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Recent research has shown that bifacial PV modules with a glass/glass packaging are prone to different PID mechanisms occurring simultaneously on the front and the rear side of the solar cell. With this in mind, researchers investigating the impact of PID on each side of the bifacial solar cell separately apply PID stress to one side of bifacial PV modules according to stress method (b) as described in the IEC TS 62804-1, that is, contacting the surface with a conductive electrode. Yet, in this paper, we show that such practice of PID testing might result in an unintended development of an electric field between the environmental chamber and the nonstressed side of the solar cell. Through our experimental study, we reveal that this electric field results in unintended bifacial PID stress of bifacial solar cells, which goes along with misleading interpretations of the evolving PID mechanisms and susceptibility of bifacial PV modules. Next to the methodology concerns, we discuss three possible solutions to prevent such unintended PID mechanisms from occurring.

International audience; Through the H2020 BE-SMART project, we work on the validation and industrialization of new materials (and processes) for manufacturing next-generation cost-efficient, reliable and highly aesthetic/performing BIPV. On this basis, we aim at introducing novel multifunctional and transformative BIPV elements, in the concept/form of Energy Positive Glazing (EPoG). The project's developments so far indicate the high potential of e.g. using colored encapsulants, interferential filter technique and/or ceramic-based colored glazing for implementing novel “transformative” BIPV with high aesthetic quality. Yet, since BIPV's primary function is electricity production, we need to understand and quantify the impact of such coloration solutions on the performance (and reliability, in longer terms) of future BIPV. In this paper, we present an experimental comparative study on the optical and electrical performance of multiple color coated and patterned BIPV glazing solutions, towards their upscaling and commercialization. In particular, we performed optical transmission measurements and light intensity-/angle-depent IV characterization on 25 different colored glass samples and 10 different colored/patterned glass PV laminates respectively. The measurement results and their discussion presented in this paper provide valuable insights into the optical-electrical performance of the investigated colored BIPV glazing, as well as a first identification of BIPV industry-relevant colors and patterns with the best potential “compromise” between aesthetics and performance, for future energy positive glazing applications.

Towards tackling the evident practical challenges of fault detection and diagnosis for PV modules, especially in large-scale installations, this paper proposes two different techniques for advanced inspection mapping of PV plants; aerial triangulation and terrestrial georeferencing. The former uses data of aerial thermal/visual imagery of operating PV modules, obtained by an unmanned aerial vehicle (UAV), to generate static “inspection maps”, in the form of true orthophoto mosaics. On the other hand, georeferencing is used to associate terrestrial thermal/visual imagery, obtained at distinct positions in a PV plant, with geographic data. By such way, inspection is based on a dynamic virtual map of the installation. Both mapping techniques were tested in two grid-connected PV systems, of a total installed power of 70.2 KWp. Several defective modules were easily and accurately detected, typically as abnormal temperature profiles, in the infrared (IR) spectrum. In addition, specific thermal image patterns of operating modules, were validated and quantified by additional diagnostic measurements, and were assigned to possible fault types. On the basis of the experience feedback, the potential of the proposed techniques and their limitations, for further application to PV plants of larger scale, are also discussed.

Photovoltaic (PV) waste, associated to the exponentially growing PV installations on global scale, presents today an emerging environmental challenge but also brings unprecedented and multifold value creation opportunities. In this context, significant PV business and research and development (R&D) efforts shift towards establishing a more sustainable, environmentally friendly and economically viable end-of-life (EoL) management for PV modules: including recycling, recovery of raw materials, repair/refurbishment and even re-use of decommissioned or failed PV modules. In the CIRCUSOL project, PV partners aspire to formalize the repair/refurbish and re-use value chains in the PV industry and propose a circular business model, based on a product-service system (PSS). Towards these goals, this review study introduces the relevant research groundwork, a status overview and today's R&D and business challenges in PV recycling, repair/refurbishment and re-certification aspects for second-life PV modules. The topics and the relevant reported literature are examined from both circular economy and technology perspective. The review indicates a considerable technological and operational know-how in PV EoL management that already exists and continuously evolves in mature PV markets. On the other hand, R&D in repair/refurbishment of decommissioned and/or failed PV modules remains scarce, and best practices and commercial services for reliability testing/re-certification and trading of second-life PV modules are neither standardized nor consolidated into any PSS or business model. H2020 Environment, Grant/Award Number: 776680; H2020 Marie Sklodowska-Curie Actions, Grant/Award Number: 752117; European Union's Horizon 2020, Grant/Award Numbers: 752117 and 776680

Simulation tools are increasingly employed towards quantifying the lifetime of photovoltaic (PV) modules while providing valuable insights into the various failure modes. The use of the finite element method (FEM) in this regard has been especially popular because of its flexibility and the ability to quantify stress levels for a large variety of scenarios ranging from process-induced stress up to field conditions. The thermo-mechanical behaviour of the module or its components is often considered due to the link with common field failures such as cell cracks, interconnection failures, glass fracture, delamination and many others. However, the approaches used, the various inputs considered and the obtained results are highly scattered and sometimes conflicting. This work provides a structured review of the reported simulation approaches and resulting insights obtained through thermo-mechanical finite element simulations on commercial as well as novel PV module technologies. The influence and validity of various inputs such as the used material models, boundary conditions and other assumptions are discussed. Learnings and best practices can be leveraged by future simulations to expand on and accelerate the design-for-reliability capabilities of finite element models for PV modules.

