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<< Click to Display Table of Contents >> Loss diagram |
  
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<< Click to Display Table of Contents >> Loss diagram |
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The loss diagram provides a quick and insight look into the quality of a PV system design, by identifying the main sources of losses.
It is always present on the Simulation report, for the whole year. It is also available for each month, using the buttons "Detailed results > Predefined graphs" in the project's dialog. This allows to evaluate the seasonal effect and impact of the different losses.
Please refer to Array losses, general considerations for a general explanation of the losses in PVsyst.
The array losses start from the rough evaluation of the nominal energy, using the global effective irradiance and the array MPP nominal efficiency at STC. Then it gives the detail of the PV model behaviour according to the environmental variables.
In stand-alone systems, the diagram gives a detail of the battery use, that is which part of the energy effectively transits by the battery. Minimizing the battery use is of some importance for the lifetime (number of charge/discharge cycles).
| NB: | Each loss is defined as percentage of the previous energy quantity. Therefore the percent values are of course not additive: when grouping the losses, the overall percentage is not the sum of the detailed values! |
| NB: | The accounting of the individual losses is far from being a trivial problem! The simulation process and some variable definitions had to be deeply reformulated for obtaining a coherent figure. |
| And some contributions are impossible to evaluate rigorously. For example in stand-alone systems, the ohmic losses are evaluated using the usual relation Ploss=R * I². But in reality the array resistance modifies the PV operating point and the whole circuit equilibrium, so that a more accurate calculation would probably be simulating the complete system with and without this resistance, and evaluate the differences. But even with this method, some loss contributions will be transferred to other ones. |
By the way, even if some individual losses are not quite well determined, the Energy values at each main step of the simulation are in principle correctly calculated.
You can refer to the following pages for a detailed description of the individual variables: