pvlib.iam.martin_ruiz_diffuse#
- pvlib.iam.martin_ruiz_diffuse(surface_tilt, a_r=0.16, c1=0.4244, c2=None)[source]#
Determine the incidence angle modifiers (IAM) for sky diffuse and ground-reflected irradiance using the Martin and Ruiz incident angle model.
As described in [1], the IAMs result from integrals that assume the incoming sky diffuse and ground-reflected irradiance are isotropic.
- Parameters:
surface_tilt (float or array-like, default 0) – Surface tilt angles in decimal degrees. The tilt angle is defined as degrees from horizontal (e.g. surface facing up = 0, surface facing horizon = 90) surface_tilt must be in the range [0, 180]
a_r (numeric) – The angular losses coefficient described in equation 3 of [1]. This is an empirical dimensionless parameter. Values of a_r are generally on the order of 0.08 to 0.25 for flat-plate PV modules. a_r must be greater than zero.
c1 (float) – First fitting parameter for the expressions that approximate the integral of diffuse irradiance coming from different directions. c1 is given as the constant 4 / 3 / pi (0.4244) in [1].
c2 (float) – Second fitting parameter for the expressions that approximate the integral of diffuse irradiance coming from different directions. If c2 is not specified, it will be calculated according to the linear relationship given in [3].
- Returns:
iam (dict) – Incident Angle Modifier (see iam) values for each type of diffuse irradiance:
’sky’: radiation from the sky dome
’ground’: radiation reflected from the ground
Notes
Sky and ground modifiers are complementary: iam_sky for tilt = 30 is equal to iam_ground for tilt = 180 - 30. For vertical surfaces, tilt = 90, the two factors are equal.
References