IMPACT OF DIFFERENT ALBEDO LEVELS ON THE ESTIMATE OF ENERGY GENERATION OF BIFACIAL PHOTOVOLTAIC SYSTEMS

Abstract

Solar energy is a continuously evolving field, with a particular focus on optimizing the performance of photovoltaic modules. Constantly, new technologies and methodologies are being developed. This study presents a detailed analysis of the Energy Performance Index (EPI) of bifacial crystalline silicon modules under various albedo conditions. Using data from incident irradiance on the module plane and operating temperature measured in a pilot plant with state-of-the-art bifacial modules at the UFSC Photovoltaic Laboratory, the research was conducted in two phases. In the first phase, all systems were subjected to the same albedo conditions (black tarp). This phase aimed to quantify the intrinsic differences between systems, independent of albedo, so that this variable could be analyzed separately in the subsequent phase. The second phase covered a period of 12 complete months of data with albedo levels ranging from 0.26 (crushed rock) to 0.52 (white gravel). The analysis of the study results on the energy performance of bifacial modules exposed to different albedos allowed quantifying the energy gain from different types of soil. The gains were based on the scenario employing crushed rock under the systems, with sandy soil (albedo of 0.41) showing a relative loss of 2.37%, kaolin (albedo of 0.43) gaining 1.35%, and white gravel gaining 4.9%. The results indicate that there was no significant correlation between the EPI and the soil albedo level. Seasonal analysis revealed higher EPI values during winter months and lower values in other seasons, suggesting that temperature losses may not be well modeled by the simulation. To isolate the effect of soil albedo, a correlation analysis between measured and simulated incident irradiance on the back of the modules was conducted. It was observed that, for soils with higher albedo, the measured/simulated ratio is lower, indicating an overestimation in the incident irradiance on the back of the modules of up to almost 20%. Overall, the results suggest an overly optimistic estimate by the software for bifacial modules, with annual EPI values ranging from 94.5% to 96.0%.