pvlib.iam.ashrae¶
-
pvlib.iam.
ashrae
(aoi, b=0.05)[source]¶ Determine the incidence angle modifier using the ASHRAE transmission model.
The ASHRAE (American Society of Heating, Refrigeration, and Air Conditioning Engineers) transmission model is developed in [1], and in [2]. The model has been used in software such as PVSyst [3].
Parameters: - aoi (numeric) – The angle of incidence (AOI) between the module normal vector and the sun-beam vector in degrees. Angles of nan will result in nan.
- b (float, default 0.05) – A parameter to adjust the incidence angle modifier as a function of angle of incidence. Typical values are on the order of 0.05 [3].
Returns: iam (numeric) – The incident angle modifier (IAM). Returns zero for all abs(aoi) >= 90 and for all
iam
values that would be less than 0.Notes
The incidence angle modifier is calculated as
\[IAM = 1 - b (\sec(aoi) - 1)\]As AOI approaches 90 degrees, the model yields negative values for IAM; negative IAM values are set to zero in this implementation.
References
[1] Souka A.F., Safwat H.H., “Determination of the optimum orientations for the double exposure flat-plate collector and its reflections”. Solar Energy vol .10, pp 170-174. 1966. [2] ASHRAE standard 93-77 [3] PVsyst Contextual Help. https://files.pvsyst.com/help/index.html?iam_loss.htm retrieved on October 14, 2019