Choice and Definition of the Best Figures of Merit for the Analysis of PV Plants Application to the French Pilot Installation of Paomia

Summary

The analysis of a PV plant is considered in two manners:

• 1- Instantaneous measurements: data are recorded simultaneously at different points of the PV chain, and under various operating conditions. Coefficients are proposed to describe the efficiency of each component in its aptitude to transfer correctly the energy flow. A peculiar attention is given to the definition of the reference energy as recorded by a pyranometer or a calibrated cell or module. Mismatch effects in the PV field can be estimated. A portable data acquisition system, able to record I-V curves of large PV plants (up to 100 kWp) in less than 10 ms, is described breafly as well as the associated software that gives the mean parameters of the array.

• 2- Measurements over long periods: they give another view of the plant. The significance of several figures of merit is discussed. It is shown that it is difficult, through them, to estimate correctly the performances of installations if actual operating conditions are forgotten. As a consequence a direct comparison between plants is made very hazardous in most cases.

The instantaneous response and the long term behaviour of the Paomia Rondulinu 50 kWp plant are presented and used as a support for the discussion on these two families of figures of merit.