Bifacial PV Performance Evaluation with reference to the Solar Spectrum and Broadband Irradiance

This paper investigates the measured performance of bifacial PV modules with reference to their solar inputs. A pyranometer and spectrometer are used to gather front- and rear- plane-of-array (POA) global and spectral irradiance data. An I-V curve tracer is used to characterise the electrical output of a bifacial PV module. A comparison is presented between the measured bifacial PV output and estimated bifacial PV module performance as determined using both a measured global POA and a measured spectral description of irradiance. This work shows that as sky conditions tend towards cloudy conditions, the use of a spectral description of irradiance, as measured using a spectrometer, yields more accurately predicted bifacial PV module performance and should therefore be incorporated in forecasting of bifacial PV systems. The estimated percentage increase provided by the rear-side of the bifacial module as determined using the spectrometer under-estimates the measured percentage increase provided by the rear-side by 3.3% and 4.11% in clear sky and partly cloudy conditions respectively and overestimates the measured percentage increase by 3.11% in overcast conditions. The estimated percentage increase provided by the rear-side of the bifacial module as determined using the pyranometer under-estimates the measured percentage increase provided by the rear-side by 2.87% and 3.17% in clear sky and partly cloudy conditions respectively and overestimates the measured percentage increase by 3.96% in overcast conditions.The measured percentage increased yield provided by the rear-side generation of a bifacial PV module is also stated. The average percentage increased yield provided by the rear-side generation of the bifacial module, as determined from measured behaviour, is 7,28% for the average short-circuit current and 5.25% for the maximum power point