The equation used in the EnergyPlus source code for Surface Outside Face Beam Solar Incident Angle Cosine Value calculation does not match other sources for this same value.
Energy Plus: cos(θ_i ) = sin(α)sin(β) + cos(α)cos(β)*cos(γ-γ_s)
Other Sources: cos(θ_i ) = sin(α)cos(β) + cos(α)sin(β)*cos(γ-γ_s)
θ_i=angle of incidence
α=solar altitude
β=surface tilt
γ=wall azimuth
γ_s=solar azimuth
The EnergyPlus Reference manual does not explicitly state this equation. Is there another reference that states how EnergyPlus calculates Surface Outside Face Beam Solar Incident Angle Cosine Value?
