Position Of Sun Research Articles

Solar radius determined from PICARD/SODISM observations and extremely weak wavelength dependence in the visible and the near-infrared

Context. In 2015, the International Astronomical Union (IAU) passed Resolution B3, which defined a set of nominal conversion constants for stellar and planetary astronomy. Resolution B3 defined a new value of the nominal solar radius (R⊙N = 695 700 km km) that is different from the canonical value used until now (695 990 km). The nominal solar radius is consistent with helioseismic estimates. Recent results obtained from ground-based instruments, balloon flights, or space-based instruments highlight solar radius values that are significantly different. These results are related to the direct measurements of the photospheric solar radius, which are mainly based on the inflection point position methods. The discrepancy between the seismic radius and the photospheric solar radius can be explained by the difference between the height at disk center and the inflection point of the intensity profile on the solar limb. At 535.7 nm (photosphere), there may be a difference of ∼330 km between the two definitions of the solar radius. Aims. The main objective of this work is to present new results of the solar radius in the near-ultraviolet, the visible, and the near-infrared from PICARD space-based and ground-based observations. Simulations show the strong influence of atmosphere effects (refraction and turbulence) on ground-based solar radius determinations and highlight the interest of space-based solar radius determinations, particularly during planet transits (Venus or Mercury), in order to obtain more realistic and accurate measurements. Methods. Solar radius observations during the 2012 Venus transit have been made with the SOlar Diameter Imager and Surface Mapper (SODISM) telescope on board the PICARD spacecraft. We used the transit of Venus as an absolute calibration to determine the solar radius accurately at several wavelengths. Our results are based on the determination of the inflection point position of the solar limb-darkening function (the most common solar radius definition). A realistic uncertainty budget is provided for each solar radius obtained with the PICARD space-based telescope during the 2012 Venus transit. The uncertainty budget considers several sources of error (detection of the centers of Venus and Sun in PICARD images, positions of Sun and Venus from ephemeris (planetary theory), PICARD on-board timing, PICARD spacecraft position, and optical distortion correction from PICARD images). Results. We obtain new values of the solar radius from the PICARD mission at several wavelengths and in different solar atmosphere regions. The PICARD spacecraft with its SODISM telescope was used to measure the radius of the Sun during the Venus transit in 2012. At 535.7 nm, the solar radius is equal to 696 134 ± 261 km (combined standard uncertainty based (ξ) on the uncertainty budget). At 607.1 nm, the solar radius is equal to 696 156 ± 145 km (ξ), and the standard deviation of the solar radius mean value is ±22 km. At 782.2 nm, the solar radius is equal to 696 192 ± 247 km (ξ). The PICARD space-based results as well as PICARD ground-based results show that the solar radius wavelength dependence in the visible and the near-infrared is extremely weak. The differences in inflection point position of the solar radius at 607.1 nm, 782.2 nm, and 1025.0 nm from a reference at 535.7 nm are less than 60 km for the different PICARD measurements.

ReLiShaft: realistic real-time light shaft generation taking sky illumination into account

Rendering atmospheric phenomena is known to have its basis in the fields of atmospheric optics and meteorology and is increasingly used in games and movies. Although many researchers have focused on generating and enhancing realistic light shafts, there is still room for improvement in terms of both qualification and quantification. In this paper, a new technique, called ReLiShaft, is presented to generate realistic light shafts for outdoor rendering. In the first step, a realistic light shaft with respect to the sun position and sky colour in any specific location, date and time is constructed in real-time. Then, Hemicube visibility-test radiosity is employed to reveal the effect of a generated sky colour on environments. Two different methods are considered for indoor and outdoor rendering, ray marching based on epipolar sampling for indoor environments, and filtering on regular epipolar of z-partitioning for outdoor environments. Shadow maps and shadow volumes are integrated to consider the computational costs. Through this technique, the light shaft colour is adjusted according to the sky colour in any specific location, date and time. The results show different light shaft colours in different times of day in real-time.

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>

Photovoltaic Generation Solar Automatic Tracking System

A new solar automatic tracking system is designed in this paper. The system is a closed-loop servo system with a brushless DC servomotor and a photoelectric encoder etc. Firstly, the circuit schematic, the clock circuit, the servo driver and photoelectric encoder circuit are mainly analyzed. Then, the main program flow chart, and the time obtaining subroutine, the azimuth and elevation angle calculating subroutine and the motor drive subroutine are illustrated. Moreover, the servo system transmission mechanism is designed. It adopts a planetary reducer connected to a slewing drive. Finally, experiments results show the system can track the sun position in real time. It has high precision, low energy consumption, long life and perfect protective function etc.