Photovoltaic (PV) solar energy recorded an exponential growth, in worldwide scale, over the last decade. Inevitably, mature PV markets are becoming highly competitive, boosting the need for research and development (R&D) on efficiency and reliability optimization, maintenance and fault diagnosis of key components, such as the PV modules. Indeed, a significant number of studies and technical papers have been published up today, based on an extensive feedback from both laboratory and real (field) investigations of faults and advanced diagnosis applications, especially for crystalline silicon (c-Si) PV modules. Undoubtedly, such experience is of particular interest for current PV plant operators, future investors, maintenance engineers and the R&D sector of PV industry. However, up today, such research, published in the form of reports, technical papers or even books, remains mostly dispersed and unclassified. This paper represents a comprehensive effort to review and highlight recent advances, ongoing research and future prospects, as reported in the literature, on the classification of faults in c-Si PV modules and advanced diagnosis in the field, by means of the increasingly popular method of infrared thermal (IRT) imaging. In particular, the first main part of this paper, reviews the characteristics of the most common fault types of operating PV modules, in terms of electrical and thermal response. Then, the second part gives a thorough review of recently published research, as well as the state-of-the-art, in the fields of IRT-based fault diagnosis and thermal image processing. On the basis of these two individual though supplementary review parts, an overview table is presented, followed by a discussion on the future prospects and challenges, towards the understanding and diagnosis of faults and their propagation in operating PV modules.

Today, investigations on degradation and failure mechanisms in solar cells are often based on accelerated ageing tests (AAT), where failure effects are reproduced and quantified within a much shorter time period than the actual lifetime. This paper presents a study upon a novel approach of AAT for high concentration photovoltaic (HCPV) cells. The intended approach aims to overcome several limitations encountered in most of the AAT adopted up today, proposing the use of an alternative experimental set-up for performing nearly 400 times faster and more realistic thermal cycles, under real sun conditions (irradiation cycling), without the involvement of any environmental chamber. The cumulative impact of such very rapid irradiation/thermal cycles on the ageing of HCPV assemblies can be determined, both quantitatively and qualitatively, by evaluating specific pre-ageing and post-ageing diagnostic measurements by means of I–V characterization and scanning acoustic microscopy (SAM). The proposed irradiation/thermal cycling arrangement was successfully employed for performing accelerated ageing of both HCPV assemblies (cell receiver and heat sink) and bare HCPV cell receivers. Ultimate goal of this AAT approach is to provide the basis for a future work on the reliability analysis of the main degradation mechanisms and failure propagation in HCPV cell assemblies. 2015 Elsevier Ltd. All rights reserved.

The combination of increasing operational voltages beyond 1000 V in photovoltaic (PV) installations and the emergence of new PV technologies requires a critical assessment of the susceptibility to potential-induced degradation (PID). Since this failure mode can trigger significant and rapid power losses, it is considered among the most critical failure modes with a high financial impact. Insights in the physical mechanism of the performance loss and its driving factors are critical to develop adapted characterization methods and mitigation solutions. PID in p-type solar cells is triggered by sodium (Na) that diffuses into stacking faults of the silicon lattice, causing shunt paths through the pn-junction. In addition, it is hypothesised that for bifacialp-PERC solar cells positive charges, such as Na+, accumulate in/on the negatively charged AlOxrear passivation layer due to the potential difference between the glass and the rear cell surface. This significantly increases surface recombination. However, the degradation behaviour observed in bifacial monocrystallinep-PERC solar cells under PID stress from both sides (bifacial PID stress) does not match with just one of the degradation mechanisms. A comprehensive test matrix was carried out to understand the physical origin of PID in front emitter bifacialp-PERC solar cells in a glass/glass packaging. The results show that bifacialp-PERC solar cells under bifacial PID stress suffer from both shunting of the pn-junction and increased surface recombination at their rear side. Hereby, we prove that the glass/glass packaging in combination with bifacial solar cells can significantly increase the severity of PID.

Today, conventional condition monitoring of installed, operating photovoltaic (PV) modules is mainly based on electrical measurements and performance evaluation. However, such practices exhibit restricted fault-detection ability. This study proposes the use of standard thermal image processing and the Canny edge detection operator as diagnostic tools for module-related faults that lead to hot-spot heating effects. The intended techniques were applied on thermal images of defective PV modules, from several field infrared thermographic measurements conducted during this study. The whole approach provided promising results with the detection of hot-spot formations that were diagnosed to specific defective cells in each inspected module. These evolving hot spots lead to abnormally low performance of the PV modules, a fact that is also validated by the manufacturer's standard electrical tests.

