基于新能源集控平台的光伏组件清洗分析系统的设计

灰尘是影响光伏电站发电效率的关键因素之一,其会大幅降低光伏电站的发电量。为降低积灰对光伏电站发电量损失影响的程度,电站需定期清洗光伏组件,因此,基于新能源集控平台设计了一款光伏组件清洗分析系统。该系统通过建立清洗计算模型,提出光伏组件无积灰理论发电量算法,量化了积灰损失发电量,推算光伏组件的最优清洗周期。结果显示：该系统能够为光伏组件清洗提供合理的决策依据。     

太阳能电池板表面灰尘擦除试验研究

荒漠地区电池板表面积灰严重影响光伏组件发电效率,因此有效擦除电池板积灰的问题已成为维护光伏电站的主要工作之一。为此,测量了GS-50非晶硅薄膜光伏组件在0、3.1、4.8、7.2、14.9、24.5g/m2不同积灰条件下的平均输出功率,设计了可调节清洁参数的灰尘清洁装置,研究了擦除速率、擦除压力、擦除次数和擦除方式等工艺参数对光伏清洁效果的影响。结果表明,不同擦除速率下光伏发电转换效率保持在4%左右;擦除压力比擦除次数的影响明显,在擦除压力为250N时连续擦除三次清洁效果达到最佳;木条刷与圆盘刷组方式的清洁效果最好。     

太阳电池积灰对其发电性能影响的研究

以太阳电池为研究对象,通过Matlab建立数学模型,对太阳电池的输出特性进行仿真研究。然后通过天津地区实际的太阳电池进行测试实验,建立太阳电池输出功率与积灰密度关系的数学模型。研究结果表明:随太阳电池表面积灰密度的增加,太阳电池的输出功率相应的减少,且得到在一定条件下(辐照度为1000 W/m2、温度为25℃),太阳电池输出功率与积灰密度的数学公式。最后通过数据分析得出天津地区太阳电池积灰会造成光伏组件年均降低发电效率约为6%。     

积灰阴影遮挡对光伏发电系统的影响

阐述了太阳能光伏电池积灰的成因、积灰的物理及化学性质和形态分类,解释了积灰的遮挡效应、腐蚀效应和热斑效应,应用MATLAB应用软件搭建光伏电池及光伏发电仿真系统,研究积灰阴影遮挡对光伏发电系统的影响。分析光伏发电系统的原理,利用MATLAB建立光伏发电系统模型,利用搭建好的模型针对光伏组件的积灰与局部阴影来进行仿真,用定性和定量分析积灰与阴影遮挡对光伏组件及其发电系统的影响,指出了对于光伏板组件上积灰清洗的重要性。     

西安城区灰尘对分布式光伏电站输出功率的影响分析

根据光伏组件输出易受积灰影响的特点,分析了城区灰尘对分布式光伏电站的影响。并在西安城区某分布式光伏电站中设计对比实验,实验表明在"降尘"天气影响下,城区灰尘对光伏系统输出功率降低影响很大,在本实验中达到15%。     

北京地区多种光伏组件发电性能对比实验研究

该课题组设计建造了一座光伏试验电站,对单晶硅光伏组件、多晶硅光伏组件、非晶硅光伏组件、铜铟镓硒光伏组件和碲化镉光伏组件进行长期监测,对监测数据进行统计并分析了温度、弱光和湿度对不同光伏组件的影响,设计了阴影遮挡试验和灰尘清洗试验。研究表明,薄膜光伏组件的温度效应优于晶硅光伏组件,其输出功率损失低于晶硅光伏组件;对于晶硅光伏组件由于表面积尘和阴影遮挡而引起的输出功率损失要高于薄膜光伏组件;而弱光和湿度对光伏组件发电性能的影响没有明显差异。通过分析试验电站的监测数据,发现铜铟镓硒光伏组件单位装机容量的发电量最高,其发电量高出多晶硅光伏组件5.72%,而次于铜铟镓硒光伏组件发电能力的是单晶硅光伏组件和多晶硅光伏组件。     

