Unresolvable NaN error in the heat loss calculations

Hi,

When I run the attached model using the attached weather file (from  energyplus.net/weather ), I get the error "unresolvable NaN error in the heat loss calculations". However, I don't get this error using the default weather files in the SAM solar resource folder. The following are my questions:
1. Can you check if the format of the attached weather file is accurate?
2. