Simplified architectural method for the solar control optimization of awnings and external walls in houses in hot and dry climates

In extremely hot and dry climates, like northwestern Mexico, solar gain reduction in houses using solar passive techniques is important for improving comfort inside the construction and to save costs in electrical cooling during the whole year, because the winter season is also hot in those regions. A new one-dimension method is proposed to analyze the interaction between two common shading devices: awnings and external walls to reduce insulation on the facade and inside the house due to fenestration. The method is demonstrated by optimizing a typical dwelling with an azimuth of 90° (east), which, achieves 45% reduction in direct solar insulation during the summer solstice on the profile of the facade. Results showed that this method is simple and reliable in increasing the shadow on the facade and to block completely the solar beam radiation on the windowpane with optimal relations between these shading devices.     

Reassessment of fenestration characteristics for residential buildings in hot climates: energy and economic analysis

This paper attempts to resolve the reported contradiction in the literature about the characteristics of high-performance/cost-effective fenestration of residential buildings, particularly in hot climates. The considered issues are the window glazing property (ten commercial glazing types), facade orientation (four main orientations), window-to-wall ratio (WWR) (0.2–0.8), and solar shading overhangs and side-fins (nine shading conditions). The results of the simulated runs reveal that the glazing quality has a superior effect over the other fenestration parameters and controls their effect on the energy consumption of residential buildings. Thus, using low-performance windows on buildings yields larger effects of WWR, facade orientation, and solar shading than high-performance windows. As the WWR increases from 0.2 to 0.8, the building energy consumption using the low-performance window increases 6.46 times than that using the high-performance window. The best facade orientation is changed from north to south according to the glazing properties. In addition, the solar shading need is correlated as a function of a window-glazing property and WWR. The cost analysis shows that the high-performance windows without solar shading are cost-effective as they have the largest net present cost compared to low-performance windows with or without solar shading. Accordingly, replacing low-performance windows with high-performance ones, in an existing residential building, saves about 12.7 MWh of electricity and 11.05 tons of CO₂ annually.     

Using a shading matrix to estimate the shading factor and the irradiation in a three-dimensional model of a receiving surface in an urban environment

In an urban environment, grid-connected building integrated photovoltaic (PV) systems can be subject to complex shading patterns. The study of the shadows projected by nearby buildings and other elements around a PV surface permits cutting down energy losses due to the module’s partial shading and improving the system’s performance ratio, so that the energy production costs can be lower. This paper presents a methodology that estimates the shading factor and irradiation on a three-dimensional model of a receiving surface in an urban environment. The main innovations introduced by this methodology are the building of a shading matrix composed by direct shading factor values around the whole sky dome and the analysis of the shading impacts on direct beam, isotropic diffuse, circumsolar diffuse and horizon brightening diffuse solar radiation components. The shading matrix improves the time spent on long simulation periods and permits an easy numerical integration over the sky to obtain the diffuse shading factors. Using this feature, a plug-in to the Google SketchUp three-dimensional modeling software was built to test this methodology. A series of similar results were obtained between actual measurements and estimates conducted by the plug-in.     

Optimal distribution for photovoltaic solar trackers to minimize power losses caused by shadows

The typical design of photovoltaic facilities with photovoltaic solar trackers is achieved using a squared or diagonal distribution of the trackers. In general, this is a good distribution for harvesting most solar radiation. However, these facilities can be affected by shadows of environmental objects like buildings, vegetation, etc. In this paper, a metaheuristic method based on evolution strategies is presented for calculating the best location of each tracker on a building of irregular shape, considering the shadows caused by obstacles and photovoltaic trackers. The evolution strategies will use the energy readings obtained by a photovoltaic tracker distribution to look for the best location. In the calculus of the energy, solar charts are used to combine the solar radiation received and shadows suffered by the tracker for each solar position.     

