Irradiation at design

Dear collegues,
It seems that the Irradiation at design works differently in the physical and the empirical model for a typical CSP plant with molten salts thermal storage. In empirical model is a key parameter to control de charge rate of the TES whereas in the physical model, and with a fixed amount of loops (fixed aperture area), it affects very little the plant output (1% changes on gross and net production with 30% reference DNI variations).
Please clarify how are the reference DNI and plant dimensioning related (i.e. charge rate, pumping size…). Our goal is to be able to modify the thermal storage charge rate of the physical model for plant optimizations, and the reference DNI as well, is this feasible?
Thanks in advance,
Regards

Hello,
The reference DNI value should not affect the annual output very much when you specify the field aperture area explicitly instead of using the solar multiple. Because the empirical model uses the value to calculate HCE heat losses, it has more of an effect on the annual output than in the physical model.
When you use the solar multiple to size the system, the reference DNI value is used to calculate the field area. In that case, the value does affect the annual output because it affects the field area.
For a more detailed description of these calculations, please see the reference manuals listed on the Performance Model Documentation page of this website.
Best regards,

Paul.