The ratio of rear-side efficiency to front-side efficiency. Typically a value between 0.65 and 0.9 provided on the bifacial module datasheeet. This is to account for the fact that photovoltaic cells on the rear of the module are usually less efficient than the cells on the front of the module. The bifaciality does not affect the solar irradiance on the rear of the module.

Ground reflectance. A value of 0 would mean that the ground is completely non-reflective, and a value of 1 would mean that it is completely reflective. Specify either a pipe-delimited array of 12 monthly values or a single value to be used for all months.

Use hourly or subhourly albedo data from the weather file instead of the monthly albedo values, if available. 0 means do not use weather file albedo values, 1 means use weather file albedo values.

Reduction in incident solar irradiance caused by dust or other seasonal soiling of the module surface that reduce the radiation incident on the subarray. Soiling losses cause a uniform reduction in the total irradiance incident on each subarray. Specify a pipe-delimited array of 12 monthly values.