Incident Angle Of Sunlight Research Articles

Micro-patterned glass for energy-efficient windows

Development of novel energy-efficient components is a topic of prime importance in building design. In this contribution, we propose a micro-patterned glass window which can be designed to efficiently reduce the energy demands of buildings located within an area of hot and cold seasons. The proposed patterned structure can be applied to any panes of glass in single or multi-pane windows. We first define the total positive power as a characteristic parameter for evaluating the effectiveness of using the designed window in reducing the average thermal power demands of a given building. Then, a full-wave numerical method is employed to analyze the performance of the proposed structure with respect to the defined characteristics. Our model accurately accounts for sunlight incident angle variations corresponding to different times of the days in every season. In addition, the variations of glass refractive index throughout the solar spectrum, non-polarized nature of the sun light, and typical dimension scales used in building windows are taken into account. Our numerical results show more than 80 W and 160 W total positive power for an optimized single-pane micro-patterned window with unit area and a double-pane one, respectively. We also present the design procedure of the proposed structure for a given geographical location of the building.

Low frequency error analysis and calibration for multiple star sensors system of GaoFen7 satellite

ABSTRACT The GaoFen7 (GF7) optical satellite is the first Chinese civilian sub-meter high-resolution stereo mapping satellite and is equipped with a double linear array camera and laser altimeter to achieve large-scale topographic mapping. To improve the accuracy of attitude determination, an attitude determination system comprised of four star sensors is loaded. According to the measurement accuracy and steady performance, the star sensors 1a and 1b is usually used together for satellite attitude calculation, which is called the conventional mode of attitude determination. Then, the combination of star sensors 2a and 2b is called the unconventional mode of attitude determination. Affected by variations in the incident angle of sunlight and solar radiation, thermal deformation occurs in the body and installation structure of the star sensor, which causes Attitude Low-Frequency Error (ALFE) and seriously influences the consistency of attitude determination results of different combination modes for multiple star sensors system. This study proposes an ALFE analysis and calibration approach for the multiple star sensors system of GF7 satellite to ensure the consistency of attitude determination results of different combination modes. Based on the statistical characteristics of the angles of the three axes, the installation parameters of the four star sensors are first calibrated. After analyzing the characteristics of the optical axis angles within 1420 orbit periods over 135 days, the segmented ALFE compensation model between the unconventional and conventional modes is proposed based on the Fourier series model and input parameter of latitude. Based on the on-orbit installation parameters and the ALFE model, the precise attitude determination results of the unconventional mode are calculated. Experimental results show that the attitude determination consistency after compensation is better than 2”. Moreover, the reliable application time range of the compensation model is 30 days to satisfy the requirements for high-precision attitude determination of GF7 satellite.

Prediction of regional vegetation cover using spatial image features and semantic segmentation

Vegetation is an essential part of our ecosystem; it also determines health of our planet. According to “The State of the World’s Forests 2020” only 31% of the global land area is covered with vegetation. This paper presents a superior way of representing vegetation cover in a region by utilizing Atmospherically Resistant Vegetation Index (ARVI) as vital features out of multispectral satellite images. These images comprise Green, Blue, Red and Near Infrared bands data which was further utilized by U-Net to efficiently segment satellite images. In remote sensing greenery of environment is traditionally determined using NDVI, one of the critical imperfections with this method is that it is liable to compute inaccurate values as a consequence of variations in soil, air moisture and shadowing affected by varying incidence angle of sunlight. On the other hand, ARVI is immune to such flaws and integration with deep learning provides a better solution for segmenting regional vegetation and predicting its coverage up to some extent. This method can be employed for predicting vegetation in any region along with assisting in events such as repopulating trees and urban planning while conserving beauty of our nature.

Simulation of Amorphous Silicon Carbide Photonic Crystal Absorption Layer for Solar Cells

In this work, the amorphous silicon carbide (a-SiC) with low cost and high extinction coefficient was used as the light absorption layer of solar cells, and the photonic crystal (PC) structure and defect structure were introduced. By optimizing the scatterer shape, structural parameters and defect types of photonic crystal, the absorption efficiency of the light absorption layer was further improved. The results show that the photonic crystal absorption layer with vacancy line defect is better than the perfect photonic crystal absorption layer. Meanwhile, the absorption efficiency of the photonic crystal absorption layer significantly improves in the case that the scatterer is an elliptical cylindrical air hole scatterer. When the incident light is in the wavelength range of 0.30~0.80 μm and the absorption layer height is 0.60 μm, the absorption efficiency of the absorption layer can reach 95.60%. Compared with the absorption layer without photonic crystal structure, the absorption layer is increased by 43.24%. At the same time, the absorption layer has little dependence on the incidence angle of sunlight. When the incidence angle is 65°, the absorption efficiency is still higher than 80%.

