Time Step for SAM Model Simulations

Dear Paul,

I developed a code for calculating the absorbed energy of a full tracker panel. My Perez model equations are the same as SAM. The problem is that SAM full 2 axis tracker seems to be 12 points tracker not a full two axis tracker when it uses hourly data. As you said, SAM calculates each sub array surface angles for each of the 8760 hours of the simulation. For systems with trackers, the surface angles in a given hour are fixed over the hour. My calculation with time step 24 seconds shows that the annual energy will be increased by about 9 percentage in comparison with SAM two axis tracker with 1 hour time step. Also, I input hourly radiation data from SAM to my code and set the time step to 1 hour, my code matched with SAM by about 0.5 percentage difference. Hope it clarifies my question.

Best regards

Hi Paul,

Do you know of any free sources of 15 minute weather data?

Lars

Dear Lars,
I don't know of free sources of 15-minute data, but NREL's new National Solar Radiation Database (NSRDB) now offers free 30-minute data for the U.S., parts of Canada, Central and South America, and a large region surrounding India:
nsrdb.nrel.gov/
The next version of SAM (due for release any time now) will download hourly data from this new database.
Best regards,

Paul.

Dear Paul;
By searching through the documentation and forum related to SAM, i found that SAM kernel use TRNSYS libraries consequently SAM must normally be able to do purely dynamic simulation, however i can't find any application or example illustrating that SAM can be used to perform purely dynamic simulation. I wonder if i can do this kind of simulation with SAM or not?
Best regards
Jaouad

Dear Jaouad,

SAM 2014.1.14 is the newest version to use TRNSYS components (for the concentrating solar power models only). More recent versions of SAM are written in C++ and use the SAM Simulation Core (SSC). For information about SAM's source code, see sam.nrel.gov/opensource .

SAM has always been a techno-economic model designed to generate reasonable estimates of hourly, monthly, and annual electric power generation for use in a financial model. It runs time series simulations (hour-by-hour, or subhourly down to one minute time steps), so does not model electrical or thermal transients that occur on smaller time scales.

Best regards,
Paul.