CSP Parabolic Trough Physical - SF HTF (Oil) Mass Flow Balance

Dear community:

I've been trying to close the SF HTF (Oil) mass flow balance ("Field HTF mass flow rate total" = "TES HTF mass flow rate - field side of HX" + "Cycle HTF mass flow rate") but I continuously get inconsistent results. The Excel file shared illustrates the issue, the balance is presented in column AJ.

Any idea of what is going on? Thanks!

Javier Pastoriza.

Dear Javier,

Please see this related posts and let me know if it resolves your question:

sam.nrel.gov/component/kunena/forum-general/1036

Best regards,
Paul.

Thanks Paul for your answer.

I understand SAM uses iterative algorithms and convergence error are part of them, that is natural. However, my query still remains given the relative error magnitude, at time step level, I can see on the SF HTF mass balance calculated using the variables presented in my initial query. I would like to take it forward differentiating different operation scenarios if you allow me.

(1) SF Off + TES Discharging + Cycle On: min rel. error = 0% / max rel. error = 0%
(2) SF On + TES Discharging + Cycle On: min rel. error = -0.10% / max rel. error = 0.09%
(3) SF On + TES Idle + Cycle On: min rel. error = -0.08% / max rel. error = 35.54%
(4) SF On + TES Charging + Cycle Off: min rel. error = 0% / max rel. error = 94.24% (single time step)
(5) SF On + TES Charging + Cycle On: min rel. error = -4.60% / max rel. error = 33.35%

The relative error size makes me think we are facing something else than convergence errors. I could be missing or misinterpretating the problem.

Warm regards.

Javier Pastoriza.

Hi Javier,

Attached is an Excel file that shows the mass balance for the physical trough model.

Best regards,
Paul.

Thanks Paul, the balance works fine in the file you shared, no question. May I know the software version used to get this balance?

Nevertheless, the balance issue I have presented can be easily replicated when using the version 2018.11.11 just running the default case of the Trough Physical Model.

Javier Pastoriza.

Hi Javier,

I believe my colleague used SAM 2021.12.02 to generate the data in the Excel file.

Best regards,
Paul.