Movement Of Sun Research Articles

Perspectives on the SUN Movement: Waterlow lecture delivered at the International Congress of Nutrition in Granada, 16 September 2013.

The Waterlow lecture was named to commemorate Professor John Waterlow, an eminent figure in nutrition during the last half of the 20th century. David Nabarro worked with Professor Waterlow for a period of his career and was invited to deliver the Waterlow lecture during the International Congress of Nutrition in Granada on 16 September 2013.

Light coupling into the Whispering Gallery Modes of a fiber array thin film solar cell for fixed partial Sun tracking

We propose the use of whispering gallery mode coupling in a novel configuration based on implementing a thin film cell on the backside of an array of parallel fibers. We performed numerical calculations using the parameters of a thin film organic cell which demonstrate that light coupling becomes more effective as the angle for the incident light relative to the fiber array normal increases up to an optimal angle close to 55 deg. At this angle the power conversion efficiency of the fiber array solar cell we propose becomes 30% times larger than the one from an equivalent planar cell configuration. We demonstrate that the micro fiber array solar cell we propose may perform an effective partial tracking of the sun movement for over 100 degrees without any mechanical help. In addition, in the event that such fiber array cell would be installed with the adequate orientation on a vertical façade, an optimal photon-to-charge conversion would be reached for sunlight incident at 55 deg with respect to the horizon line, very close to the yearly average position for the sun at Latitude of 40 deg.

Mechanical Sun-Tracking Technique Implemented for Maximum Power Point Tracking of a PV System for Effective Energy Supply

This paper elucidates a single axis solar tracker system that automatically searches the optimum PV panel position with respect to the sun by means of a DC motor controlled by an intelligent drive unit that receives input signals from light dependent sensors. A prototype of the mechanical maximum power point tracker (MMPPT) was implemented with a motor size of 48W. The power supply unit consists of only supply source which is the AC mains. The sensor unit consists of six sensors. While five are fixed and adjacently aligned at 36 o to each other (tracking sensors), the sixth one is movable as it is attached to the surface of the PV panel (feedback sensor). The control unit is divided into two parts: A priority voltage selector and a movement controller. The priority voltage selector comprises of cascaded comparators which compares the five voltage outputs from the sensors and selects the highest voltage (priority voltage).The movement controller compares the feedback voltage with the priority voltage and logically decides whether to move the motor clockwise or anti-clockwise. The solar panel is allowed to move from east to west and back forth with a maximum allowable angle of 180 o . Its movement is in only one axis. The prototype built carries the panel from eastward to westward tracking the sun movement from sun rise to sun set and then reset to face eastward as darkness sets in. The results obtained from the prototype MMPPT were used to compare with the results obtained from fixed panel under the same environmental conditions and at the same time interval of 30 minutes using the same type of PV panel. The result from MMPPT has a gain of 5.77% over its counterpart which is fixed panel. http://dx.doi.org/10.4314/njt.v33i2.13

Synthesis of Four Bar Slider Mechanism for Finitely Three Separated Positions

Movement of the heliostat tracking sun is able to achieve through simple four bar mechanism. Design methods for four bar linkage encompass a mathematical approach, trial and error method, function generation, motion synthesis and path synthesis. The paper presents a study of motion synthesis of four bar slider mechanism applies to heliostat movement. Mathematical equations used for the synthesis are presented and the results are compared with the graphical method. Procedure of various methods to determine the length and position of the links in case of desired positions of the coupler are presented. As a conclusion, both methods are able to achieve wanted results with an acceptable degree of accuracy. However, the graphical method is helpful to provide better insight of the system during designing the solution compared to the mathematical method.

Flexible-textured polydimethylsiloxane antireflection structure for enhancing omnidirectional photovoltaic performance of Cu(In,Ga)Se_2 solar cells

Because of the Sun's movement across the sky, broadband and omnidirectional light harvesting is a major development in photovoltaic technology. This study reports the fabrication and characterization of flexible-textured polydimethylsiloxane (PDMS) film on Cu(In,Ga)Se2 (CIGS) solar cells, which is one of the simplest and cheapest peel-off processes for fabricating a three-dimensional structure. A cell containing a textured PDMS film enhanced the short-circuit current density from 22.12 to 23.93 mA/cm2 in a simulated one-sun scenario. The omnidirectional antireflection of CIGS solar cells containing various PDMS films is also investigated. This study uses an angle-resolved reflectance spectroscope to investigate the omnidirectional and broadband optical properties of the proposed PDMS film. This improvement in light harvesting is attributable to the scattering of the PDMS film and the gradual refractive index profile between the PDMS microstructures and air. The flexible-textured PDMS film is suitable for creating an antireflective coating for a diverse range of photovoltaic devices.

