PTGen/DELSOL3 intermediate results for CSP Power Tower model

Thanks Mike

I got It.
Thanks, Paul

Jingpeng Wang

Mike, Paul,
When comparing the avarage azimutal receiver flux values that come out from the DELSOL3 files (like DELSOL3_Flux_172_012.txt, whith the ones in the flux_map.csv / fluxmap.csv files, which are the ones used by the power tower model, I find a big discrepancy. The azimutal average DELSOL3 floxes do make sense, but the floxes in the flux_map.csv / fluxmap.csv do not make sense (they are about 207% the value from the DELSOL3 results, and above the maximum peak flux specified in the receiver (an for all azimutal positions!!).
If the info from the flux_map.csv / fluxmap.csv files is the one read in by the power tower model, I'm affraid there could be a significant error in thje results.
Is it a bug, or am I missing something?
Thanks

Xavier,

The values in the intermediate flux map file "fluxmap.csv" are not the final values that are used in SAM. This is a bit confusing, but our method for determining incident flux requires that we modify the flux values that go into SAM. Basically, we generate 96 flux maps to approximately represent the flux distribution on the receiver throughout the year. Each flux map is closely related to (but not exactly the same as) the adjacent flux maps so that we are able to approximate flux distribution by choosing the flux map that was generated at a sun position close to the one at any given time step throughout the simulation. Of course, the magnitude of the flux values during any time step does not necessarily correspond to the base values that were generated and put in the fluxmap.csv file before the annual simulation, so we scale the flux map according to the incident DNI and the actual field optical efficiency that's calculated during the time step.

In other words, the simulation process is: (1) generate 96 "representative" flux maps with DELSOL for the given field layout and plant location before the annual simulation. (2) Divide the values in the flux map by the reported field efficiency and the design-point DNI value, and save the values in fluxmap.csv. (3) Run an annual-hourly simulation, and calculate the field efficiency during each hour according to the table in "eff_array.dat". (4) Select the flux map that best represents the sun position during the current time step. (5) Scale the flux values by the calculated field efficiency and the current DNI value from the weather file.

Hopefully this clears up the confusion.

One note: in future versions, we will be changing the definition of the flux in the fluxmap file to be completely normalized (i.e. so that the values in each array sum to 1.). This should further reduce confusion and address a small discrepancy between the reported field efficiency value and the magnitude of the flux values in DELSOL. However, the process I describe here will remain roughly the same.

Mike

Dear Paul,

I can't access to the "version of PTGen with the option to save files" that you posted the 2012-06-23. Is it possible to post it again?

Best regards,
Clotilde