Mapping the performance of PV modules, effects of module type and data averaging

A method is presented for estimating the energy yield of photovoltaic (PV) modules at arbitrary locations in a large geographical area. The method applies a mathematical model for the energy performance of PV modules as a function of in-plane irradiance and module temperature and combines this with solar irradiation estimates from satellite data and ambient temperature values from ground station measurements. The method is applied to three different PV technologies: crystalline silicon, CuInSe₂ and CdTe based thin-film technology in order to map their performance in fixed installations across most of Europe and to identify and quantify regional performance factors. It is found that there is a clear technology dependence of the geographical variation in PV performance. It is also shown that using long-term average values of irradiance and temperature leads to a systematic positive bias in the results of up to 3%. It is suggested to use joint probability density functions of temperature and irradiance to overcome this bias.     

单面和双面单晶硅光伏组件的发电性能实证

针对p型PERC单面单晶硅光伏组件和n型双面单晶硅光伏组件,利用光伏组件户外实证测试系统,分析了2016年12月15日~2018年7月20日期间,上海市嘉定区某屋顶的地面采用白板背景时双面和单面组件,以及水泥背景时双面组件的等效发电时长,并对白板背景和水泥背景时双面组件较单面组件的发电量增益情况进行了分析;计算了组件的PR值;分析了阴天和晴天时组件最大输出功率与组件背板温度、太阳辐照度和环境温度的关系;最后对比了单面和双面组件运行13个月后的衰减值。该实证结果为单面和双面组件的户外实证发电性能提供了数据支撑,并对双面组件较单面组件的发电量增益情况进行了有效证明。     

Effect of spectral irradiance distribution on the outdoor performance of amorphous Si//thin-film crystalline Si stacked photovoltaic modules

Effects of spectral irradiance distributions on the outdoor performance of amorphous Si//thin-film crystalline Si stacked photovoltaic (PV) modules installed at Shiga-prefecture in Japan have been investigated. Outdoor solar spectrum measurements revealed that more than 95% of annual total spectra were blue-rich compared to AM1.5 standard solar spectrum. The outdoor performance of the modules had a higher spectral dependence than that of polycrystalline Si modules. Also, the peak of the histogram of annual spectral indexes well corresponded to the peak of the outdoor performance. The results indicate that the actual spectral irradiance distribution is important in designing stacked PV modules.     

Thermal aspects of c-Si photovoltaic module energy rating

Standard test conditions (STC) of photovoltaic (PV) modules are not representative of field conditions; PV module operating temperature often rises up to 30 °C above STC temperature (25 °C), causing a performance drop of 0.5%/°C for crystalline silicium modules. Normal operating cell temperature (NOCT) provides better estimates of PV module temperature rise. It has nevertheless to be measured; moreover NOCT wind speed conditions do not always fit field conditions. The purpose of this work is to model average PV module temperature at given irradiance levels as a function of meteorological parameters and PV module implementation. Thus, no empirical knowledge of PV module thermal behaviour is required for energy rating basing on irradiation distributions over irradiance levels.     

不同技术类型光伏组件的户外发电性能及衰减分析

对在广东省顺德地区(属于亚热带季风气候)运行的异质结(HIT)光伏组件、铜铟镓硒(CIGS)薄膜光伏组件、碲化镉(CdTe)薄膜光伏组件这3种不同技术类型的光伏组件的户外发电性能进行了比较,并对这3种光伏组件的功率衰减情况进行了定量分析.截至2019年12月,上述3种光伏组件的户外累计运行时间长达12年,其室内I-V特...     

An improved modeling method to determine the model parameters of photovoltaic (PV) modules using differential evolution (DE)

To accurately model the PV module, it is crucial to include the effects of irradiance and temperature when computing the value of the model parameters. Considering the importance of this issue, this paper proposes an improved modeling approach using differential evolution (DE) method. Unlike other PV modeling techniques, this approach enables the computation of model parameters at any irradiance and temperature point using only the information provided by the manufacturer’s data sheet. The key to this improvement is the ability of DE to simultaneously compute all the model parameters at different irradiance and temperature. To validate the accuracy of the proposed model, three PV modules of different types (multi-crystalline, mono-crystalline and thin-film) are tested. The performance of the model is evaluated against the popular single diode model with series resistance R_s. It is found that the proposed model gives superior results for any irradiance and temperature variations. The modeling method is useful for PV simulator developers who require comprehensive and accurate model for the PV module.     

