Calculating the shading reduction coefficient of photovoltaic system efficiency using the anisotropic sky scattering model

The front-row shading reduction coefficient is a key parameter used to calculate the system efficiency of a photovoltaic (PV) power station. Based on the Hay anisotropic sky scattering model, the variation rule of solar radiation intensity on the surface of the PV array during the shaded period is simulated, combined with the voltage–current characteristics of the PV modules, and the shadow occlusion operating mode of the PV array is modeled. A method for calculating the loss coefficient of front shadow occlusion based on the division of the PV cell string unit and Hay anisotropic sky scattering model is proposed. This algorithm can accurately evaluate the degree of influence of the PV array layout, wiring mode, array spacing, PV module specifications, and solar radiation on PV power station system efficiency. It provides a basis for optimizing the PV array layout, reducing system loss, and improving PV system efficiency.     

Mathematical model for calculating the shaded and sunlit areas in a circular courtyard geometry

This paper presents a mathematical model that was developed specifically to calculate the produced shaded and sunlit areas in a circular courtyard geometry. It examines the interaction taking place between the sun at any time throughout the year and a circular courtyard form with any dimensions and proportions in any place on the earth. This model was included in a new computer program, which allowed detailed investigation to be undertaken into the effect of circular courtyard proportions on the generated wall and floor exposed and shaded areas. The results showed that changing the form's proportions significantly influences the shading or exposure potential of the internal courtyard envelope.     

A mini-scale modeling approach to natural daylight utilization in building design

This paper purposes on shading devices as natural daylight utilization component for building design. It was proved that a proper setting for shading device could conspicuously promote the room lighting performance. Natural daylight which includes directional sunlight, diffused skylight and reflected light can also exert as a perspective of energy conservation in buildings. In order to verify a simple approach can also be workable, a mini-scale model (1:20) is employed in this study. It reveals that when a suitable altitude and azimuth is maintained, in regards to the vertical shading device and the sun position, not only is shading achieved, but the area of the daylight zone can also be substantially increased. The experiment investigated and analyzed the details of this modeling data and subsequently proposed relevant design criterion for vertical shading devices that both users and designers can apply. Namely, it proved that a mini-scale model could also assist in natural daylight utilization and building energy-conservation design.     

A graphical multi-objective performance evaluation method with architect-friendly mode

In response to the inadaptation and difficulties for architects in the use of engineering simulation tools and optimization methods, a method is proposed for graphical performance evaluation achieved with a developed plugin for Grasshopper as an architect-friendly tool to support design exploration in early stage. The proposed method follows forward workflow for interactive feedback of performance, focusing on thermal and visual comfort upon a variety of design options. A case study of shading design is demonstrated. The demonstration illustrated an intuitive and graphical process for qualitative performance evaluation, which is assisted by an overall ratio ranking the integrated performance of design options for a quantitative comparison. Compared with engineering optimization methods that focus on optimal performance-based solutions, the proposed method presented graphical feedbacks on design performance that are interactive with the designer for performance-informed decision making. In this way, the proposed method stimulates the effective and positive application of engineering tools and judgment at the early stage of iterative design.     

A Practical and Controllable Hair and Fur Model for Production Path Tracing

We present an energy‐conserving fiber shading model for hair and fur that is efficient enough for path tracing. Our model adopts a near‐field formulation to avoid the expensive integral across the fiber, accounts for all high order internal reflection events with a single lobe, and proposes a novel, closed‐form distribution for azimuthal roughness based on the logistic distribution. Additionally, we derive, through simulation, a parameterization that relates intuitive user controls such as multiple‐scattering albedo and isotropic cylinder roughness to the underlying physical parameters.     

真空玻璃平板光伏构件光学物理性能检测与应用

本文首先介绍了真空玻璃平板光伏构件,然后根据相关标准测试该种构件的光学物理性能,最后分析该种构件在全国各气候分区的应用适宜性。     

Experimental study of free convection in a window with a heated between-panes blind

An experimental study has been conducted to examine free convection in a window with an enclosed aluminum venetian-type blind. The unique feature of this experiment was that the blind slats were heated electrically to simulate absorbed solar radiation. Convective heat transfer measurements and temperature field visualization were obtained using a Mach-Zehnder laser interferometer. Optical measurements were made for two glazing spacings, two blind slat angles, two blind heat flux levels, and two glazing temperature differences. Both local and average convective heat flux data were obtained in the center region of the tall air-filled enclosure. At the widest glazing spacing, the temperature field was found to be unsteady. For these cases, the temporal fluctuation of the local convective heat transfer was time-averaged using a high speed camera. The experimental results have been compared to a simplified method in the literature for predicting the center-glass heat flux for this configuration.     

Calculation procedure of the shading factor under complex boundary conditions

Together with the evolution of buildings and systems, energy assessment models have become more and more detailed, requiring a precise evaluation of the building loads and gains.For an accurate analysis of solar heat gains, technical standards introduce an external shading reduction coefficient of the incident solar radiation, called shading factor. Its value is provided for simple geometries, which are usually not suitable to properly describe a real environment. In addition, the relations adopted to evaluate the shading factor are based on simplified hypotheses, which cause non-negligible errors when compared to more complex algorithms.The objective of this study is the development of a calculation procedure of the shading factor under complex boundary conditions. The algorithms have been implemented in a software tool written in Matlab language. It can provide for the value of the shading factor on a generically oriented and tilted surface. After setting the site and the time for the simulation, generic-shaped windows can be modelled. The external environment, which can be imported from DXF files, can include a horizon profile, generic-shaped obstructions and vegetation. The calculation can be performed for every sky condition: clear, average or generic. In addition, the simulation can be run to obtain instantaneous, daily average or monthly average shading factor values.     

Off-normal solar optical property measurements using an integrating sphere

Shading devices attached to windows can be used to control solar gain and hence reduce building peak load and annual energy consumption. The performance of a shading device in this regard is strongly dependent on its solar optical properties. The current study discusses a unique measurement technique that was used to obtain off-normal solar optical properties of flat shading materials. The off-normal properties were needed in order to develop solar optical property models both for shading materials and shading devices. These models provide useful input to building peak load calculation and annual energy simulation tools. Special sample holders were designed and fabricated to facilitate measurements using a commercial spectrophotometer with integrating sphere attachment. A combination of theory and companion tests were used to confirm the validity of the approach.     

Real time discrete shading

A shading technique for voxel-based images, termedcongradient shading, is presented. As the surface information is not available in voxel representation, the surface normal must be recovered from the 3D discrete voxel map itself. The technique defines the normal as one of a finite set of neighborhood-estimated gradients and can thus employ precalculated look-up tables. Furthermore, a table-driven mechanism permits changing the light source parameters by merely redefining the look-up table. The technique uses only simple arithmetic operations and is thus suitable for hardware implementation. Since it has been implemented not as a post-processor, but as part of the projection pipeline of the cube architecture, congradient shading can be executed in real time. Two versions of the technique in real time. Two versions of the technique have been conceived and implemented:unidirectional shading, in which the gradient is estimated only from neighborhoods along the scan-lines;bidirectional shading, in which both horizontal and vertical components of the gradient are considered. In spite of the simplicity of the technique, the results are practically indistinguishable from images generated by conventional techniques.This work was supported by the National Science Foundation under grants DCR 8603603, CCR 8743478, CCR 8717016, and MIP 8805130