Position Of Sun Research Articles

Statistical estimation of hourly diffuse radiation intensity of Budapest City

AbstractThe vulnerability of fossil fuel prices to worldwide events such as the recent coronavirus (COVID‐19) pandemics increases the interest in renewable energy resources that offer more stable energy generation costs. Solar energy is one of the most abundant renewable energy resources that have gained significant interest in the last decades with various challenges related to the forecastingof the energy production from these systems. Solar radiation intensity varies due to the daily and seasonal changes in the sun's position in addition to the variation in the sky clearness from one location to another which is considered as an important factor that affects the deployment of solar energy systems. This study aims to develop statistical models—mainly regression models and parametric model based on ASHRAE model—to estimate the hourly diffuse radiation in Budapest as a case study using the measured hourly global and diffuse radiation between 2011 and 2018. The prediction models relate the clearness index (which is obtained from the extraterrestrial and global radiation) and the global radiation through a generalized equation. The parametric model was developed by finding the optimal site‐specific constants of ASHRAE model for Budapest using the measured data that minimize the root mean square error. In addition, this study presents a comparison between the results from the developed models and the models reported in the literature. The results indicate that all the developed regression models had close correlation coefficients (R2) where the linear, power, and exponential models had the largest R2 (.69). Finally, the linear model was evaluated on a dataset outside the test data range where the linear model was capable of predicting the diffuse radiation with much better R2 (.93).

DESIGN AND APPLICATION OF SOLAR TRACKING SYSTEM USING OPTIMIZED FUZZY LOGIC CONTROLLER BY GENETIC ALGORITHM

This study describes an intelligent control algorithm for the solar tracking system (STS) providing maximum performance from the photovoltaic panel according to different sun positions. The solar tracking system is designed as dual axis to increase the efficiency of photovoltaic panels. DC motors are preferred in order to minimize cost and to control the azimuth and zenith angles in the solar tracking system. Fuzzy logic algorithms are used to adjust the speed of these motors to track the sun’s position with a high degree of accuracy. After designing a fuzzy logic controller in order to control the motors, membership functions of controller and control rules are simultaneously found by genetic algorithms which is an optimization algorithm based on natural selection and genetic mechanics. As a result in the study, the power performance analysis is compared between a photovoltaic panel positioned on the designed solar tracking system and a photovoltaic panel positioned on the static system. According to comparison results, the photovoltaic panel positioned on the solar tracking system is observed that it shows higher performance at varying rates of depending on the seasons.

Evaluation of the Consistency of Simultaneously Acquired Sentinel-2 and Landsat 8 Imagery on Plastic Covered Greenhouses

Remote sensing techniques based on medium resolution satellite imagery are being widely applied for mapping plastic covered greenhouses (PCG). This article aims at testing the spectral consistency of surface reflectance values of Sentinel-2 MSI (S2 L2A) and Landsat 8 OLI (L8 L2 and the pansharpened and atmospherically corrected product from L1T product; L8 PANSH) data in PCG areas located in Spain, Morocco, Italy and Turkey. The six corresponding bands of S2 and L8, together with the normalized difference vegetation index (NDVI), were generated through an OBIA approach for each PCG study site. The coefficient of determination (r2) and the root mean square error (RMSE) were computed in sixteen cloud-free simultaneously acquired image pairs from the four study sites to evaluate the coherence between the two sensors. It was found that the S2 and L8 correlation (r2 > 0.840, RMSE < 9.917%) was quite good in most bands and NDVI. However, the correlation of the two sensors fluctuated between study sites, showing occasional sun glint effects on PCG roofs related to the sensor orbit and sun position. Moreover, higher surface reflectance discrepancies between L8 L2 and L8 PANSH data, mainly in the visible bands, were always observed in areas with high-level aerosol values derived from the aerosol quality band included in the L8 L2 product (SR aerosol). In this way, the consistency between L8 PANSH and S2 L2A was improved mainly in high-level aerosol areas according to the SR aerosol band.

