pvperfsolar performance modeling

Reference / Incidence-angle modifier, beam

Model option

ASHRAE b₀

The one-coefficient ASHRAE formula

Inputs used: ASHRAE b₀, AR-coated glass, module.iam_angles_deg, iam.angles_deg

Method

The accepted fraction follows the one-coefficient formula of the ASHRAE collector test standard. The coefficient describes how fast the acceptance falls as the sun moves away from perpendicular; 0.05 describes plain glass. FF is held at 0 where the formula goes negative, above 87.3° for b0b_0 = 0.05.

The math

F(θ)=max⁡ ⁣(0, 1−b0(1cos⁡θ−1))(1)F(\theta) = \max\!\left(0,\ 1 - b_0\left(\frac{1}{\cos\theta} - 1\right)\right) \tag{1}

where

Symbol Meaning Unit
F(θ)F(\theta) the accepted fraction at incidence angle θ\theta —
θ\theta the incidence angle: between the sun and the perpendicular to the module plane degrees
b0b_0 the ASHRAE coefficient —

References

  1. ASHRAE Standard 93-2010, Methods of testing to determine the thermal performance of solar collectors (incidence-angle modifier)

API

iam.kind = ashrae, iam.b0 = 0.05

Symbols follow the symbol registry.