Design and implementation of real-time monitoring based on Android and HMI of PV tower system for laboratory scale

The performance of photovoltaic (PV) cannot be described by the user, so it is difficult to anticipate when it’s undesirable or fault condition occurs. Therefore, the monitoring of PV output parameters is needed. In this case, the parameters that can be displayed are current and voltage value. The parameter data are obtained from PV tracking of the sun position by MPPT Perturb and Observe (P&O) method used in a mechanical system of the dual axis solar tracker. In this experiment, there are two monitoring methods used, which are Real-time Online Monitoring Based on Android system and Human Machine Interface (HMI) display monitoring which is controlled by Arduino Mega 2560. Both methods are expected to show the performance of PV in real-time, remotely or not. The results of this experiment are Android apps and HMI that can monitor the PV output condition. To maintain the PV system in real-time, they keep the device under the supervision and extend its lifetime for more prolonged use.

The Impact of Aspect Ratio on External Heat Gain of Multi-storey Office Buildings in Jakarta

The narrow land in big cities such as Jakarta, increases the amount of high rise building, especially multi-storey office building. Office building consumes much energy to provide air conditioning to meet the thermal comfort inside the building. On the other hand, the building shape, building envelope, and building orientation to the sun's position are the main factors in building design aspects that affect the amount of cooling load. This study aims to investigate the impact of the aspect ratio or the ratio of the longer dimension of an oblong plan to the shorter, on external heat gain of multi-storey office building. Variables examined include the transparent and solid area of building envelope, the total area of the surface of the building envelope in any orientation, and the volume of the building, as well as the influence of those proportion on the external heat gain. This study uses mathematical calculations to predict the cooling load of the building, particularly external heat gain through the walls, roof and glass, as well as comparative analysis of models studied. The study also aims to generate the design criteria of building form and proportion of multi-storey office buildings envelope with lower external heat gain. In Jakarta climatic conditions, the result on rectangular building plan with aspect ratio of 1 to 4 shows that the external heat gain did not differ significantly, and the smallest heat gain is found on the aspect ratio of 1.8. Results also showed that the greater aspect ratio, the greater reduction of external heat gain obtained by changing the orientation of the longest side facing east-west into the north-south, about 2.79% up to 42.14% on the aspect ratio of 1.1 to 4. In addition, it is known that in same building volume, changing the number of floors from 10 to 50 can improve the external heat gain almost twice.

Control of plant leaf movements by the lunisolar tidal force.

Background Investigations into the diurnal ascent and descent of leaves of beans and other species, as well as experimental interventions into these movements, such as exposures to light at different times during the movement cycle, led to the concept of an endogenous 'clock' as a regulator of these oscillations. The causal origin of leaf movement can be traced to processes that modulate cell volume in target tissues of the pulvinus and petiole. However, these elements of the leaf-movement process do not sufficiently account for the rhythms that are generated following germination in constant light or dark conditions, or when plants are transferred to similar free-running conditions. Scope To further unravel the regulation of leaf-movement rhythms, many of the published time courses of leaf movements that provided evidence for the concept of the endogenous clock were analysed in conjunction with the contemporaneous time courses of the lunisolar tidal acceleration. This was accomplished by application of the Etide program, which estimates, with high temporal resolution, local gravitational changes as a consequence of the diurnal variations of the lunisolar gravitational force due to the orbits and relative positions of Earth, Moon and Sun. To substantiate the results obtained in earthbound laboratories additional experiments were performed in the International Space Station (ISS). Tidal recurrence within the ISS exhibited a periodicity of 45 min. In all instances investigated, it was evident that a synchronism exists between the times of the turning points of both the lunisolar tide and of the leaftide when the direction of leaf movement changes. This finding of synchrony documents that the lunisolar tide is a regulator of the leaftide, and that the rhythm of leaf movement is not of endogenous origin but is an expression of an exogenous lunisolar clock impressed upon the leaf-movement apparatus. Conclusions A huge number of correlations between leaftide and Etide time courses were established for leaf movement rhythms in natural conditions of the greenhouse, in conditions of constant light or dark, and under the microgravity conditions of the International Space Station. Even the apparently spontaneous short-period, small-amplitude rhythms recorded from leaves under unusual growth conditions are consistent with the hypothesis of a lunisolar zeitgeber. Synchronism between leaftide and Etide is discussed in terms of classical and quantum mechanics.