Development of a Spherical Solar Collector with a Cylindrical Receiver

Solar energy can be used for substitution of the depleting fossil fuels in thermal applications and electricity generation through thermal route. For medium and high temperature applications, a system for collecting solar energy at high temperatures was developed and built in this research work. The system, built at the center of development of renewable energy of the Algiers, consists of a 2θm= 60o included angle, R0 = 0.90 m diameter spherical reflector with a cylindrical receiver filled with water, tracking reflector which moves into the focus following the sun's movement. The system is capable of heating water or other fluids to temperatures above 350oC, thus making it possible to obtain process heat for domestic use and to store solar energy in a compact and economical way. An analysis of the system's optical characteristics was performed to aid in the design of the spherical reflector and cylindrical receiver. The thermal performance of the system was analyzed. The effects of mirror reflection, concentration ratio, heat transfer to the fluid (water), incidence angle, size and form of the cylindrical receiver, environmental conditions (wind, ambient temperature), have been studied by means of thermal model.The performance of the spherical reflector was tested by the temperature of the water. Total efficiencies (solar to thermal) of ηth= 60% -70% were obtained for a wide range of temperatures up to 350oC. The results of the present study show that it is possible to use the spherical reflector for systems requiring process heat and make possible substantial utilization of solar energy and considerable savings relative to fossil energy in the sunny countries of the world.

Suryanamaskara exercise enhances sustained attention

Background: The Suryanamaskara (SN) exercise is a comprehensive yoga technique which incorporates physical activity, breath regulation, relaxation and awareness. Apart from improving physical stamina and endurance, SN has been shown to influence an individual's perception and performance. But its immediate effect on sustained attention was not reported adequately. Objective: The study was designed to assess the immediate effect of 108 SN on sustained attention, efficiency and speed of visual scanning in subjects participated in Rathasapthami day (the seventh day following the Sun's northerly movement). Materials and Methods: In this single and mixed group pre-post study, 96 subjects with mean age 33.15 ± 13.61 years participated. The Six Letter Cancellation Test (SLCT) and Digit Letter Substitution Test (DLST) data were collected immediately before and after 108 SN. Statistical Analysis: Means, Standard Deviations, Kolmogorov-Smirnov test and Wilcoxon Signed Ranks Test were used for analyzing the data with the help of SPSS-16. Results: When compare with predata analysis, the SLCT showed 30.61% increase (P < 0.001) in Total Attempted (TA), 81.58% decrease (P < 0.01) in Wrongly Attempted (WA) and 31.87% increase (P < 0.001) in Net Score (NS). Similarly, the DLST showed 38.71% increase (P < 0.001) in TA, 13.64% decrease (P = 0.001) in WA and 35.44% increase (P < 0.001) in NA. Thus, the analysis of SLCT and DLST scores shows that SN was associated with increase in TA and NS and decrease in WA scores. Conclusion: When compared with pre data analysis, the post analysis of SLCT and DLST scores showed that the SN was associated with increase in TA and NS and decrease in WA scores. Thus, the SN holds great promise in enhancing sustained attention in healthy individuals. Well-designed studies are needed before a strong recommendation can be made.

Image-based relighting from a sparse set of outdoor images

We propose a novel method for relighting the image of outdoor scenes viewed from a fixed camera based on a sparse set of images of the same scene under different illumination. Unlike previous methods which require capturing images under pre-designed lighting or employing the 3D model of the target objects, our method adopts the technique of basis image which encapsulates material and geometry information of the scene into one image. We present a new method to calculate the basis images of an outdoor scene based on the sampling images captured in different time of a day, the relighting images corresponding to new sunlight incidence directions with arbitrary intensity can then be generated with these basis images. Besides, the subordinate shadow effect adhering to the sun's movement is also simulated, producing a visually plausible relighting result. Experiments demonstrate the efficiency and validity of our approach.

Nutrition in Sub-Saharan Africa: Setting the Stage for a Post-2015 Take-off

The MDGs have provided opportunities for addressing undernutrition in sub‐Saharan Africa. The link between addressing undernutrition and human capital development has been a key message. The African Union (AU) now realises the unique role nutrition plays in Africa's development. The AU's NEPAD (New Partnership for Africa's Development) and CAADP (Comprehensive Africa Agriculture Development Programme) have incorporated nutrition in their programmes. Additionally, 30 October is now commemorated as Africa Food and Nutrition Day. Through the SUN Movement, many African countries have committed to address undernutrition. Moving forward, the momentum for nutrition must be sustained. Commitments made must be reflected in increased resources and effective programmes. Africa must take advantage of ICT (information and communication technology); strengthen democratic structures and empower women to maximise their contribution to development; create safety nets for the vulnerable; and close the inequity gap. Civil society must remind governments of their commitments. Sub‐Saharan Africa must take advantage of this favourable environment and put the continent on an accelerated course of action.

