the parabolic trough simulation result

Dear Paul Gilman,

Thanks and hope you have a nice day.

I think the energy from storage that will go to the power block at nighttime hours also comes from the energy produced by field, am I wrong and why?

if i am right, the sum energy to power block should be less than the sum energy produced by field because of heat loss.

Best regards

Lisen

Dear Lisen,

You are correct that all of the energy comes from the solar field, and that the energy delivered to the power block is less than the energy from the filed because of thermal losses.

Because the hourly "Cycle thermal input" includes both heat from the field and storage, the sum of the hourly values is greater than the sum of hourly "Field thermal power output." But, as you can see from the table, if you consider the hourly "TES thermal energy into storage," you can see why that is.

Best regards,
Paul.

Dear Paul Gilman?

Thanks for your quick reply.

We can see solar plant is charging into the storage and meanwhile generating electricity at the time of 1/2/2018 13:00 in the table you attached. But I am confused that "Field thermal power produced (MWt)" is less than "Cycle thermal power input (MWt)" plus "TES thermal energy into storage (MWt)",155.148

Dear Lisen,

In that time step, the power cycle starts operating. Because of the "Power block startup time" and "Fraction of thermal power needed for startup" inputs on the Power Cycle page, the power cycle does not operate at its full capacity because it needs time to warm up. The power cycle operates at 50% capacity during this startup hour, and the excess power available from the solar field goes into storage.

Best regards,
Paul.

Dear Paul

During power cycle startup periods, is the PC startup thermal power (MWt) sent to TES, since the power cycle is not consuming it?

I'm slightly uncertain where this startup power gets allocated to in SAM. If I understand correctly, the PC startup thermal power is subtracted from the "gross" PC input thermal energy in order to account for the fact that the power cycle will not be running at conditions output during a startup. 

I look forward to hearing from you. 

Best regards
Louw

Hi Louw,

This issue should mostly be resolved in SAM 2020.11.29, just released this week.

For the Physical Trough model, there is a remaining issue that we should have time and resources to fix for the next version of SAM: In time steps when the solar field starts up, the time series results show more field thermal power leaving in HTF than goes to TES or the power cycle. This is because SAM models trough startup as a "recirculated" process where the warm outlet goes back to the cold inlet until the outlet reaches a threshold startup temperature.

For this recirculated model to work, it sets the inlet properties equal to the outlet properties at the end of the previous time step. This means that during a given time step, the outlet will slowly heat, but the model has to “dump” that energy because the inlet temperature is fixed. The model minimizes the influence of this by dividing the hourly time steps into 10 minute intervals so it can reset the inlet temperature before the outlet drifts too far away. (This contributes to making the physical trough model slower than it might be.)
 
A solution to this problem is for us to create a new variable to show this dumped energy so that field thermal power leaving in HTF is consistent with TES and cycle energy streams.
 
A better solution would be to connect the trough output to the cold tank during startup and actually keep that heat in the system, but that would require more time and effort to implement than we have available for now.


Best regards,
Paul.