Thermal energy absorbed and Solar field thermal output

Hello

I am trying to simulate a parabolic trough collector thermal plant. I have been studying the results from SAM and I understand the sequence of calculus of thermal parameters but I have still some doubts with some of these parameters:

1. I would like to know how is obtained the parameter “Thermal energy absorbed”. I have calculated this parameter with the following formula:

Thermal energy absorbed = Total incident thermal energy * Collector average optical efficiency - Receiver thermal losses

Nevertheless, I have found some differences among my results and SAM. What other parameters are used to obtain “Thermal energy absorbed”?

2. I don’t understand the step between the “Thermal energy absorbed” and “Solar field thermal output”. I see that “Solar field startup energy” affects to the value of “Solar field thermal output”, but it is not the only parameter that affects. What is the “Solar field startup energy”? What other parameters affect to the “Solar field thermal output”?

I am working with the version 2012.5.11

Best regards

Igor

Dear Igor,

For SAM's physical trough model, you can refer to the Technial Manual for the SAM Physical Trough model for an explanation of the energy calculations. For a link, see the citation under Concentrating Solar Power (CSP) Models on the Performance Models page of the SAM website.

You can also study the source code itself. The source code files are in the SAM installation folder, and are listed for each CSP model in the model's overview topic in Help. For example, for the physical trough model, you can find the list of source code files in Help under Concentrating Solar Power, Parabolic Trough Physical, Trough Physical Overview.

Best regards,
Paul.

Dear Paul

I have read the Technical Manual and part of the code but I have still the same doubts.

I think that I have understood the physical meaning of the parameter "Thermal energy absorbed": is the thermal energy absorbed by the collectors, before thermal losses and including optical losses. Nevertheless, I can't fit my results with those of SAM.

Moreover, I don't understand the parameter "Solar field thermal output". I have studied the results from SAM and it seems that "Solar field thermal output" is, more or less, the Thermal energy absorbed less the Solar field startup energy and the piping losses. What is the meaning of the Solar field startup energy? Why it has values different from 0 during the day?

Can you explain me these parameters? I have found no answer in the manual. Please find attached an Excel spreadsheet with my calculations and my differences with SAM.

Thanks in advance

Igor

Dear Paul,

I continue with my doubts. I think that I can't fit my results with those of SAM due to the defocusing of the colector.

Nevertheless, I continue ignoring what is the meaning of the "Solar field thermal output", where is this parameter measured in a solar plant.

Thanks in advance

Igor

Dear Igor,

The solar field thermal output is the thermal energy at the solar field outlet:



Best regards,
Paul.

Hi Paul,

I have read "Technical Manual for the SAM Physical Trough Model." Wagner, M. J.; Gilman, P. (2011).
and this other

"Draft CSP Reference Manual" Friday, December 05,2008 ( www.nrel.gov/analysis/sam/pdfs/sam_csp_reference_manual_2.5.pdf ); but it doesn't the same than the actual version, because of the change of the names of the results.

Could you recommend me an actualized article about the SAM's results?; I don't know where I could found the warm up of the solar field and the meaning and formulation of these others parameters:

1. “Thermal energy absorbed (MWh), hourly”. Is it correct that Igor says?...Is it the energy that is absorbed by collectors?....and why is negative?

2 How I could calculate the warm-up energy of the solar field?

3 And the energy that is necessary to start up the power block?...I only can see the "Solar field startup energy (MWh), hourly"......


Pt: I want to see the results formulation and it's meaning

Please give me clear answers

Regards