用于太阳能光电水泵的菲涅耳透镜聚光收集器

报道了具有第二级Ｖ形槽聚光器的玻璃直纹菲涅尔透镜与ＬＧＢＧ高效太阳电池组成的低倍聚光收集器的试验结果。宽度为３０ｍｍ、长度为１．５８ｍ的太阳电池组件，经聚光后峰值功率从７Ｗ增大到４４Ｗ，比常规太阳电池费用减少６０％，系统总费用降低４０％。     

复合抛物面聚光太阳能PV/T系统的实验研究

设计并搭建了CPC低倍聚光太阳能PV/T单通道空气系统实验台,对不同工作环境下聚光PV/T系统的热电性能进行了实验研究。实验研究结果显示:在聚光条件下,系统的各表面温度随光照强度的增加而升高,随下部通道入口空气流速的增加而降低。聚光PV/T系统的最大输出功率可达到60W,比对应相同电池面积平板系统最大输出功率高20W。聚光PV/T系统的各效率随光照强度增加而增大,系统的最大电效率为11%,最大热效率为70%,最大火用效率为16%,比单纯发电时最大火用效率提高约5%。实验获得了一批新的有价值的实验数据,为聚光太阳能光伏光热系统的进一步研究提供了依据。     

Experimental analysis of a two‐axis tracking system for solar parabolic dish collector

In this paper, an attempt has been made to develop a two‐axis tracking system for solar parabolic dish concentrator and experimentally evaluated the performance of the tracking system. In this proposed design, the sensor design uses the illumination produced by the convex lens on the apex of a pyramid to align the dish in‐line with the sun. The change in incident angle of the solar rays on the lens surface shifts the area of illumination from the apex of the pyramid towards its faces. Photodiodes placed on the faces of the pyramid are used as the sensitive elements to detect the movement of the sun. The sensor output is fed to a microcontroller‐based system to drive the stepper motor on the basis of the programmed algorithm such that it receives normal incidence of sunlight on the sensor. To evaluate the performance of the proposed system, a conventional available 1‐W photovoltaic (PV) panel is placed at the focal point to measure the short circuit current and open circuit voltage. With respect to the conventional solar PV panel, it is observed that the positioning accuracy of the proposed tracking system enhances the short circuit current of 0.11 A by 86%. Thus, the proposed tracking system can be used in a stand‐alone parabolic dish with concentrating PV module as the focal point for further studies.     

Non-concentrating and asymmetric compound parabolic concentrating building façade integrated photovoltaics: An experimental comparison

Concentration of solar energy increases the illuminated flux on the photovoltaic (PV) surface thus less PV material is required. A novel asymmetric compound parabolic photovoltaic concentrator has been characterised experimentally with a similar non-concentrating system. Different numbers of PV strings connected within the system have been analysed and a power ratio of 1.62 measured compared to a similar non-concentrating PV panel with the same cell area. The solar to electrical conversion efficiency of 8.6% and 6.8% was achieved for the non-concentrating panel the concentrating system, respectively. The measured average solar cell temperature of the PV in the concentrator system was only 12 °C higher than that of the similar non-concentrating system with same cell area.     

Maximum power output of a solar PV module at various latitudes as influenced by the swing angle of the sun

The effect of the maximum swing angle of the sun (0°, 15°, 30°, 45° and 60°) away from the normal is observed on the maximum power output of an amorphous silicon solar PV module using a solar simulator. Studies reveal that as the panel inclination is increased, the maximum power produced (P_mp) by the module decreases. Solar equations are used to compute the maximum swing angle of the sun away from the normal position of the panel at noon (λ) during March, June, September and December months and are computed for various selected locations such as Mumbai, Ludhiana, Fargo, London and Moscow. An analogy between the simulated study and λ (for real operation conditions) for polar-mounted inclinations of PV panels is established and the effect of λ on the percent reduction of maximum power produced (P_mp) by the PV solar panel is studied.     

