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Summary

The NOCT-SAM model scales from Nominal Operating Cell Temperature with adjustments for wind speed. This model is based on the System Advisor Model (SAM) implementation. In PlantPredict, array height and mounting standoff distance are hard-coded to default values.

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Inputs

NameSymbolUnitsDescription
Ambient Air TemperatureTaT_a°CDry-bulb air temperature
Wind Speedvwv_wm/sWind velocity
Effective POA IrradianceGeffG_{eff}W/m²Effective irradiance after all optical losses
Plane-of-Array IrradianceGPOAG_{POA}W/m²Total POA irradiance
Module STC EfficiencyηSTC\eta_{STC}—Module efficiency at standard test conditions
Nominal Operating Cell TempNOCTNOCT°CNominal operating cell temperature
Transmittance-Absorptanceτα\tau \alpha—Transmittance-absorptance product
Cell-to-Module Temp DiffΔTc−m\Delta T_{c-m}°CTemperature difference between cell and module surface
Reference IrradianceGrefG_{ref}W/m²Reference irradiance (typically 1000 W/m²)

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Outputs

NameSymbolUnitsDescription
Cell TemperatureTcT_c°COperating temperature of PV cells
Surface TemperatureTmT_m°CModule surface (back-of-module) temperature

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Detailed Description

The NOCT-SAM model derives the cell temperature by scaling Nominal Operating Cell Temperature: Tc=Ta+GPOA800⋅(NOCTadj−20)⋅(1−ηSTCταadj)⋅9.55.7+3.8⋅vw′T_c = T_a + \frac{G_{POA}}{800} \cdot (NOCT_{adj} - 20) \cdot \left(1 - \frac{\eta_{STC}}{\tau\alpha_{adj}}\right) \cdot \frac{9.5}{5.7 + 3.8 \cdot v_w'}

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Adjusted Wind Speed

In PlantPredict, array height is hard-coded to 1 story: vw′=0.51⋅vwv_w' = 0.51 \cdot v_w

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Adjusted NOCT

In PlantPredict, mounting standoff is hard-coded to 4 inches, resulting in no NOCT adjustment: NOCTadj=NOCTNOCT_{adj} = NOCT

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Irradiance Ratio

irrratio=GeffGPOAirr_{ratio} = \frac{G_{eff}}{G_{POA}} ταadj=τα⋅irrratio\tau\alpha_{adj} = \tau\alpha \cdot irr_{ratio}

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Module Surface Temperature

Tm=Tc−GeffGref⋅ΔTc−mT_m = T_c - \frac{G_{eff}}{G_{ref}} \cdot \Delta T_{c-m}

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References

  • Gilman, P., et al. (2018). SAM photovoltaic model technical reference update. NREL/TP-6A20-67399, National Renewable Energy Laboratory.