDVI (Normalized Difference Vegetation Index) of UAV imagery decreased after 9 a.m. and showed a minimum value at 13 a.m. and increased since then. The solar zenith angle and the NDVI of UAV imagery showed a positive linear relationship. Therefore, in order to quantitatively compare and analyze the time series vegetation index, it is necessary to establish a UAV flight plan considering the change of solar zenith angle. It is thought that it will be necessary to examine cloudy days with various crop in the future. Relationship between solar zenith angle and NDVI calculated by UAV imagery.

Energy sustainability performance of a sliding cover solar greenhouse: Solar energy capture aspects

A new-type of Sliding cover Energy-saving solar Greenhouse (SEG) has been developed. It is addressing several structural problems of traditional solar greenhouses, mainly energy capture and balance features. At northern latitudes, solar irradiance in wintertime is limited, which, along with extreme low outside temperatures, raises many energy sustainability issues. Capturing incident energy primarily depends on south-facing shape and cover transmittance characteristics, and this paper sets out an analysis framework for heat gain, leaving out other heat balance conservation factors (insolation). A circular shape has been selected for the SEG and is compared to Liaoshen-type Solar Greenhouse (LSG) that uses an elliptical south shape, used in traditional Chinese solar greenhouses. The SEG replaces passive north wall heat storage of LSG with active heat storage in water, thus creating an advantage in stored energy management. The shape factors and aperture efficiencies of the two designs were analysed and experimentally assessed during typical clear-sky days in four seasons. This provides a theoretical basis for structural and environmental optimisation. The design of SEG moved the ridge forward and increased the lighting roof angle, resulting in better solar radiation capture for winter sun altitudes. The newly-introduced SEG design exhibits better winter energy capture and less summer cooling load and features, by construction, and better performance in many other aspects, including potential automatic intelligent management actions. In addition to the SEG's energy capture analysis, along with briefing on light and temperature superiority, the design may also compensate for its higher constructional cost by superior automation capacity that calls for a combined holistic intelligent solution and offers many operational sustainability advantages.

A novel algorithm for estimating the relative rotation angle of solar azimuth through single-pixel rings from polar coordinate transformation for imaging polarization navigation sensors

Polarized skylight provides navigation compass for many polarization sensitive birds and insects. In this paper, a method based on polar coordinate transformation (PCTA) is proposed to use all the polarization information of the polarization angle image. First, a polar coordinate system is set up on the image of angle of polarization (AOP), and then the single pixel ring corresponding to each pole diameter is extracted. After that, the corresponding point of the same pixel value is found from the two consecutive single pixel rings, and the relative rotation angle of the solar meridian is calculated according to the trigonometric relationship. Finally, simulation and outdoor experiments are performed. The algorithm is preliminarily tested and the accuracy of the simulation is in −0.004°∼+0.045°. The outdoor static experiment is carried out on a roof of a building on campus. The experiment shows that the outdoor static experimental precision is within 0.63°. In order to be applied to the estimation of the actual carrier rotation angle, the dynamic application research experiment is carried out. The center region is chosen as the true value of AOP. The error is about −0.7°∼+0.5°. It proves that the proposed algorithm is effective and accurate.

Predicting Climate-Driven Habitat Shifting of the near Threatened Satyr Tragopan (Tragopan Satyra; Galliformes) in the Himalayas

Current rates of climatic change will affect the structure and function of community assemblages on Earth. In recent decades, advances in modelling techniques have illuminated the potential effects of various climatic scenarios on biodiversity hotspots, including community assemblages in the Himalayas. These techniques have been used to test the effects of representative concentration pathways (RCPs) AR5-2050, based on future greenhouse gas emission trajectories of climate change scenario/year combinations, on pheasants. Current bioclimatic variables, Miroc-esm, Hadgem2-AO and Gfdl-cm3, in future climate change scenario models, were used to predict the future distribution and the gain/loss of future habitat area, within the Himalayas, of the pheasant, Satyr Tragopon (Tragopan satyra). The results indicate that future climatic conditions may significantly affect the future distribution of Satyr Tragopon and the effectiveness of protective areas (PAs). Using the python based GIS toolkit, SDM projection, regions of high risk under climate change scenarios were identified. To predict the present distribution of the species, environment parameters of bioclimatic variables, red reflectance, blue reflectance, solar azimuth angle, altitude, slope, aspect, NDVI, EVI, VI, and LCLU were used. The forest cover (NDVI) and the canopy cover (EVI), and variables affecting forest structure, namely altitude, slope, solar azimuth angle and Bio7, were the primary factors dictating the present distribution of T. satyra. The predicted trend of habitat shifting of T. satyra in the Himalayas to higher altitudes and latitudes will gradually become more prominent with climate warming.