光伏组件自动清洗系统的应用研究

针对积灰影响光伏组件发电量且现有光伏组件清洗方式不能满足大规模光伏电站清洗需求的情况，设计了1套光伏组件自动清洗系统。该自动清洗系统由水源、水泵、喷淋系统和可编程逻辑控制器(PLC)控制柜等组成，其可同时对3个光伏阵列进行清洗，实现光伏组件的自动清洗；然后以某8.2 MW光伏电站为例，研究了清洗前后光伏组件的I-V特性、表面温度、短路电流、开路电压、输出功率、光能转化效率的变化情况；最后分析了积灰对光伏电站经济性的影响。研究结果显示：1)相较于清洗前，清洗后光伏组件的I-V特性、表面温度、短路电流、开路电压、输出功率、光能转化效率均得到明显改善；2)当光伏组件表面处于稠密积灰状态时，经济损失基本平稳，日经济损失最高约可达4268元。由此可以说明，利用光伏组件自动清洗系统对光伏组件进行定期清洗尤为重要。     

积灰对屋顶光伏电站性能的影响

探讨了积灰问题对屋顶光伏电站电性能和热性能的影响。在积灰的初始阶段,组件的发电量下降得较为明显;同时,积灰并未明显改变组件的温度,表明积灰不会改变光伏电池片实时发电效率。积灰对光伏电站发电量的影响主要表现在组件表面太阳光透过率的变化。     

荒漠地区电池板表面灰尘特性分析

高海拔荒漠地区光伏电池板表面上往往会积累大量灰尘,严重影响光伏发电效率。由于灰尘的成分、形貌和粒径等特性不同,导致积灰对光伏发电的影响也不同。文章检测了光伏电池板表面灰尘成分,测定观察了灰尘粒径及形貌,并根据电池板清洗现状分析荒漠地区地下水所含的阴阳离子成分;根据格尔木荒漠地区灰尘成分,给出了灰尘对电池板发电效率的影响曲线;通过灰尘粒径的测定,分析了灰尘粒径对电池板的遮挡影响和对灰尘擦除的影响。文章还分析了光伏电池板清洁用水的成分及特性,结合灰尘自身特点,探讨了往清洗用水中添加化学试剂的方案,为荒漠地区光伏电池板表面的清洁维护提供理论依据。     

阴影遮蔽条件下光伏发电效率的增大方法

受阴影遮蔽影响,光伏阵列输出功率下降,功率曲线呈现多峰值,使传统的最大功率点(MPPT)算法失效陷入局部极值点。基于光伏电池的等效电路模型,在正常和有阴影遮蔽情况下对光伏组件串并联输出特性进行仿真,分析功率曲线上局部极值点的产生原因及变化规律。针对阴影遮蔽对光伏发电效率的影响,提出建立微型光伏发电系统,采用光伏组件间解耦的方法,跟踪每个光伏组件的最大功率点,使光伏发电效率达到最优。试验结果验证了该方法的可行性,为今后光伏电站的建设提供了指导。     

Comparative analysis of diffused solar radiation models for optimum tilt angle determination for Indian locations

Tilt angle and orientation greatly are influenced on the performance of the solar photo voltaic panels. The tilt angle of solar photovoltaic panels is one of the important parameters for the optimum sizing of solar photovoltaic systems. This paper analyses six different isotropic and anisotropic diffused solar radiation models for optimum tilt angle determination. The predicted optimum tilt angles are compared with the experimentally measured values for summer season under outdoor conditions. The Liu and Jordan model is found to exhibit t lowest error as compared to other models for the location.     

Optical performance of inclined south-north axis three-positions tracked solar panels

In this work, the optical performance of solar panels with a new sun-tracking technique was theoretically investigated based on the proposed mathematical method and monthly horizontal radiation. The mechanism of the investigated sun-tracking is that the attitude angle of solar panels is daily adjusted three times at three fixed positions: eastward, southward, and westward in the morning, noon, and afternoon, respectively, by rotating solar panels about the inclined south-north axis (ISNA-3P sun-tracking). Calculation results showed that, for ISNA-3P tracked solar panels with a yearly fixed tilt-angle of the ISNA, the maximum annual collectible radiation on ISNA-3P tracked solar panels was about 93% of that on a solar panel with 2-axis sun-tracking; whereas for those with the ISNA being yearly adjusted four times at three fixed tilt-angles, it was about 96%. Results also indicated that the attempt to further increase the annual solar gain on ISNA-3P tracked solar panels by seasonally optimizing design of the sun-tracking system for maximizing solar gain in each of four seasons was not efficient, and thus not advisable in practical applications. Optimal parametric designs of such sun-tracking system for maximizing the annual solar gain on solar panels in different cases were also presented.     

