Instantaneous Power Generation of Monofacial and Bifacial Photovoltaic Modules Under Tracker-Induced Albedo Variations

This paper presents an experimental comparison of the instantaneous power generation of standard and bifacial photovoltaic modules under real operating conditions. The study focuses on short-term effects caused by spatially variable albedo and tracker-induced changes in module orientation. Both modules were installed on the same mobile single-axis tracking platform and had identical rated front-side power, which ensured nearly identical operating conditions and independent MPPT operation. The experimental campaign included five ground surfaces: grass, river sand, grey paver, light aggregate, and dark aggregate. For each surface, electrical parameters and albedo were recorded over the full investigated geometrical range, covering relative solar azimuth from −60° to +60° and module tilt from 0° to 90°. The measured increase in power generation of the bifacial module relative to the standard module depended strongly on the ground surface. Over the full investigated range, the gain was 6.4% for grass, 11.3% for river sand, 5.9% for grey paver, 13.6% for light aggregate, and 4.5% for dark aggregate. These results confirm that, in bifacial photovoltaic systems with tracking, the ground surface and its reflective properties significantly affect the rear-side contribution and instantaneous power output. Consequently, albedo should not be treated as a constant or spatially homogeneous parameter when assessing short-term bifacial PV performance.