Creating a Site-Specific TMY3 Weather Input File for SAM

Aloha and thanks so much for the prompt response, Paul! Your plots helped me figure out what I was doing wrong with DISC input, and now the output seems more reasonable -- see initial sanity check attached.

One remaining issue is the time-step used for creating a TMY3 data file. I set up my site weather station to output 15-minute averages of GHI, and in a spreadsheet I average the four periods to get hourly data, then I use the ending time of the hour as the time-step (i.e., the average of 1215, 1230, 1245 and 1300 data is logged against hour 1300). Solar noon here runs from around 1238 to 1246, so I thought that particular time-step convention would be a good approximation, but every now and then DISC calculates a negative value for DNI. I suspect the issue arises because the time-step of my GHI database is not completely synchronized with the sun position calculations in DISC. I'll fool around with my database averaging times (or maybe just use the xx45 data) to see if I can get the negative numbers to go away, but if you have any thoughts on that please let me know.

The next question (re SAM required inputs) is how to derive DHI from GHI and DNI? Is DHI = GHI - DNI? Or is DHI = GHI - (DNI*cos sun angle)? Or something more complicated?

Thanks again for all your help!

Denning

Denning - did you try selecting "Total and Beam" on the Array page? I think that that will permit you to use GHI and DNI.

"** For the PV Component model, the Radiation Components settings on the Array page determine whether
SAM uses the diffuse or global horizontal radiation value. By default, SAM uses the beam and diffuse
components and ignores the total horizontal radiation from the weather file."

Curt Elmore

Hello Sir paul, I have a question,  How can we use a solar database like (NASA-SSE, Meteonorm, Helioclim...) as an input for System Advisor Model (SAM) software?? because i need it for my thesis about CSP technology in Morocco, Ouarzazate, because as you know i can't find it in SAM, the only USA's data is available,  if u help me i will be very thankful...?

Dear loubaba,

You can use weather data from any source, as long as it is in a file that uses a format that SAM can read.

The easiest format to use is the SAM CSV file because you can easily create and modify it using a spreadsheet program or text editor.

For a description of the SAM CSV format, please see the SAM Help system.

Best regards,
Paul.

Paul / Ioubaba

I've been creating solar weather files in a format acceptable to SAM - either SMW or CSV format - using NASA MERRA data as input. Happy to share my approach if you're interested.

Kind regards

Angus

Hello sir

Thank you so much for reply, Can I have the link directly of the function on which i have to work in, for creating the TMY files, because I got the data from Ouarzazate PVGIS and I do not know how to enter it in the SAM Software, the PVGIS data is given as a html file...