Design and fabrication of solar panel with sun position tracker

Timelessly, the sun has been paramount source of energy for life on earth and a large portion of the energy is utilized just for warmth and lighting. Decisively, daylight can be utilized as another form of energy by completely harvesting the light rays from the sun into a reliable sustainable source of energy. The main objective of this work is to develop a new solar panel design with better energy harvesting efficiency with the capability of tracking the position of the sun using real-time tracker. Three solar panels are stacked above one another without overshadowing the below ones. Solar concentrator is also employed to focus the sun irradiance onto panels. To ensure maximum power harvested, solar panel needs to be perpendicular to the sun’s array. Therefore, solar panels are rotated using combination of servo motors, Real Time Clock (RTC) and Arduino Mega 2560 to certain angles at certain period. The result is then compared with the conventional solar panel system, and it is found that the new design generates 50 kW/h extra energy, which is about 21.24% greater than the static conventional system. The overall increment of the average output power is about 28.5% which is for all the working hours over three days' testing time. Besides, it is found that the performance of the proposed system could be influenced by the operating temperature of the PV modules.

PERBEDAAN AWAL WAKTU SHALAT DUNIA: Analisis Aplikasi Athan Tinjauan Terhadap Posisi Matahari dan Letak Geografis

Changes in the position of the sun and the difference in places with old and long nights. There are interesting things to examine changes in the position of the sun and situation, to the differences in the beginning of world prayer time, by analyzing the schedules available at the application athan. This study sampled the methods of the Islamic Sciences of Karachi University, the method of Umm Al Qura Committee, the Egyptian General Authority of Survey method, the method of the Islamic Society of North America each of 3 (three) cities, the method of the World Muslim League 5 (five) total samples 17 city / country and sun position at 8 days. The problem studied is the large number of positions of the sun and the location of different places for the time used for various kinds of information and their use. The results showed that a significant initial number occurred when the sun's position was in the opposite direction (Sun) (June 22) and South backline (December 22), both for the disputed regions in the Northern Hemisphere or in the Southern Hemisphere and the position of the sun was more dominant compared to geographical location

The Design of Off-grid Home Photovoltaic Power Generation System Considering Multi-weather Conditions

In the traditional fixed-installed off-grid photovoltaic power generation system, there are disadvantages such as insufficient solar energy collection and low solar energy utilization. In order to be able to effectively develop and utilize solar energy, the method of solar position tracking is generally used. In this paper, a single-chip microcomputer is selected as the main control chip, and a photovoltaic power generation system that combines two methods of photoelectric tracking and computational solar tracking and takes into account various meteorological factors is realized. The latitude and longitude information and time information collected by the single-chip microcomputer are used to calculate the sun position, and the photoelectric position is used to monitor the sun position. The design can automatically change the tracking scheme according to the weather conditions, so that the tracking system can run stably under various weather conditions.

Modeling the transmittance of anisotropic diffuse radiation towards estimating energy losses in solar panel coverings

The performance assessment of photovoltaic arrays involves estimating the energy that is lost due to different sources, such as optical losses in the protective coverings. These transparent coatings do not transmit all incoming solar radiation due to partial reflections and absorptions that intensify with the angle of solar incidence. In the case of beam radiation, which consists of parallel rays with a deterministic incidence, the transmittance can be assessed with well-known analytical models. Alternately, more complex diffuse radiation consists of scattered rays with stochastic and anisotropic distributions. Consequently, the transmittance of diffuse radiation is commonly ignored or oversimplified with limited models. This work presents a new set of general models for estimating the transmittance of anisotropic diffuse radiation. Transmittance was determined from surface integrals models solved over the geometrical regions corresponding to the diffuse radiation components, i.e., sky isotropic, circumsolar, horizon brightening, and albedo. This approach was validated against stochastic rays simulations, which converged with RMSE below 0.05% transmittance. The surface integrals were then solved for the relevant discretized input ranges, and regression models were fitted to capture the resulting behavior. With high flexibility, the inputs of these regression models allow for specifying the covering characteristics and the sun and panel angular positions. The proposed models allowed us to incorporate the estimation of transmittance losses to a broader energy harvesting analysis. In a case study, the effect on annual energy was calculated comparing four transmittance modeling approaches with three different covering specifications, three panel inclinations, three sky models, and in two locations. The range of variation due to the covering specifications can result in energy losses of 16.33% compared to using a covering with the highest transmittance. The findings and methods presented in this work have implications in areas ranging from the modeling of energy harvesting to the design and development of solar panels and protective transparent coatings.

