SPLTRAK Abstract Submission
Effects of solar spectrum and albedo on the performance of bifacial Si heterojunction mini-modules
Marco Leonardi1,4, Roberto Corso1,4, Gabriella Milazzo1, Andrea Scuto1, Carmelo Connelli2, Marina Foti2, Cosimo Gerardi2, Fabrizio Bizzarri3, Stefania M. Privitera1, Salvatore A. Lombardo1
1National Research Council, Institute for Microelectronics and Microsystems (CNR-IMM), Catania, Italy
/2Enel Green Power, Catania, Italy
/3Enel Green Power, Rome, Italy
/4Department of Physics and Astronomy, Catania, 95123, Italy, Catania, Italy

Bifacial photovoltaics represents a compelling technology for the future development of photovoltaics. Compared to the standard monofacial modules, bifacial ones register higher energy yield at reduced costs; however, a thorough evaluation of all the factors that contribute to their performance is advisable. In this work, we compare the dependencies of the performance of bifacial and monofacial mini-modules on the impinging solar radiation intensity, spectrum, and ground albedo. Monofacial and bifacial mini-modules realized with n-type Si heterojunction solar cells (characterized by high short circuit current, open-circuit voltage and bifaciality factor) were tested in outdoor conditions. Using two different types of ground, with a low and high albedo, we have continuously monitored the electrical characteristics of the modules from the open- to the short-circuit condition. We monitored the open-circuit voltage and short circuit current values and the power at maximum power point for each operation cycle, and we collected experimental data on the spectral distribution of incident solar light and the intensity of the light reflected from the ground. Using this approach, we have simultaneously and directly compared monofacial and bifacial module electrical performances, evaluating their correlation with the impinging light conditions. The experimental data reveal an increase in the intensity of light reflected by the ground in the afternoon, which translates into an increase in power output in the case of bifacial systems. Another factor that contributes to this phenomenon is the high responsivity of the cells to infrared light, which is especially effective in the afternoon when the solar spectrum is shifted to the infrared region. The results confirm the effectiveness of bifaciality in improving the power output, proving that this technology plays a crucial role throughout the whole day, both in low and high irradiance conditions.