Determining optimum tilt angles and orientations of photovoltaic panels in Sanliurfa, Turkey

The performance of a photovoltaic (PV) panel is affected by its orientation and its tilt angle with the horizontal plane. This is because both of these parameters change the amount of solar energy received by the surface of the PV panel. A mathematical model was used to estimate the total solar radiation on the tilted PV surface, and to determine optimum tilt angles for a PV panel installed in Sanliurfa, Turkey. The optimum tilt angles were determined by searching for the values of angles for which the total radiation on the PV surface was maximum for the period studied. The study also investigated the effect of two-axis solar tracking on energy gain compared to a fixed PV panel. This study determined that the monthly optimum tilt angle for a PV panel changes throughout the year with its minimum value as 13° in June and maximum value as 61° in December. The results showed that the gains in the amount of solar radiation throughout the year received by the PV panel mounted at monthly optimum tilt angles with respect to seasonal optimum angles and tilt angel equal to latitude were 1.1% and 3.9%, respectively. Furthermore, daily average of 29.3% gain in total solar radiation results in an daily average of 34.6% gain in generated power with two-axis solar tracking compared to a south facing PV panel fixed at 14° tilt angle on a particular day in July in Sanliurfa, Turkey.     

Performance enhancement of partially shaded solar PV array using novel shade dispersion technique

Solar photo voltaic array (SPVA) generates a smaller amount of power than the standard rating of the panel due to the partial shading effect. Since the modules of the arrays receive different solar irradiations, the P-V characteristics of photovoltaic (PV) arrays contain multiple peaks or local peaks. This paper presents an innovative method (magic square) in order to increase the generated power by configuring the modules of a shaded photovoltaic array. In this approach, the physical location of the modules in the total cross tied (TCT) connected in the solar PV array is rearranged based on the magic square arrangement pattern. This connection is done without altering any electrical configurations of the modules in the PV array. This method can distribute the shading effect over the entire PVarray, without concentrating on any row of modules and can achieve global peaks. For different types of shading patterns, the output power of the solar PV array with the proposed magic square configuration is compared with the traditional configurations and the performance is calculated. This paper presents a new reconfiguration technique for solar PV arrays, which increases the PV power under different shading conditions. The proposed technique facilitates the distribution of the effect of shading over the entire array, thereby, reducing the mismatch losses caused by partial shading. The theoretical calculations are tested through simulations in Matlab/ Simulink to validate the results. A comparison of power loss for different types of topologies under different types of shading patterns for a 4×4 array is also explained.     

双面光伏组件辐照度模型的研究

针对双面光伏组件正面和背面获均能吸收太阳光的特点,通过光线跟踪辐照度模型分析,构建区分阴影区和无阴影区的热传输理论视觉因子太阳辐照度模型。模拟结果表明:当双面光伏组件倾斜角比单面组件增加约4°,在地面反射率为30%和50%的情况下,年辐照度增益可提高17.41%和28.79%;且随着离地高度与行间距增加,年辐照度可进一步提高。双面光伏组件辐照度模型为双面光伏组件电站安装时的地面反射率、最佳倾斜角、离地高度及行间距的设置提供了理论支撑。     

Numerical determination of adequate air gaps for building-integrated photovoltaics

The efficiency of photovoltaic (PV) devices is approximately inversely proportional to the cell temperature and the air gap of PV modules over or beside a building envelope can facilitate ventilation cooling of building-integrated photovoltaics. The effect of gap size on the performance of one type of PV module (with dimensions 1209 × 537 × 50 mm) in terms of cell temperature has been determined numerically for a range of roof pitches and panel lengths under two different settings of solar heat gains. It has been found that under constant solar heat gain, the air velocity behind PV modules due to natural convection in general increases with roof pitch angle. For a given location where solar heat gain varies with inclination from horizontal plane, however, the air velocity increases up to a pitch angle of about 60 degrees and then decreases with increasing roof pitch. The mean and maximum PV temperatures decrease with the increase in pitch angle and air gap. The mean PV temperature also decreases with increasing panel length for air gaps greater than or equal to 0.08 m, whereas the maximum PV temperature generally increases with panel length but decreases when the length of a roof-mounted panel increases from two modules to three modules and the air gap is between 0.1 and 0.11 m. Without adequate air circulation, overheating of PV modules would occur and hot spots could form near the top of modules with potential cell temperatures over 80 °C above ambient air temperature under bright sunshine.     

