A review of next generation bifacial solar farms: predictive modeling of energy yield, economics, and reliability

Photovoltaic (PV) cell technology has made great progress over the past few decades, bringing the PV energy cost down to a point where it is competitive to conventional electricity prices. While monofacial panels have historically dominated the market, recent developments in the manufacturing of bifacial panels (collecting light from both faces) have made them accessible for commercial applications. It is therefore imperative to define the design principles so that the steeply expanding market of bifacial modules and PV farms stays on an efficient path. In this paper, we will discuss physics-based models for these next-generation bifacial PV farms for analyzing yield and costs. Besides the conventional farm configurations, tracking systems are gaining market shares aiming to enhance the yield at a lower cost. Within +/- 30 degrees latitudes, we predict a 20%-30% energy gain for fixed-tilt bifacial over monofacial modules and an additional 20%-40% gain for single-axis bifacial tracking. Compound systems such as agrophotovoltaics and floating PV applications may be the possible future for a sustainable merger of food-water-energy systems. We show a competing relation between active light collection on crops and energy yield in an agrophotovoltaics system vs panel density-the final design will be decided by the crop yield or light usage efficacy constraint. The output reliability in terms of soiling and module degradation is also explained in this paper. Solar farms are expected to see 2%-5% loss in revenue in Asia and the Middle East even after optimal cleaning. Additionally, the bifacial modules degrade similar to 0.5%-0.6%/year. While there have been several physics-based degradation analyses, the bifacial technology lacks a large enough data set of long-term degradation studies for accurate predictions. The combined economics of reliability against yield will decide the viability of the next generation bifacial PV industry.