Study of ocean thermal energy resources in Para’baya, West Sulawesi

Ocean thermal is one of the renewable energy resources. In 1981, a design of Ocean Thermal Energy Conversion (OTEC) pilot power plant was proven could produce electricity. The performance of OTEC depends on the possible temperature differences of the warm and cold seawater, at least 20°C. In the coastal of Para’baya, this requirement can be satisfied since the distance to reach the 1000 m depth is less than 10,000 m from the shore. The result of ocean thermal power calculation in Makassar Strait shows that Para’baya could produce higher power than any other place in west coast of Sulawesi, with an average power output of 120.35 kW. This ocean thermal study, in the coast of Para’baya, used sea surface temperatures (SST) data from the result of Long-term Indonesian Throughflow Model Simulation (LITHMOS) over 24 years (1982 – 2006), and sea temperature data at 1000 m depth from the World Ocean Atlas (WOA) 2009. The result shows that ocean thermal energy distributions in the Makassar Strait were affected by the combination of gust, wind direction, and sun position which varies in each season. Maximum ocean thermal power is reached during the first transitional season (March, April, May) with output power of 128 kW, and the minimum power is achieved during the dry season (June, July, August) with an output power of 114 kW.

Facial exposure to ultraviolet radiation: Predicted sun protection effectiveness of various hat styles.

Solar ultraviolet radiation (UVR) doses received by individuals are highly influenced by behavioural and environmental factors. This study aimed at quantifying hats' sun protection effectiveness in various exposure conditions, by predicting UVR exposure doses and their anatomical distributions. A well-defined 3-dimensional head morphology and 4 hat styles (a cap, a helmet, a middle- and a wide-brimmed hat) were added to a previously published model. Midday (12:00-14:00) and daily (08:00-17:00) seasonal UVR doses were estimated at various facial skin zones, with and without hat wear, accounting for each UVR component. Protection effectiveness was calculated by the relative reduction in predicted UVR dose, expressed as a predictive protection factor (PPF). The unprotected entire face received 2.5 times higher UVR doses during a summer midday compared to a winter midday (3.3 vs 1.3 standard erythema dose [SED]) with highest doses received at the nose (6.1 SED). During a cloudless summer day, the lowest mean UVR dose is received by the entire face protected by a wide-brimmed hat (1.7 SED). No hat reached 100% protection at any facial skin zone (PPFmax : 76%). Hats' sun protection effectiveness varied highly with environmental conditions and was mainly limited by the high contribution of diffuse UVR, irrespective of hat style. Larger brim sizes afforded greater facial protection than smaller brim sizes except around midday when the sun position is high. Consideration of diffuse and reflected UVR in sun educational messages could improve sun protection effectiveness.

Large area colloidal photonic crystals for light trapping in flexible organic photovoltaic modules applied using a roll-to-roll Langmuir-Blodgett method

For the first time, the application of large-area 2D colloidal photonic crystals for light trapping in flexible OPV modules is demonstrated via the study of a broad range of light trapping structures deposited simply and cheaply using our novel roll-to-roll Langmuir–Blodgett technique. Commercially available flexible OPV modules with a size of 10 cm × 14 cm were used. Colloidal silica spheres with diameters ranging from 50 nm to 740 nm were used for the photonic crystal fabrication. The photonic structures made from SiO2 spheres with diameters of 50 nm and 120 nm demonstrate good antireflective properties in the visible and near-infrared spectral range, which have a pronounced positive effect on the photocurrent and the power conversion efficiency in OPV modules at all angles of the light incidence. The 2D photonic crystals made from SiO2 spheres with diameters of 600 nm and 740 nm show strong diffractive scattering of incident light in the forward direction, which results in significant light trapping effects in the OPV modules which again gives rise to an improvement in the cell characteristics. The observed light trapping effects vary only slightly with angle of incidence, suggesting that such photonic crystal layers could be of direct benefit in terms of the response of the OPV modules without the need to track the sun position as it moves across the sky.

Analysis of an Attached Sunspace with a Thermal Inertia Floor

An attached sunspace is a partially or fully glazed enclosure, usually located on the first floor, facing south (in the Northern Hemisphere) and adjacent to a conditioned room. Because of the length and orientation of the glazed area, the temperature in the sunspace is usually higher than outside the building. As a Trombe–Mitchel wall, the sunspace has a considerable mass that accumulates thermal energy, but in this case the thermal mass is located in the floor. This capacity to accumulate thermal energy confers the attached sunspace features beyond passive insulation. The sunspace studied in this paper is part of an experimental building located in the North of Spain that was built in the frame of the so-called ARFRISOL project. It consists of a south-facing glazed exterior wall with both clear glass and semi-transparent photovoltaic panels, an intermediate space with a thick layer of sand over a concrete floor, and a partially glazed interior wall. In this paper, a three-dimensional computational model has been implemented to analyse the thermal behaviour inside the sunspace. This analysis takes into account, among other factors, the effects of sun position, incident solar irradiation and temperature both inside and outside.

