# NOCT Cell Temperature

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

 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.