pecos.metrics.pv module

pecos.metrics.pv.ac_performance_ratio(acpower, poa, DC_power_rating, tfilter=None, per_day=True)

The daily AC performance ratio (\(PR_{AC}\)) is defined in IEC 61724 as:

\(PR_{AC}=\dfrac{Y_{fAC}}{Yr}\)

where \(Y_fAC\) is ths the AC system yield defined as the measured AC energy produced by the PV system in the day (kWh/d) divided by the rated power of the PV system. The definition of this rating is not specified in IEC 61724, but is defined here as DC power rating at STC conditions (1000 W/m2, cell temperature of 25 C, and AM1.5 spectrum). \(Y_r\) is the plane-of-array insolation (kWh/m2) divided by the reference irradiance (1000 W/m2). \(Y_r\) is in units of time.

Parameters:

acpower : Pandas DataFrame

AC power

poa : Pandas DataFrame

Plane of array irradiance

DC_power_rating : float

DC power rating at STC conditions

tfilter : Pandas Series (default = None)

Time filter containing boolean values for each time index

per_day : Boolean (default = True)

Flag indicating if the results shoudl be computed per day

Returns:

PR_AC : Pandas DataFrame or float

AC performance ratio, if per_day = True, then a dataframe indexed by day is returned, otherwise a single vlaue is returned for the entire dataset.

pecos.metrics.pv.clearness_index(dni, tfilter=None, per_day=True)

Clearness index (\(Kt\)) is defined as:

\(Kt=\dfrac{DN\_insolation}{Ex\_insolation}\)

where \(DN\_insolation\) is the direct-normal insolation in one day (kWh/m2/d) \(Ex\_insolation\) is the the extraterestrial insolation in one day (kWh/m2/d). Computed using pvlib.irradiance.extraradiation.

Parameters:

dni : Pandas DataFrame

Direct normal irradiance

tfilter : Pandas Series (default = None)

Time filter containing boolean values for each time index

per_day : Boolean (default = True)

Flag indicating if the results shoudl be computed per day

Returns:

Kt : Pandas DataFrame or float

Clearness index, if per_day = True, then a dataframe indexed by day is returned, otherwise a single vlaue is returned for the entire dataset.