WEAK LIGHT PERFORMANCE AND ANNUAL YIELDS OF PV MODULES AND SYSTEMS AS A RESULT OF THE BASIC PARAMETER SET OF INDUSTRIAL SOLAR CELLS

The weak light performance of multi- and mono-crystalline PV modules are known to be dependent on the used cell type, but also vary from cell supplier to cell supplier using even the same cell type . It is shown, that this is a result from the characteristic distribution of the parasitic resistances. This paper shows that these differences can lead to 10% difference in annual energy yields of photovoltaic systems. This itself provides a major optimisation opportunity. The corresponding energy yields of identical designed reference PV systems are differing in a range, which is roughly of the same order as the efficiency variation for actual crystalline silicon modules found on the market. This underlines the on-going need for an extension of the STC parameters to characterize the potential energy yield of PV modules. For practical use, state-of-the-art industrial cell and module testing equipment provides reliable values for the parasitic resistances and currents by extracting the basic parameter set from the measured IV curves at different intensity levels as well as in the dark, i.e. values for the shunt resistances, 2 nd diode contributions and series resistances in the cells and the European module efficiency for the modules.