Absorptivity

What it is

The fraction of the incoming light the module absorbs. The absorbed light that is not converted to electricity heats the module.

Typical values and how to get it

0.9 unless the PAN file carries a value. If not given: 0.9.

How it is applied

$$T = T_{amb} + \frac{a\,G\,(1 - \eta)}{U_c + U_v\,v}$$

where

Symbol	Meaning	Unit
$T$	the cell temperature	°C
$T_{amb}$	the ambient temperature	°C
$a$	this input	—
$G$	the effective irradiance on the module plane	W/m²
$\eta$	the module efficiency: its operating value with Prilliman, its rated value with Faiman	—
$U_c$	the constant heat-loss factor	W/(m²·K)
$U_v$	the wind heat-loss factor	W/(m²·K) per m/s
$v$	the wind speed of the weather file	m/s

References

1. Faiman 2008, Assessing the outdoor operating temperature of photovoltaic modules, Progress in Photovoltaics 16(4) 307–315
2. pvlib-python 0.16.1 source code (github.com/pvlib/pvlib-python), reference implementation: pvlib/temperature.py, pvsyst_cell()

API

thermal.absorptivity

Symbols follow the symbol registry.