Plane orientation irradiance POA

Many people are measuring the irradiance with a solarimeter in the plane of the array (POA). In the simulation, this corresponds to the GlobInc value.

When importing these measured data, if you don't have horizontal weather data measurements, you can use this POA measurement. In this case you have to define the orientation of the solarimeter.

NB: In tracking systems, the solarimeter may also be fixed to the tracker's axis. PVsyst is able to use these data, as far as the tracking strategy corresponds to the PVsyst tracking mode. In this case be careful: it the solarimeter is within the tracker's array, it will encounter the shading of the neighbour trackers, especially on the diffuse and albedo components.

For use in the simulations, PVsyst will recalculate the Horizontal Global and Diffuse irradiations, which are likely to produce this tilted plane irradiation (reverse transposition).

During the data analysis and simulation comparisons, PVsyst will exclusively use the Global on horizontal plane as starting point. This is necessary as the optical treatment (shadings, IAM, etc) requires the beam, diffuse and albedo components.

These GlobHor values may possibly be used for other plane orientations, provided that these orientations are not too different. These values cannot be quite correct for other orientations, as they loose some information about the irradiance behind the plane.

Be careful: as the transposition process uses the solar geometry, the time shift when registrating the data should be very well defined already at the meteo data import stage.