Performance modeling and investigation of fixed, single and dual-axis tracking photovoltaic panel in Monastir city, Tunisia

Presented in this paper was an overview on research works on solar radiation basics and photovoltaic generation. Also, a complete PV modeling and investigation on the effect of using multi-axes sun-tracking systems on the electrical generation was carried out to evaluate its performance using the case study of the Monastir city, Tunisia. The effects of azimuth and tilt angles on the output power of a photovoltaic module were investigated. The instantaneous increments of the output power generated by a photovoltaic module mounted on a single and dual-axis tracking system relative to a traditional fixed panel were estimated. The results show that the yearly optimal tilt angle of a fixed panel faced due to the south is close to 0.9 times Monastir latitude. The gain made by the module mounted on a single-axis tracking panel relative to a traditional fixed panel was analyzed. The monthly increments of the gain are more noticeable for two critical periods which correspond to those surrounding the summer and the winter solstice dates. It reaches the value of 10.34% and 15% in the summer and winter solstice periods, respectively. However, the yearly gain relative to a fixed panel installed with the yearly optimal tilt angle is 5.76%. In some applications, covering loads at early morning or late afternoon hours and in order to more optimize the solar systems exploitation suggest the adjustment of the PV panel orientation to azimuth angles different from the south direction by using a dual-axis tracking installation. The gain made by this recommendation relative to a traditional fixed panel is evaluated. This gain reaches 30% and 44% respectively in the winter and summer solstice days.     

Improvement in artificial neural network-based estimation of grid connected photovoltaic power output

This paper presents a method to improve the accuracy of artificial neural network (ANN)–based estimation of photovoltaic (PV) power output by introducing two more inputs, solar zenith angle and solar azimuth angle, in addition to the most widely used environmental information, plane-of-array irradiance and module temperature. Solar zenith angle and solar azimuth angle define the solar position in the sky; hence, the loss of modeling accuracy due to impacts of solar angle-of-incidence and solar spectrum is reduced or eliminated. The observed data from two sites where local climates are significantly different is used to train and test the proposed network. The good performance of the proposed network is verified by comparing with existing ANN model, algebraic model, and polynomial regression model which use environmental information only of plane-of-array irradiance and module temperature. Our results show that the proposed ANN model greatly improves the accuracy of estimation in the long term under various weather conditions. It is also demonstrated that the improvement in estimating outdoor PV power output by adding solar zenith angle and azimuth angle as inputs is useful for other data-driven methods like support vector machine regression and Gaussian process regression.     

On the investigation of photovoltaic output power reduction due to dust accumulation and weather conditions

Certain environmental conditions such as accumulation of dust and change in weather conditions affect the amount of solar radiation received by photovoltaic (PV) panel surfaces and thus have a significant effect on panel efficiency. This study conducted an experimental investigation in Surabaya, Indonesia, on the effect of these factors on output PV power reduction from the surface of a PV module. The module was exposed to outside weather conditions and connected to a measurement system developed using a rule-based model to identify different environmental conditions. The rule-based model, a clear sky solar irradiance model that included solar position, and a PV temperature model were then used to estimate the PV output power, and tests were also conducted using an ARM Cortex-M4 microcontroller STM32F407 as a standalone digital controller equipped with voltage, current, temperature, and humidity sensors to measure real time PV output power. In this system, humidity was monitored to identify dusty, cloudy, and rainy conditions. Validated test results demonstrate that the prediction error of PV power output based on the model is 3.6% compared to field measurements under clean surface conditions. The effects of dust accumulation and weather conditions on PV panel power output were then analyzed after one to four weeks of exposure. Results revealed that two weeks of dust accumulation caused a PV power output reduction of 10.8% in an average relative humidity of 52.24%. Results of the experiment under rainy conditions revealed a decrease in PV output power of more than 40% in average relative humidity of 76.32%, and a decrease in output power during cloudy conditions of more than 45% in an average relative humidity of 60.45% was observed. This study reveals that local environmental conditions, i.e., dust, rain, and partial cloud, significantly reduce PV power output.     