相同参数不同形状局部阴影对光伏阵列输出特性的影响

对包括并联结构(SP)、网状结构(TCT)、桥式结构(BL)和蜂巢结构(HC)在内的4种光伏阵列结构在相同面积、不同形状类型局部阴影下的输出特性进行对比研究。结果表明:透光因子和面积相同、形状类型不同的局部阴影对4种结构光伏阵列输出特性的影响各不相同,其中TCT结构受离散型局部阴影的影响最小,而SP、BL和HC结构受竖向规则型局部阴影的影响最小,且BL和HC结构在功率输出和成本之间都建立了较好的平衡性。     

Determination of energy output losses due to shading of building-integrated photovoltaic arrays using a raytracing technique

In this contribution a simulation procedure is described which was developed as a working tool to calculate the energy output of building-integrated photovoltaic (PV) arrays experiencing shading or reflection effects. A three-quadrant solar cell model incorporating the reverse bias characteristics and breakdown voltage is verified by current-voltage (I–V) measurements performed on commercially manufactured mc-Si solar cells under controlled laboratory conditions. For the simulations, a point matrix giving the irradiation distribution over the PV array is calculated for each hour using a raytracing technique. With a raytracing technique, shading of both beam and diffuse irradiation as well as primary and secondary reflections can be modelled. The results of two cases studies simulated using this technique are presented and analysed. In conclusion, general guidelines based on the simulation results are drawn up. These guidelines aim to assist architects and engineers in planning an optimized layout strategy of building-integrated PV arrays to reduce energy losses caused by shading.     

Dye solar modules for facade applications: Recent results from project ColorSol

With respect to a first market introduction, one advantage of dye solar cell (DSC) modules is the combination of photovoltaic (PV) solar electricity with decorative aspects. We report on the recent results achieved in the frame of the German project ColorSol. The project focuses on the application field of building-integrated PVs (facades, PV-glazing, etc.). Design concepts, as well as scenarios for the application of the DSC technology in architecture and facade planning are developed and the application potential is quantified in cooperation with potential users. Prototypes of glass facade elements (70 cm×200 cm) have been developed which consist of several serially interconnected DSC modules each with a size of 30 cm×30 cm. The results of module characteristics under various outdoor illumination conditions and under partial shading are reported. Visual impressions of the DSC facade elements are presented.     

A comparative analysis of the radiant effect of external sunshades on glass surface temperatures

The paper is part of a larger study, in which the author investigates the effects of radiant heat transfer from exterior shading devices on the surface temperatures of glass using an experimental setup at the Solar Laboratory at Arizona State University, Arizona, USA. Shading devices play an important role in controlling the amount of direct solar radiation entering the interior of a building. Designers provide various material alternatives while designing these exterior-shading devices. The main idea is to improve the aesthetic appearance of the building facade while at the same time providing an efficient shading system to the fenestration. One important effect that is overlooked by most of the currently available whole building simulation tools is the long-wave radiant (re-radiation) effect these shading devices have on the glass temperatures. The paper investigates the radiant effect using sunshades made of three different materials and compares the effectiveness of RADTHERM (a simulation tool used to simulate the experiment).     

Simulation for an optimal application of BIPV through parameter variation

The degree of efficiency of Building Integrated Photovoltaic (BIPV) as a shading device and the variation of the electrical power generation over 1 year in a real building has already been experimentally investigated in my earlier research. In this paper, the influence of the angle of the solar cell panel, albedo of earth, building azimuth, and of solar cell panels under shading on the power generation are theoretically studied to further optimize BIPV implementation. For the validation of the theoretical work, experimental results of the Samsung Institute of Engineering and Construction Company building are used with a wind velocity of the weather data (TRY, test reference year) of Suwon area, Korea. The efficiency of the BIPV system as a shading device was compared at different months. In this work, the simulation program SOLCEL, for the calculation of a shading/sunlit area on solar cell module and facade, surface temperature of solar cell module, effective solar irradiance on solar cell module and the power generation of a BIPV as a shading device, was developed and validated. The SOLCEL can be applied to develop a multi functional Building Integrated Photovoltaic which could improve power generation, thermal comfort, natural lighting, cooling and heating, etc.     

