Simulation of partial shading on solar photovoltaic modules with experimental verification

With rapidly growing energy demands and increased consciousness about the environment, PV installations are being increasingly used in various applications such as communications and lighting. However, one of the major challenges in using a PV source is that they are often subjected to partial shading and rapid fluctuations of shading. In many cases, the PV arrays get partially shaded due to various reasons, resulting in lower energy production yields. This further leads to nonlinearities in characteristics, causing it to get more complicated if the entire array does not receive uniform insolation. In this study, a Simulink-based mathematical model of a PV system has been developed to simulate the performance of a PV system for the various conditions of partial shading. The simulated results have been compared with experimentally obtained results of the various configurations of shading that were used for the partial shading conditions on a commercially available PV module.     

Performance of a PV panel under different shading strengths

Solar radiation and the surface temperature of a PV panel are the two key parameters that play an important role in the performance of the PV panel. The shading on the panel surface reduces the solar radiation falling on its surface, thus degrading the panel performance. Moreover, the effect of shading is also influenced by the panel configuration. The performance of the PV panel under different levels of shading strength and panel configuration is the main focus of this study. It was reported that, due to 50% shading of a single cell, the reduction in maximum power output was 25.71%. Similarly, the reduction in maximum power output was 70.27% with 50% shading of the panel surface. Further, in this study, the reduction in the PV panel power output was reported as 16.54% and 6.03% for the series and parallel configuration, under the same level of shading condition.     

Exergetic performance assessment of a solar photovoltaic thermal (PV/T) air collector

In this paper, an attempt is made to evaluate the exergetic performance of a solar photovoltaic thermal (PV/T) air collector. A detailed energy and exergy analysis is carried out to calculate the thermal and electrical parameters, exergy components and exergy efficiency of a typical PV/T air collector. Some corrections are done on related heat loss coefficients. An improved electrical model is used to estimate the electrical parameters of a PV/T air collector. Further, a modified equation for the exergy efficiency of a PV/T air collector is derived in terms of design and climatic parameters. A computer simulation program is also developed to calculate the thermal and electrical parameters of a PV/T air collector. The results of numerical simulation are in good agreement with the experimental measurements noted in the previous literature. Finally, parametric studies have been carried out. It is observed that the modified exergy efficiency obtained in this paper is in good agreement with the one given by the previous literature. It is also found that the thermal efficiency, electrical efficiency, overall energy efficiency and exergy efficiency of PV/T air collector is about 17.18%, 10.01%, 45% and 10.75% respectively for a sample climatic, operating and design parameters.     

Modelling and simulation-based performance study of a transformerless single-stage grid-connected photovoltaic system in Indian ambient conditions

This paper presents a transformerless single-stage full-bridge inverter for a grid-connected photovoltaic system (GCPVS) and its performances based on power loss, efficiency, and total harmonic distortion for the conditions: (a) seasonal variations of inputs in the photovoltaic (PV) system, (b) variation of grid voltage, and (c) variation of carrier frequency and Modulation Index of sinusoidal pulse-width modulation of the inverter. A typical 2.8 kWp, 368 V nominal PV array-based GCPVS is modelled and simulated to evaluate proper load matching in Indian ambient and grid conditions prior to practical implementation. Detailed analyses on system powers, power losses, efficiency, and harmonic distortions as well as selection of parameters for the simulation model are presented. The impacts of penetrating PV power into electric grid are investigated in order to predict the possible unwanted consequences.     

自然冷却下太阳能PV板发电效率的影响研究

基于一维稳态传热模型,通过数值模拟与计算,进行了自然冷却条件下散热肋片对PV板发电效率的影响研究,对不同因素包括PV板水平倾角、空气温度、风速和肋片高度等对PV板发电效率的影响进行了研究,研究结果对于PV板被动式冷却设计具有一定的实际意义和参考价值。     

组合布局对建筑立面风驱雨分布影响特性的数值分析

风驱雨（Wind-Driven Rain,简称WDR）是建筑外立面最主要的水分来源,为外墙材料耐久性能及建筑温湿环境的重要影响因素。目前,WDR分布特性的研究主要针对单体建筑布局,考虑群体布局条件下建筑立面WDR分布以及受布局扰动影响的研究仍比较缺乏。基于欧拉多相流模型的WDR数值模拟方法,在验证方法对两建筑串列布局下较复杂WDR场具有较好模拟适用性的前提下,针对两建筑串列布局方式,考虑施扰建筑高度(h)及间距(d)变化,模拟不同工况下受扰建筑迎风面WDR分布,通过与单体布局情况进行比较,重点分析受扰建筑迎面风WDR分布特点及局部区域WDR变化规律,获取该布局变化时气动干扰对受扰建筑迎风面WDR分布的影响特性。结果表明：受扰建筑迎风面WDR分布受施扰建筑高度变化影响较大,受间距变化的影响相对较小,而局部区域干扰因子更能有效反映受扰建筑立面WDR分布的气动干扰影响。     

Development and performance evaluation of a methodology,based on distributed computing,for speeding EnergyPlus simulation

