Inquiry regarding pump behavior with full TES in CSP plant simulation

During my simulations using SAM 2022.11.21 for a CSP plant with a solar tower and molten salt TES, I observed an unexpected behavior. Despite programming the control system for a maximum load equal to the nominal value (for the power block), I noticed that when the hot tank reaches full capacity, the pumps exhibit a slightly higher flow rate than the nominal setpoint (See attached figure. Mass flow TES cold out in blue, Mass flow TES hot out in orange, and TES charge state in brown). I am curious to understand the reasons behind this phenomenon. Are there specific considerations, whether related to performance, costs, or other factors, that could explain or justify this behavior?

 

Dear Paul

Thank you for your prompt response.

Unfortunately, I am unable to share the simulation files due to constraints related to a non-disclosure and confidentiality agreements associated with the project.

However, upon further investigation, I discovered that the parameter "maximum turbine over design operation" in "Power cycle" tab was configured with its default value of 1.05. Subsequent to modifying this parameter to 1, the observed issue was resolved. It is noteworthy to mention that I am uncertain if this parameter is directly linked to the control strategy, but its adjustment appeared to have a significant impact on the observed behavior.

I hope this information proves helpful in further questions.

Best regards.