Encapsulant discoloration is a common type of degradation in photovoltaic (PV) modules, which significantly affects its performance and reliability under field conditions. This paper presents the ...nondestructive characterization techniques for investigation of encapsulant discoloration in crystalline-silicon PV modules. These characterization techniques have been channelized and applied to investigate various aspects of discoloration effects on 20 years old field-exposed PV modules. Dark lock-in thermography (DLIT) has been exploited for investigation of temperature variation and defects caused by uneven discoloration over the cells, while electroluminescence (EL) imaging has been proposed for relative quantification of extent of discoloration in a PV module. The spatially-resolved images obtained from both the techniques provided the qualitative and quantitative information about the optical and electrical effects of discoloration in a module, which is not possible by the conventional visual inspection method alone. The electrical methods including proposed differential current analysis, I–V measurement and insulation resistance test have also been used to aid this investigation. The results obtained from these techniques show that the power degradation due to discoloration was attributed to significant reduction in fill factor by non-uniform discoloration and increase in series resistance of cell contacts, and to some extent by its direct effect of light reduction. Electrical mismatch appeared to play an important role in accelerating the encapsulant discoloration in the module. These nondestructive characterization approaches can enable to inspect large number of PV modules in their actual encapsulated form by fast and efficient manner.
•Nondestructive techniques for optical and electrical discoloration effects in module.•DLIT and EL reveal electrical mismatch and quantification of discoloration in module.•Differential current analysis estimates relative discoloration extent over cells.•Significant FF reduction due to electrical mismatch and Rs increase by discoloration.•Electrical mismatch appears as an accelerating factor for module discoloration.
This paper presents the analysis of visual degradation data collected during an All-India Survey of Photovoltaic Module Degradation conducted in 2013, in which 57 crystalline silicon modules were ...inspected in the five different climatic zones of India. Analysis of the data indicates that the highest percentage of modules suffered discoloration in the Hot and Dry climatic zone, with the Hot and Humid zone coming in second in the list. A higher percentage of modules have suffered corrosion in the Hot and Humid zone, as compared with other zones. The modules installed in the Cold climate suffered the least degradation. Both discoloration and corrosion have been seen in modules across all age groups, even in some of the modules installed less than five years ago. On the other hand, delamination and backsheet degradation have been seen only in modules more than a decade old. The visual degradation data have been correlated with the electrical performance data and reaffirm the direct relation between encapsulant discoloration and reduction in short-circuit current and output power, as well as that of series resistance with metal corrosion.
The accuracy of outdoor performance of a photovoltaic (PV) array can be improved by considering the spectral effects. In this paper, the impact of seasonal spectral variations on the three different ...silicon PV technologies: single junction amorphous silicon (a-Si), Hetero-junction with Intrinsic Thin-layer (HIT) and multi crystalline silicon (mc-Si) has been presented first time in Indian environmental conditions. The spectral effect on HIT PV module technology has been presented first time along with the first simultaneous study of variation in spectral indicators by useful fraction (UF), average photon energy (APE) and spectral mismatch factor (MMF), based on monthly and seasonal data. The maximum observed variation in UF was 26.4, 8.2, 10.8 %, while in MMF, variation was up to 24.7, 7.6, 8.2 % for a-Si, HIT and mc-Si, respectively, and in APE variation was up to 15.3 %. Among all three technology modules, first time reported HIT technology showed the least variation while maximum variation was observed in a-Si technology. The observed spectral effect variations have been discussed on Performance Ratio and compared with reported results of other global sites. The value and trends of spectral parameters are important to understand the effect of spectral variation on different technology. This study is especially important in Indian subcontinent perspective because of the strong monsoon season, where observed variation in the spectrum-related parameter found to be highest among all the seasons.
Development of white LED based PV lighting systems Sastry, O.S.; Kamala Devi, V.; Pant, P.C. ...
Solar energy materials and solar cells,
09/2010, Letnik:
94, Številka:
9
Journal Article, Conference Proceeding
Recenzirano
A high performance white light emitting diode (WLED) based PV lighting system has been developed under a joint project of SEC and ANERT. The system has been analyzed using the test set-ups developed ...as a part of advanced lighting laboratory (ALL). The results show that the performance is one of the best among the systems developed in the capacity range.
