O.S. Sastry

Visual Degradation in Field-Aged Crystalline Silicon PV Modules in India and Correlation With Electrical Degradation

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.

Performance degradation in field-aged crystalline silicon PV modules in different indian climatic conditions

A survey of field-aged crystalline silicon modules in various climatic conditions in India was carried out, focusing on modules, which show visible signs of degradation. Analysis of the survey data indicates that the power degradation rate is highest in the Hot & Dry climatic zone, followed by the Hot & Humid zone, while it is least in the Cold zone. The degradation in power output of crystalline silicon modules is primarily due to reduction in the short-circuit current, followed by decrease in fill factor while the decrease in open-circuit voltage is very small. Analysis of the survey data also indicates that degradation rate of multi-crystalline silicon is slightly higher than that of mono crystalline silicon.

Detection and characterisation of delamination in PV modules by active infrared thermography

The paper presents a fast and efficient method for the detection and characterisation of delamination in photovoltaic (PV) modules by using active infrared thermography approach. A discrete part of PV module was irradiated by step heating and its thermal image sequence was used to detect and analyse delamination. Different types of heating source for thermal excitation for this application have been studied. An electro-thermal model was developed to simulate the active thermography approach for the characterisation of delamination in PV module by equivalent resistance–capacitance (RC) network using a circuit simulator. This simulation approach was used to estimate the extent of delamination in the module and to determine the optimum parameters for the characterisation of delamination. Different applications based on front and backsides of heating the module were also proposed in this paper. The proposed method has the potential to be employed for the quality check of PV modules during inline production as well as for the predictive maintenance of outdoor PV plants.

Linking performance of PV systems in India with socio-economic aspects of installation

A survey of PV modules in the field for more than 5 years in India has been conducted The analysis revealed that module degradation rates are linked with the social and behavioral issues of the end users. The appropriateness in system installation, maintenance and hence the degradation depends on the type of ownership of the system, the financial model for the installation and the end purpose. We found that whenever there are cash flows associated with the installations in terms of savings or income generation, the maintenance activities are properly done, irrespective of the type of ownership of the system. Community owned PV installations were found to be better installed and maintained than individual systems because of the presence of institutionalized mechanisms for operation and maintenance.

Characterization of field exposed thin film modules

Test arrays of thin film modules have been deployed at the Solar Energy Centre near New Delhi, India since 2002-2003. Performances of these arrays were reported by O.S. Sastry [1]. This paper reports on NREL efforts to support SEC by performing detailed characterization of selected modules from the array. Modules were selected to demonstrate both average and worst case power loss over the 8 years of outdoor exposure. The modules characterized included CdTe, CIS and three different types of a-Si. All but one of the a-Si types were glass-glass construction. None of the modules had edge seals. Detailed results of these tests are presented along with our conclusions about the causes of the power loss for each technology.

Comparison of curve correction procedure of current and voltage as per IEC 60891 for thin film technology

The performance of PV module is compared through measuring I-V characteristics at STC. But usually in the real outdoors the PV module behaves differently. To estimate the power and energy rating under different climatic conditions, I-V curves are extrapolated by applying corrections. In this paper we have examined I-V curves correction procedure as per IEC 60891 for different temperature and irradiance conditions of three thin film PV technologies viz. CIGS, CdTe, Micro-morph, and a comparison is made with measured data in real outdoor conditions. Deviations from estimated and measured output for three different correction procedures are compared. The correction procedure 3 gives the best results as compared to procedure 1 & procedure 2.

All India Survey of Photovoltaic Module Degradation 2014: Survey methodology and statistics

This paper presents an overview of the 2nd All India Survey of Photovoltaic Module Degradation, conducted in the months of September to December 2014. A total of 1080 modules belonging to different photovoltaic technologies were inspected from 45 different sites which are spread across the 5 different climatic zones of India. This is the first survey in India in which electroluminescence, illuminated and dark I-V measurements, insulation resistance and various other tests were carried out on PV modules installed in the field. The goal of the survey is to determine the degradation in the field-aged PV modules and find correlations between visual, electrical and physical degradation of the PV modules. The purpose of this paper is to present an overview of the survey methodology and statistics to the PV community.

Correlation of electrical and visual degradation seen in field survey in India

This paper presents an analysis of the electrical and visual degradation data gathered in the 2nd All India Survey of Photovoltaic Module Reliability, conducted in 2014, in which a total of 1148 modules were inspected in different climatic zones of India. The modules in the Hot Climates are seen to degrade faster than modules in the Non-Hot climates. Fill Factor (FF) reduction has been found to be the main cause for power reduction in young modules (less than 5 years old), while for old modules (more than 5 years), Isc reduction is the main culprit. Visual degradation in the modules has been quantified and correlated with the degradation in various electrical parameters. The degradation in Isc correlates with the discoloration and delamination of the encapsulant and the degradation in the FF correlates well with the extent of the corrosion in the metallization.

The synergistic effect of air mass on outdoor performance for different PV module in India

ABSTRACT 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.

Modeling the performance of HIT technology for composite climatic zone of India

This paper presents performance modeling of HIT technology modules based on weather parameters. A comparison has been made between experimental data, and the calculated data using PVUSA and matrix formation methods. It is found that for the reported model, the values of percentage of confidence for the error band -10 % to +10 % for different seasons are ranging from 70% to 95%. But for the monsoon season the confidence value of percentage is low as compared to others seasons. The modeling is done with different clearness index value for cloudy and clear sky condition and its confidence value varies from 76% to 95%.