As ecological awareness has intensified during the past two decades, renewable energy sources (RES) and, consequently, photovoltaic (PV) systems have undergone an impressively fast evolution. However, the sustainability of an installed PV system can only be achieved through its performance optimisation by reducing any source of fault, structural defect or malfunction during either the manufacturing or the operating (after installation) stage. This paper suggests the use of a hot-spot detection tool for PV modules, based on condition monitoring by infrared thermography. The experimentation of the intended approach includes several daily sets of in-situ thermography measurements of specific PV arrays, installed on the rooftop of a laboratory building in the School of Engineering Campus of Democritus University of Thrace (DUTH), Greece. Further processing of the obtained thermal images, by means of a basic image histogram and line profile analysis, provides useful data for the detection and quantification of hot spots within each PV module. In particular, specific variations in the morphological features of both thermal images’ histograms and linear profiles witness the presence of defects, their source within the module and, ultimately, their impact on the degradation of the inspected PV array’s performance due to the hot-spot heating effect.

This paper presents a preliminary study upon a novel approach proposed for highly accelerated ageing and reliability optimization of high concentrating photovoltaic (HCPV) cells and assemblies. The intended approach aims to overcome several limitations of some current accelerated ageing tests (AAT) adopted up today, proposing the use of an alternative experimental set-up for performing faster and more realistic thermal cycles, under real sun, without the involvement of environmental chamber. The study also includes specific characterization techniques, before and after each AAT sequence, which respectively provide the initial and final diagnosis on the condition of the tested sample. The acquired data from these diagnostic/characterization methods are then used as indices to determine both quantitatively and qualitatively the severity of degradation and, thus, the ageing level for each tested HCPV assembly or cell sample. Ultimate goal of such "initial diagnosis - AAT - final diagnosis" sequences is to provide the basis for a future work on the reliability analysis of the main degradation mechanisms and confident prediction of failure propagation in HCPV cells, by means of acceleration factor (AF) and mean-time-to-failure (MTTF) estimations.

A prototype HCPV module developed by the French company Heliotrop has been characterized in both outdoor and indoor conditions. Heliotrop HCPV technology [1] combines high efficiency triple junction cells (≈40% efficiency) and very high solar concentration level (1024X) using Fresnel lenses as optical concentrators.

HRQoL in children with asthma depends on multiple factors, among which asthma severity and level of control are believed to play a vital role. The determinants of the connection between asthma severity and asthma control with quality of life remain unclear.Primary aim of the study was to evaluate the HRQoL in children with asthma and to determine the factors that affect it.In total 504 children and one of their parents were recruited during a regular follow up visit in an outpatient asthma clinic. The measures used were the DISABKIDS smiley measure (DSmM), chronic generic measure-long form (DCGM-37) and the Condition-specific modules for asthma along with a special form for collecting demographic and clinical characteristics.Three hundred fifteen children with mean age 5.35 years (Group A) and 189 with mean age 10.79 years (Group B), were recruited. Children with controlled asthma had significant higher mean score than the other asthma control groups (P 0.001). Corticosteroid use, asthma severity, number of visits in doctor's office and lack of asthma control were significantly associated with the DCGM-37 scores as well as Impact Scale and Worry Scale. Lack of Asthma Control was the only factor that was associated with negative HRQoL in all the multiple regression models, controlling for the effect of the other covariates, in both age groups.In conclusion, the evaluation of asthma HRQoL independently reflects the asthma control state and a dimension of its severity. These results highlight the need to modify asthma management strategy.

Today, to ensure efficient operation of a photovoltaic (PV) system renders as an undoubtedly major concern. Toward this direction, scope of this work is the assessment of infrared thermography as a PV module’s condition monitoring and, subsequently, performance evaluation method. The idea is based on the fact that any abnormality to the temperature pattern of an under inspection equipment implies a dysfunction case. In particular, specific thermographic measurements were applied to a PV module with known, abnormally low performance. Following the basic processing of the acquired thermal images, the extracted temperature data were contrasted with the PV module’s expected operating temperature. The results validated the presence of a problematic solar cell that refers to a “hot spot” within the tested PV module. This paper concludes with a discussion regarding the advantages, the limitations, and, ultimately, the potentiality of the intended approaches as reliable condition monitoring method through performance evaluation of PV modules.

Spirometry was performed on 88 children with insulindependent diabetes mellitus (IDDM) and 216 healthy controls living in Sheffield. Children with IDDM had significantly lower percentage predicted forced vital capacity (FVC) than did control children or reference norms. There was no evidence that the reduced FVC was confined to a subgroup of children, and there was no correlation with duration of IDDM or glycemic control. A longitudinal study of 27 children with IDDM did not show progressive deterioration in percentage predicted FVC with age. These findings suggest that a tendency toward reduced lung volumes exists in IDDM and may not be a direct result of the metabolic disturbances in the disease.