Study of bypass diodes configuration on PV modules

A procedure of simulation and modelling solar cells and PV modules, working partially shadowed in Pspice environment, is presented. Simulation results have been contrasted with real measured data from a commercial PV module of 209 Wp from Siliken. Some cases of study are presented as application examples of this simulation methodology, showing its potential on the design of bypass diodes configuration to include in a PV module and also on the study of PV generators working in partial shading conditions.     

Numerical investigation of the solar concentrating characteristics of 3D CPC and CPC-DC

A Monte Carlo Ray Tracing (MCRT) method was expanded with a bisection module to solve high-order nonlinear equations. Applying this modified MCRT method, the solar concentrating characteristics of a 3D Compound Parabolic Concentrator (3D CPC) were investigated. Moreover, a two-stage solar concentrator formed by a dish concentrator in tandem with a single 3D CPC (CPC-DC) was presented in this paper. Considering the influence of the tracking errors and slope errors, the solar concentrating performances of the CPC-DC was performed using the modified MCRT method. For DC having a rim angle of 45°, the numerical results show that the interception efficiency of the DC is about 4.0% higher than that of CPC-DC, but the concentrator ratio of the CPC-DC is twice as large as that of DC.     

Application of compound parabolic concentrators to solar photovoltaic conversion: A comprehensive review

The use of concentrating systems has been proposed as a way to reduce the cost of electrical energy from photovoltaic (PV) module. Since 1970s, different solar collector designs have been used to increase energy flux on the PV module. This study aims at providing a comprehensive review of development in the application of compound parabolic concentrators (CPCs) to solar photovoltaic conversion for the past five decades. By narrowing down the application of CPCs to electrical energy only gives a reader an opportunity to clearly understand the detail development stages, challenges, and research opportunities for further improvement. From this review, it has been found that during 1970s, all studies on the application of CPCs to solar photovoltaic conversion were mainly focused on establishing technical feasibility and cost effectiveness. Thereafter (1981‐May 2018), extensive studies were carried out to resolve challenges that were observed during the establishment stage. However, it has been found that even though the power output of the PV modules with the CPC was always higher than similar modules without the CPC, the values were less than the expected (theoretical) results. This was due to optical losses, series resistance losses, non‐uniform illumination effect, and high operating cell temperature effect. In addition, high cost of the PV‐CPC systems and low concentration ratio of the CPCs were also the main concerns of various researchers.     

PV-GIS: a web-based solar radiation database for the calculation of PV potential in Europe

Solar radiation is a key factor determining electricity produced by photovoltaic (PV) systems. This paper presents a solar radiation database of Europe developed in the geographical information system, and three interactive web applications providing an access to it. The database includes monthly and yearly average values of the global irradiation on horizontal and inclined surfaces, as well as climatic parameters needed for an assessment of the potential PV electricity generation (Linke atmospheric turbidity, the ratio of diffuse to global irradiation, an optimum inclination angle of modules to maximize energy yield). In the first web application, a user may browse radiation maps and query irradiation incident on a PV module for different inclination angles. The second application simulates daily profiles of irradiance for a chosen month and module inclination and orientation. The third web application estimates electricity generation for a chosen PV configuration. It also calculates optimal inclination and orientation of a PV module for a given location. The database and the applications are accessible at http://re.jrc.cec.ev.int/pvgis/pv/imaps/imaps.htm.     

