Measurement of Thermal and Electrical Parameters in Photovoltaic Systems for Predictive and Cross-Correlated Monitorization

Abstract

Photovoltaic electricity generation is growing at an almost exponential rate worldwide, reaching 400 GWp of installed capacity in 2018. Different types of installations, ranging from small building integrated systems to large plants, require different maintenance strategies, including strategies for monitorization and data processing. In this article, we present three case studies at different scales (from hundreds of Wp to a 2.1 MWp plant), where automated parameter monitorization and data analysis has been carried out, aiming to detect failures and provide recommendations for optimum maintenance procedures. For larger systems, the data collected by the inverters provides the best source of information, and the cross-correlated analysis which uses these data is the best strategy to detect failures in module strings and failures in the inverters themselves (an average of 32.2% of inverters with failures was found after ten years of operation). In regards to determining which module is failing, the analysis of thermographic images is reliable and allows the detection of the failed module within the string (up to 1.5% for grave failures and 9.1% of medium failures for the solar plant after eleven years of activity). Photovoltaic (PV) systems at different scales require different methods for monitorization: Medium and large systems depend on inverter automated data acquisition, which can be complemented with thermographic images. Nevertheless, if the purpose of the monitorization is to obtain detailed information about the degradation processes of the solar cells, it becomes necessary to measure the environmental (irradiance and ambient temperature), thermal and electrical parameters (I-V characterization) of the modules and compare the experimental data with the modelling results. This is only achievable in small systems.

Evaluation of Solar Radiation Transposition Models for Passive Energy Management and Building Integrated Photovoltaics

“…A comparison of modelled irradiance on the tilted surface based on the two transposition models using the horizontal pyranometer data (BF5) as input against the measured data from the pyranometer mounted on the vertical surface at different orientations (CMP3) was performed. Details about data collection, transmission and database organization are provided in [47]. A direct intercomparison of the two pyranometers was performed by placing them at specific orientation and collecting global irradiance data simultaneously.…”

“…Figure 10 shows the statistical analysis of the environmental conditions for one year of data (2018) collected by the monitoring system installed in Murcia (Spain). Further details about the monitoring system can be found on [47]. As can be noted, the probability of occurrence of the working conditions defined by the standard test conditions (standard test conditions-1000 W/m 2 , AM 1.5, module temperature 25 • C) are hardly ever met in real operating conditions compared with the probability of low irradiance (<200 W/m 2 ) and medium temperature (15-25 • C) for vertical surfaces.…”

On Field Infrared Thermography Sensing for PV System Efficiency Assessment: Results and Comparison with Electrical Models

“…Therefore, the infrared thermography (IRT) has been successfully applied for PV system diagnosis, since it entails some advantages, like contactless and nondestructive detection, fast inspection on large areas, and the continuity of operation of the PV system during the diagnosis phase [25,26].…”

Low-cost infrared thermography in aid of photovoltaic panels degradation research

“…IR Thermal Analysis is a non-invasive technique (no disconnection required) used to observe the temperature of an object, equipment or machinery to verify the temperatures under operation. As for PV systems is concerned, IR thermography is used to identify failures in PV cells or in electrical connections [3][4][5][6][7][8][9], providing relevant information that facilitates the O& M of PV sites. However, IR thermal cameras normally used in PV thermal analysis are expensive.…”