NOCT, module's rated NOCT

Method

The equation is that of the NOCT option (1): the rise at nominal operating conditions, 800 W/m² at 20 °C ambient, scaled by the irradiance, reduced by the module efficiency over the transmittance-absorptance product, and cooled by the wind with the weather file's wind speed times 0.51. The nominal operating cell temperature is the module's own: the rated NOCT of its CEC database entry plus the standoff adjustment of the Physics tab. The irradiance is the effective irradiance on the front side, after the glass-reflection step and after the spectral modifier when that acts on the effective irradiance. Values the model fills in: a module without a rated NOCT (one read from a PAN file) uses 45 °C, and the run's warnings say so; the standoff adjustment is 0 °C if not given, the value for a ground or rack mount, whatever the racking.

Settings

Mounting standoff	Adjustment of the NOCT
Ground or rack mount, or more than 3.5 inch (8.9 cm) from the roof	0 °C
2.5 to 3.5 inch (6.4 to 8.9 cm)	2 °C
1.5 to 2.5 inch (3.8 to 6.4 cm)	6 °C
0.5 to 1.5 inch (1.3 to 3.8 cm)	11 °C
Less than 0.5 inch (1.3 cm)	18 °C
Wind factor	0.51 (arrays less than 6.7 m above the ground)

The math

$$T = T_{amb} + \frac{G}{800}\,(T_{NOCT} - 20)\left(1 - \frac{\eta}{\tau\alpha}\right)\frac{9.5}{5.7 + 3.8\,v'},\qquad v' = \max(0.001,\ 0.51\,v) \tag{1}$$

where

Symbol	Meaning	Unit
$T$	the cell temperature	°C
$T_{amb}$	the ambient temperature	°C
$G$	the effective irradiance on the front side	W/m²
$T_{NOCT}$	the module's rated NOCT plus the standoff adjustment	°C
$\eta$	the module's reference efficiency	—
$\tau\alpha$	the transmittance-absorptance product	—
$v'$	the wind speed at the modules	m/s
$v$	the wind speed	m/s

References

1. Duffie & Beckman, Solar Engineering of Thermal Processes, 4th ed., Wiley 2013
2. Gilman, DiOrio, Freeman, Janzou, Dobos & Ryberg 2018, SAM Photovoltaic Model Technical Reference Update, NREL/TP-6A20-67399
3. NREL SAM Simulation Core (SSC) source code, release 2026.7.3, github.com/NatLabRockies/ssc: shared/lib_cec6par.cpp, cec6par_module_t and noct_celltemp_t; ssc/cmod_pvwattsv8.cpp, the module parameters of each module type

API

thermal.model = noct_module, thermal.noct_standoff_adjust_c, module.cec.t_noct_c

Symbols follow the symbol registry.