A novel model for photovoltaic array performance prediction

Based on the I–V curves of a photovoltaic (PV) module, a novel and simple model is proposed in this paper to predict the PV module performance for engineering applications. Five parameters are introduced in this model to account for the complex dependence of the PV module performance upon solar-irradiance intensity and PV module temperature. Accordingly, the most important parameters, i.e. the short-circuit current, open-circuit voltage, fill factor and maximum power-output of the PV module, may be determined under different solar irradiance intensities and module temperatures. To validate the developed model, field measured data from one existing building-integrated photovoltaic system (BIPV) in Hong Kong was studied, and good agreements between the simulated results and the field data are found. This model is simple and especially useful for engineers to calculate the actual performances of the PV modules under operating conditions, with limited data provided by the PV module manufacturers needed.     

Seasonal variation analysis of the outdoor performance of amorphous Si photovoltaic modules using the contour map

The effects of module temperature (T_mod) and spectral irradiance distribution on the outdoor performance of amorphous Si (a-Si) photovoltaic (PV) modules were investigated using contour maps. Compared to PV modules based on crystalline Si, such as single-crystalline Si (sc-Si) and multicrystalline Si, a-Si PV modules exhibit complex behavior with seasonal variation. In this study, we statistically analyzed the outdoor performance of a-Si and sc-Si PV modules. The influence of environmental factors on outdoor performance of a-Si PV modules was analyzed for two seasons, spring and autumn, in which the data periods had nearly the same average T_mod and integrated irradiation. The outdoor performance of the a-Si PV module depends on both temperature history and light-induced degradation.     

Improved artificial neural network method for predicting photovoltaic output performance

To ensure the safety and stability of power grids with photovoltaic (PV) generation integration, it is necessary to predict the output performance of PV modules under varying operating conditions. In this paper, an improved artificial neural network (ANN) method is proposed to predict the electrical characteristics of a PV module by combining several neural networks under different environmental conditions. To study the dependence of the output performance on the solar irradiance and temperature, the proposed neural network model is composed of four neural networks, it called multi- neural network (MANN). Each neural network consists of three layers, in which the input is solar radiation, and the module temperature and output are five physical parameters of the single diode model. The experimental data were divided into four groups and used for training the neural networks. The electrical properties of PV modules, including I–V curves, P– V curves, and normalized root mean square error, were obtained and discussed. The effectiveness and accuracy of this method is verified by the experimental data for different types of PV modules. Compared with the traditional single-ANN (SANN) method, the proposed method shows better accuracy under different operating conditions.     

Validation of the Sandia model with indoor and outdoor measurements for semi-transparent amorphous silicon PV modules

This paper presents a set of indoor and outdoor measurement methods and procedures to determine the empirical coefficients of the Sandia Array Performance Model (SAPM) for a semi-transparent amorphous silicon (a-Si) PV module. After determining and inputting the total 39 parameters into the SAPM, the dynamic power output of the a-Si PV module was predicted. In order to validate the accuracy of using SAPM for simulating the energy output of the a-Si PV module, a long-term outdoor testing campaign was conducted. The results indicated that the SAPM with indoor and outdoor measured coefficients could accurately simulate the energy output of the a-Si PV module on sunny days, but it didn't work well on overcast days due to the inappropriate spectral correction as well as the equipment measuring error caused by the intense fluctuation of solar irradiance on overcast days. Specifically, all the errors between the simulated daily energy output and the measured one were less than 4% on sunny days. In order to achieve a better prediction performance for a-Si PV technologies, the SAPM was suggested to incorporate a more comprehensive spectral correction function to correct the impact of solar spectrum on overcast days in future.     

