Bifacial system design

• Applying elevation from roof/surface
• Selecting surface reflectance (albedo factor)
• Checking the bifacial gain on the Derating table of the Reports page
• Formula used for calculating Isc BNPI current rating

SolarPlus bifacial modelling is a View Factor model or to be more explicit Empirical View Factor-based Bifacial Gain Model including:

• elevation effect,

• effective albedo,

• ground coverage ratio and

• tilt correction factor

Applying elevation from roof/surface

1. Go to the Balance of System section in the array designer

2. Set mounting type as tilt frame

3. Set the appropriate tilt angle

4. Set Elevation from surface in meters as required. This is the height between the surface and the bottom edge of the panel.

Set array tilt frame row angle and row to row spacing.

SolarPlus provides calculation of optimal row-to-row distance based on mid-winter shading between the hours of 10am-2pm OR 9am to 3pm.

See more on SolarPlus row spacing calculator here

Selecting surface reflectance (albedo factor)

1. Go to the Solar & Battery designer section

2. Scroll down to the Derating section

3. Select the Surface Reflectance value (the albedo factor is mentioned in brackets)

Checking the bifacial gain on the Derating table of the Reports page

The bifacial gain is displayed in the Derating table of the Reports page (Designer view) as below:

Formula used for calculating Isc BNPI current rating

The short circuit current for each tracker (combination of inverter, module and number of strings) where bifacial modules are used is calculated based on BNPI (Bifacial NamePlate Irradiance) data for the module. 

If the Isc BNPI is not stated on the module datasheet, the short-circuit current rating for bifacial panels is calculated as follows:

Isc BNPI = Isc STC *(1+0.135*BF), where BF is the bifaciality factor