Correlation of the loss in photovoltaic module performance with the ageing behaviour of the backsheets used

The influence of the type of backsheet on the electrical performance of test modules was evaluated before and after increasing time of accelerated ageing (damp heat [DH] exposure). Besides the measurement of the electrical power of the modules and the performance of the cells by electroluminescence, the ageing‐induced changes within the polymeric encapsulate and backsheets were investigated by means of vibrational spectroscopy and by thermo analytical methods. In addition, the permeability of the backsheets in the original and aged state was determined. This wide set of test parameters and methods allowed for the detection of correlations between (i) physical and chemical properties as well as their ageing‐induced changes of the materials and (ii) the module performance. A clear dependence of the relative loss in power output upon exposure under DH conditions for 2000 h could be observed for a set of identical test modules varied in composition only in the type of back cover used. While the modules containing gas‐tight backsheets and glass experienced only little loss in the relative power output, some modules with permeable backsheets showed a significant relative decrease in the power output and fill factor in dependence of the backsheet type used. Cell degradation could be visualised by recording electroluminescence images before and after the accelerated ageing test. The permeation properties of the backsheet used and their ageing‐induced changes seem to have an influence on the module performance. However, the absolute values neither of the water vapour transmission rate (WVTR) nor of the oxygen transmission rate (OTR) are directly linked to the loss in power output upon accelerated ageing under DH conditions. It could be shown that the ageing‐induced changes (relative transmission rates) between WVTR and OTR can be correlated with the module performance. These ageing‐induced changes in the permeation behaviour of the backsheets can be explained by (i) physical changes (e.g. post‐crystallisation, changes in the crystal structure or the crystalline microstructure) and (ii) chemical ageing effects such as a decrease in the molecular mass of the polyester (PET) polymer chains because of hydrolytic polymer degradation leading to a change in the crystallisation behaviour of PET. Hydrolytic degradation (= chemical ageing) of the PET core layer was observed (with varying extent) for all PET‐based backsheets and can, thus, not be directly correlated with the loss in performance of the corresponding test modules. The physical ageing effects, however, were detected only for those backsheets showing (i) strong deviating changes in the relative permeation rates for oxygen and water vapour upon accelerated ageing and (ii) a clear loss in electrical performance. Copyright © 2015 John Wiley & Sons, Ltd.     

Design and realization of transparent solar modules based on luminescent solar concentrators integrating nanostructured photonic crystals

Herein, we present a prototype of a photovoltaic module that combines a luminescent solar concentrator integrating one‐dimensional photonic crystals and in‐plane CuInGaSe₂ (CIGS) solar cells. Highly uniform and wide‐area nanostructured multilayers with photonic crystal properties were deposited by a cost‐efficient and scalable liquid processing amenable to large‐scale fabrication. Their role is to both maximize light absorption in the targeted spectral range, determined by the fluorophore employed, and minimize losses caused by emission at angles within the escape cone of the planar concentrator. From a structural perspective, the porous nature of the layers facilitates the integration with the thermoplastic polymers typically used to encapsulate and seal these modules. Judicious design of the module geometry, as well as of the optical properties of the dielectric mirrors employed, allows optimizing light guiding and hence photovoltaic performance while preserving a great deal of transparency. Optimized in‐plane designs like the one herein proposed are of relevance for building integrated photovoltaics, as ease of fabrication, long‐term stability and improved performance are simultaneously achieved. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.     

Maximum power point tracker based on maximum power point resistance modeling

This paper presents a new, simple, accurate, and inexpensive practical methodology and experimental solution for the modeling of conventional (domestic and commercial facilities) photovoltaic generators (PVG), so that they can work at their maximum power point (MPP). The PVG may be a panel, an array of panels, or a photovoltaic field. As a starting restriction (actual) it has to be assumed that it is not possible to isolate the PVG variables dependence (mainly current, voltage, and hence power) with solar radiation and temperature, because they are highly correlated. This methodology proposes the modeling facility on its MPP by its MPP resistance (R_MPP = V_MPP/I_MPP), being V_MPP and I_MPP the voltage and current of the PVG, respectively, at its MPP. The analysis shows, by simulation first and then experimentally, that R_MPP does not present significant temperature dependencies, at least in the usual range. This important result allows us to model the PVG only in terms of solar radiation. From a set of experimental data, different models to estimate R_MPP are proposed. The obtained results are very accurate. These models allow an immediate practical application that it is also developed in the paper: MPP tracker (MPPT) design by the calculation of the DC/DC converter duty cycle which places the PVG at its MPP directly and continuously. This new methodology and experimental system has been registered in the Spanish Patent and Trademark Office with the number P201530352. Copyright © 2015 John Wiley & Sons, Ltd.     