Photovoltaic (PV) performance modelling in the absence of onsite measured plane of array irradiance (POA) and module temperature

In this study, the outputs from a simple PV performance model were compared to measurements of AC power for three PV systems located across Sydney, Australia. The study aimed to investigate the level of uncertainty and bias of the model when onsite measurements of plane of array (POA) irradiance and module temperature were not available. The results demonstrated that the simple PV performance model estimated the AC performance with a low level of model bias (NBME = ±3.2%) and uncertainty (NRMSE < 6%) when onsite measurements of POA irradiance and module temperatures were available. For POA irradiance, the results indicated that modelling uncertainty increased significantly (NRMSE < 13%) when alternative methods to estimate POA irradiance were utilised. For module temperature, the results indicated that the choice of model coefficients had a significant impact on the performance of the module temperature models. In particular, for the three parallel roof mounted PV systems studied, the results suggested that the open rack/free standing or well ventilated module temperature coefficients should be used within the module temperature models investigated. This selection of coefficients was not directly evident given the PV systems investigated were parallel roof mounted PV systems, not free standing rack mounted arrays.     

Performance of Si-based PV rooftop systems operated under distinct four seasons

We have investigated the electrical energy yield of hydrogenated amorphous silicon (a-Si:H) single-junction and crystalline (c-Si) photovoltaic (PV) rooftop systems operated under distinct four seasons. The impact of the module type and installed tilt angle on the annual electrical energy yield has been monitored and then compared with the data predicted by the computer simulation. Despite a good temperature coefficient and less shading effect of a-Si:H single-junction modules, the energy output gain of the a-Si:H single-junction PV generator is only 2.7% compared to the c-Si PV generator installed using c-Si PV modules. It is inferred that a nominal rated power of the a-Si:H single-junction modules determined by an indoor light soaking test is not suitable for the design of PV systems operated under distinct four seasons. Thus, the nominal rated power of the a-Si:H single-junction PV modules should be determined through a proper outdoor exposure test considering thermal annealing and light soaking effects under various seasonal weather conditions. In addition, it is found that the performance of the Si-based PV rooftop systems operated under distinct four seasons could be improved by simply toggling the tilt angle considering the plane-of-array irradiance and snowfall effect.     

Simple, fast and accurate two-diode model for photovoltaic modules

This paper proposes an improved modeling approach for the two-diode model of photovoltaic (PV) module. The main contribution of this work is the simplification of the current equation, in which only four parameters are required, compared to six or more in the previously developed two-diode models. Furthermore the values of the series and parallel resistances are computed using a simple and fast iterative method. To validate the accuracy of the proposed model, six PV modules of different types (multi-crystalline, mono-crystalline and thin-film) from various manufacturers are tested. The performance of the model is evaluated against the popular single diode models. It is found that the proposed model is superior when subjected to irradiance and temperature variations. In particular the model matches very accurately for all important points of the I-V curves, i.e. the peak power, short-circuit current and open circuit voltage. The modeling method is useful for PV power converter designers and circuit simulator developers who require simple, fast yet accurate model for the PV module.     

Ten years outdoor operation of silicon based photovoltaic modules at central latitude of Japan

For the estimation of energy output from photovoltaic (PV) modules, considering the impact of degradation is essential. In this study, the longtime outdoor performance of various types of silicon-based PV modules [single crystalline Si (sc-Si), multi crystalline Si (mc-Si), amorphous Si (a-Si), a-Si/micro crystalline Si tandem, and a-Si/a-SiGe/a-SiGe three-stack (3-stack)] which were installed at the same outdoor exposure condition in Shiga Prefecture, Japan were investigated using Performance Ratio (PR) as an index of performance of PV modules for ten years from 2000 to 2009. Yearly PR and monthly PR were analyzed and degradation rates (DR) were calculated. The DR was different on the kinds of PV modules from 0.404 to 3.51%/year. The a-Si PV module showed the largest DR and the 3-stack PV module had the least trend to degrade. The analysis of the monthly DR indicated that the high DR of the a-Si PV module was due to the quite large DR in summer, whereas the monthly DR of sc-Si and mc-Si PV modules did not differ much from each other throughout the years.     

Uniqueness verification of solar spectrum index of average photon energy for evaluating outdoor performance of photovoltaic modules

To analyze the effect of a spectral irradiance distribution of solar spectra on the outdoor performance of photovoltaic (PV) modules, an index for the spectral distribution is needed. Average photon energy (APE) which represents the average energy per photons included in a spectrum is one of these. In this study, the uniqueness of APE to the spectral irradiance distribution was statistically analyzed to assure that an APE value uniquely yields the shape of a solar spectrum. The similar methodology adopted in International Electrotechnical Commission to rate the spectral matching of a solar simulator was used for the analysis. The results showed that an APE value yielded a spectral irradiance distribution with quite small standard deviation. The analysis using APE showed that the outdoor performance of crystalline Si PV modules depended almost only on a module temperature, while that of amorphous Si ones mainly depended on APE. The behaviors were reasonable considering from the operation mechanisms of the PV modules. These results demonstrate that APE is a reasonable and useful index to describe the spectral irradiance distribution for evaluating the outdoor performance of PV modules.     