A COMPUTATIONALLY CHEAP TRICK TO DETERMINE SHADOW IN A VOXEL MODEL

Abstract. Representation of scenes on the Earth surface by using voxels is gaining attention because of its suitability for integrating heterogeneous data sources in simulations and quantitative models. Computation of shadows in such models is needed, for example, to obtain crop suitability of agricultural fields in the presence of trees and buildings, or to analyze urban heat island causes and effects. We present an efficient algorithm to compute which of the voxels in a dataset receive direct sunlight, given the solar azimuth and elevation angles. The algorithm can work with multiple (sparse and dense) voxel storage strategies.

ABSORBER PLATES POSITION INFLUENCE ON SOLAR COLLECTOR OPERATION EFFICIENCY

In order to increase the operating efficiency of solar power generating system its absorbing surface must be continuously turned towards the Sun. Modern Sun tracking systems are analyzed. Operation of solar air wall-type collector is considered. Collector’s absorber plates were situated in two ways – horizontally and vertically. Operation of the collector with horizontally situated plates is to turn of the plates towards the Sun according to solar altitude angle. Vertically situated plates position depends on solar azimuth angle. Cross shading of the absorbers plates during Sun tracking is calculated. To estimate the collector efficiency its operation within two days of the year (1.01.2016 and 11.06.2016) is studied. In order to compare the collectors’ characteristics with different types of the absorber the mathematical model is built.

Improvement of light-shelf performance through the use of a diffusion sheet

Several studies have addressed the issue of increases in the energy consumption associated with lighting in buildings. The light-shelf is a natural lighting system that efficiently reduces the amount of energy consumed for lighting by drawing natural light into a room through reflection. However, the performance of the light-shelf is reduced as a result of external environmental factors, such as the solar azimuth, and it can also produce glare while drawing natural light into the room. The present study examined the use of a light-shelf with a diffusion sheet, with the goal of improving LED lighting efficiency and reducing glare, and set out to validate its efficacy by evaluating its performance according to the position at which the diffusion sheet was attached. As part of the present study, performance evaluation cases were configured according to the diffusion sheet application and attachment position, and evaluations were conducted using a full-size test-bed. It was found that a conventional light-shelf brought more light into a room than that with the diffusion sheet, but glare was generated at certain angles in each season. However, the proposed light-shelf with the diffusion sheet attached to the upper window glass was analyzed and found to be effective at reducing lighting energy consumption by 2% while improving the glare and uniformity compared to that of a conventional light-shelf. This study is meaningful since it establishes the basic data for future light shelf design by deriving relevant variables and considering lighting energy reduction and glare.

Study on skylight polarization patterns over the ocean for polarized light navigation application.

Polarized skylight navigation has excellent navigation performance with no error accumulation over time and low susceptibility to interference. The skylight polarization distribution contains rich directional information, such as the solar meridian, the neutral point, and the polarization angle, which plays a key role in the polarization navigation. But up to now the polarizations of both sunlit and moonlit skies have been investigated mainly over the land. In this work, the polarization distribution patterns of the skylight over the East China Sea and the Yellow Sea were studied. The polarization patterns were captured continuously during daytime and nighttime by using a full-sky imaging polarimetry system and then compared with the simulation results using the libRadtran radiative transfer software package. The result shows that the skylight polarization distribution over the sea has almost the same pattern as that on the land. The accuracy of the angle of polarization and the degree of polarization dropped significantly under the cloudy sky. It was found that when the ship sailed on the sea, the direction of the real meridian was close to the solar azimuth during the daytime and close to the lunar azimuth during the nighttime. It was also found that the nautical twilight polarization distribution was affected by both the solar polarization and the lunar polarization, but the solar polarization was dominant. The experiments show that the skylight polarization distribution pattern over the sea can still be applied in the field of polarization navigation. Thus, it is feasible for ships and unmanned aerial vehicles to use the polarized skylight to navigate and orient on the sea.

