pvlib.pvsystem.pvwatts_dc#
- pvlib.pvsystem.pvwatts_dc(effective_irradiance, temp_cell, pdc0, gamma_pdc, temp_ref=25.0, k=None, cap_adjustment=False)[source]#
Implement NREL’s PVWatts (Version 5) DC power model.
- Parameters:
effective_irradiance (numeric) – Irradiance transmitted to the PV cells. To be fully consistent with PVWatts, the user must have already applied angle of incidence losses, but not soiling, spectral, etc. [Wm⁻²]
temp_cell (numeric) – Cell temperature [C].
pdc0 (numeric) – Power of the modules at 1000 Wm⁻² and cell reference temperature. [W]
gamma_pdc (numeric) – The temperature coefficient of power. Typically -0.002 to -0.005 per degree C. [1/°C]
temp_ref (numeric, default 25.0) – Cell reference temperature. PVWatts defines it to be 25 °C and is included here for flexibility. [°C]
k (numeric, optional) – Irradiance correction factor, defined in [2]. Typically positive. [unitless]
cap_adjustment (Boolean, default False) – If True, only apply the optional adjustment at and below 1000 Wm⁻²
- Returns:
pdc (numeric) – DC power. [W]
Notes
The PVWatts Version 5 DC model [1] is:
\[P_{dc} = \frac{G_{poa eff}}{1000} P_{dc0} ( 1 + \gamma_{pdc} (T_{cell} - T_{ref}))\]This model has also been referred to as the power temperature coefficient model.
An optional adjustment can be applied to \(P_{dc}\) as described in [2]. The adjustment accounts for the variation in module efficiency with irradiance. The piece-wise adjustment to power is parameterized by k, where k is the reduction in actual power at 200 Wm⁻² relative to power calculated at 200 Wm⁻² as 0.2*`pdc0`. For example, a module that is rated at 500 W at STC but produces 95 W at 200 Wm⁻² (a 5% relative reduction in efficiency) would have a value of k = 0.01.
\[k=\frac{0.2P_{dc0}-P_{200}}{P_{dc0}}\]For positive k values, and k is typically positive, this adjustment would also increase relative efficiency when irradiance is above 1000 Wm⁻². This may not be desired, as modules with nonlinear irradiance response often have peak efficiency near 1000 Wm⁻², and it is either flat or declining at higher irradiance. An optional parameter, cap_adjustment, can address this by modifying the adjustment from [2] to only apply below 1000 Wm⁻².
Note that
pdc0is also used as a symbol inpvlib.inverter.pvwatts().pdc0in this function refers to the DC power of the modules at reference conditions.pdc0inpvlib.inverter.pvwatts()refers to the DC power input limit of the inverter.References