Performance evaluation of a linear Fresnel collector with catoptric subsets

In this paper, the optical, thermal and overall performance of a linear Fresnel collector with catoptric subsets is reported. Subsets consist of mirrors which focus on the receiver while they maintain their relative positions with respect to each other. Ray tracing modelling is used for the estimation of the optical performance of the collector. A thermal analysis is performed in order to assess the thermal and the overall efficiency of the collector. A comparison is attempted between the specific collector and a more typical one, which involves mirrors strips, uniformly distributed to the same land area. Two materials with different reflectivity values and optical errors, i.e. glass mirrors and aluminium sheets, are considered for the reflecting surface of the primary mirrors.Results indicate that the performance of the collector with the catoptric subsets is similar to that of the collector with the uniformly distributed mirrors for sun positions close to solar noon and lower for large sun inclinations. Each design gives its own temperature distribution on the receiver but similar thermal performance. However, the catoptric-subset design provides a robust configuration which requires a lower number of rotating parts; therefore, it deserves further techno-economic analysis, to better evaluate its potential.

GIS tool to predict photosynthetically active radiation in a Dry Valley

AbstractUnderstanding primary productivity is a core research area of the National Science Foundation's Long-Term Ecological Research Network. This study presents the development of the GIS-based Topographic Solar Photosynthetically Active Radiation (T-sPAR) toolbox for Taylor Valley. It maps surface photosynthetically active radiation using four meteorological stations with ~20 years of data. T-sPAR estimates were validated with ground-truth data collected at Taylor Valley's major lakes during the 2014–15 and 2015–16 field seasons. The average daily error ranges from 0.13 mol photons m-2 day-1 (0.6%) at Lake Fryxell to 3.8 mol photons m-2 day-1 (5.8%) at Lake Hoare. We attribute error to variability in terrain and sun position. Finally, a user interface was developed in order to estimate total daily surface photosynthetically active radiation for any location and date within the basin. T-sPAR improves upon existing toolboxes and models by allowing for the inclusion of a statistical treatment of light attenuation due to cloud cover. The T-sPAR toolbox could be used to inform biological sampling sites based on radiation distribution, which could collectively improve estimates of net primary productivity, in some cases by up to 25%.

Concept of Time in Indian Astronomy

Time is an important tool for mankind. We follow it with clocks and calendars. It is very important to measure time, as it keeps track of the age of people, animals and anything around us. Measuring time is always relative and not absolute.The need for fixing proper time for performing rituals urged the astronomical quest in India..Astronomy is a science which plays a vital role in our day to day life.The Hindu Calendar is called Pañcāṅga. Pañcāṅga is a tool for knowing the movement and position of various celestial objects. It is used to calculate the auspicious timings of any day for performing the rituals.It is based on the positions of Sun and Moon.Calculation and measurement of time had been a need and an enigma for man from time immemorial. As time passed man used various methods and devices for its measurement. Man keeps improving upon his methods and devices.

Influence of the Sun Position and Platform Orientation on the Quality of Imagery Obtained from Unmanned Aerial Vehicles

Images acquired at a low altitude can be the source of accurate information about various environmental phenomena. Often, however, this information is distorted by various factors, so a correction of the images needs to be performed to recreate the actual reflective properties of the imaged area. Due to the low flight altitude, the correction of images from UAVs (unmanned aerial vehicles) is usually limited to noise reduction and detector errors. The article shows the influence of the Sun position and platform deviation angles on the quality of images obtained by UAVs. Tilting the camera placed on an unmanned platform leads to incorrect exposures of imagery, and the order of this distortion depends on the position of the Sun during imaging. An image can be considered in three-dimensional space, where the x and y coordinates determine the position of the pixel and the third dimension determines its exposure. This assumption is the basis for the proposed method of image exposure compensation. A three-dimensional transformation by rotation is used to determine the adjustment matrix to correct the image quality. The adjustments depend on the angles of the platform and the difference between the direction of flight and the position of the Sun. An additional factor regulates the value of the adjustment depending on the ratio of the pitch and roll angles. The experiments were carried out for two sets of data obtained with different unmanned systems. The correction method used can improve the block exposure by up to 60%. The method gives the best results for simple systems, not equipped with lighting compensation systems.

