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Cells Size Determination

Usefulness

Cell sizes are rarely mentioned in datasheets.

In PVsyst, cell sizes are primarily used when calculating electrical shading losses for bottom-cell width correction. The bottom cell band width will be the cell size in normal cases, or half the cell size with Twin-half-cut cells modules positioned in portrait.

It can also be used when evaluating PV module (or system) efficiency relative to the effective active area (which is uncommon) rather than the total module area.

Determination

Determining cell sizes is not straightforward. It should be based on several criteria:

  • The number of cells electrically connected in series (related to Vmp: approximately 0.56 to 0.57 V/cell in modern "standard" technology modules),
  • The number of submodules (i.e. the number of diodes),
  • The submodules layout. We always suppose that all sub-modules are connected in series.
  • The number of cells in width in the module (the program typically accounts for about 50 mm for the edges, frame, and spacing).
  • The number of cells (or fractions of cells) in the length of the module,
  • The total cell area, which is typically between 88% and 91% of the total module area.
  • PVsyst adjusts the final sizes to the normalized cell sizes when possible.

These criteria are not always sufficient for a reliable definition of sizes. They may fail for special modules such as those with tiles, small modules with fractional cells, etc.

Therefore it is always possible to explicitly define the cell sizes by hand, directly in the dialog.

Procedure

After ensuring that you have correct values for:

  • The module sizes
  • The number of cells in series and parallel,
  • The number of diodes,
  • The Submodule partition (layout)

you will get this dialog (this example is for a twin half-cut cells module):

CellSizeDeterm

It is always possible to manually modify the sizes (width and height) of the cell. You will have a warning at the bottom of the dialog if your choice is not compatible with all the module data.

The checkbox to the right of the cell area indicates whether the values comply with PVsyst's calculation.

You can always retrieve the PVsyst determination (if valid) by clicking on this checkbox.