Artificial neural network‐based photovoltaic module temperature estimation for tropical climate of Malaysia and its impact on photovoltaic system energy yield

This article presents an artificial neural network (ANN)‐based approach for predicting photovoltaic (PV) module temperature using meteorological variables. The proposed approach utilizes actual hourly records of various meteorological parameters, such as ambient temperature T_a, solar irradiation G, relative humidity RH, and wind speed Ws as input variables. The hourly meteorological data were collected over 9 months in the year 2009 from a 92‐kWp installed PV system in Selangor, Malaysia. The data were divided into two sets: training data, which are a set of 1849 (April–October) hourly data, and 578 (November–December) hourly records of working as test data. Four ANN models have been developed by using different combination of meteorological parameters as inputs, and, for each model, the output is the PV module temperature T_m. It was found that the model using all parameters, including RH and Ws as inputs, gave the most accurate results with correlation coefficient (r) 95.9%, and 0.41, 0.1, and 4.5% for MBE, RMSE, and MPE, respectively. To show the superiority and applicability of the developed ANN model, results from the proposed ANN model have been compared with the conventional model adopted by Malaysia Energy Center and another mathematical model based on regression. With the model's simplicity, the proposed approach can be used as an effective tool for predicting the PV module temperature, for any type of PV systems, in remote or rural locations with no direct measurement equipments. The developed model also will be very useful in studying PV system performance and estimating its energy output. Copyright © 2013 John Wiley & Sons, Ltd.     

An Efficient Wind–Photovoltaic Hybrid Generation System Using Doubly Excited Permanent-Magnet Brushless Machine

With ever-increasing concerns on energy issues, the development of renewable energy sources is becoming more and more attractive. This paper first reviews both the wind power and photovoltaic (PV) power generation techniques and their maximum-power-point tracking (MPPT) methods. Then, a new stand-alone wind–PV hybrid generation system is proposed for application to remote and isolated areas. For the wind power generation branch, a new doubly excited permanent-magnet brushless machine is used to capture the maximum wind power by using online flux control. For the PV power generation branch, a single-ended primary inductance converter is adopted to harness the maximum solar power by tuning the duty cycle. The experimental results confirm that the proposed hybrid generation system can provide high efficiency with the use of MPPT.      

A PSO‐based maximum power point tracking for photovoltaic systems under environmental and partially shaded conditions

To increase the efficiency of photovoltaic (PV) systems, maximum power point (MPP) tracking of the solar arrays is needed. Solar arrays output power depends on the solar irradiance and temperature. Also the mismatch phenomenon caused by partial shade will affect the output power of solar systems and lead to the incorrect operation of conventional MPP tracker. Under partially shaded conditions, the solar array power–current characteristic has multiple maximum. This paper presents a maximum power point tracking (MPPT) with particle swarm optimization method for PV systems under partially shaded condition. The performance of the proposed method is compared with perturb and observe (P&O), improved P&O, voltage‐based maximum power point tracking and current‐based maximum power point tracking algorithms, especially, under partially shaded condition. Simulation results confirm that proposed MPPT algorithm with high accuracy can track the peak power point under different insolation, temperature and partially shaded conditions, and it has the best performance in comparison with four mentioned MPPT algorithms. Also under rapidly changing atmospheric conditions, the P&O algorithm is diverged. Copyright © 2013 John Wiley & Sons, Ltd.     

模糊控制在光伏水泵灌溉系统中的应用

在水泵灌溉系统中利用太阳能作为动力,可解决边远地区能源动力缺乏难题。考虑到光伏电池的输出特性随负载及外界环境的变化而变化,在灌溉器的控制模块中引入模糊控制技术,通过DC/DC变换器通流率的变化量随模糊规则可变的控制,使太阳电池阵列始终处于最大功率输出状态,提高光伏器件的效能、获得最大扬水量。仿真实验结果显示,该系统具有比用功率比较法捕捉太阳电池阵列最大功率点更快且脉动小的特点。     

Effects of shadowing on photovoltaic module performance

A procedure of simulation and modelling PV modules' performance, working partially shadowed, is presented. Several shadow rates have been tested on a single cell forming part of a PV module having 36 solar cells serially connected, and the influence of shadow rate in most of the important PV module characteristic parameters has been evaluated.The correlation between PV module output lowering due to shadowing and the variation of resistive losses is also reported. Copyright © 2007 John Wiley & Sons, Ltd.     

