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bifacialvf_mismatch - Bifacial PV View Factor model with Mismatch routines

python, configuration factor model, electrical model mismatch for bifacial modules.

Original bilinear interpolation code by Sara MacAlpine Python translation & Updates by Silvana Ayala

bifacialvf Original code by Bill Marion Python translation by Silvana Ayala Updates by Chris Deline

(Forthcoming) PVMismatch add-on Original code by PVMismatch For this version of bifacialvf_Mismach to work, PVMismatch must be installed (pip install pvmismatch)

Based on the publication: Marion, B., MacAlpine, S., Deline, C., Asgharzadeh, A., Toor, F., Riley, D., … Hansen, C. (2017). A Practical Irradiance Model for Bifacial PV Modules: Preprint. In 44th IEEE Photovoltaic Specialists Conference. Washington, DC. NREL/CP-5J00-67847

Bilinear Interpolation based on the publication: De Soto, W., Klein, S. A., & Beckman, W. A. (2006). Improvement and validation of a model for photovoltaic array performance. Solar Energy, 80(1), 78–88.

Marion, B., Rummel, S., & Anderberg, A. (2004). Current--voltage curve translation by bilinear interpolation. Progress in Photovoltaics: Research and Applications, 12(8), 593–607.


bifacialvf is a self-contained view factor (or configuration factor) model which replicates a 5-row PV system of infinite extent perpendicular to the module rows. The function returns the irradiance profile along the middle (interior) row by default, but user interface options include 'first', 'interior', 'last', and 'single'. Single-axis tracking is supported, and hourly output files based on TMY inputs are saved. Spatial nonuniformity is reported, with multiple rear-facing irradiances collected on the back of each module row.

Bilinear interpolation code add-on to bifacialvf (description below) to pre-generate IV arrays and bifacial coefficients, and to examine the energy production with back side irradiance mismatch for either a portrait or landscape module.
Included are IV curves and bifacial info for a Yingli (standard) module.


This software is written for Python 2 or 3. NREL recommends Anaconda Python.

Install using pip

bifacialvf is at the Python Package Index (PyPI). Use pip to install the latest release in your conda environment or virtualenv:

(myenv)$ pip install bifacialvf

Install development mode from GitHub

For those interested in contributing to bifacialvf:

  1. Clone the bifacialvf repository: $ git clone bifacialvf-master
  2. Navigate to the repository directory where is located: $ cd bifacialvf-master
  3. Install via pip in development mode: $ pip install -e .


import bifacialvf

bifacialvf.simulate(inputTMY, outputfile, tilt, azm, clearance, rowspacing)
(data, metadata) = bifacialvf.loadVFresults(outputfile)

For more usage examples, see the Jupyter notebooks in \docs\

## Prerequisites

* [NumPy](
* [pvlib python](

## Main Functions

        TMYtoread, writefiletitle,  beta, sazm, C=1, D=0.5,
        rowType = 'interior', transFactor=0.01, cellRows=6,
        PVfrontSurface='glass', PVbackSurface='glass',  albedo=0.62,
        tracking=False, backtrack=False, r2r=1.5, Cv=0.05, offset=0)

This is the main runfile.  Hourly TMY3 inputs are read, and an outputfile is saved with
a number of irradiance points along the module chord specified by `cellRows`.


read in saved file from `bifacialvf.simulate`.  If no filename is passed, a tkinter GUI opens for file selection

## Subroutines

BilinearInterpolation calculation for landscape modules

BilinearInterpolation calculation for Portrait modules 

Solar position and irradiance-related helper files including
`hrSolarPos`, `perezComp`, `solarPos`, and `sunIncident`

View Factor helper files to help with configuration-factor calculation
1-axis tracking and self-shading calculation.
Subroutines include:
`getBackSurfaceIrradiances`, `getFrontSurfaceIrradiances`, `getGroundShadeFactors`,
`getSkyConfigurationFactors`, `trackingBFvaluescalculator`, `rowSpacing`


Bifacial PV View Factor model for system performance calculation




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