A European research group has developed a new “empirical” method for measuring the rear radiation from the Bifacial PV system. The proposed approach was tested at various European locations and it turned out to be possible to enable annual performance calculations with a permanent share value of the rear radiation.
Scientists from the University of Ljubljana of Slovenia and Spain’s University or Jaén have developed a new empirical model for calculating the radiation from the back of bifacial PV systems.
“The core of the work is a new empirical model for irradiation of the back,” said the corresponding author Kristijan Brecl PV -Magazine. “So far, all Back -Side radiation models were based on the geometry of the PV system and solar radiation values. As far as we know, this is the first empirical model on the market. The results may not be extraordinary, but are comparable to the exact physical models.”
The model uses a Gaussian function to describe how the rear radiation changes with the Azimutoek of the sun.
The team explained that most back -side radiation models are based on analytical methods. They are based on physics and geometry, using site-specific data such as PV system geometry, Albedo and surroundings. They are considered more accurate, but cannot easily be applied to another site without knowing all relevant parameters. An empirical model, on the other hand, uses measured data and statistical analysis. They are more versatile, but offer less accuracy on hours or daily. For the annual simulation, the team emphasized, they offer acceptable results.
The proposed new empirical model was developed using nine bifacial PV modules that were installed in South Spain. Five of them had covered their front with a white film and were used as rear radiation sensors. Additional instrumentation included a pyranometer of the Arran, a reference cell and a nearby Albottodom.
Image: University of Ljubljana, Renewable Energy, CC by 4.0
The model simulates the irradiation of the back by determining the share compared to the radiation of the Array aircraft.
“The share of the rear radiation in the total radiation received by a bifacial module is generally consistent during the day, with deviations in the morning and evening hours in the summer when the sun shines from behind,” the group said. “Our new empirical model simulates the share of the rear radiation as a ratio of the back-to-front irradiation with regard to the solar Azimut. The share is modeled by an exponential comparison of inverse Gaussian distribution form with the parameters derived from the measured data in the training period.”
The validation of the model was performed on PV modules at two other locations in Europe, namely Ljubljana, Slovenia and Neuchâtel, Switzerland. Moreover, the group also compared the results of the empirical model with itself previously developed Performance assessment model-the direct diffuse power assessment model for Bifacial PV modules (DDPRBIFI) model.
“The results will be used to improve the performance assessment model. Our goal in the future is to validate the model on large PV systems and for special locations/circumstances,” Brecl added. “The most important message of our current paper is that a detailed modeling of the irradiation of the back is not essential for PV system performance assessment studies. An annual share for irradiation of the back can be used for fast and simple calculations.”
The new methodology was presented in “Is an exact back -side radiation modeling essential for bifacial PV systems?“Published in Renewable energy.
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