The nominal operating cell temperature (NOCT) cell temperature model is used in the PV performance modeling application SAM and takes the form:
$$T_c = T_a + \frac{E_{POA}}{800} (T_{noct,adj} – 20) \left(1 – \frac{\eta_{ref}}{\tau\alpha}\right) \frac{9.5}{5.7 + 3.8 v_{w,adj}}$$
where
- $$T_c$$ is cell temperature (°C)
- $$T_a$$ is ambient temperature (°C)
- $$E_{POA}$$ is the irradiance incident on the plane of the module or array (W/m$$^2$$)
- $$T_{noct,adj}$$ is the module’s nominal operating cell temperature, adjusted for mounting stand-off (°C)
- $$\eta_{ref}$$ is the module efficiency at STC (unitless)
- $$\tau\alpha$$ is a combined coefficient representing transmittance and absorptance effects (unitless)
- $$v_{w,adj}$$ is wind speed, adjusted for height above ground (m/s)
$$v_{w,adj}$$ is calculated from wind speed $$v_w$$ as $$0.51 v_w$$ for installations one story or lower and $$0.61 v_w$$ otherwise.
$$T_{noct,adj}$$ is calculated from the module’s nominal operating cell temperature $$T_{noct}$$, according to the mounting standoff height (in inches):
$$
T_{noct, adj} = \begin{cases}
T_{noct} & \text{open rack} \\
T_{noct} + 2 & 2.5-3.5 \\
T_{noct} + 6 & 1.5-2.5 \\
T_{noct} + 11 & 0.5-1.5 \\
T_{noct} + 18 & 0.0-0.5
\end{cases}
$$
The NOCT temperature model is implemented in pvlib-python with pvlib.temperature.noct_sam.
References
[1] Gilman, P., Dobos, A., DiOrio, N., Freeman, J., Janzou, S., Ryberg, D., 2018, “SAM Photovoltaic Model Technical Reference Update”, National Renewable Energy Laboratory Report NREL/TP-6A20-67399.