This article presents an approach for speeding EnergyPlus simulations. The computing run time of an energy simulation depends on several variables and is directly proportional to the simulation RunPeriod. In the proposed approach, data parallelization is achieved by breaking an annual simulation into several segments of smaller RunPeriod, each handled by a separate computer/processor. The speed gain achieved by running 12 one-month RunPeriod segments in parallel as compared to single simulation of 12 months is between three and six times. Segmentation of simulation has resulted in minor deviations between the results obtained through segmented simulations and annual simulations. Methods for reducing these deviations on annual and monthly basis are presented in this article using 12 benchmark models each simulated for five cities. On annual basis, a maximum deviation of 0.06% was observed in cooling, heating, and lighting consumption. In a month-to-month comparison between the segments and annual simulation, the maximum deviation was 1.7% for heating and 0.8% for cooling.     

Solution of a class of load combination problems by directional simulation

The load combination problem of Ferry Borges-Castanheta may be effectively handled by the Rackwitz-Fiessler algorithm provided the load pulses have absolutely continuous distribution function. However, realistic modelling of extraordinary actions requires the load pulse distributions to have a concentrated probability at zero. In principle this discontinuity may be handled by conditioning such that the combination problem reduces to several problems with absolutely continuous distribution functions. With just some few extraordinary actions taking part in the combination problem this method of conditioning becomes quite cumbersome and even impracticable.If it is assumed that the single load pulses are clipped normal random variables, i.e. of the form max{0, X} where X is normal, then a combination of the RF-algorithm and directional Monte Carlo simulation technique turns out to be useful. At any given argument the directional simulation method gives not only a confidence interval for the value of the distribution function but also a confidence interval for the value of the density function of a random variable defined as a sum of clipped dependent or independent normal variables. This is just what is needed in the RF-algorithm in order to apply the principle of normal tail approximation on the distribution of the sum.     

浅谈大空间火灾烟气运动规律的计算机模拟

分析并讨论了当前大尺度空间火灾烟气运动规律的计算机模拟研究现状。结果表明,采用大涡模拟方法结合多单元区域模拟是研究火灾烟气运动规律的发展趋势。     

Year-round numerical simulation of a parabolic solar collector under Lebanese conditions: Beirut case study

A detailed thermal and optical numerical model is developed to simulate the performance of a small-scale parabolic collector having an evacuated receiver line with selective coating, taking into account different energy balances and interactions with the surrounding. An analytical model is developed to estimate the direct, diffuse and global solar radiation intensities on inclined surfaces. The collector performance model was validated using published experimental data. A year-round dynamic simulation for the collector performance under Beirut climatic conditions was carried out with an economic and environmental analysis. The outlet water temperature could reach a maximum of 114°C in July and 52°C in December by employing a collector of about 6 m² aperture area with 0.01 kg/s water flow rate. The maximum daily thermal energy production is attained in July with 22.267 kWh while January exhibits the lowest thermal energy production with 6.704 kWh per day with a maximum thermal efficiency of 72%.     

A comparison of the UK Standard Assessment Procedure and detailed simulation of solar energy systems for dwellings

The drive to reduce worldwide carbon emissions that are directly associated with dwellings and to achieve a zero carbon home dictates that renewable energy technologies will have an increasingly large role in the built environment. The Standard Assessment Procedure (SAP), formulated by the Building Research Establishment (BRE), is the UK Government's approved methodology for assessing the energy ratings of dwellings. This article presents an evaluation of the advantage given to SAP ratings by the domestic installation of typical photovoltaic (PV) and solar domestic hot-water (SDHW) systems in the UK. Comparable PV and SDHW systems will also be simulated with more detailed modelling packages. Results suggest that calculation variances can exist between the SAP methodology and detailed simulation methods, especially for higher performance systems that deviate from the default efficiency parameters.     

Realisation of incremental conductance the MPPT algorithm for a solar photovoltaic system

This paper presents the modelling, simulation and hardware implementation of the incremental conductance (INC) maximum power point tracking (MPPT) algorithm. The extraction of maximum power from the solar photovoltaic system was made by integrating the PV module with a DC–DC converter and utilising the MPPT algorithm. In this work, the INC MPPT algorithm is practically implemented on an Arduino Uno board to track the maximum power point (MPP) and also simulated in Matlab/Simulink under the same environmental conditions. The performance of the INC algorithm was also compared with the conventional Perturb and Observe (P&O) MPPT algorithm. The experimental and simulation results are provided for both MPPT techniques. Matlab/Simulink was used for simulation studies.     

