Bifacial photovoltaic modules collect light from both sides, unlike their monofacial equivalents, which only harness photons impinging their sun-facing side. The market share of bifacial photovoltaics is predicted to increase drastically in the next few years, aided by the fact that bifacial modules are compatible with existing manufacturing lines and could last longer in the field than monofacial modules, because they require double-glass encapsulation. In appropriate deployment conditions, bifacial modules can produce more electricity than monofacial modules. However, the electricity production gain and the economic gain that can be expected from bifacial modules highly depends on their deployment conditions. Now, Muhammad Ashraful Alam and colleagues from Purdue University and NREL in the United States provide an analysis framework to estimate the potential gain in electricity yield across the globe for a variety of module configurations.
Worldwide minute-by-minute solar irradiance is calculated from 22 years of average meteorological satellite data. Irradiance is split into the direct, diffuse and albedo components falling on bifacial modules, taking into account self-shading (that is, when the module itself shades the ground and limits the amount of albedo light that can reach its back side). An opto–electro–thermal model of the photovoltaic module is then used to convert the amount of absorbed light into annual electricity yields for standalone modules. The study shows that optimally tilted modules placed on the ground with an albedo of 0.25 (typical of vegetation cover) only lead to a 10% bifacial gain globally relative to monofacial modules. However, increasing the ground albedo to 0.5 (typical of white concrete) and lifting the optimally tilted modules one metre above ground leads to 30% bifacial gain globally. Finally, the researchers provide a set of empirical equations that can be used to optimize the configuration of bifacial modules (elevation, azimuth angle, tilt angle) at various locations.