Skip to content

Array-Coupling Voltage optimisation

This tool evaluates the PV-array performance as function of a fixed user's operating voltage.

The MPP operating voltage of a PV array varies along the day and the year, according to Irradiance and Module temperature. Estimating the performances for a given fixed voltage is depending on:

  • The climate (will not be identical for tropical and medium-latitude).
  • The weather data distribution.(the optimum may be computed for a year, or a given season).
  • The PV plane orientation.
  • The Array composition (PV module, number of modules in series/parallel).
  • The protection diode voltage drop.
  • The Array wiring resistance: at the user level, the ohmic voltage drop will lower the nominal array output proportionnaly to the instantaneous current.

The Relative average power yield (or efficiency) for different user voltage values is computed using weather data hourly data, over a given period.

Observing the results may lead to the following remarks:

  • The Optimal fixed voltage is very near from the average MPP voltage.
  • Pure MPP operation gives a rather low yield increase of about 1.5 to 2% with respect to the operation near the optimal voltage. In practice, this implies that benefits of a MPP converter may be cancelled by the inefficiency of this device, when the operating voltage is well adapted.
  • The Efficiency is rather flat when modifying the user's voltage, but drops more sharply toward high voltages.
  • The diode and ohmic resistance voltage drops may be a significant contribution affecting the user's voltage match.
  • In middle latitude climates, the usual 36-cells modules match well the battery charging voltage (about 14V for a 12V-battery). In very hot climates, especially with long wiring circuits, this could require modules with more cells.
  • Special 33-cells modules are only suited for very simple installations without protection diode (not recommended).