Improving Photovoltaic Panel (PV) Efficiency via Two Axis Sun Tracking System

In this paper two axis sun tracking method is used to absorb maximum power from the sun's rays on the solar panel via calculating the sun’s altitude and azimuth angles, which describe the solar position on the Iraqi capital Baghdad for the hours 6:00, 7:00, 8:00, 9:00, 12:00, 15:00 and 17:00 per day. The angles were calculated in an average approach within one month, so certain values were determined for each month. The daily energy achieved was calculated for the solar tracking method compared with the fixed tracking method. Designed, modeled and simulated a control circuit consisting of reference position truth table, PI Controller and two servomotors that tracked the sun position to adjust the PV panel perpendicular on the rays of the sun. The results obtained by a simulation software MATLAB/Simulink.

Design and Implement of Dual Axis Solar Tracker System Based Arduino

The computer control plays important role in the solar cell design and development of dual axis solar tracker for the sun's position. The main goal of this paper is to maximize energy output to reduce panel temperature (cooling), to increase efficiency of the PV panel. Small-scale solar is developed through a complete hardware and software in order to function accurately. The main parts in this work are Arduino Uno R3, kit relay, LDR (Light Dependent Resistor), LM35 (temperature sensor), high-efficiency solar panel and satellite motor. The Protuse software is used with (Arduino Uno) as embedded computer control. The results show the effectiveness of the complete tracking system.

A visual-inertial system to determine accurate solar insolation and optimal PV panel orientation at a point and over an area

To provide the best return on investments it is often required to assess the suitability of a site for installation of solar photovoltaic panel and quantify shading and atmospheric losses. The shading analysis is generally done using light detection and ranging or 3D geographic information system-based approaches which are cost-effective only for large-scale analysis. In several cases, particularly in developing countries, LiDAR data or 3D GIS are not available. In this study, a terrestrial image-based system is developed to accurately estimate solar insolation at a place. The positions of obstructions obtained using captured images are integrated with sun position model to provide solar insolation and optimal solar panel orientation. To further refine the result, the effect of sky conditions on the obtained solar insolation is also considered at monthly and yearly scale. About 40% reduction in solar insolation is observed due to shading which rose to 51% when the atmospheric conditions were included in the analysis of the selected sites. Further, an approach to estimate solar insolation over an area using some discrete point location is also presented and demonstrated. Results from 30 sites show that the obtained error in insolation estimate over an area is within 4%.

Evidence of a dynamically evolving Galactic warp

In a cosmological setting, the disc of a galaxy is expected to continuously experience gravitational torques and perturbations from a variety of sources, which can cause the disc to wobble, flare and warp. Specifically, the study of galactic warps and their dynamical nature can potentially reveal key information on the formation history of galaxies and the mass distribution of their halos. Our Milky Way presents a unique case study for galactic warps, thanks to the detailed knowledge of its stellar distribution and kinematics. Using a simple model of how the warp's orientation is changing with time, we here measure the precession rate of the Milky Way's warp using 12 million giant stars from Gaia Data Release 2, finding that it is precessing at $10.86 \pm 0.03_{stat} \pm 3.20_{sys}$ km/s/kpc in the direction of Galactic rotation, about one third the angular velocity at the Sun's position in the Galaxy. The direction and magnitude of the warp's precession rate favour the scenario that the warp is the results of a recent or ongoing encounter with a satellite galaxy, rather than the relic of the ancient assembly history of the Galaxy.

Minimizing the Cosine Loss in a Solar Tower Power Plant by a Change in the Heliostat Position and Number

Concentrating Solar Power (CSP) focuses sunlight in order to use the heat energy of the sun. In a central receiver system configuration, many mirrors (heliostats) individually track the sun and reflect the concentrated solar energy onto a receiver on top of a tower. The receiver contains the working fluid which is heated by the concentrated solar radiation. The useful energy that absorbed by the water flows through the receiver in solar tower plant depending on the angle between the solar rays and the position of heliostat in the region of work. Heliostat will reflect the incident solar radiation in the direction of the receiver founded in the top of the tower, in order to get a maximum incident solar radiation on the heliostat reflection area. Because of the cosine factor loss effect due to the sun position is variable along the day from sunrise to sunset, which must be in a minimum value, therefore an automated tracking system with dual axes as a control system with sensors had been built and used to stay the sunrays incident on the receiver, and enable the heliostat to flow the sun where it was

Improved stomatal opening enhances photosynthetic rate and biomass production in fluctuating light.

