POA Decomposition Model

Hi 
I am working on inputting actual 1 minute POA data for the month of June.  I created a file for 1 minute time series annual data that I pasted in my June values (see attached). However, I keep getting POA decomposition model calculated negative direct normal irradiance at each time stamp and either the simulation fails or the results assume zero POA irradiance and negative annual energy.  I have set PV Albedo and Radiation option on the Location and Resource page to "POA from pyranometer".  Not sure what else I am missing. I tried using time series PSMv3 data from the location and interpolating to 1 minute to create the file for my data but that was throwing a 303 error so I used a file from a different location but updated my June data, time zone, lat and long.

Thank you, 
Beth

Hi Beth,

See this GitHub issue for more information about the errors: github.com/NREL/SAM/issues/610

SAM requires a weather file with a complete year's worth of data. The file you attached only had data up to June, so I was not able to test it.

Best regards,
Paul.

Good morning

I got the same problem. I have a weather file with POA as input, but SAM are not decomposing this data to DHI and DNI. My POA data is from a pyranometer, so I'm checking the checkbox "POA from pyranometer".

I've read the solution on github, but I didn't get where I have to change in my weather file? I tried to set to zero values under 200, it didn't work. I did the same thing to time steps with low sun angles, but also didn't work. As result I get a negative energy production. I say change something in the weather file because I used the file "phoenix_az_fake_poa" from github issue #610 and it worked, but to mine ("FVT.-5.249.-37.974.RMY.00M_SAM_1hr") it doesn't. Feel comfortable to simulate with those files. The system's sizing is indifferent.

Could you help me?


Best regards

For the POA from pyranometer option on the Location and Resource page, SAM requires atmospheric pressure data in the weather file in addition to ambient temperature, wind speed, and POA irradiance data.

This is for a correction to the air mass during spring and summer in the northern hemisphere when the sun rises north of east and sets north of west.

Best regards,
Paul.

Hi Paul,

While importing POA irradiance data from a reference cell i encountered some production non correlating to the irradiance data.
I suspect this has something to do with the decomposition into DHI and DNI. Could you please guide what could be the steps to resolve this issue?

Steps followed so far:
1. Download a hourly TMY file for a location in Denmark 
2. Interpolate it using the Macro in SAM to 15 min resolution.
3. Add a column "poa" to this weather file which has the measured 15 min data from pyranometer (Only until mid April 2023)
4. Filled the remaining dataset (for rest of the year) with values of GHI from the existing weather file, so that we have "poa" data for a complete year.
5. Under "Albedo- Sky Diffuse Model - Irradiance Data (Advanced)" tab, selected "Weather File Irradiance Data" as "POA from reference cell"
6. Production spikes were seen during late evenings even though measured POA had no spikes. Although the calculated DHI and DNI had spikes. What is causing this and how to fix this?

Hi Pradeep,

Would it be possible for you to share the files that are generating these results. I can't replicate this issue without knowing the location in Denmark (particularly the latitude) and without the TMY file and POA data you are using.

If you prefer not to share the data on this public form, you can email them to the This email address is being protected from spambots. You need JavaScript enabled to view it..

Best regards,
Paul.