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

This value is the probability that the user's needs cannot be supplied (i.e. the time fraction 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 values into a realistic random sequence of 365 days (according to Collares-Pereira model). Then it performs a day-by-day balance of the tank state, in order to accumulate a realistic "LOL" yearly value.

This process is repeated with different pump and PV-array sizes, in order to find the "exact" devices matching the required "LOL".