太阳能光伏应用中的蓄电池研究

分析了在光伏应用中的蓄电池的主要特点,并阐述了当前在太阳能光伏系统中主要使用的蓄电池是铅酸、Cd/Ni、MH/Ni电池,分析和比较了价格、充放电效率、自放电和寿命等基本性能,对于光伏系统中对蓄电池的性能和寿命有重大影响的因素(放电深度、充放电电流和工作温度等)进行了分析。     

一种新颖的光伏发电系统Cuk型软开关变换器的研究

提出了一种新型的Cuk型零电压转换(ZVT-PWM)软开关变换器,实验验证了该变换器可以实现主开关管和辅助开关管的软开关功能,而且主开关管不受最小占空比限制,辅助二极管反向恢复电流损耗小,这对整个系统效率的提高十分有益。     

HgCdTe光伏器件多层钝化膜等离子体处理的研究

在HgCdT e光伏探测器件S iO2+ZnS复合介质膜钝化中,引入O+2清洗和A+r刻蚀两种等离子体处理工艺,大大提高薄膜附着力,成功制备出优良的光伏器件。对处理前后的样品进行场发射扫描电子显微镜扫描、原子力显微镜扫描和二次离子质谱测试后发现,O+2清洗对去除样品表面的残余光刻胶效果显著;而A r+刻蚀使ZnS表面更为粗糙,增加了成核中心,使S iO2和ZnS表面互相渗透,增强了两层介质膜的附着力。     

滩涂光伏GFRP管桩原位承载试验及反馈分析研究

目前滩涂光伏基础结构主要采用预应力混凝土(PHC)管桩方案,在经济性与施工便利性上存在一定劣势。为提高滩涂光伏施工效率,针对滩涂场地地基承载力较弱、土方开挖困难等特点,在满足承载性能的基础上,优化桩基础施工便利性,提出采用具有重量优势的纤维复合材料桩——玻璃纤维(GFRP)管桩,探索GFRP管桩的承载性能。通过开展现场承载试验,获取GFRP管桩的承载力表现并与PHC管桩进行对比,同时结合数值模拟进行反馈分析。反馈分析及对比成果显示：PHC管桩能够稳定加载至2.0倍设计荷载,而GFRP管桩加载至1.2倍设计荷载之后出现较大挠度。结果表明GFRP管桩的承载性能满足设计荷载要求,但是在变形控制方面劣于现有PHC管桩方案,相比之下PHC管桩具有更充足的安全裕度。通过对GFRP材料桩基础的研究和探索,提出GFRP管桩制作工艺的改进措施,对GFRP管桩今后需要进一步研究的重点进行了展望。     

光伏跟踪支架产品特点及发展趋势

从发电原理和平准化度电成本角度来看,光伏是未来最有发展潜力的新能源利用方式.作为光伏发电系统的关键设备之一,至少需要从成本和可靠性两个维度来理解跟踪支架产品的特点.文章根据现有支架行业主流企业的产品特点,对跟踪支架的发展趋势进行预测.     

光伏电力混合储能系统的能量管理策略研究

文章提出了一种光伏电力混合储能系统的能量管理控制策略,主要应用于含有光伏电源(Photovoltaic,PV)、电池能量存储(Battery Energy Storage, BES)和交流负载的发电网络系统中。该策略能够充分利用电力系统中组合架构之间的连接关系,有效缓解了目前电网中BES系统存在的过充电、欠充电等问题,并将充放电电流控制在一个相对稳定的范围内,延长了电池的使用寿命。分别在含有传统铅酸和锂离子电池的混合能量系统中使用6 kVA电源转换器进行实验,结果证明了所提出的能量管理策略的正确性和有效性。     

Effect of chlorination and fluorination of benzothiadiazole on the performance of polymer solar cells

In order to explore the effects of chlorine and fluorine on photophysical properties and the differences, in this work, we synthesized five new polymers, P1 – P5 , in which benzo[1,2-b:4,5-b]dithiophene as the electron donating and benzothiadiazole as electron withdrawing. Analysis of these five polymers showed that the introduction of Cl and F atoms can deeper the highest occupied molecular orbital of these polymers and enhance the absorption of light by the species, thereby improving V_oc and J_sc. Chlorination has a stronger ability to reduce energy levels and broaden the absorption spectrum compared to fluorination. Among them, P2 showed an efficiency of 4.08% with J_sc of 11.28 mA/cm², V_oc of 0.79 V, and fill factor (FF) of 0.45. Since chlorination is easier than fluorination in terms of synthesis, it is advantageous for practical applications. Therefore, we think that chlorination should not be ignored when designing high efficiency photovoltaic materials, especially when their fluorinated counterparts have proven to have good properties.