Low-cost system for sunlight incidence angle measurement using optical fiber

The development and optimization of renewable energy systems are some of the most necessary topics to advance towards secure and sustainable energy models. Photovoltaic energy is one of those sustainable options that could contribute to the reduction of greenhouse gas emissions. The optimal angle of solar incidence producing the highest absorption in a day is an important parameter to install photovoltaic systems. This value is often estimated using simulation models based on geographic location; however, those models ignore the influence of nearby obstruction objects, albedo, and local weather conditions. Such a problem is addressed in this work by designing a system to estimate the optimum angle of solar incidence for the photovoltaic panels. The system is based on an arrangement of 33 measurement points spaced in arcs every 45 degrees in azimuth and every 22.5 degrees in elevation, which provides a wide range for analysis. The light captured by each optical fiber is transmitted to a flat array where the power is measured using a single RGB camera.

A low-cost system for real-time measuring of the sunlight incident angle using IoT

The incidence angle of solar irradiance is an important parameter for sizing and locate photovoltaic systems, which affects the installation design and has a high influence in the power production of photovoltaic panels. This angle is traditionally estimated considering the geographical position, however, this approach ignores the existence of local elements that affect the generation, such as weather conditions, topography, constructions with high reflection, among others. Therefore, this work presents the design and construction of a measurement device with nine irradiance sensors, which are located at different angles on two orthogonal axes within a semisphere. Since the angles of the sensors are known, a model to determine the direction of the maximum incidence irradiance, at each instant of time, can be calculated from the on-site measurements. In this way, it is also possible to calculate the panel inclination and orientation producing the maximum power for a particular location. The device acquires the irradiance magnitude in the nine sensors in real time, and it is transmitted using the Internet to simplify data recollection. Finally, the device uses a low-cost platform, which makes possible the adoption of this solution in a wide range of applications, e.g. design, diagnostic or reconfiguration of PV arrays.

Enhancement in photoelectric performance of dye-sensitized solar cells with inverted pyramid structures based on nanoimprint lithography

The sunlight incident on outdoor solar cells comes from all directions, and the surface reflectance of covered glass of solar cells increases with the sunlight incident angle. The above-mentioned factors together lead to the absorption loss and low utilization of incident photons. An antireflection (AR) layer with micro-/nano-structures provides an omnidirectional-antireflection characteristic because of a gradual refractive index, which is a practical approach for solving the existing problems and further improving the photoelectric conversion efficiency (PCE) of solar cells. Micrometer-sized inverted pyramid structured polydimethylsiloxane AR layers were fabricated on surfaces of dye-sensitized solar cells (DSSCs) by a cost-effective method—nanoimprint lithography. Results show that the AR layers significantly reduce the reflectance and improve the PCE of DSSCs at oblique incidence. Reflectance decreases by 5.6%–10.58%, and the PCE relatively increases by 5.83%–15.25% in the light incidence angle range of 20°–60°. Meanwhile, the AR layer exhibits a hydrophobic surface with a water contact angle of ∼98.1°, which increases by 40.2° compared with the DSSC without the AR layer, and it further provides self-cleaning potential. Moreover, nanoimprint lithography could be integrated with industrial roll-to-roll technology, which reduces the fabrication cost and possesses industrial application potential.

Analysis Photovoltaic System in Relation to Tracking and Non-Tracking System

The increasing demand of electricity has been a great concern in recent years. The increasing demand and environmental (global warming) issues urged scientists to evolve in the field of renewable energy. Solar energy is one of the major sources of renewable energy. Electrical energy is produced by photovoltaic cells when they allow light particles to knock free electrons from atoms. The amount of electrical output produced by the system is dependent on amount of solar energy received by PV cells. To increase solar energy output, a fixed solar panel inclined towards the optimal point is usually used. The collection of solar energy is increased by using solar tracking systems i.e. single axis or dual axis, which continuously track the sun using incidence angle of sunlight. The analysis is carried out to compare the performance between tracking and non-tracking photovoltaic systems. Data of specific solar panel systems is analysed and compared with simulations and actual outputs to compute performance ratios and deduce conclusions. The average performance ratio is found out to be 0.73 for non-tracking system and 0.90 (17% more than non-tracking systems) for tracking systems. The accuracy of estimated output of a PV system can be improved by using more accurate solar irradiance data, accurate weather conditions, exact system losses and matched inverter efficiency. The efficiency of a PV system can be improved by using solar trackers, using more efficient solar panels, installing them in a less shaded area, cleaning the panels on regular intervals, and using more efficient electricalcomponents.

