CSP Time Series Results

Hello!
There are some doubts that I'm having when analysing the results in Time series. Is there any help specifying what each result means?

The temperature of the HTF at the end of solar field is the Field Timestep-averaged outlet temperature or Loop Timestep-averaged outlet temperature? What is the difference between those values?

The temperature that the fluid enters the turbine is the PC HTF inlet temperature?

TES thermal capacity is calculated based on some inputs and its value is the equivalent thermal capacity of the storage tanks, assuming the thermal storage system is fully charged. Analysing the results, how can there be defocusing if the TES thermal capacity (2 MWht) is not full?

Hi Bernardo,

Please see this post for a discussion of field and loop timestep-averaged temperature: sam.nrel.gov/forum/forum-general/1910 .

Over a given time step, if the solar field is producing more power than the TES can absorb, SAM defocuses collectors in the field to attempt to ensure that the TES is full at the end of the time step. Because calculating the field defocus fraction is an iterative process, the solution may not always be perfect.

SAM considers the TES to be full when it cannot accept additional mass of HTF, so if the hot tank temperature is colder than design and the tank is full, then the charge state will be less than capacity, but there is no room for additional charging.

If you enable dispatch optimization on the System Control page, the dispatch model may decide to leave some room TES for a future time step (although this should be rare).

The field can also defocus if it can’t absorb all the flux without exceeding mass flow or temperature constraints. Types of defocus are covered in this post: sam.nrel.gov/forum/forum-general/3841

As for the results in your screenshot, we could not replicate them exactly because we do not have the weather file you are using. The mass flow and field fraction plots show that whenever the field is defocused, the mass flow is always 6. That suggests that the field is
is defocusing because of receiver mass flow / temperature constraints. One exception is hour 17 on July 19 where it looks like TES is full. Note from the description in the post I linked above that the time series output “Field optical focus fraction” includes only “plant control” defocus (collectors are defocused to avoid exceeding power cycle design limits) while “Field fraction of focused SCA” includes both plant control defocus and receiver control defocus (collectors defocus to avoid exceeding receiver design limits) signals.

Best regards,
Paul.

Hi Bernardo,

I revised my original response above. Please let me know if you have any additional questions or need clarification.

Best regards,
Paul.

Hi Paul.
In advance, a big thank you for your reply and your help. 
Now, I understand why the results were like this!

Just a question about Field fraction of focused SCA: what do you mean by receiver control defocus? What is it phiysical meaning?
This is the most suitable result to analyze the defocusing fraction, right?

Is there any possibility of contacting you in another way, if you could help me to validate the model I am studying, given that my scale is quite small?

Best regards,
Bernardo.

Hi Bernardo,

I revised my original reply above to add clarification of "plant defocus control" and "receiver defocus control."

This forum is the best way to contact us. You can also This email address is being protected from spambots. You need JavaScript enabled to view it. us.

We don't have the resources to provide a detailed review of your .sam files, but can answer specific questions about your analysis.

Best regards,
Paul.

Hi Paul.
Thank you for your answer, now I am enlightened.

I have my model almost finished, but I am dealing with some errors when simulating. 
Seeing the results, especially the "Field fraction of focused SCA", most of the times that the field defocus because the máx single loop flow rate was achieved (6kg/s), as you said, " That suggests that the field is is defocusing because of receiver mass flow / temperature constraints". I tried to increase that value to 12 kg/s and the model doesn't run due to an error... I am not understanding why it happen... I tried to increase this value to not have so much waste due to defocus.

My model just have 1 single loop, the "header design min/max flow velocity" doesn't necessarily have to be the same of  "min/max flow velocity" because the diameter of the header piping is not the same as diameter of the receptor, right?

Please, find the program attached if you could take a look...

Best regards,
Bernardo.