API¶

Modules, methods, classes and attributes are explained here.

BifacialVF Package¶

View Factors¶

ViewFactor module - VF calculation helper files for bifacial-viewfactor

@author Bill Marion @translated to python by sayala 06/09/17

Get Back Surface Irradiances¶

bifacialvf.vf.getBackSurfaceIrradiances(rowType, maxShadow, PVbackSurface, beta, sazm, dni, dhi, C, D, albedo, zen, azm, cellRows, pvBackSH, rearGroundGHI, frontGroundGHI, frontReflected, offset=0)[source]¶

This method calculates the AOI corrected irradiance on the back of the PV module/panel. 11/19/2015

Added rowType and other changes to distinguish between types of rows. 4/19/2016

Added input of offset of reference cell from PV module back (in PV panel slope lengths) for modeling Sara’s reference cell measurements, should be set to zero for PV module cell irradiances.

Added while loop so projected Xs aren’t too negative causing array index problems (<0) 12/13/2016:

while (projectedX1 < -100.0 || projectedX2 < -100.0):
    # Offset so array indexes are >= -100.0  12/13/2016

    projectedX1 += 100.0;
    projectedX2 += 100.0;

Parameters:

rowType (str) – Type of row: “first”, “interior”, “last”, or “single”
maxShadow – Maximum shadow length projected to the front(-) or rear (+) from the front of the module
PVbackSurface – PV module back surface material type, either “glass” or “ARglass”
beta – Tilt from horizontal of the PV modules/panels (deg) (for front surface)
sazm – Surface azimuth of PV panels (deg) (for front surface)
dni – Direct normal irradiance (W/m2)
dhi – Diffuse horizontal irradiance (W/m2)
C – Ground clearance of PV panel (in PV panel slope lengths)
D – Horizontal distance between rows of PV panels (in PV panel slope lengths)
albedo – Ground albedo
zen – Sun zenith (in radians)
azm – Sun azimuth (in radians)
pvBackSH – Decimal fraction of the back surface of the PV panel that is shaded, 0.0 to 1.0
rearGroundGHI (array of size [100]) – Global horizontal irradiance for each of 100 ground segments (W/m2)
frontGroundGHI (array of size [100]) – Global horizontal irradiance for each of 100 ground segments (W/m2)
frontReflected (array of size [cellRows]) – Irradiance reflected from the front of the PV module/panel (W/m2) in the row behind the one of interest
offset – Offset of reference cell from PV module back (in PV panel slope lengths), set to zero for PV module cell irradiances

Returns:

backGTI (array of size [cellRows]) – AOI corrected irradiance on back side of PV module/panel, one for each cell row (W/m2)
aveGroundGHI (numeric) – Average GHI on ground under PV array

Notes

1-degree hemispherical segment AOI correction factor for glass (index=0) and ARglass (index=1)

Get Front Surface Irradiances¶

bifacialvf.vf.getFrontSurfaceIrradiances(rowType, maxShadow, PVfrontSurface, beta, sazm, dni, dhi, C, D, albedo, zen, azm, cellRows, pvFrontSH, frontGroundGHI)[source]¶

This method calculates the AOI corrected irradiance on the front of the PV module/panel and the irradiance reflected from the the front of the PV module/panel. 11/12/2015

Added row type and MaxShadow and changed code to accommodate 4/19/2015

Parameters:

rowType (str) – Type of row: “first”, “interior”, “last”, or “single”
maxShadow – Maximum shadow length projected to the front (-) or rear (+) from the front of the module row (in PV panel slope lengths), only used for rowTypes other than “interior”
PVfrontSurface – PV module front surface material type, either “glass” or “ARglass”
beta – Tilt from horizontal of the PV modules/panels (deg)
sazm – Surface azimuth of PV panels (deg)
dni – Direct normal irradiance (W/m2)
dhi – Diffuse horizontal irradiance (W/m2)
C – Ground clearance of PV panel (in PV panel slope lengths)
D – Horizontal distance between rows of PV panels (in PV panel slope lengths)
albedo – Ground albedo
zen – Sun zenith (in radians)
azm – Sun azimuth (in radians)
pvFrontSH – Decimal fraction of the front surface of the PV panel that is shaded, 0.0 to 1.0
froutGroundGHI (array of size [100]) – Global horizontal irradiance for each of 100 ground segments in front of the module row

Returns:

frontGTI (array of size [cellRows]) – AOI corrected irradiance on front side of PV module/panel, one for each cell row (W/m2)
frontReflected (array of size [cellRows]) – Irradiance reflected from the front of the PV module/panel (W/m2)
aveGroundGHI (numeric) – Average GHI on the ground (includes effects of shading by array) from the array frontGroundGHI[100]

Notes

1-degree hemispherical segment AOI correction factor for glass (index=0) and ARglass (index=1). Creates a list containing 5 lists, each of 8 items, all set to 0