Measurements on pointing error and field of view of Cimel-318 Sun photometers in the scope of AERONET

Abstract. Sensitivity studies indicate that among the diverse error sources of ground-based sky radiometer observations, the pointing error plays an important role in the correct retrieval of aerosol properties. The accurate pointing is specially critical for the characterization of desert dust aerosol. The present work relies on the analysis of two new measurement procedures (cross and matrix) specifically designed for the evaluation of the pointing error in the standard instrument of the Aerosol Robotic Network (AERONET), the Cimel CE-318 Sun photometer. The first part of the analysis contains a preliminary study whose results conclude on the need of a Sun movement correction for an accurate evaluation of the pointing error from both new measurements. Once this correction is applied, both measurements show equivalent results with differences under 0.01° in the pointing error estimations. The second part of the analysis includes the incorporation of the cross procedure in the AERONET routine measurement protocol in order to monitor the pointing error in field instruments. The pointing error was evaluated using the data collected for more than a year, in 7 Sun photometers belonging to AERONET sites. The registered pointing error values were generally smaller than 0.1°, though in some instruments values up to 0.3° have been observed. Moreover, the pointing error analysis shows that this measurement can be useful to detect mechanical problems in the robots or dirtiness in the 4-quadrant detector used to track the Sun. Specifically, these mechanical faults can be detected due to the stable behavior of the values over time and vs. the solar zenith angle. Finally, the matrix procedure can be used to derive the value of the solid view angle of the instruments. The methodology has been implemented and applied for the characterization of 5 Sun photometers. To validate the method, a comparison with solid angles obtained from the vicarious calibration method was developed. The differences between both techniques are below 3%.

Exploring the Visuospatial Challenge of Learning About Day and Night and the Sun's Path

ABSTRACTThe role of visualization and model‐based reasoning has become increasingly significant in science education across a range of contexts. It is generally recognized that supporting learning in developing causal explanations for observed astronomical events presents considerable pedagogic challenge. Understanding the Sun's apparent movement across the sky requires a sophisticated interpretation of visuospatial relations. This study explores how preservice teachers employ models in reasoning about this phenomenon. It adopts a research methodology that attempts to capture the fine detail of learning using a range of strategies to determine student teachers’ use of models in visuospatial reasoning. This included individual learners documenting their responses during taught sessions as part of the process of capturing their personal perceptions. Student reflections on their own learning were subsequently discussed during follow‐up audiotaped interviews. The findings revealed four different models of visuospatial reasoning used by the student teachers and highlighted subtle differences between individuals. The ways participants used these to make sense of the phenomenon and how this contributes to our understanding of model‐based reasoning in basic astronomy are discussed. © 2013 Wiley Periodicals, Inc. Sci Ed 97:772–796, 2013

A droplet manipulation on a liquid crystal and polymer composite film as a concentrator and a sun tracker for a concentrating photovoltaic system

We demonstrate a droplet manipulation on a liquid crystal and polymer composite film (LCPCF) as a concentrator and a sun tracker for a concentrating photovoltaic (CPV) system with a steady output electric power. The CPV system adopts a liquid lens on LCPCF whose curvature is not only tunable but position is also bistably switchable based on liquid crystal orientations on LCPCF. The change of curvature of the liquid lens results in a tunable concentration ratio which helps to increase photocurrent at a low illumination and prevent the effect of the series resistance at a high illumination. Moreover, the change of the position of the liquid lens helps to track sun owing to sun movement. Therefore, the output power of such a system is steady no matter the sunlight condition and the angle of incident light. The operating principles and experiments are investigated. The concept in this paper can be extended to design optical components for obtaining steady output power of the solar cell at indoor or outdoor use and also tracking sunlight.