Estimation of the maximum power temperature coefficients of PV modules at different time scales

The maximum power temperature coefficients of a-Si modules are negative in indoor measurements, whereas the performance increases with module temperature in outdoor measurements. In order to resolve the discrepancy, we investigate the temperature coefficients of a-Si modules by two different methods corresponding to two different time scales. The results are that the temperature coefficient for a shorter time scale of several hours is negative, although the temperature coefficient for a longer time scale of seasons is positive. These results suggest that the discrepancy in temperature coefficient is partially caused by the effects of thermal annealing and light soaking. Therefore, the history of module temperature and received solar irradiance would be required for the correction of the performance of a-Si modules. In addition, we reveal that the effect of solar spectrum is also a contributory factor in the discrepancy.     

Impact of environment factors on solar cell parameters of a-Si∥μc-Si photovoltaic modules

The behavior of amorphous silicon∥micro crystalline silicon (a-Si∥μc-Si) tandem-type photovoltaic (PV) module is complex because the output current is limited by the lower current component cell. Also, the outdoor behaviors are not fully understood. The impact of environment factors on solar cell parameters of a-Si∥μc-Si PV module was quantitatively analyzed and the module was compared with other silicon-based PV modules (single crystalline silicon (sc-Si) and amorphous silicon (a-Si)). The contour maps of solar cell parameters were constructed as a function of irradiance and module temperature. The contour map of a-Si∥μc-Si PV modules is similar to that of a-Si modules. The results imply that output characteristics of a-Si∥μc-Si PV modules are mainly influenced by the a-Si top cell. Furthermore, the efficiency of a-Si∥μc-Si PV modules was compared other solar cell parameters and the contour map of efficiency is similar to that of fill factor.     

PV power conversion and short-term forecasting in a tropical,densely-built environment in Singapore

With the substantial growth of solar photovoltaic installations worldwide, forecasting irradiance becomes a critical step in providing a reliable integration of solar electricity into electric power grids. In Singapore, the number of PV installation has increased with a growth rate of 70% over the past 6 years. Within the next decade, solar power could represent up to 20% of the instant power generation. Challenges for PV grid integration in Singapore arise from the high variability in cloud movements and irradiance patterns due to the tropical climate. For a thorough analysis and modeling of the impact of an increasing share of variable PV power on the electric power system, it is indispensable (i) to have an accurate conversion model from irradiance to solar power generation, and (ii) to carry out irradiance forecasting on various time scales. In this work, we demonstrate how common assumptions and simplifications in PV power conversion methods negatively affect the output estimates of PV systems power in a tropical and densely-built environment such as in Singapore. In the second part, we propose and test a novel hybrid model for short-term irradiance forecasting for short-term intervals. The hybrid model outperforms the persistence forecast and other common statistical methods.     

异质结光伏组件的发电效果研究

为研究异质结光伏组件的实际发电效果,收集某光伏发电站近两年的发电量数据,得到单块组件的月均发电量.通过对比分析,验证该异质结光伏组件相对于多晶光伏组件在发电效率方面的优越性,且与理论增益相符.通过计算冬夏两季的月均发电量和月均辐照度,证明相比多晶光伏组件,温度升高对该异质结光伏组件的功率影响更小,与理论上异质结光伏组件...     

Evaluation of the impact of solar spectrum and temperature variations on output power of silicon-based photovoltaic modules

Various types of silicon-based photovoltaic modules were installed at the same outdoor exposure site in Japan. The output parameters of the modules were measured and also incident irradiance, incident spectrum, and module temperature were recorded at the same time. A statistical analysis method has been proposed to separate the influences of spectrum variations and module temperature variations on the output performance of the modules. Moreover, with this method, the performance of polycrystalline silicon, amorphous silicon, and three-stacked amorphous silicon photovoltaic modules were analyzed.