How is energy yield modeled for bifacial solar PV systems?

Bifacial modeling adds rear-side irradiance contribution. Factors: ground reflectance (albedo - 20% typical, up to 70% for snow), module height and row pitch (affect view factors), structure shading (mounting affects rear irradiance uniformity), rear-side efficiency (typically 70-90% of front), soiling on both sides, and mismatch (uneven rear irradiance). Models use view factor calculations (3D ray tracing or 2D simplification) to determine rear irradiance. Bifacial gain typically 5-15% for ground-mount, less for rooftop. Validation uses rear-side pyranometers. NREL's bifacial radiance tool provides open-source modeling capability.