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Sensorless approach for PV panel temperature monitoring

Source：pv magazine

Researchers at the Dubai Electricity and Water Authority (DEWA) R&D Center have developed a novel sensorless self-thermometry approach to estimate PV module operating temperature.

Dubbed the Shift-Factor method, the new method works by analyzing changes in either the open-circuit voltage (Voc) or maximum power point voltage (Vmp).

“By correlating these electrical responses with irradiance and module temperature, this method not only offers a flexible and non-intrusive approach to temperature estimation but also serves to verify or rectify sensor data, effectively complementing and enhancing the reliability of traditional sensor-based measurements,” said the researchers.

The work was recently published in “Self-Thermometry of PV Modules: Shift-Factor Approach Compared to Sandia, Faiman, and IEC 60904-5 Models,” by Progress in Photovoltaics: Research and Applications.

It was a result of an effort to establish a “self-sufficient, data-driven approach to estimating module temperature, minimizing dependence on external meteorological inputs, while maintaining accuracy in performance evaluation,” according to corresponding author Shahzada Pamir.

“It builds on existing expertise in modelling, diagnostics, and field validation, offering a novel approach to sensorless monitoring,” Pamir told pv magazine. The same organization has been researching remote and non-destructive methods for solar performance analysis.

Characterizing the model as a “simplified yet robust framework” to estimate PV module temperature directly from electrical parameters, using a shift-factor that adapts to real-world conditions, Pamir said that it had been benchmarked against established models, such as Sandia, Faiman, and IEC 60904-5, and that it demonstrated a “strong practical value for large-scale monitoring, particularly in high-irradiance and high-temperature environments.”

In the comparison of the four models, the team found that the Shift-Factor model using Voc achieved the lowest overall root mean square error (RMSE) at 1.600 C, outperforming IEC 60904-5, which was 1.639 C, Sandia with 2.510 C, and Faiman at 3.688 C.

Data from continuous monitoring of the electrical outputs of the outdoor test setup at the DEWA R&D Center in Dubai were used to compare the results. The setup had a variety of PV modules equipped with temperature sensors in a standalone configuration, at a tilt angle of 25 degrees.

The team said that the IEC 60904-5 method offered “slightly better precision” and lower centralized RMSE, but it suffers from higher bias. And it is limited because it relies solely on Voc, which is not always available in commercial systems, whereas the Shift Factor can use Voc or Vmp, a parameter “routinely logged” by PV inverters through maximum power point tracking (MPPT), noted the researchers.

They went on to say that the proposed Shift-Factor model is “broadly adaptable” to other silicon and thin-film PV cell technologies, including bifacial configurations. This is because it is “derived empirically and does not rely on module-specific thermal parameters or heat transfer assumptions,” they said.

The DEWA research group is now integrating the model into broader PV digital twins environments for PV systems. “This next phase focuses on predictive diagnostics and system-level optimization, with the goal of enhancing long-term reliability and energy yield forecasting for large solar installations operating in desert climates,” said Pamir.