The Dawn Sky Brightness Observations in the Preliminary Shubuh Prayer Time Determination

<span class="mceitemhidden"><span lang="IN">The indication of began to enter the shubuh prayer time is when emerge the morning dawn and lasted until the sun rises. The sun</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="hiddensuggestion"><span lang="IN">position</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="mceitemhidden"><span lang="IN">when emerge the morning dawn is below the intrinsic horizon marked with a minus sign (-) with the value of a certain height. The Ministry of Religious Affairs has set the sun altitudes of dawn in the shubuh prayer time with minus (-) 19°+ sunrise/sunset altitudes as standard is the reference time of dawn prayers in Indonesia. However, this provision in fact reap discourse in some quarters because it is not</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="hiddengrammarerror"><span lang="IN">in accordance with</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="mceitemhidden"><span lang="IN">the phenomenon of morning dawn emergence at the beginning of the shubuh prayer time empirically. This study aims to decide the morning dawn, as the beginning of dawn determinant</span></span><span class="mceitemhidden"><span lang="IN">.</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="mceitemhidden"><span lang="IN">The tool used in this study is the Sky Quality Meter (</span></span><span class="hiddenspellerror"><span lang="IN">SQM</span></span><span class="mceitemhidden"><span lang="IN">), to detecting the morning dawn emergence as a sign of the beginning of the shubuh prayer time. The results of this study found that the brightness of the sky throughout the night or the morning dawn in</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="hiddenspellerror"><span lang="IN">Tayu</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="mceitemhidden"><span lang="IN">Beach,</span></span><span class="apple-converted-space"><span lang="IN"> </span></span><span class="hiddenspellerror"><span lang="IN">Pati</span></span><span class="mceitemhidden"><span lang="IN">, Central Java, in the span of four days of observation that is at 4: 31 </span></span><span class="mceitemhidden"><span lang="EN-GB">a.m</span></span><span class="mceitemhidden"><span lang="IN"> with an average altitude of the sun is -17°(17°below the horizon)</span></span><span class="mceitemhidden"><span lang="IN">.</span></span>

Pengaplikasian Astrolabe dalam Hisab Awal Waktu Shalat

Astrolabe is a classical instrument in astronomy that is often used to determine the position of celestial bodies without calculating. The notables who played role in the formulation of the astrolabe concept and work system were Hipparchus, Claudius Ptolemy and Theon. Muslim astronomers also had an important role in the development of the astrolabe. The application of astrolabe in reckoning the beginning of prayer time is very easy. But before it can be applied in reckoning prayer time, the astrolabe needs to be equipped with the Sun's altitude lines at the beginning of the prayer time for one year at a location. So the astrolabe can easily be applied to reckon the beginning of prayer times without the need to do calculations. But the Sun's data on the astrolabe are constant as well as the attitude of the Sun at the beginning of prayer time. Those are what reduce the accuracy of the beginning of prayer times reckoning result with the astrolabe.

Performance of the east–west oriented single-axis tracked collector

Chang [1] proposed a method to determine the gain of a tracked panel, rotated about a horizontal east-west axis with continuous adjustment to minimize the angle of incidence, according to three kinds of radiation sources will be considered, i.e. the extraterrestrial radiation, global radiation predicted by empirical models under clear sky situation and global radiation observed in Taichung (φ = 24.2° N), Taiwan. In this article, Chang [1] incorrectly calculated the daily variation of the solar azimuth angle. The mentioned error could have its influence on all other results. The present comments are focused on correcting the calculated solar azimuth angle by Chang [1] and to discuss the sensitivity of other calculated values to this observed error.

Accurate tool for express optical efficiency analysis of cylindrical light-tubes with arbitrary aspect ratios

The vertical straight pipes are a desirable technology for delivery daylight into interior spaces because this concept benefits from luminance distribution of the whole upper hemisphere, including sunlight that is most important source of light under clear sky conditions. Vertical pipes can transport sunbeams to deep interiors independent of solar azimuth and/or room orientation. Currently, the tools for modelling different pipes are widely available, but their accuracy decreases as the aspect ratio of a light-pipe increases. In sunny environments with high solar altitudes and favorable clear skies the tubular light-guides allow to deliver daylight into deep offices, halls, or even underground spaces in building cores. The optical efficiency of such systems strongly depends on number of reflections the beams undergo on their path from the top to the bottom of a light pipe. In general, dense-grid and high CPU requirements meet when accurate numerical predictions are required. Such computations are non-attractive if intended for routine (mass) modelling.In this paper we introduce an analytical solution to the optical efficiency of straight pipes that is applicable to all aspect ratios and provides accurate predictions with very low demands on processor time. The new analytical model is validated and benchmarked against accurate HOLIGILM calculations, while showing the percent deviations are kept below 10% for most cases studied.

Angle between terminator and meridian: flat geometry versus formulae of solar azimuth and an easy approach to the daylight map

The calculation of the angle between the day-night line on the Earth’s surface, a terminator, and the meridian at a given point, at dawn or at sunset, can easily be performed either by means of flat geometry or, for those familiarized with astronomy, through formulae for the Sun’s azimuth and elevation, both derived from spherical trigonometry. The two procedures are compared. An auxiliary angle obtained in the process of derivation via planar geometry becomes useful to represent the daylight map on a terrestrial planisphere.