The Impact of Reflectance Variation in Silicon Heterojunction Solar Cells and Modules on the Perception of Color Differences

The color produced by visible light that reflects from the photovoltaic modules can influence visual aesthetics for colored photovoltaic applications, such as the building integrated photovoltaic and the vehicles integrated photovoltaic. How two colors lying close together can be perceived by the human eye is important for aesthetic design. In this article, we investigate the reflectance spectra variation caused by the variation of indium tin oxide thickness and incidence angle of sunlight based on the well-known silicon heterojunction solar cells and modules. By converting the reflectance spectra into the Delta E 2000 value, we quantify whether differences in color can be perceived. The colors are also predicted based on the standard red, green, and blue color space. The results show that the reflectance variation because of an ITO thickness deviation of 5 nm in SHJ solar cells leads to a perceptible color difference, which can be suppressed after encapsulation but is still perceptible on close observation. The ITO thickness deviation should be controlled within 3 nm to produce a nearly imperceptible visual appearance. The color difference of SHJ modules with an ITO thickness of 70 nm is nearly imperceptible if the incidence angle is below 70°. For comparison, the color differences of the passivated emitter and rear contact solar cells using SiNx as an antireflection layer is also investigated.

Factors affecting wavelength-resolved ultraviolet irradiance indoors and their impacts on indoor photochemistry.

We measured wavelength-resolved ultraviolet (UV) irradiance in multiple indoor environments and quantified the effects of variables such as light source, solar angles, cloud cover, window type, and electric light color temperature on indoor photon fluxes. The majority of the 77 windows and window samples investigated completely attenuated sunlight at wavelengths shorter than 320nm; despite variations among individual windows leading to differences in indoor HONO photolysis rate constants (JHONO ) and local hydroxyl radical (OH) concentrations of up to a factor of 50, wavelength-resolved transmittance was similar between windows in residential and non-residential buildings. We report mathematical relationships that predict indoor solar UV irradiance as a function of solar zenith angle, incident angle of sunlight on windows, and distance from windows and surfaces for direct and diffuse sunlight. Using these relationships, we predict elevated indoor steady-state OH concentrations (0.80-7.4×106 molec cm-3 ) under illumination by direct and diffuse sunlight and fluorescent tubes near windows or light sources. However, elevated OH concentrations at 1m from the source are only predicted under direct sunlight. We predict that reflections from indoor surfaces will have minor contributions to room-averaged indoor UV irradiance. These results may improve parameterization of indoor chemistry models.

Design and preliminary performance analysis of a novel solar-gas combined cycle system

Aiming at deepening the grid penetration of solar energy and reducing the carbon emission, a novel solar-gas combined cycle (SGCC) system using the solar direct steam generation (SDSG) technology is proposed in this study. The design principle and configuration of the proposed SGCC system is provided. The EBSILON code is used to establish the calculation model of the SGCC system. The performance comparison of the SGCC system for five different typical cities of China is carried out and the solar collector field area of the SGCC system is optimized. The results show that the best region in the five cities for the operation of the proposed SGCC system is Yulin City and the solar multiple of 1.25 can lead to the minimum average energy cost of solar utilization sub-system. Effects of eight typical parameters on the performance of the SGCC system are investigated, including the gas turbine load rate, solar DNI, ambient temperature, relative humidity, atmospheric pressure, incident angle of sunlight, intake pressure loss and exhaust pressure loss of gas turbine. The results indicate that the SGCC system is greatly influenced by the ambient temperature and the optimal ambient temperature is approximately 10.0 °C.

Photovoltaic Effect Related to Methylammonium Cation Orientation and Carrier Transport Properties in High-Performance Perovskite Solar Cells.