Get Ground Shade Factors¶

bifacialvf.vf.getGroundShadeFactors(rowType, beta, C, D, elv, azm, sazm)[source]¶

This method determines if the ground is shaded from direct beam radiation for points on the ground from the leading edge of one row of PV panels to the leading edge of the next row of PV panels behind it. This row-to-row dimension is divided into 100 ground segments and a ground shade factor is returned for each ground segment, with values of 1 for shaded segments and values of 0 for non shaded segments. The fractional amounts of shading of the front and back surfaces of the PV panel are also returned. 8/20/2015

4/18/2016 - Modified to account for different row types. Because the ground factors may now be different depending on row, they are calculated for the row-to-row dimension to the rear of the leading module edge and to the front of the leading edge. Also returned is the maximum shadow length projected to the front or rear from the front of the module row

Parameters:

rowType (str) – “first”, “interior”, “last”, or “single”
beta – Tilt from horizontal of the PV modules/panels (deg)
C – Ground clearance of PV panel (in PV panel slope lengths)
D – Horizontal distance between rows of PV panels (in PV panel slope lengths)
elv – Sun elevation (in radians)
azm – Sun azimuth (in radians)
sazm – Surface azimuth of PV panels (deg)

Returns:

pvFrontSH (numeric) – Decimal fraction of the front surface of the PV panel that is shaded, 0.0 to 1.0
pvBackSH (numeric) – Decimal fraction of the back surface of the PV panel that is shaded, 0.0 to 1.0
rearGroundSH (array of size [100]) – Ground shade factors for ground segments to the rear, 0 = not shaded, 1 = shaded
frontGroundSH (array of size [100]) – Ground shade factors for ground segments to the front, 0 = not shaded, 1 = shaded
maxShadow (numeric) – Maximum shadow length projected to the front(-) or rear (+) from the front of the module row (in PV panel slope lengths), only used later for rowTypes other than “interior”

Get Sky Configuration Factors¶

bifacialvf.vf.getSkyConfigurationFactors(rowType, beta, C, D)[source]¶

This method determines the sky configuration factors for points on the ground from the leading edge of one row of PV panels to the leading edge of the next row of PV panels behind it. This row-to-row dimension is divided into 100 ground segments and a sky configuration factor is returned for each ground segment. The sky configuration factor represents the fraction of the isotropic diffuse sky radiation (unobstructed) that is present on the ground when partially obstructed by the rows of PV panels. The equations follow that on pages in the notebook dated 8/12/2015. 8/20/2015

4/15/2016 Modifed for calculations other than just the interior rows. Row type is identified with the string rowType, with the possilbe values:

first = first row of the array
interior = interior row of array
last = last row of the array
single = a single row array

Because the sky configuration factors may now be different depending on row, they are calculated for the row-to-row dimension to the rear of the leading module edge and to the front of the leading edge.

Parameters:

rowType (str) – “first”, “interior”, “last”, or “single”
beta (float) – Tilt from horizontal of the PV modules/panels (deg)
C (float) – Ground clearance of PV panel (in PV module/panel slope lengths)
D (float) – Horizontal distance between rows of PV panels (in PV module/panel slope lengths)

Returns:

rearSkyConfigFactors (array of size [100]) – Sky configuration factors to rear of leading PVmodule edge (decimal fraction)
frontSkyConfigFactors (array of size [100]) – Sky configuration factors to rear of leading PVmodule edge (decimal fraction)

Notes

The horizontal distance between rows, D, is from the back edge of one row to the front edge of the next, and it is not the row-to-row spacing.

Row Spacing¶

bifacialvf.vf.rowSpacing(beta, sazm, lat, lng, tz, hour, minute)[source]¶

This method determines the horizontal distance D between rows of PV panels (in PV module/panel slope lengths) for no shading on December 21 (north hemisphere) June 21 (south hemisphere) for a module tilt angle beta and surface azimuth sazm, and a given latitude, longitude, and time zone and for the time passed to the method (typically 9 am).

(Ref: the row-to-row spacing is then D + cos(beta)) 8/21/2015

Parameters:	beta (double) – Tilt from horizontal of the PV modules/panels (deg) sazm (double) – Surface azimuth of the PV modules/panels (deg) lat (double) – Site latitude (deg) lng (double) – Site longitude (deg) tz (double) – Time zone (hrs) hour (int) – hour for no shading criteria minute (double) – minute for no shading
Returns:	D (numeric) – Horizontal distance between rows of PV panels (in PV panel slope lengths)

Tracking Bifacial Values Calculator¶

bifacialvf.vf.trackingBFvaluescalculator(beta, hub_height, r2r)[source]¶

1-axis tracking helper file

Parameters:

beta (series of floats, or float) – Tilt from horizontal of the PV modules/panels, in radians
hub_height (float) – tracker hub height
r2r (float) – Row-to-row distance (in PV panel slope lengths)

Returns:

C (float) – ground clearance of PV panel
D (float) – row-to-row distance (each in PV panel slope lengths)