Analytically calculating shading in regular arrays of sun-pointing collectors

A method is presented for deriving an algorithm for analytically calculating shading of sun-pointing solar collectors by other identical collectors in the field. The method is particularly suited to regularly-spaced collectors, with convex aperture shapes. Using this method, an algorithm suitable for circular-aperture collectors is derived. The algorithm is validated against results obtained using an existing algorithm, and an example for usage of the algorithm as a tool for validating assumptions of an existing algorithm is presented.     

Dependence of diffuse light blocking on the ground cover ratio for stationary PV arrays

Three 10 kWp grid connected PV systems have been realised on the flat roofs of office buildings in Portugal and the Netherlands. Monitoring results of these systems show that (interarray) shading leads to losses up to 14% at a ground cover ratio (GCR) of 0.61 and an inclination of 30°, when the fraction of diffuse light is relatively large. A large facade behind the system may cause losses in the order of 5%.

A simple model has been constructed which explains these losses in terms of loss of aperture. The model shows that at high GCRs it is best to place arrays at an inclination which is as low as possible, in order to obtain the highest possible yield. By means of a case study it is shown how to optimise system size for lowest kW h price, given a specific available area.     

A mathematical model for shading calculations

A mathematical model for shading calculations is developed. Closed form expressions for shadow position of an isolated point on a plane surface with arbitrary orientation are derived. By parallel projection methods these expressions can be applied for shadow calculations of relatively complex objects. Furthermore, for some particular plane surface orientations the shadow cast is presented by the shading diagrams. The use of such diagrams for analysis is also discussed on few illustrative examples.     

Positioning of PV panels for reduction in line losses and mismatch losses in PV array

Partial shading decreases the power output of PV arrays due to mismatch losses. These losses are dependent on the shading pattern and the relative positions of shaded modules in the array. Various static and dynamic reconfiguration techniques have earlier been proposed to mitigate these losses. In an earlier proposed static reconfiguration technique, the power generation is enhanced by altering the physical location of the PV panels using a random Sudoku configuration without modifying the TCT (Total-Cross-Tied) based electrical connections. However, this arrangement faces drawbacks due to ineffective dispersion of shade and significant increase in wiring required. In this work, an optimal Sudoku arrangement to overcome these drawbacks is formulated. Further analysis indicate that the global peak of the optimal Sudoku based PV array occurs as the right most peak in the curve for most shading conditions, thus evidently obviating the need for complex MPPT (Maximum-Power-Point-Tracking) algorithms. The proposed configuration is compared with various other existing reconfiguration schemes in terms of power output and the comparison is presented. In addition, a general formulation is proposed to expand this pattern to any generic array. A strategy is also proposed to make such an interconnection practicable for very large size PV arrays.     

Effect of louver shading devices on building energy requirements

External louvers are increasingly used to provide solar protection for building glazed surfaces. In this work, a general study of the effect of louver shading devices applied to different façades of a building is carried out, for different locations (latitudes). Building energy requirements for a building in the cooling and heating seasons is quantified for different window and louver areas, under climatic conditions of Mexico (Mexico), Cairo (Egypt), Lisbon (Portugal), Madrid (Spain) and London (UK). Also, operative and indoor temperatures were calculated through simulations using TRNSYS software, whereas the model for the shading geometry study was solved with EES software. Both horizontal and vertical louver layouts were considered. The results show that the integration of louver shading devices in the building leads to indoor comfortable thermal conditions and may lead to significant energy savings, by comparison to a building without shading devices.     