基于遗传算法的太阳能飞艇光伏阵列优化研究

太阳能飞艇依赖于光伏阵列提供能量,但曲面面形引起的非均匀光照会造成光伏阵列的能量损失。文章将遗传算法引入光伏阵列优化研究,通过优化光伏阵列拓扑结构,降低模块间的失配现象,从而达到增大输出功率的目的。首先基于光伏电池的单二极管模型,给出光伏阵列的仿真方法。其次提出基于遗传算法的光伏阵列拓扑结构的优化方法,采用序列编码方式,将光伏阵列拓扑结构转化为染色体编码,通过染色体基因位的交叉变异实现光伏阵列拓扑结构的优化。以某太阳能飞艇为例进行仿真验证,优化后光伏阵列平均输出功率增大2.32%,仿真结果表明所提方法能够有效提高太阳能飞艇光伏阵列的输出功率。     

Impact of individual atmospheric parameters on CPV system power,energy yield and cost of energy

The performance of concentrator photovoltaic systems can be characterised by the power output under reference conditions and the output energy yield under realistic solar illumination. For a range of locations, the frequency distribution of individual atmospheric parameters and their quantitative impact on power output of a concentrator photovoltaic system have been evaluated, with aerosols shown to have a substantial impact on performance at many sites. Limited knowledge of atmospheric parameters results in a difference of up to 75% in simulated energy yield over an annual period and up to 75% deviation in the expected levelised cost of energy. Copyright © 2013 John Wiley & Sons, Ltd.     

Solar‐Driven Alkaline Water Electrolysis with Multifunctional Catalysts

Alkaline water electrolysis (AWE) holds great promise for a truly sustainable energy future if it can be driven by renewable energy sources such as solar and wind. The main challenge arises from the serious partial loading issue when intermittent and unstable renewable energy is coupled to water electrolyzers. An energy storage device can mitigate this incompatibility between water electrolyzer and renewable energy sources. Herein, an AWE device driven by solar photovoltaic (PV) through a full cell of lithium‐ion battery (LIB) as an energy reservoir is demonstrated (PV?LIB?AWE). Stable power output from LIB drives the water electrolyzer for steady hydrogen production, and thus overcomes the partial loading issue of AWE. Moreover, a multifunctional hierarchical material, porous nickel oxide decorated nitrogen‐doped carbon (NC) support, with excellent electrochemical performances for LIBs, oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) for the PV?LIB?AWE system is developed. Density functional theory calculations show that the strong interaction between metal oxide and NC tailors the electronic structure and then optimizes activation energy of OER process. PV?LIB?AWE integrated system demonstrated here offers an alternative approach to drive water electrolysis with intermittent renewable energy for a truly sustainable energy future.     

Optimal sizing of photovoltaic‐hydro power plant

The work presents a technological concept of energetically independent and ecologically sustainable system of electric energy production by joint operation of photovoltaic (PV) and hydro electric (HE) power plant as a unique technological system of solar hydroelectric (SHE) power plant. The sustainability of such system is based exclusively on the solar energy input, as the renewable and pure energy resource, and the use of hydro energy, due to the possibility of its continuous production of energy and its well‐known flexibility in covering the consumers' needs. For the purpose of connecting all relevant values into one integral SHE system, a mathematical model was developed for selecting the optimal size of the PV power plant as the key element for estimating the technological feasibility of the overall solution. The model was tested on electric energy supply from the island of Vis in Croatia. The obtained power of the PV power plant was 41 MW_p which corresponds to collector field of approximately 25 ha, while the estimated related storage was 20 hm³. The results show that the subject model describes the SHE very well and that the proposed concept of joint operation of PV and HE power plants is real and possible. The application of such sustainable SHE systems could significantly increase PV industry worldwide, i.e. the share of solar energy in energy balances of numerous countries. Proposed hybrid simulation‐dynamic programming model is suitable to optimize PV plant in accordance with system characteristics. Copyright © 2009 John Wiley & Sons, Ltd.     

Solar irradiation and PV module temperature dispersion at a large‐scale PV plant

When evaluating the performance of a photovoltaic (PV) system, it is extremely important to correctly measure the plant operating conditions: incident irradiation and cell temperature. At large‐size PV plants, the possible dispersion of the plant operating conditions may affect the representativeness of the values measured at one single point. The available literature contains many observations on irradiance dispersion (typically associated to high temporal resolution experiments) and its effects on the PV power output (unexpected power transients, power fluctuations, etc.). However no studies have been made on the long‐term energy‐related effects of geographic dispersion of solar irradiation, which could affect, for example, to the uncertainty in determining energy performance indexes like PR. This paper analyses the geographical dispersion in the PV operating conditions observed at low temporal resolutions (day, month and year) at two PV plants located, respectively, in the south of Portugal and the north of Spain. It shows that daily irradiation deviations are significantly higher than is commonly supposed. Furthermore, once the measurement points are a certain distance apart (a few hundred metres), the deviations in irradiation appear to be independent of distance. This could help to determine how many irradiance sensors to install in order to reduce uncertainty. Daily mean temperature differences between different points at a large‐scale PV plant range from 1 to 7 K and are not related to the distance between measurement points. Copyright © 2014 John Wiley & Sons, Ltd.     