A practical field study of various solar cells on their performance in Malaysia

A practical field study has been carried out with the intention to analyze and compare the performance of various types of commercially available solar panels under Malaysia's weather. Four different types of solar panels, such as mono-crystalline silicon, multi-crystalline silicon, amorphous silicon and copper–indium–diselenide (CIS) solar panels are used for the practical field study. A number of performance related parameters have been collected using data logger over a period of three consecutive days in the hope that this would give some initial information on the real performance of different solar panels. Results show that mono-crystalline silicon and multi-crystalline silicon solar module perform better when they are under hot sun, whereas the CIS and triple junction amorphous silicon solar panel perform better when it is cloudy and has diffused sunshine. Furthermore, the efficiency of crystalline silicon solar panel has been found to drop when the temperature rises higher. This phenomenon does not appear in the CIS and amorphous silicon solar panels, which shows that the performance of CIS and amorphous silicon solar cells are better in terms of power conversion efficiency and overall performance ratio. Better performance of thin film solar cells like amorphous silicon and CIS are observed from the initial results, which draws attention over the selection of solar panels and also may encourage the usage of these in tropical weather like Malaysia.     

The effect of dust accumulation on line-focus parabolic trough solar collector performance

Based on the major Department of Energy Solar Industrial Process Heat Program, it has been determined that the existing techniques for predicting the performance of parabolic trough solar collectors greatly overpredict the thermal output of these systems. The objective of the research reported herein is to improve the predictive capability of existing models by incorporating a factor that accounts for dust and dirt accumulation on the optical surfaces. This has been accomplished by modifying the optical efficiency with a dust factor to account for the reduced reflectivity of the mirror and reduced transmissivity of the cover glass. This technique has been developed independent of the test data used for verification. The dust factors have been developed from exposure tests conducted at six different sites, so that it is also independent of location and collector type. Wash frequency and optical degradation rate are input to the model to compute the time varying dust factors. Recommendations for these parameters are provided based on long-term observations. The complete model is then used to provide realistic predictions of real-world performance of solar IPH systems.     

Optical performance of vertical axis three azimuth angles tracked solar panels

In this work, a new sun-tracking concept was proposed, and the optical performance of solar panels with such sun-tracking system was theoretically investigated based on the developed mathematical method and monthly horizontal radiation. The mechanism of the proposed sun-tracking technique is that the azimuth angle of solar panels is daily adjusted three times at three fixed positions: eastward, southward and westward in the morning, noon, and afternoon, respectively, by rotating solar panels about the vertical axis (3A sun-tracking, in short). The analysis indicated that the tilt-angle of solar panels, β_3A, azimuth angle of solar panels in the morning and afternoon from due south, ?_a, and solar hour angle when the azimuth angle adjustment was made in the morning and afternoon, ω_a, were three key parameters affecting the optical performance of such tracked solar panels. Calculation results showed that, for 3A tracked solar panels with a yearly fixed tilt-angle, the maximum annual collectible radiation was above 92% of that on a solar panel with full 2-axis sun-tracking; whereas for those with the tilt-angle being seasonally adjusted, it was above 95%. Results also showed that yearly or seasonally optimal values of β_3A, ?_a and ω_a for maximizing annual solar gain were related to site latitudes, and empirical correlations for a quick estimation of optimal values of these parameters were proposed based on climatic data of 32 sites in China.     

Domestic hot water and solar energy in Ireland

Two systems are discussed which involve the use of solar energy to supply domestic hot-water requirements and their usefulness in Ireland is examined. the systems are evaluated for thermal performance and cost-effectiveness but the use of a computer simulation model of a system involving a typical commercially available solar panel. It is shown that such systems may be economically justified when compared with electricity, but only if the water supply is directly heated by solar panels and only if the installed cost of such panels is low. Further, it appears that the system performance is relatively insensitive to the panel orientation and consequently that retro-fit installations on existing houses are unlikely to cause difficulties.     

