Industry consensus on calculating future years generation

[André Mermoud]

I don't know any well-established consensus for the simulation of the degradation of a PV system.

The usual way is to take the module efficiency degradation into account.

Manufacturer's warranty usually corresponds to about -1%/year, but the very few experimental studies about this subject indicate a lower degradation rate (around -0.3%/year on 25-years installations at Supsi - Switzerland).

Usually the yield diminution is assumed to be directly in accordance with this degradation.

But a recent study pointed out the fact that all modules don't degrade identically, but with a spread around the average, so that the mismatch also increases along the years.

In PVsyst, we intend to provide a tool for the estimation of this phenomenon soon.

The performances of other parts of the equipment (like inverters) probably don't degrade significantly, but may be subject to failures. The "instantaneous" loss may be accounted by the "Unavailability" during the simulation, and provision for the repair or replacement should be included the maintenance costs.