Preprocessing of Multi-Time Instant PV Generation Data

For the evaluation of system overlimit risk indices in a PV-integrated power system, PV generation data at specific instants of time (in each day for several years) are required to be collected. Such data have inherent annual periodic variations, which are different at various places. These variations are skewed and/or multimodal, which contributes significantly toward the overall variance of data and is primarily attributable to the Sun's position. This letter proposes a regression model that assumes the observed data as a function of few influencing factors related to the Sun's position and trend in data. Finally, the estimated variations using the developed model are removed from the data to characterize the unpredictable components.

Detection of low tension cosmic superstrings

Cosmic superstrings of string theory differ from conventional cosmic strings of field theory. We review how the physical and cosmological properties of the macroscopic string loops influence experimental searches for these relics from the epoch of inflation. The universe's average density of cosmic superstrings can easily exceed that of conventional cosmic strings having the same tension by two or more orders of magnitude. The cosmological behavior of the remnant superstring loops is qualitatively distinct because the string tension is exponentially smaller than the string scale in flux compactifications in string theory. Low tension superstring loops live longer, experience less recoil (rocket effect from the emission of gravitational radiation) and tend to cluster like dark matter in galaxies. Clustering enhances the string loop density with respect to the cosmological average in collapsed structures in the universe. The enhancement at the Sun's position is ∼ 105. We develop a model encapsulating the leading order string theory effects, the current understanding of the string network loop production and the influence of cosmological structure formation suitable for forecasting the detection of superstring loops via optical microlensing, gravitational wave bursts and fast radio bursts. We evaluate the detection rate of bursts from cusps and kinks by LIGO- and LISA-like experiments. Clustering dominates rates for G μ < 10−11.9 (LIGO cusp), G μ<10−11.2 (LISA cusp), G μ < 10−10.6 (LISA kink); we forecast experimentally accessible gravitational wave bursts for G μ>10−14.2 (LIGO cusp), G μ>10−15 (LISA cusp) and G μ>10− 14.1 (LISA kink).

Experimental investigation of the daily performance of an integrated linear Fresnel reflector system

The objective of this work is to investigate the daily and the instantaneous performance of a linear Fresnel reflector (LFR) experimentally and numerically. The examined LFR has an inverted flat plate receiver with a 36 m2 total collecting aperture area and is coupled to a storage tank of 1 m3 volume. This system is investigated experimentally for daily operation in the period from May to October for the climate conditions of Athens (Greece), using water as the working fluid (temperature levels up to 100 °C). Moreover, a detailed mathematical model for the prediction of the instantaneous and of the daily performance is developed. This model is validated with the experimental results for 52 operating days and it estimates the daily useful energy production with a mean error of 3%. This modeling is based on the energy balance on the collector loop and the storage tank. The emphasis is given on the determination of the optical losses of the collector, which are associated with the sun position during the day. It is found that the maximum useful heat production is about 8.4 kW, while the maximum daily heat production is about 260 MJ. The results of this work can be exploited for the evaluation of integrated solar concentrating systems and especially of linear Fresnel reflectors.

Modeling water vapor impacts on the solar irradiance reaching the receiver of a solar tower plant by means of artificial neural networks

This work analyses the influence of water vapor on the atmospheric transmission loss of solar radiation between heliostats and the receiver of solar power tower plants. To this purpose, an atmospheric transmission code (MODTRAN) is used to generate values of direct normal irradiance (DNI) reaching the mirror and the receiver under different geometries (including sun position, tower height, and mirror-to-receiver slant range) and atmospheric conditions related to water vapor and aerosols. These variables are then used as inputs to an artificial neural network (ANN), which is trained to calculate the corresponding DNI attenuation. Two different aerosol scenarios are simulated: an ideal aerosol-free atmosphere, and a widely different one corresponding to semi-hazy conditions. The developed ANN model is then able to provide the DNI attenuation over a wide range of the input variables considered here, with root mean square differences of only 0.8%. The transmission loss due to water vapor is found to decrease with sun elevation. This is explained by the saturation effect in the incident irradiance at the mirror. The simplicity and accuracy of the algorithm are its great strengths, allowing its anticipated inclusion into the actual energy simulation codes currently used for solar tower plant design.