数值模拟对起火点处物体燃烧特性研究的作用

利用FDS对一起商住合用房火灾事故进行火灾数值模拟重构,通过模拟得出不同热释放速率增长速率下高斯热通量、辐射热通量等参数和烧损情况,与实际火灾场景烟熏痕迹和烧损情况进行对比,证明数值模拟的合理性,对起火点处引起火灾的起火物的燃烧特性进行更好的调查分析。并且通过模拟不同热释放增长速率下氧气浓度、二氧化碳和一氧化碳的变化,对人员死亡原因进行分析。     

The influence of simulation time-resolution on the matching between on-site micro-wind generation and building electric demand

This paper is to investigate the unique impact of simulation time-resolutions on energy matching between on-site micro-wind turbine and household electric demand. The focused indices are on-site electrical energy fraction (OEFe), on-site electrical energy matching (OEMe), and their errors (e_OEF and e_OEM). The methodology consists of parametric analyses with respect to time-resolution levels, averaging methods, demand profiles, turbine capacities, and wind conditions. Two averaging methods are used: ‘Speed Averaging’ and ‘Power Averaging’. With a coarser resolution, two averaging effects have been found. One is an overestimation effect by both the averaging methods, which are more likely to be encountered especially when a high-resolution generation curve frequently crosses intermittent long spikes of a demand curve. The other effect is an underestimation effect on OEFe simultaneously occurring with the Speed Averaging Method under the conditions of (1) a low wind speed and (2) a high unstable wind speed and a low turbine capacity.     

Thermal zoning and interzonal airflow in the design and simulation of solar houses: a sensitivity analysis

Many assumptions must be made about thermal zoning and interzonal airflow for modelling the performance of buildings. This is particularly important for solar homes, which are subjected to high levels of periodic solar heat gains in certain zones. The way in which these passive solar heat gains are distributed to other zones of a building has a significant effect on predicted energy performance, thermal comfort and optimal design selection. This article presents a comprehensive sensitivity analysis that quantifies the effect of thermal zoning and interzonal airflow on building performance, optimal south-facing glazing area, and thermal comfort. The effect of controlled shades to control unwanted solar gains is also explored. Results show that passive solar buildings, in particular, can benefit from increased air circulation with a forced air system because it allows solar gains to be redistributed and thus reduces direct gain zone overheating and total energy consumption.     

障碍物对氯乙烯气体泄漏扩散影响的模拟研究

针对化工企业气柜泄漏造成人员伤亡等问题,利用Fluent软件对3种障碍物情况下气体扩散进行数值模拟研究.结果表明,障碍物对泄漏源上风侧气体浓度的影响远远小于下风侧.泄漏初期,障碍物、泄漏速率为下风侧氯乙烯气体浓度的主导因素;泄漏中期,下风侧氯乙烯气体在重力、初速度、风速的共同作用下,浓度维持短暂稳定;泄漏后期,环境风速...     

青藏高原热融湖对冻土工程影响的数值模拟

热融湖的侧向热侵蚀对周围冻土工程产生较大影响。在柱坐标下,运用带相变的数值热传导模型,预测了热融湖影响下冻土路基的地温场发展状况和可能造成的工程病害。预测结果表明：在不考虑湖岸坍塌后退、面积扩大的情况下,热融湖对冻土路基的热影响主要受湖底年平均温度和湖边到路基的距离两个因子的影响。湖底年平均温度越高,对路基的热影响越严重;湖边到路基的距离越近,对路基的热影响亦越严重。突出的表现在坡脚、路基中心平均地温升高和融化夹层在水平、竖直方向的发展。如果考虑热融湖的湖岸坍塌后退,实际增温要比模拟的结果更明显,影响更严重。     

区域地下水流对王河煤矿水害影响数值模拟

王河煤矿位于荥巩矿区中部,为荥巩矿区水害最为严重的矿井之一.为了分析区域地下水流对王河煤矿水害的影响,本文在分析荥巩矿区地质及水文地质条件的基础上,利用GMS建立了荥巩矿区地下水流三维数值模拟模型,确定了水文地质参数和渗流场分布情况.结果表明,荥巩矿区地下水补给量为1831.12×104m3/a,排泄量为4862.88...     

软土地区邻近堆载对桩基影响的数值模拟研究

对软土地区地面堆载对邻近桩基影响进行了数值模拟研究,模拟分析了填土对邻近桩基的地面沉降水平位移、桩身变形、桩身轴力、桩身弯矩等的影响,得出桩身位移变化规律以及填土高度对桩基影响的安全距离。     

Numerical simulation of the top coal caving process using the discrete element method

How to understand the top coal caving process and increase the top coal recovery ratio is one of the urgent problems to resolve for longwall top coal caving technology. This paper discusses a new theory and technology of top coal caving with vibration. The vibration device is mounted on the shield beam of the top coal caving support. The vibrator destroys the arch structure formed during the top coal caving process, which results in the smooth top coal caving process, and in this way the top coal recovery ratio is increased. The distinct element method (DEM) numerical software particle flow code in 2 dimensions (PFC2D) is used for the numerical simulation. It is proven that the vibration can easily destroy the arch structure which is formed during the top coal caving process. The parameters about when the arch structure would be formed during the top coal caving process have been obtained. The movement of the top coal caving process under the vibration condition makes a more stable layer uniform caving performance. The aim of the top coal caving with vibration technology, to increase the top coal recovery ratio and to lower the waste content rate, has been achieved.