A research team from the Universitat Politècnica de València and Spanish engineering company Grupotec has investigated the gap between nominal module bifaciality and actual performance under operating conditions in utility-scale PV plants.

The study The bifacial gain gap: Nominal and regulatory vs. effective performance across five utility-scale PV sites was published in Renewable Energy.

The researchers analyzed two years of operational data from a 50 MW bifacial PV plant equipped with single-axis trackers in Spain. They subsequently validated their findings using data from four additional solar installations in Spain and the United Kingdom.

Their analysis revealed significant differences between nominal module bifaciality and effective bifacial performance at plant level, with mounting configurations, irradiance, temperature and operating conditions all influencing the contribution of rear-side irradiance to power generation.

At the reference plant, the modules have a nominal bifaciality factor of 0.70. However, the researchers calculated an average effective bifaciality of 0.610 on a time-weighted basis and 0.599 on an irradiance-weighted basis, representing a reduction of approximately 13% to 15% from the nominal value.

The discrepancy was particularly pronounced at medium and high irradiance levels, which account for a substantial share of annual electricity generation. At irradiance levels above 600 W/m², effective bifaciality dropped below 0.60, falling to approximately 0.55 to 0.57 at irradiance levels exceeding 1,000 W/m².

The researchers used 15-minute supervisory control and data acquisition (SCADA) records collected in 2024 and 2025, including meteorological measurements and string-level electrical data.

Rear-side irradiance was measured using albedometers equipped with pyranometers, while module temperatures were recorded using PT100 sensors installed on the rear surface of the modules.

Source link