Assessment of the impact of meteorological conditions on pyrheliometer calibration

Pyrheliometer calibration must be done following strict procedures in order to ensure the required robustness and accuracy. These procedures are described in the ISO 9059:1990 and ASTM E 816 – 15 international standards. However, their application requires information that may not always be available or may be subjective, inaccurate or incomplete, as for example, the determination of “percent of cloud coverage” or “the existence of clouds 15° around the Sun”. The irradiance measurements made by the reference and test instruments involved should also be collected over wide periods after, close to and before solar noon, which might not always be the case depending on the weather conditions during calibration. When those data are not available, the standard cannot be applied properly, and the experts have to decide which data can be used for the calibration. In this study, the abovementioned two main standards for pyrheliometer calibration were thoroughly reviewed, and a harmonized protocol is proposed that uses only the main data recorded. Nineteen field pyrheliometers were calibrated to verify the proposed procedure, and the results show its robustness. After calibration, we analyzed the variability in the calibration constant and the influence of some experimental conditions on the calibration results. As in previous references, the results show that variations in solar elevation and wind speed during the day still influenced the calibration constants of most of the test devices. On the contrary, neither the angle between the wind direction and the solar azimuth nor Linke turbidity seemed to influence the calibration constants calculated. The influence of the Linke turbidity is low as the viewing geometry of all involved pyrheliometers is very similar to each other and as low turbidity prevailed. The correlation between the solar elevation and the wind speed was analyzed and calibration constants were found to vary linearly with solar elevation and wind speed, respectively. Pyrheliometer calibration measurement testing was carried out in Summer 2014 at the Plataforma Solar de Almeria (PSA) in the context of the Solar Facilities for the European Research Area 2 Project (SFERA2).

Remote estimation of complete urban surface temperature using only directional radiometric temperatures

Complete urban surface temperature (Tc) is a key variable for quantifying the urban surface - atmosphere interactions. The estimation of Tc usually requires detailed knowledge of surface geometry and facet temperatures, which are difficult to obtain by remote sensing. Therefore, simple but efficient strategies for the remote estimation of Tc are currently lacking. Facing this challenge, we proposed a comprehensive solution to estimate Tc remotely using only the directional radiometric temperatures (DRTs) without the assistance of ground-based information. By comparing Tc with the nadir temperature (T0), DRTs within the entire hemisphere, and solid-angle integral temperature (SIT), we obtain the following results: (1) The optimal viewing azimuth and zenith angles at which the DRTs are the closest to Tc are φs±90° (φs is the solar azimuth angle) and 45–60°, respectively. (2) The estimation of Tc could be further improved once the DRTs from all-direction are available, and the MAE for the SIT that most closely approximated Tc is only 0.87 K. (3) The MAE of the SIT that best approximates Tc by combining only four DRTs and a kernel-driven model is only slightly higher than that of the specific SIT based on the original DRTs, indicating that the remote estimation of Tc using limited DRTs is plausible. These proposed strategies are generally simple and effective, and can help facilitate the estimation of Tc and therefore help advance the thermal remote sensing of urban climate and environment.

The Solar Ultraviolet Environment at the Ocean.

Atmospheric and oceanic radiative transfer models were used to compute spectral radiances between 285 and 400 nm onto horizontal and vertical plane surfaces over water. The calculations kept track of the contributions by the sun's direct beam, by diffuse-sky radiance, by radiance reflected from the sea surface and by water-leaving radiance. Clear, hazy and cloudy sky conditions were simulated for a range of solar zenith angles, wind speeds and atmospheric ozone concentrations. The radiances were used to estimate erythemal exposures due to the sun and sky, as well as from radiation reflected by the sea surface and backscattered from the water column. Diffuse-sky irradiance is usually greater than direct-sun irradiance at wavelengths below 330 nm, and reflected and water-leaving irradiance accounts for <20% of the UV exposure on a vertical surface. Total exposure depends strongly on solar zenith angle and azimuth angle relative to the sun. Sea surface roughness affects the UV exposures by only a few percent. For very clear waters and the sun high in the sky, the UV index within the water can be >10 at depths down to two meters and >6 down to 5 m.

Comments on solar azimuth angle

Three appropriate relationships for determining the solar azimuth angle with respect to the south direction were considered for giving some comments on the available algorithms for solar azimuth angle calculation. The application of each of the trigonometric functions (sinγs, cosγs and tanγs, where γs is the solar azimuth) for determining γs is discussed with regard to the simplicity and generality. It was found that cosγs could be modified in a very simple way in order to be general in determining the solar azimuth angle all over the year. The modified cosγs was compared with those available in literature formulas and formulations with regard to the generality and simplicity. A comparison with available results is provided.