Effect of air gap on the performance of building-integrated photovoltaics

Ventilation of photovoltaic (PV) modules installed over or beside a building envelope can reduce the module temperature and increase the electrical conversion efficiency. A computational fluid dynamics (CFD) method has been used to assess the effect of the size of air gap between PV modules and the building envelope on the PV performance in terms of cell temperature for a range of roof pitches and panel lengths and to determine the minimum air gap that is required to minimise PV overheating. It has been found that the mean PV temperature and the maximum PV temperature associated with hot spots decrease with the increase in pitch angle and air gap. The mean PV temperature also decreases with increasing panel length for air gaps greater than or equal to 0.08 m whereas the maximum PV temperature generally increases with panel length. To reduce possible overheating of PV modules and hot spots near the top of modules requires a minimum air gap of 0.12–0.15 m for multiple module installation and 0.14–0.16 m for single module installation depending on roof pitches.     

获得最大日照度的协调控制方法的研究——多镜面聚光型太阳能光伏系统

针对目前太阳能聚光方式,提出了采用平面镜反射聚光的多镜面阵全跟踪聚光方案.首先描述了多镜面聚光型太阳能光伏系统的基本结构及其跟踪控制原理和方法.通过对多镜面阵聚光系统对太阳全方位跟踪控制分析,推出了太阳电池组件和平面镜阵在跟踪过程中方位角、倾角及空间位置变化的运动方程.通过建立了平面镜阵与太阳电池组件之间的运动关系,实现太阳电池组件跟踪控制以及平面镜阵之间的跟踪协调控制,并对此系统进行了定量分析和数值计算.     

串并联太阳能电池弧形光伏组件的发电性能研究

将弧形光伏组件安装在建筑和汽车上获取电能,已受到人们越来越多的关注。为获得更高的输出功率,有必要研究由互连太阳能电池组成的、电流不匹配的弧形光伏组件的特性。研究重点关注由串并联太阳能电池组成的弧形光伏组件的发电性能,设计了不同曲率的非平面微型光伏模块,并通过测量获取光伏模块的参数。与平面光伏模块相比,弧形光伏模块的发电量较小。此外,利用二极管模型分析了光伏模块的特性,说明并联比串联功率高的原因。最后研究了实际应用中太阳能电池的互连问题。结果表明,在理想模型下并联能获取更多电能,但大尺寸的光伏模块会产生更大电流,可能会在实际运行中产生额外损耗。因此,在实际应用中设计弧形光伏组件时也应考虑太阳能电池的互连。     

Design concept and mathematical model of a bi-fluid photovoltaic/thermal (PV/T) solar collector

This paper presents an improved design of a photovoltaic/thermal (PV/T) solar collector integrating a PV panel with a serpentine-shaped copper tube as the water heating component and a single pass air channel as the air heating component. In addition to the electricity generated, this type of collector enables the production of both hot air and water, increasing the total efficiency per unit area compared to the conventional PV/T solar collector. The use of both fluids (bi-fluid) also creates a greater range of thermal applications and offers options in which hot and/or cold air and/or water can be utilized depending on the energy needs and applications. In this paper, the design concept of the bi-fluid PV/T solar collector is emphasized with 2D steady state energy balance equations for the bi-fluid configuration are developed, validated and used to predict the performance of the bi-fluid solar collector for a range of mass flow rates of air and water. The performance of the collector is then compared when the fluids are operated independently and simultaneously. The simulations indicate that when both fluids are operated independently the overall thermal and electrical performance of the solar collector is considered as satisfactory and when operated simultaneously the overall performance is higher. The bi-fluid PV/T solar collector discussed in this paper will add insights to the new knowledge of optimizing the utilization of solar energy by a PV/T solar collector and has potential applications in various fields.