DNI PARAMETRIC

Dear Sir,

I'm simulating a CSP Molten Salt Power Tower, and I'm trying to make a parametric study varying different variables. One of them I'm changing is DNI at design point, but I'm realising any parameter is changing when I vary it.
Is that right? I suppose I need to change some other values when varying DNI, but I'm not sure which ones should I select.

Thanks for your help,
Javier.

Hi Javier,

When you change the value of an input value, SAM generally does not change the value of other interdependent inputs, so you have to change the values of all related input variables.

SAM uses design DNI value along with other design parameter values to determine the nominal capacities of the solar field and other components in the system.

I am not sure exactly what you mean by "...I'm changing is DNI at design point, but I'm realizing any parameter is changing when I vary it."

Can you tell me more about what you are expecting to see?

Best regards,
Paul.

Hi Paul!

First of all, thanks for your answer.

I'm trying to analyze how the plant performance is influenced by DNI. I'm not expecting SAM to change any input (sorry, I expressed myself wrong), but some outputs should vary, shouldn't they? I mean, annual energy production and hourly production should change for an array of DNI values. Am I wrong?
For your info, I'm simulating an existing plant, so there are many inputs I cannot change (number of heliostats, receiver and cycle power...).

Thanks again,
Javier

Dear Javier,

The design DNI is different from the hourly DNI values in the weather file. The design DNI is used to calculate the nameplate capacities. For example, a system with a 100 MW nameplate capacity and design DNI of 950 W/m2 means that the solar field and power block will generate 100 MW during times when the DNI is 950 W/m2 (and when other design conditions are met).

The weather files has DNI, ambient temperature, wind speed, and other hourly data that SAM uses during the simulation to calculate the system's electrical output in each hour of the year based on the solar resource and meteorological conditions.

These videos about SAM's CSP models explain more about how they work:

sam.nrel.gov/concentrating-solar-power/csp-videos.html

Best regards,
Paul.

Thanks for your help, Paul!