Solar cells based on organic-inorganic hybrid halide perovskites (OIHHPs) have been widely studied because of their increasing power conversion efficiency. Extensive research has been conducted in electrical and optical properties and device fabrication. However, in terms of material science, the photovoltaic effects of OIHHP are still not well understood. Here, we theoretically investigate the photovoltaic phenomena of MAPbI3 (MA = CH3NH3+) under standard AM 1.5G sunlight illumination, considering the MA cation orientation, light incident angle, polarization, and photon energy, using Keldysh nonequilibrium Green's function formalism combined with density functional theory calculations. It is found that the short-circuit current density Jsc has a maximum value of 383.149 A/m2 when the MA orientation is parallel to the transport direction, whereas it is negligible when the MA orientation is orthogonal to the transport direction. In addition, full consideration is also given to the direction of incidence of sunlight and its polarization state. Nevertheless, of all factors considered, MA orientation plays the decisive role, for Jsc still has a respectable value of 364.112 A/m2 even for a 90° sunlight incident angle relative to the transport direction, so long as the MAs are aligned in the transport direction. The increase in the photocurrent is attributed to an increase in the transmission coefficient of low-energy holes, as well as improvement of the velocities and mobilities of electrons and holes in the MAPbI3-based device with [001] MA orientation. The results suggest that during the designing of high-performance OIHHP-based solar cells and photoelectronic devices, the crystal orientation and MA cation orientation relative to the transport direction should be carefully considered as they directly affect carrier transport properties.

High-efficiency white-light solar window using waveguide glass plate

A high-efficiency white-light solar window is proposed for building-integrated photovoltaic (BIPV) applications. In the solar window, incident light is scattered at a waveguide plate and guided into GaAs cell arrays at the edges of the window frame. The optical characteristics of the waveguide plate are designed and evaluated using a ray-tracing simulation, and the solar window is fabricated and assembled with three-dimensional printing. The solar window exhibits an almost constant transmittance, with an average of about 21.6% in the visible range of 400–800 nm and a color rendering index of about 97.8 for sunlight, which is a neutral color that does not distort the colors of indoor objects under sunlight through the window. The solar window achieves a geometric concentration gain of 1.14 and edge collection ratio (ECR) of about 27.0%, which is constantly obtainable regardless of the incident angle of sunlight, and it exhibits an efficiency of 6.368%, a very high value for conventional transparent solar cells and modules. The method for optimizing the window efficiency and effective indoor illuminance by increasing the size of the solar window is also presented. These results can contribute to the further development of high-performance and large-area BIPV windows.

Design of an optimal fuzzy controller to obtain maximum power in solar power generation system

P-V characteristic of the solar cells are nonlinear and depends on the environmental conditions such as irradiations, sunlight incident angle, cell temperature, and load conditions. Therefore it is crucial to operate the photovoltaic module at its maximum power point (MPP) all the time. Hence, a Maximum power point tracking (MPPT) methods are used to maximize the PV module output power by tracking continuously the MPP.In this paper, fuzzy logic controllers (FLC) are designed for maximum power point tracking (MPPT) in a photovoltaic system and then fuzzy membership functions of the fuzzy controller are optimized using Firefly Algorithm (FA) to generate the proper duty cycle. FA which is inspired by natural species to optimize nonlinear functions is one of the most successful and low-cost algorithms in this field. Finally, PV system with FLC-FA is compared with other methods like perturbation and observation (P&O) and fuzzy controller- Particle swarm optimization (PSO). According to the simulation results, asymmetric fuzzy membership functions based on FA increase tracking speed of MPPT and improve tracking accuracy compared to P&O, symmetric fuzzy membership functions and asymmetric fuzzy membership functions based on PSO.

Effects of receiver parameters on the optical performance of a fixed-focus Fresnel lens solar concentrator/cavity receiver system in solar cooker

To facilitate building integration with solar cooker for household, a solar cooker based on a fixed-focus Fresnel lens solar concentrator/cavity receiver system was proposed. To increase the system optical efficiency, the cavity receiver with bottom reflective cone was used as a fixed receiver. Expecting to optimize the system and receiver of better optical performance, the effects of receiver parameters on it were studied. To evaluate the effects, a significance test of key factors was conducted. Comparative analysis of fixed-focus food cooking system was undertaken. The analysis shows that average optical efficiencies using cavity receiver with bottom reflective cone of spherical, cylindrical, conical are 72.23%, 68.37% and 76.40%, respectively, while that of their corresponding conventional cavity receivers are 68.49%, 31.91% and 74.61%. The former significantly increased 3.74%, 36.46% and 1.79%, respectively. Moreover, cavity receiver with bottom reflective cone angle 90° is able to hold a higher amount of incoming energy from concentrator, compared to other three angles. Increasing the bottom reflective cone reflectivity and cavity receiver surface absorptivity can improve optical efficiency. In addition, the cavity receiver surface absorptivity and concentrated sunlight incidence angle have the most significant influence on the optical efficiency and flux uniformity, respectively. The conical cavity receiver with bottom reflective cone is the most suitable one for system. This work is expected to be useful for further optimization of solar concentrator/cavity receiver system.