From irradiance to output power fluctuations: the PV plant as a low pass filter

The power generated by large grid‐connected photovoltaic (PV) plants depends greatly on the solar irradiance. This paper studies the effects of the solar irradiance variability analyzing experimental 1‐s data collected throughout a year at six PV plants, totaling 18 MWp. Each PV plant was modeled as a first order filter function based on an analysis in the frequency domain of the irradiance data and the output power signals. An empiric expression which relates the filter parameters and the PV plant size has been proposed. This simple model has been successfully validated precisely determining the daily maximum output power fluctuation from incident irradiance measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance,cost and life‐cycle assessment study of hybrid PVT/AIR solar systems

An alternative and cost‐effective solution to building integrated PV systems is to use hybrid photovoltaic/thermal (PV/T) solar systems. These systems consist of PV modules with an air channel at their rear surface, where ambient air is circulating in the channel for PV cooling and the extracted heat can be used for building thermal needs. To increase the system thermal efficiency, additional glazing is necessary, but this results in the decrease of the PV module electrical output from the additional optical losses of the solar radiation. PV/T solar systems with air heat extraction have been extensively studied at the University of Patras. Prototypes in their standard form and also with low‐cost modifications have been tested, aiming to achieve improved PV/T systems. An energetic and environmental assessment for the PV and PV/T systems tested has been performed by the University of Rome ‘La Sapienza’, implementing the specific software SimaPro 5·1 regarding the life‐cycle assessment (LCA) methodology applied. In this paper electrical and thermal energy output results for PV and PV/T systems are given, focusing on their performance improvements and environmental impact, considering their construction and operation requirements. The new outcome of the study was that the glazed type PV/T systems present optimum performance regarding energy, cost and LCA results. Copyright © 2005 John Wiley & Sons, Ltd.     

A simplified model based on clearness index for estimating yearly performance of hybrid PV energy systems

A simplified model for estimating the energy contribution of PV converter in a hybrid PV–wind system is presented. The simplified model determines the yearly solar fraction, that is the fraction of energy demand provided by PV, and the remaining loss of load (LOL) is assumed to be provided by wind turbines. The novel model is based on simulation results derived from 8 years of measured hour‐by‐hour solar irradiation data from five different locations in the world. The system performance is simulated by the PV–wind energy simulation program of the Cardiff School of Engineering (ARES). An hourly constant load profile is assumed. The performance of a PV system is primarily dependent on the solar irradiation distribution in a given location for the period of time in question. The new model correlates the location dependence observed in the yearly solar fraction curves of different data sets with one of the most characteristic solar irradiation distribution parameters, the yearly clearness index of the respective solar irradiation data. The new model requires the yearly clearness index value, which is commonly available for most locations throughout the world, as input. As the novel model is validated with solar irradiation data from different locations in the world, it could be used for predicting the solar fraction in a hybrid PV system with a very high level of accuracy, for a wide range of climates. Copyright © 2002 John Wiley & Sons, Ltd.     

Evaluation of solar energy potential and PV module performance in the Gobi Desert of Mongolia

Here, we present the results of evaluation of solar energy potential and photovoltaic (PV) module performance from actual data measured over a period of more than 2 years in the Gobi Desert of Mongolia. To allow estimation of solar energy potentials and durability of PV systems in the Gobi Desert area, a data acquisition system, including crystalline silicon (c‐Si), polycrystalline silicon (p‐Si) modules, and two sets of precision pyranometers, thermometers, and anemometer, was installed at Sainshand City in October 2002. This system measures 23 parameters, including solar irradiation and meteorological parameters, every 10 min. High output gain was observed due to operation at extremely low ambient temperatures and the module performance ratios (PRs) were high (>1·0) in winter. In summary, the present study showed that a PV module with a high temperature coefficient, such as crystalline silicon, is advantageous for use in the Gobi Desert area. Copyright © 2006 John Wiley & Sons, Ltd.     

A novel analytical model for determining the maximum power point of thin film photovoltaic module

Achieving the maximum power output from photovoltaic (PV) modules is indispensable for the operation of grid‐connected PV power systems under varied atmospheric conditions. In recent years, the study of PV energy for different applications has attracted more and more attention because solar energy is clean and renewable. We propose an efficient direct‐prediction method to enhance the utilization efficiency of thin film PV modules by tackling the problem of tracking time and overcoming the difficulty of calculation. The proposed method is based on the p–n junction recombination mechanism and can be applied to all kinds of PV modules. Its performance is not influenced by weather conditions such as illumination or temperature. The experimental results show that the proposed method provides high‐accuracy estimation of the maximum power point (MPP) for thin film PV modules with an average error of 1.68% and 1.65% under various irradiation intensities and temperatures, respectively. The experimental results confirm that the proposed method can simply and accurately estimate the MPP for thin film PV modules under various irradiation intensities and temperatures. In future, the proposed method will be used to shed light on the optimization of the MPP tracking control model in PV systems. Copyright © 2012 John Wiley & Sons, Ltd.     