Solar Photovoltaic Water Pumping (SPVWP) systems have established their potential as the most dependable and economically viable systems compared to the diesel based or grid-based electrical pumps. ...This paper presents an in-depth investigation of the energy efficiency of SPVWP system based on solar radiation, temperature, and operational heads. The study also identifies the shortcomings in the conventional design method based on Best Efficiency Point (BEP) concept that is applicable only in case of fixed frequency and voltage type pumps. However, in the case of SPVWP systems, due to variations in the solar intensity, ambient temperature, and water head, BEP concept does not offer the best efficiency design. The study experimentally proves that the model based on weighted system efficiency and Solar Operational Duty Head (SODH) increases the performance of SPVWP system (∼9% gain) and is consistently provide higher efficiencies in any season or under any climatic conditions.
•Energy efficiency of SPVWP system is investigated to find the shortcomming in the conventional design method of SPVWP system.•Best efficiency concept for selection of motor-Pump, misleads on overall energy efficiency, leads to losses.•BEP method of selection of motor-pump set is applicable only in case of fixed frequency and voltage type grid supply.•Study guides the selection of a proper pump based on the new concept Solar Operational Duty Head (SODH).•About 9 % gain in water output is observed through the new concept Solar operational Duty Head.
The effect of air mass (AM) on the performance of multi-crystalline silicon (m-Si), amorphous silicon (a-Si), and hetero-junction with intrinsic thin layer (HIT)-technology-based photovoltaic (PV) ...modules are evaluated for representative day of four seasons during the year 2011 for composite climate of India. To find the best performing PV module technology with respect to AM at the site, annual energy yields and performance ratio against different AM bands (AM 1-4.5) are plotted. It is found that HIT modules perform better than m-Si and a-Si at each AM band. Annual energy yields for all three technologies decrease with increasing order of AM bands. The performance ratio for HIT and m-SI modules initially increases and then decreases with increasing order of AM bands. However, for a-Si modules, the performance ratio decreases with increasing order of the AM bands.
The importance of reliability and degradation of photovoltaic (PV) systems as a renewable energy resource is well recognized. In the present study, a thermal model has been developed to estimate the ...temperature, efficiency and thermal losses for N series connected Glass/cell/polymer sheet and Glass/cell/glass PV modules with hot solar cells in terms of climate and design parameters. The numerical computation has been performed for larger number of days as June (summer) and December (winter) following the temperature of hot solar cells at the National Institute of Solar Energy, Gurugram, India. In the case of string 1 (3 hot solar cells) of Glass/cell/polymer sheet has higher short circuit current than the Glass/cell/glass PV modules string 2 (7 hot solar cells). Similarly, leakage current of Glass/cell/polymer sheet PV module with 7 hot solar cells is marginally higher in comparison to Glass/cell/polymer sheet PV module with 3 hot solar cells. Further, 1% electrical efficiency has been improved due to shadow on hot solar cells in Glass/cell/polymer sheet and Glass/cell/glass PV modules.
•Thermal modelling of hot solar cell connected in series with both configuration PV modules has been done.•Hot spot temperature has been observed for PV modules under different weather conditions.•Leakage current has been observed for glass/cell/polymer sheet PV modules.•Shading effect has been performed for both glass/cell/polymer sheet and glass/cell/glass PV modules.