Flat Concentrator Photovoltaic System with Lateral Displacement Tracking for Residential Rooftops

We present a design for a flat concentrating photovoltaic (CPV) system that requires only lateral displacement for sun-tracking, intended for residential rooftop applications. Compared with flat-plate photovoltaics (PVs), CPV technology is essential for reducing the use of semi-conductor materials, which also enables cheaper solar power generation. Existing CPV designs are more bulky and complex than traditional PV panel techniques and are therefore better suited to solar farms than rooftop use. In this study, we explore an alternate approach, employing a mirror-coated lenslet array, to demonstrate a flat CPV system for rooftop installation. This mirror-coated lenslet array collects solar radiation and concentrates it with a very short focal length. The lateral movement of lenslet focal points according to a changing incident angle of sunlight allows for the use of a lateral displacement tracking mechanism. A square array of solar cells integrated on a transparent sheet is placed on top of a mirror-coated lenslet array to collect focused sunlight and convert it to electricity. The proposed CPV panel can be achieved with a 35 mm thickness. Simulation models were developed using commercial optical design software (LightTools). The simulation demonstrates an optical efficiency of up to 89.5% when the concentration ratio of the system is fixed to 50×. The simplicity of the structure enables cheaper mass production. Our quest for a lateral displacement sun-tracking mechanism also shows that the system has a high tolerance, thereby enabling cost savings by replacing a highly precise, active sun-tracking system with a lower-accuracy system. The presented flat CPV is a strong candidate for a low-cost, high-efficiency solar energy system that can be installed on the rooftops of residential buildings to deliver energy savings.

The effect of substrate morphological structure on photoelectrical conversion performance of silicon solar cell

A novel method is proposed to evaluate electrical characteristics of silicon solar cell at real operating conditions. Silicon solar cells with different substrate morphological structures have various photoelectrical performances. The effect of substrate morphological structure on photoelectrical conversation performance of silicon solar cell has been investigated by illustration analysis, mathematical model and I-V test system. Results show that the solar cell with the porous-sponge like substrate has better electrical characteristics than those with conical like substrate morphological structure. The output power of porous substrate solar cell can exceed by 11% at 40 degree incident angle of sunlight compared to conical substrate solar cell.

A side by side comparison of the cooling effect of building blocks with retro-reflective and diffuse-reflective walls

Solar irradiance incident to an urban canyon with traditional diffuse reflective (DR) surfaces is subjected to multiple reflections, which increase the solar absorption of urban buildings and consequently contribute to the development of the unban heat island. Retroreflective (RR) materials direct the incident radiation back to its source and thus have the potential to reduce the heat intake of the urban surfaces. This study experimentally investigates the temperatures of the inner and outer walls of two small-scale building blocks with RR and DR surfaces, respectively. Two blocks stood side by side and were set at an experimental site such that both blocks were sunlit for a half day and were shaded for the other half day. It was found that the RR wall can keep the building blocks cooler than the DR wall during a sunny weather, and that the cooling effect is very small during a cloudy weather. The RR surface loses retro-reflectivity when the sunlight incident angle on the surface exceeds a certain angle (about 40°).

Tracking control and output power optimization of a concentrator photovoltaic system with polar axis

The tracking control and output power optimization of our concentrator photovoltaic (CPV) system with polar axis has been studied. The close-loop automatic control based on real-time optical feedback is proposed to implement accurate sun-tracking of our CPV system, in which the hybrid tracking algorithm, making use of the tracking tolerance and timing, is presented. Hence, the strict requirement for the incident angle of sunlight can be satisfied to the maximum extent and the operating costs of our CPV system can be reduced. The power output maximization and tracking control optimization are achieved under the real irradiance of 910W/m2, which is verified by the corresponding data measurement and error analysis.

Numerical study on the performance of a solar chimney power plant

A 3D numerical approach that incorporates the radiation model, solar load model, and a real turbine was used in this study. Variations in turbine performance with rotational speed were studied to investigate the power-regulating strategy option for solar chimney turbines. The results of simulations with a fan model and a real turbine were compared. The findings indicated that the fan model is a convenient approach to investigate the turbine pressure drop and updraft velocity in the design of solar chimney power plant (SCPP) without considering the turbine efficiency. In addition, the influences of the incident angle of sunlight on SCPP performance were investigated for the first time, and the results revealed that considering the hourly variation of the zenith angle of the sun and conducting shading calculation when predicting SCPP performance in the design and cost analysis, particularly annual performance, were necessary.