Hi Ahmed,
The molten salt linear Fresnel model uses an older algorithm to solve for energy and mass flow and for plant control that performs poorly under certain conditions, especially during time steps when the solar field, thermal energy storage, and power cycle are all operating. This causes the error you found: On a total annual basis, it is quite small, on the order of 1%.
The molten salt power tower, physical trough, and standalone thermal energy storage models use a newer algorithm, so do not have this problem.
We hope to update the algorithm for the molten salt linear Fresnel model, perhaps in 2023, but are not sure if funding will be available for that work.
Best regards,
Paul.