pvlib.temperature.faiman_rad(poa_global, temp_air, wind_speed=1.0, ir_down=None, u0=25.0, u1=6.84, sky_view=1.0, emissivity=0.88)[source]#

Calculate cell or module temperature using the Faiman model augmented with a radiative loss term.

The Faiman model uses an empirical heat loss factor model 1 and is adopted in the IEC 61853 standards 2 and 3. The radiative loss term was proposed and developed by Driesse 4.

The model can be used to represent cell or module temperature.

Parameters
• poa_global (numeric) – Total incident irradiance [W/m^2].

• temp_air (numeric) – Ambient dry bulb temperature [C].

• wind_speed (numeric, default 1.0) – Wind speed measured at the same height for which the wind loss factor was determined. The default value 1.0 m/s is the wind speed at module height used to determine NOCT. [m/s]

• ir_down (numeric, default 0.0) – Downwelling infrared radiation from the sky, measured on a horizontal surface. [W/m^2]

• u0 (numeric, default 25.0) – Combined heat loss factor coefficient. The default value is one determined by Faiman for 7 silicon modules in the Negev desert on an open rack at 30.9° tilt. $$\left[\frac{\text{W}/{\text{m}^2}}{\text{C}}\right]$$

• u1 (numeric, default 6.84) – Combined heat loss factor influenced by wind. The default value is one determined by Faiman for 7 silicon modules in the Negev desert on an open rack at 30.9° tilt. $$\left[ \frac{\text{W}/\text{m}^2}{\text{C}\ \left( \text{m/s} \right)} \right]$$

• sky_view (numeric, default 1.0) – Effective view factor limiting the radiative exchange between the module and the sky. For a tilted array the expressions (1 + 3*cos(tilt)) / 4 can be used as a first estimate for sky_view as discussed in 4. The default value is for a horizontal module. [unitless]

• emissivity (numeric, default 0.88) – Infrared emissivity of the module surface facing the sky. The default value represents the middle of a range of values found in the literature. [unitless]

Returns

numeric, values in degrees Celsius

Notes

All arguments may be scalars or vectors. If multiple arguments are vectors they must be the same length.

When only irradiance, air temperature and wind speed inputs are provided (ir_down is None) this function calculates the same device temperature as the original faiman model. When down-welling long-wave radiation data are provided as well (ir_down is not None) the default u0 and u1 values from the original model should not be used because a portion of the radiative losses would be double-counted.

References

1

Faiman, D. (2008). “Assessing the outdoor operating temperature of photovoltaic modules.” Progress in Photovoltaics 16(4): 307-315. DOI: 10.1002/pip.813

2

“IEC 61853-2 Photovoltaic (PV) module performance testing and energy rating - Part 2: Spectral responsivity, incidence angle and module operating temperature measurements”. IEC, Geneva, 2018.

3

“IEC 61853-3 Photovoltaic (PV) module performance testing and energy rating - Part 3: Energy rating of PV modules”. IEC, Geneva, 2018.

4(1,2)

Driesse, A. et al (2022) “Improving Common PV Module Temperature Models by Incorporating Radiative Losses to the Sky”. SAND2022-11604. DOI: 10.2172/1884890