Thermal Application of PTC field with thermal storage + a question about freeze protection

Hello Paul!

I am using SAM to see the thermal energy output of a parabolic trough field with thermal storage system.
I have read your answers to similar questions in the forum. I noticed that in most cases, there was only a PTC field with no storage.
What I understand from your responses is: For a PTC solar collector field without storage, if I choose a big power block compared to my solar field, the effect of power block start-up/ shutdown and solar field defocusing would be negligible. Therefore I can use the value of solar thermal output as thermal energy from the solar field.
- What about my system that has a thermal storage, does above apply? If not could you give me some advice please?
- Another question is about freeze protection. Does this temperature have any relation with climate? For my case which is in Australia, should I consider Lower temperature or 150 C is a typical value applicable for all different locations?
Thank you for your kind help!
Fouri

Fouri,

I checked with our CSP engineers and they gave the following response to your questions:

If the goal is to run SAM only to get the solar field thermal output, then either oversizing the steam turbine or vastly oversizing the storage should have roughly the same effect. (I would recommend the thermal storage method because you need to be careful in the case where the powerblock is oversized so the "min fraction" isn't tripped at DNIs that still produce useful solar energy). For any case where the user is interested in the system behavior, then they need to carefully consider both thermal storage and powerblock inputs.

The freeze protection temperature is only a function of the HTF.

Hope this helps,
Steve

Thanks Steve.
I tried to use the turbine over sizing method as my system has thermal storage and I can not go for that option. However I am having continuous errors and the model does not converge.Could it be because of the fact that this method only works for systems without storage?
Thanks.

Dear Fouri,

Would you mind attaching a copy of your SAM file to your original post (click Edit to add the attachment)? I can try to troubleshoot the file for you.

Best regards,
Paul.