LOL "Loss-of-load" probability (Pumping)

This value is the probability that the user's needs cannot be met (i.e., the fraction of time when the tank is empty).

It may be understood as the complement of the "Solar fraction" (although it is described in terms of time rather than energy or water volume).

During the sizing process, specifying the required LOL allows for determining the required pump nominal power, and the corresponding PV array size.

The LOL is calculated using a simplified and fast yearly simulation. The program splits the monthly weather data into a realistic random sequence of 365 days (following the Collares-Pereira model), then performs a daily tank state balance to accumulate a realistic yearly LOL value.

This process is repeated with different pump and PV array sizes to find the devices that match the required LOL.