Although cognitive problems can recover over time, a subgroup of hematopoietic stem cell transplantation (HCT) survivors experience persistent cognitive problems in the long term. Despite these ...implications, studies assessing cognitive functioning in HCT survivors are limited. The aim of the present study was (1) to quantify the prevalence of cognitive impairment in patients treated with HCT who survived at least 2 years and to compare these with a matched reference group representing the general population; (2) to identify potential determinants of cognitive functioning within the HCT survivor group. Within the single-center Maastricht Observational study of late effects after Stem cell trAnsplantation, cognitive performance was assessed by a neuropsychological test battery divided into 3 cognitive domains: memory, information processing speed, and executive function and attention. An overall cognition score was calculated as the average of the domain scores. A total of 115 HCT survivors were group-matched on a 1:4 ratio to the reference group by age, sex, and level of education. Regression analyses adjusted for different sets of covariates including demographic and health- and lifestyle-related factors were used to test for differences in cognition between HCT survivors and the reference group resembling the general population. A limited set of clinical characteristics (diagnosis, type of transplant, time since treatment, conditioning regimen with total body irradiation and age at time of transplantation) were assessed as potential determinants of neurocognitive dysfunction among HCT survivors. Cognitive impairment was defined as scores in the cognitive domains < −1.5 standard deviation (SD) from what can be expected based on someone's age, sex, and education. The mean age at time of transplantation was 50.2 (SD ± 11.2) years, and the mean number of years after transplant was 8.7 (SD ± 5.7) years. The majority of HCT survivors were treated with autologous HCT (n = 73 64%). The prevalence of cognitive dysfunction was 34.8% in HCT survivors and 21.3% in the reference group (p = .002.) When adjusted for age, sex, and level of education, HCT survivors had a worse overall cognition score (b = −0.35; 95% confidence interval CI, −0.55 to −0.16; p < .001), translating into 9.0 years of higher cognitive age. Analyses of specific cognitive domain scores showed that HCT survivors scored worse on memory (b = −0.43; 95% CI, −0.73 to −0.13; p = .005), information processing speed (b = −0.33; 95% CI, −0.55 to −0.11; p = .003), and executive function and attention (b = −0.29; 95% CI, −.55 to −.03; p = .031) than the reference group. The odds of cognitive impairment were on average 2.4 times higher among HCT survivors than the reference group (odd ratio = 2.44; 95% CI, 1.47-4.07; p = .001). Within the HCT survivor group none of the tested clinical determinants of cognitive impairment were significantly associated with cognition. This cohort study showed evidence for worse cognitive functioning in HCT survivors encompassing all three cognitive domains, respectively memory, information processing speed, and executive and attention compared to a reference group that represents the general population translating into nine years of faster cognitive ageing in HCT survivors than can be expected based on their chronological age. It is important to increase awareness for signs of neurocognitive dysfunction after HCT in clinicians and HCT survivors.
The alleged reliability has led the longest warranty period for Photovoltaic (PV) modules up to 20–25 years; it becomes possible after understanding the failure mode and degradation analysis of PV ...module. Failure mode decreases the performance of the PV module throughout the long-term outdoor exposure. The main objective of the present study is to identify the failure mechanism and failure mode of solar PV modules and their impact on degradation in operating conditions. Assessment of previous studies on rate indicates the highest performance losses at initial stage of outdoor exposure and a degradation drop-off of 0.014% per year. In this context, risk priority number (RPN) analysis is carried out to identify the severity of the failure mode, which affect the system performance for c-Si technologies. However, hot spot and de-lamination are degradation modes related to safety issue with lower value of RPN <50.
•Failure mechanism and failure mode of solar PV modules in real outdoor conditions.•Studies on the mono-crystalline PV modules over a period of 25 years are considered to identify defects and failure modes.•Impact of PV module defects and failure modes on its degradation is presented.•Risk priority number (RPN) analysis for identifying the severity of the PV failure mode.
An attempt has been made to investigate the relationship of cloacal gland with testes, testosterone and fertility in different lines of Japanese quail (
Coturnix coturnix japonica). For this study, ...three lines of healthy adult male Japanese quails (<12 weeks) viz., heavy body weight (HB), white breasted (WB), and white egg shell (WES) were taken. They were housed in individual cages under uniform husbandry conditions and were provided with normal quail breeder ration and water ad libitum, with 14
h light/day. The experimental birds were selected from each of these three lines and categorized into different groups (15
birds/group) based on the increasing order of the area of cloacal gland. At the end of this experiment (24 weeks) the data indicated that size of the cloacal gland was directly proportional to foam discharge, foam weight, testicular weight, fertility and testosterone concentration in plasma. From this study it may be concluded that area of cloacal gland in Japanese quail is positively correlated with testicular weight, level of testosterone in plasma and fertility. Visual examination of cloacal gland and cloacal foam may provide a valuable non-invasive tool for predicting the fertilizing ability of individual male bird.
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