Simulation and Evaluation of Small Scale Solar Power Tower Performance under Malaysia Weather Conditions

Solar energy is the most available, clean, and inexpensive source of energy among the other renewable sources of energy. Malaysia is an encouraging location for the development of solar energy systems due to abundant sunshine (10 hours daily with average solar energy received between 1400 and 1900 kWh/m2). In this paper the design of heliostat field of 3 dual-axis heliostat units located in Ipoh, Malaysia is introduced. A mathematical model was developed to estimate the sun position and calculate the cosine losses in the field. The study includes calculating the incident solar power to a fixed target on the tower by analysing the tower height and ground distance between the heliostat and the tower base. The cosine efficiency was found for each heliostat according to the sun movement. TRNSYS software was used to simulate the cosine efficiencies and field hourly incident solar power input to the fixed target. The results show the heliostat field parameters and the total incident solar input to the receiver.

Optical performance of solar reflective concentrators: A simple method for optical assessment

In reflective concentrating systems, mirrors play an essential role in directing and concentrating the energy from the sun to the modules. Shortcomings like misalignment, shading or bending of mirrors, due to their weight or wind, imply a higher probability of attenuated energy and non-uniform illumination on the receiver. The objective of this work is to design and test a method to assess the optical quality of solar concentrators, based on the absorber reflection method (ARM), which allows minimising the distance from the camera to the concentrator. The proposed procedure allows the characterization of the optical quality of reflectors when the concentrator is working at different inclinations tracking the sun's movement. The validation measurements were performed in a two-axis Fresnel reflective solar concentrator. Results from the method developed were included in two numerical procedures, ray-tracing and the sum-of-squares. From these simulations the overall effects of the optical quality and the sunshape over the absorber were considered and compared with the measured experimental concentrated flux distribution profile.

Dandelion-shaped nanostructures for enhancing omnidirectional photovoltaic performance

Broadband and omnidirectional light harvesting is important in photovoltaic technology because of its wide spectral range of radiation and the sun's movement. This study reports the fabrication and characterization of zinc oxide (ZnO) dandelions on Cu(In,Ga)Se2 (CIGS) solar cells. The fabrication of dandelions involves the combination of self-assembled polystyrene (PS) nanospheres and the hydrothermal method, which is one of the simplest and cheapest methods of fabricating a three-dimensional, closely packed periodic structure. This study also investigates the optimization on dimension of the PS nanospheres using the rigorous coupled-wave analysis (RCWA) method. This study uses an angle-resolved reflectance spectroscope and a homemade rotatable photo I-V measurement to investigate the omnidirectional and broadband antireflections of the proposed dandelion structure. Under a simulated one-sun condition and a light incident angle of up to 60°, cells with ZnO dandelions arrays enhanced the short-circuit current density by 31.87%. Consequently, ZnO dandelions are suitable for creating an omnidirectionally antireflective coating for photovoltaic devices.

방위각 추적식 프리즘형 집광조명시스템 성능평가

This thesis introduced an azimuth tracking prismatic daylighting system. The system improved several issues of the previous passive prismatic daylighting system: low efficiency at sunrise and sunset, glare effect and polarized. The system was developed to track the movement of sun with azimuth tracking device, and it has its own power from the attached solar cells. We compared the with previous passive one in terms with system efficiency and daylighting factors(DF).

Structure and Conceptual Design of a Water-Hammering-Type Honsang for Restoration

We analyzed the manufacturing procedure, specifications, repair history, and details of celestial movements of the water-hammering type <TEX>$Honsang$</TEX> (celestial globe). Results from our study on the remaining <TEX>$Honsangs$</TEX> in China and Japan and on the reconstruction models in Korea were applied to our conceptual design of the water-hammering type <TEX>$Honsang$</TEX>. A <TEX>$Honui$</TEX> (armillary sphere) and <TEX>$Honsang$</TEX> using the water-hammering method were manufactured in <TEX>$Joseon$</TEX> in 1435 (the 17th year of King <TEX>$Sejong$</TEX>). <TEX>$Jang$</TEX> <TEX>$Yeong-Sil$</TEX> developed the <TEX>$Honsang$</TEX> system based on the water-operation method of <TEX>$Shui$</TEX> <TEX>$y{\ddot{u}}n$</TEX> <TEX>$i$</TEX> <TEX>$hsiang$</TEX> <TEX>$t'ai$</TEX> in China. Water-operation means driving water wheels using a water flow. The most important factor in this type of operation is the precision of the water clock and the control of the water wheel movement. The water-hammering type <TEX>$Honsang$</TEX> in <TEX>$Joseon$</TEX> probably adopted the <TEX>$Cheonhyeong$</TEX> (天衡; oriental escapement device) system of <TEX>$Shui$</TEX> <TEX>$y{\ddot{u}}n$</TEX> <TEX>$i$</TEX> <TEX>$hsiang$</TEX> <TEX>$t'ai$</TEX> in China and the overflow mechanism of <TEX>$Jagyeongnu$</TEX> (striking clepsydra) in <TEX>$Joseon$</TEX>, etc. In addition to the <TEX>$Cheonryun$</TEX> system, more gear instruments were needed to stage the rotation of the <TEX>$Honsang$</TEX> globe and the sun's movement. In this study, the water-hammering mechanism is analyzed in the structure of a water clock, a water wheel, the <TEX>$Cheonhyeong$</TEX> system, and the <TEX>$Giryun$</TEX> system, as an organically working operation mechanism. We expect that this study will serve as an essential basis for studies on <TEX>$Heumgyeonggaknu$</TEX>, the water-operating astronomical clock, and other astronomical clocks in the middle and latter parts of the <TEX>$Joseon$</TEX> dynasty.