基于S-V特性分析的晶硅光伏组件阴影遮障诊断

针对广泛使用的晶硅光伏组件,通过Simulink建立太阳电池双二极管精确仿真模型,对实际应用中最常见的光伏组件阴影遮挡故障进行多种工况的仿真验证。根据I-V曲线拐点、台阶、曲线下积分面积（S）下降的特征,提出一种基于S-V曲线特性的光伏组件阴影遮挡故障的在线诊断方法。该方法建立S-V曲线,根据S-V曲线分叉点位置可判断光伏组件遮挡情况,通过整体积分面积进而判断遮挡比例。对温度、辐照度进行折算,使该方法在全工况下适用。结合光伏组件功率优化器验证该诊断方法有较高的准确率,并且可准确地判断阴影遮挡面积,具有很高的实际应用价值。     

A new estimation method of irradiance on a partially shaded PV generator in grid-connected photovoltaic systems

A new method for estimating the irradiance on a partially shaded photovoltaic generator system is proposed. The basic principle of this method consists of two parts: firstly, an approximation of the obstacles’ outline or the local horizon by a set of linear functions. Here, a survey of the surroundings is based on the reading of the topographic coordinates of the only significant points of all the objects surrounding the photovoltaic generator. Secondly, the irradiance on the photovoltaic plane is estimated using an accurate model such as the Perez et al. model and assuming that the shading affects both the direct radiation and a part of the diffuse component (circumsolar component).The aim of this paper is to present the principles of the proposed method and the algorithm used for calculating the irradiance on shaded planes. In addition, the results of the comparison between the simulated and measured values of this method are presented.     

THERMAL AND AIR FLOW PHENOMENA

PASSPORT Plus is a new building thermal simulation tool, developed in the framework of PASCOOL.

It incorporates new findings from the experimental and theoretical research activities performed in PASCOOL that have been integrated in an original informatic structure.

Overall, the emphasis during the development of the program was given on dealing with problems related to cooling of buildings, especially by natural and passive techniques.

Some of the program's features include a detailed treatment of the thermal mass, external remote obstacles, external shading devices like facade obstacles and louvers, improved treatment of natural ventilation phenomena. PASSPORT Plus is a flexible numerical model, in a sense that it can be easily modified in order to adapt and incorporate new findings from ongoing and future research, independently developed modules for treating specific systems or processes, with minimum effort and changes to the program's structure.

The tool has been validated against experimental data and various other simulation programs, with very good agreement.     

基于熵权法的光热耦合综合能耗的百叶外遮阳控制策略

为探究百叶外遮阳控制策略对室内光环境、热环境及综合能耗3个方面的综合影响,采用熵权法建立光热耦合综合能耗的评价模型,利用EnergyPlus软件模拟青岛某办公建筑夏季不同百叶外遮阳角度下的光热环境及能耗,利用评价模型对光环境、热环境及综合能耗进行综合评分,最终确定最合适的百叶外遮阳角度.研究结果表明,该百叶外遮阳控制策...     

Seasonal shading of vertical south-facades with prismatic panes

Using prismatic panes, a seasonal shading responsive to the Sun's position can be realized. Thus the solar gains from direct radiation can be closely matched to the annual pattern of the heating energy requirements of buildings. The panes are suitable for window or facade elements, preferably in applications which do not need a clear view, and especially in front of transparently insulated solar walls. The direct radiation received on a vertical south-facade is reduced to 10% on clear summer days, while 90% is transmitted on clear winter days.     

建筑表面太阳投影面积的数值计算研究

根据太阳运动模型和光学几何原理建立建筑外部遮阳设施动态遮阳效果分析的数学模型.利用该模型,建筑表面上的太阳投影面积可以由建筑地点、建筑几何形状确定.算例的计算结果表明,基于该数学模型的计算值与理论值相比差别很小.该模型对建筑表面太阳投影面积和太阳辐射得热的计算具有实际应用价值,并为动态遮阳效果的研究以及新型遮阳设备的研制提供理论依据.