It has been reported that stomatal conductance often limits the steady-state photosynthetic rate. On the other hand, the stomatal limitation of photosynthesis in fluctuating light remains largely unknown, although in nature light fluctuates due to changes in sun position, cloud cover, and the overshadowing canopy. In this study, we analysed three mutant lines of Arabidopsis with increased stomatal conductance to examine to what extent stomatal opening limits photosynthesis in fluctuating light. The slac1 (slow anion channel-associated 1) and ost1 (open stomata 1) mutants with stay-open stomata, and the PATROL1 (proton ATPase translocation control 1) overexpression line with faster stomatal opening responses exhibited higher photosynthetic rates and plant growth in fluctuating light than the wild-type, whereas these four lines showed similar photosynthetic rates and plant growth in constant light. The slac1 and ost1 mutants tended to keep their stomata open in fluctuating light, resulting in lower water-use efficiency (WUE) than the wild-type. However, the PATROL1 overexpression line closed stomata when needed and opened stomata immediately upon irradiation, resulting in similar WUE to the wild-type. The present study clearly shows that there is room to optimize stomatal responses, leading to greater photosynthesis and biomass accumulation in fluctuating light in nature.

Accurate 3-D radiative transfer simulation of spectral solar irradiance during the total solar eclipse of 21 August 2017

Abstract. We calculate the variation of spectral solar irradiance in the umbral shadow of the total solar eclipse of 21 August 2017 and compare it to observations. Starting from the Sun's and Moon's positions, we derive a realistic profile of the lunar shadow at the top of the atmosphere, including the effect of solar limb darkening. Subsequently, the Monte Carlo model MYSTIC (Monte Carlo code for the phYSically correct Tracing of photons In Cloudy atmospheres) is used to simulate the transfer of solar radiation through the Earth's atmosphere. Among the effects taken into account are the atmospheric state (pressure, temperature), concentrations of major gas constituents and the curvature of the Earth, as well as the reflectance and elevation of the surrounding area. We apply the model to the total solar eclipse on 21 August 2017 at a position located in Oregon, USA, where irradiance observations were performed for wavelengths between 306 and 1020 nm. The influence of the surface reflectance, the ozone profile, the mountains surrounding the observer and aerosol is investigated. An increased sensitivity during totality is found for the reflectance, aerosol and topography, compared to non-eclipse conditions. During the eclipse, the irradiance at the surface not only depends on the total ozone column (TOC) but also on the vertical ozone distribution, which in general complicates derivations of the TOC from spectral surface irradiance. The findings are related to an analysis of the prevailing photon path and its difference compared to non-eclipse conditions. Using the most realistic estimate for each parameter, the model is compared to the irradiance observations. During totality, the relative difference between model and observations is less than 10 % in the spectral range from 400 to 1020 nm. Slightly larger deviations occur in the ultraviolet range below 400 and at 665 nm.

Efficient and Low-Cost Arduino based Solar Tracking System

Sun energy plays an important role as a primary source of energy which can be harvested successfully using solar cells. The solar cell efficiency depends on the location of sun and its light intensity. Hence, solar tracking can be exploited to maximize the efficiency of solar panel. In this work, we developed a novel system of an inexpensive automatic microcontroller-based scaled down solar tracker using Arduino platform. Servo-motor is controlled by an Arduino Mega unit in order to re-orient the solar panel according to the position of sun with the help of light dependent resistors (LDR) and servomotors. A dual-axis solar tracker prototype is designed to maximize the harvested solar energy. Experimental results show that the proposed system performs 25% better than a fixed solar panel under the same conditions.

Short term prediction of sun coverage using optical flow with GoogLeNet

One of the challenges of PV power generation is solar intermittency from weather conditions. Solar irradiance prediction is therefore required to deal with this issue. Several prediction methods have been proposed based on whole sky image processing techniques. This paper presents a combination technique of image processing with a convolution neural network (CNN) based on GoogLeNet for raising trigger events before the sun cover happens 1 to 2 min in advance. The captured sky images are preprocessed and in the next step, we use Hough transform to find the sun position and use optical flow to track cloud movement. Finally, we use a CNN to generate trigger events in advance before the sun occlusion happens. The results of prediction stage show error percentage as low as 5.26% in a clear sky day.