A large-panel unglazed roof-integrated liquid solar collector––energy and economic evaluation

Building-integrated unglazed solar collectors are cost effective solar devices that are suitable for various low temperature applications. In this article we present the design and the parametric analyses of the efficiency of a large-panel unglazed roof-integrated liquid solar collector and an economic evaluation of a large-panel solar-heating system for a swimming pool that is installed at a tourist facility on the Adriatic coast. The design of the solar collector is based on standard metal roofing; it takes into account the technological limitations of prefabricated panels, which makes the serial manufacturing of solar collectors possible. The parametric analyses of the large-panel solar collector’s efficiency were made using the finite-volume numerical method. The numerical model was verified with outdoor measurements, according to the ISO 9806 standard. The efficiency was analysed for the most important parameters: the fin length; the absorber material and thickness; the water mass flow rate; and the wind speed. A solar absorptance of 0.85 was considered in the analyses because this is the value that corresponds to the most frequently used roofing colour. The results show that the efficiency of the analysed panels at T_in=T_a is in the range between 0.26 and 0.74, and the heat loss factors are 2.9–7.9 under no-wind conditions. An economic evaluation using the payback period method was used to select the optimum design for the developed panels on the basis of equal solar gains and the known or estimated initial and operating costs. It was found that for the optimum panel design the payback period is between 1.5 and 2.7 years, based on the current price for non-renewable energy sources. The payback period for presented solar systems is up to four times shorter than for a glazed solar collector system.     

Optical performance of inclined south-north single-axis tracked solar panels

To investigate optical performance of the inclined south-north single-axis (ISN-axis, in short) tracked solar panels, a mathematical procedure to estimate the annual collectible radiation on fixed and tracked panels was suggested based on solar geometry and monthly horizontal radiation. For solar panels tracking about ISN-axis, the yearly optimal tilt-angle of ISN-axis for maximizing annual solar gain was about 3° deviating from the site latitude in most of China except in areas with poor solar resources, and the maximum annual collectible radiation on ISN-axis tracked panels was about 97–98% of that on dual-axis tracked panels; whereas for ISN-axis tracked panels with the tilt-angle of ISN-axis being adjusted four times in a year at three fixed tilt-angles, the annual collectible radiation was almost close to that on dual-axis tracked panels, the optimum date of tilt-angle adjustment of ISN-axis was 23 days from the equinoxes, and the optimum tilt-angle adjustment value for each adjustment was about 22°. Compared to fixed south-facing solar panels inclined at an optimal tilt-angle, the increase in the annual solar gain due to using ISN-axis sun tracking was above 30% in the areas with abundant solar resources and less than 20% in the areas with poor solar resources.     

Effect of dust deposition on the performance of a solar desalination plant operating in an arid desert area

The performance of a solar desalination plant (whether using thermal or photovoltaic collectors) is influenced by the ability of the glazing system to transmit solar radiation to the collector absorption surface. This ability is influenced by such factors as the intensity of solar radiation, the transmittance of the collector glazing, the tilt angle of the absorbing surface, the operating parameters of the plant, the properties of the materials of construction, etc. This paper discusses the influence of dust deposition on the evacuated tube collector field on the operating performance of the solar desalination plant at Abu Dhabi, UAE. This plant has a collector field area of 1864 m² of absorber surface and an MED (multiple effect distillation) unit for seawater desalination with a capacity of 120 m³/day of distilled water. The reduction in transmittance due to dust deposition on the amount of heat collected has been measured and its influence on the distillate production has been estimated using the computer simulation program SOLDES which has been verified previously as an effective tool for predicting the operating performance of similar plant designs. The frequency of high-pressure water jet cleaning on the performance of the plant was also investigated. It was found that dust deposition and its effect on plant performance depend strongly on the season of the year and the frequency of jet cleaning should be adjusted accordingly.     

Experimental study on the effect of dust deposition on solar photovoltaic panels in desert environment

The accumulation of dust particles deteriorates the performance of solar cells and results in appreciable losses in the generated power due to the sun irradiance scattering effects on the surface of the solar panel. This study investigates the impact of dust accumulation on photovoltaic solar modules in Baghdad city in Iraq. For this purpose an experiment has been conducted to quantify losses caused by the accumulation of dust on the surface of three identical photovoltaic solar modules. The modules have been installed with direct exposure to weather conditions, in a well controlled experimental setup. Subsequently, measurements of dust accumulation on modules have been taken on daily, weekly and monthly basis. The dust density and size distribution of aerosol particles and fibers have been also investigated and measured by a highly sensitive aerosols measuring system. The dusted module and another similar clean module have been then exposed to constant radiation and constant temperature using a solar simulator as light source. The deposition of the dust on the surface of the photovoltaic solar modules showed a reduction in both the short circuit current (I_sc) and the output power compared to the same parameters of the clean module. The average degradation rate of the efficiencies of the solar modules exposed to dust are; 6.24%, 11.8% and 18.74% calculated for exposure periods of one day, one week and one month. The experimental results are well compared with the calculations obtained by a theoretical model recently developed by the authors.