The Performance of Three Different Solar Panels for Solar Electricity Applying Solar Tracking Device under the Malaysian Climate Condition

The main objective of this study was to measure and determine the efficiency of poly-crystalline, mono-crystalline and amorphous silicon solar module by applying single-axis time/date solar tracker to the installation of photovoltaic panel (dynamic system) as a strategy to increase the performance of the modules under hot-humid climate of Malaysia. The dynamic system in this experiment was designed to support the three types of PV panels which allowed it to move with single degree of freedom (horizontally) according to the sun’s orientation (sunrise to sunset) from east to west. Studies on sun movement in equator countries have been conducted to locate the sun‘s position on site (azimuth and altitude angle) using the Stereographic Diagram and Tabulate Daily Solar Data. It was found that poly-crystalline solar module have shown better performance ratio and average module efficiency compare to the others tested PV module under Malaysian climate.

Rancang Bangun Sistem Kontrol Mekanisme Pelacakan Matahari Beserta Fasilitas Telekontrol Hemat Energi

Solar energy produced by concentrated solar heat collector panels requires tracking mechanisms for a more optimal direction. This paper presents the design and construction of a low energy solar tracking control system with telecontrol facilities. To accelerate the movement of the panel in always adjusting itself to the direction of the sun, a combination of the timer and light sensor was used. In this control system, the reference signal is taken from two pieces of light sensors while the feedback is taken from the position and temperature sensors. The program has been developed using C language and was implemented on the microcontroller ATMega8535 as the brain of the system. Telecontrol facilities for monitoring the data to a computer uses transceiver modules via RS-232 connection. A DC motor having power capacity of 0.74 watts was used and was clutched with 1:7,300 gearbox ratio. Experiments on light sensor characteristics and simulated movement of the panel were carried out. From the light sensor experiment it can be concluded that the sensor produces 0-4 volt output signal when bright 3.3-3.9 volts, when cloudy and 1.5-3.3 volts when sunny. From the simulation of panel movement, it is known that the solar tracking control system moves the panel and tracks the direction of the sun movement.

퍼지제어기를 이용한 반사경의 초점 위치제어에 관한 연구

본 논문은 태양과 반사경의 법선 벡터와 태양의 위치를 일치시키기 위하여 태양 궤적 추적 장치와 반사경의 오차 보정 장치를 설계하여 반사경의 법선 벡터와 태양의 위치를 일치시키도록 시스템을 설계하였다. 이렇게 설계된 시스템은 태양의 빛을 한 점으로 모을 수 있으며, 모여진 태양광을 광섬유를 통하여 원격지로 자연광을 보내어 유용한 광원으로 활용할 수 있다. 그러나 본 논문에서 제안한 이중화된 시스템의 제어기를 설계하기 위해서는 태양 궤적 추적 장치의 2축과 반사경 오차 보정 장치의 2축으로 구성되어 반사경의 법선 벡터에 대한 복잡한 상관관계가 존재하게 된다. 때문에 이러한 복잡한 방정식이 존재하므로 제어기 설계가 매우 복잡하게 된다. 그러나 본 논문에서는 복잡한 수학적 해석을 필요로 하지 않고 인간의 제어 해석 능력을 언어적 기법으로 표현할 수 있는 퍼지제어 기법을 활용하여 태양광을 하나의 정점으로 집광할 수 있는 시스템을 제시하고자 한다. The present study investigated the tracking system of a reflector to trace the movement of sun. The system was designed to minimize the error between the vertical vector of reflector and the position of sun. The proposed system was able to collect the sun lights at a point as a useful source of light energy and transmit the collected light to a remote area through optical fibers. Also the study successfully solved the controller design problem due to the complexity of modeling of the sun tracking system using a fuzzy logic controller which mimics human reasoning.