风光互补发电系统的能量管理研究

风光互补发电系统可充分利用本地太阳能和风能资源,具有无污染、供电质量好的优点,是解决偏远地区供电问题的最佳选择之一。为了提高风光互补发电系统的能量利用率和经济性,满足负荷的供电要求,必需对系统能量进行有效的管理。本文提出了一种简洁适用的基于储能环节控制的能量管理策略,并进行了相关的仿真和实验验证。     

Energy Management for a Residential Microgrid Using Wavelet Transform and Fuzzy Control Including a Vehicle-to-Grid System

This paper presents the design and implementation of an energy management system (EMS) with wavelet transform and fuzzy control for a residential micro-grid. The hybrid system in this paper consists of a wind turbine generator, photovoltaic (PV) panels, an electric vehicle (EV), and a super capacitor (SC), which is able to connect or disconnect to the main grid. The control strategy is responsible for compensating the difference between the generated power by the wind and solar generators and the demanded power by the loads. Wavelet transform decomposes the power difference into a smoothed component and a fast fluctuated component. The command approach used for fuzzy logic rules considers the state of charging (SOC) of EV, renewable production, and the load demand as parameters. Furthermore, the command rules are developed in order to ensure a reliable grid when taking into account the EV battery protection to decide the output power of the EV. The model of the hybrid system is developed in detail under Matlab/Simulink software environment.     

An investigation into hot‐spots in two large grid‐connected PV plants

This paper details an investigation into the appearance of hot‐spots in two large grid‐connected photovoltaics (PV) plants, which were detected after the visual inspection of trackers whose energy output was decreasing at anomalous rate. Detected hot‐spots appeared not only in the solar cells but also in resistive solder bonds (RSB) between cells and contact ribbons. Both types cause similar irreversible damage to the PV modules, but the latter are the main responsible for the detected decrease in energy output, which was confirmed in an experimental testing campaign. The results of this investigation, for example, how hot‐spots were detected or their impact on the output power of PV modules, may be of interest for the routine maintenance of large grid‐connected PV plants. Copyright © 2008 John Wiley & Sons, Ltd.     

The performance of PV‐t systems for residential application in Bangkok

This paper focused on the performance of photovoltaic‐thermal (PVT) systems working in Bangkok for residential applications. The PVT system is one which produces both electricity and low temperature heat at the same time. This paper investigated the performance of PVT systems that use different types of commercial solar PV panels. The characteristics of the PV panels were used as input parameters in the simulation. Each system comprises 2 m² of PVT collector area. Water draw patterns are those with a typical consumption of medium size houses in Bangkok, and the measured monthly average city water temperature of Bangkok has been used to estimate the energy output. The results show that the optimum water flow rate is 20 kg/h for all types of PVT collectors and the effect of water flow can improve the cell efficiency of PV cells. Moreover, the total energy output from the PVT collectors, which had glass covers is very significantly higher than those without one. The c‐Si PVT panel gave the best performance with the highest rate of primary energy reduction. The payback time of each system is 6.4, 11.8, and 13.4 years for a‐Si, mc‐Si, and c‐Si types of PVT system, respectively. This investigation concludes that from the viewpoint of system performance, c‐Si PVT is the most promising type than whereas from the viewpoint of economy, a‐Si PVT has the fastest payback time. Copyright © 2012 John Wiley & Sons, Ltd.     

Operation of series‐connected silicon‐based photovoltaic modules under partial shading conditions

Partial shading has been recognized as a major cause of energy losses in photovoltaic (PV) power generators. Partial shading has severe effects on the electrical characteristics of the PV power generator, because it causes multiple maximum power points (MPPs) to the power‐voltage curve. Multiple maxima complicate MPP tracking, and the tracking algorithms are often unable to detect the global maximum. Considerable amount of available electrical energy may be lost, when a local MPP with low power is tracked instead of the global MPP. In this paper, the electrical characteristics of series‐connected silicon‐based PV modules under various partial shading conditions are studied by using a Matlab/Simulink simulation model. The simulation model consists of 18 series‐connected PV modules, corresponding to a single‐phase grid‐connected PV power generator. The validity of the simulation model has been verified by experimental measurements. The voltage and power characteristics of the PV power generator have been investigated under various system shading and shading strength conditions. The results can be utilized to develop new MPP tracking algorithms and in designing, for example, building integrated PV power generators. Copyright © 2011 John Wiley & Sons, Ltd.