PENGUJIAN KINERJA PEMBANGKIT LISTRIK TENAGA SURYA UNTUK MENGGERAKKAN POMPA AIR

Solar Power Plants (PLTS) is a promising alternative in the provision of electrical energy. In this study built PLTS to drive the load of water pump. The performance of water pumps is tested under various weather conditions. Performed measurements of some important quantities such as voltage, current and timing of the use of the PLTS to drive the water pump. Maximum yield with a one-hour charge occurs in sunny weather conditions at 11-12 WIB. A one-hour charge can move a 75 watts water pump for two hours. Solar panels are also directed towards the sun position resulting in a 40% increase in power at 12-13 pm.&#x0D; Keywords : PLTS, Output Voltage, Output Current, Maximum Power.

태양의 지위를 이용한 진북 추출 장치의 구현

태양의 지위를 이용한 진북 추출 장치의 구현

Using a Shading Tool to Reform Window designing due to Solar Radiation

Sun is the significant criterion that plays the most important role in architectural design. The sun's heat and radiation interact with the designed components of form and façade. These shading elements exhibit different expressions according to the structure orientation and the sun position. According to the climate of structure’s location, the expressions are being used to better respond to the environment in sustainable architecture.&#x0D; In order to get to this point, it is very important to calculate the shading geometry and solar energy during the day and to provide more suitable systems in glass and window designing. According to this, in order to arrive at more suitable shading systems by supporting MATLAB program, the software is written by taking the previous works as basis and closing some of their mistakes. According to the climate data, this program takes the plan drawings of window’s zone and some other information of window, the annual shading simulations are presented. Due to these simulations incident solar radiation of window, essential element of cooling load increasing in summer calculated. Furthermore window designing will be occurred by these simulations. So for the future works the user can import the glass or other datum of window or shading monument to design more efficiency.

Modeling the potential for PV installation in residential buildings in dense urban areas

The successful deployment of distributed photovoltaic (PV) systems requires assessment of the potential of possible installations. This depends mainly on their exposure to solar radiation, which can vary substantially with location, especially in the urban landscape. This paper seeks to estimate the potential for electricity generation by building-integrated PV in typical residential building types in dense urban locations, accounting for shading by adjacent structures. 3D modeling of the shadows cast by buildings is carried out with a new R package, developed as part of the study. The algorithm can assess the shadows cast on vertical surfaces (typically walls) or horizontal ones (typically roofs), given a database of obstacles representing buildings in the form of extruded polygons, and the sun's position at any desired time interval. The methodology is demonstrated for a case-study neighborhood in Rishon LeZion, Israel, with diverse building typologies. The simulation shows which building typologies offer the greatest solar potential, calculated per dwelling, building plot area or for the entire neighborhood. The results show that although roofs are less affected by mutual shading than vertical facades, some facades (mainly south and east oriented) can still make a substantial contribution to the overall solar potential of urban buildings.

Unstructured-Mesh Terrain Analysis and Incident Solar Radiation for Continuous Hydrologic Modeling in Mountain Watersheds

This article presents a methodology for estimating total incoming solar radiation from Triangular Irregular Network (TIN) topographic meshes. The algorithm also computes terrain slope degree and aspect (slope orientation) and accounts for self shading and cast shadows, sky view fractions for diffuse radiation, remote albedo and atmospheric backscattering, by using a vectorial approach within a topocentric coordinate system establishing geometric relations between groups of TIN elements and the sun position. A normal vector to the surface of each TIN element describes its slope and aspect while spherical trigonometry allows computing a unit vector defining the position of the sun at each hour and day of the year. Sky view fraction, useful to determine diffuse and backscattered radiation, is computed for each TIN element at prescribed azimuth intervals targeting the steepest elevation gradient. A comparison between the sun zenith angle and the steepest gradient allows deciding whether or not the pivot element is shaded. Finally, remote albedo is computed from the sky view fraction complementary functions for observed albedo values of the surrounding terrain. The sensitivity of the different radiative components to seasonal changes in atmospheric transmissivitties and surrounding albedo is tested in a mountainous watershed in Wyoming. This methodology represents an improvement on the current algorithms to compute terrain and radiation values on unstructured-mesh terrain models. All terrain-related features (e.g., slope, aspect, sky view fraction) can be pre-computed and stored for easy access into a subsequent, progressive-in-time, numerical simulation.