PV Cell Temperature and Temperature-Derated Power
Cell temperature by the NOCT model, and the temperature-derated power it produces.
Example
You enter
- Ambient temperature (°C) 30
- Plane-of-array irradiance (W/m²) 800
- NOCT (C, datasheet, default 45) 45
- Module STC power (W) 400
- Power temp coefficient (%/C, e.g. -0.35) -0.35
You get
- Cell temperature 55 C
- Power at cell temperature 358 W
- Temperature loss 10.5%
Checked against published worked examples from: Florida State University SESEC.
Details, formula, and sources
ScopeCell temperature from the NOCT model T_cell = T_amb + (NOCT-20) G/800 and the temperature-derated power P = P_stc(1 + gamma(T_cell-25)). A 400 W module at 30 C air, 800 W/m^2 runs 55 C, a 10.5% temperature derate (358 W on its STC rating; at 800 W/m^2 the actual output is about 0.8 x that, since the derate does not scale for irradiance); a cool 10 C morning derates only 3.5%. The datasheet governs.
Formula or tableT_cell = T_amb + (NOCT - 20) x G/800; P = P_stc x (1 + (gamma/100)(T_cell - 25)); loss = (1 - P/P_stc) x 100.
Source and editionThe PV NOCT cell-temperature model and the datasheet power temperature coefficient, by name.
Free accessThe NOCT model and temperature-coefficient derate are standard PV design relations (NREL / module datasheets). The module datasheet governs the coefficients.
What governsEstimate. AHJ and licensed professional govern.
API field namesT_amb_C, G_wm2, NOCT_C, P_stc_W, gamma, T_cell_C, P_W, loss_pct
- NOCT model T_cell = T_amb + (NOCT - 20) x G/800PV design practice / NREL
- Power derate P = P_stc x (1 + gamma/100 x (T_cell - 25)); gamma ~ -0.35%/C siliconmodule datasheet
- Temperature only no irradiance scaling and no soiling/wiring/inverter/shading lossesscope of this tile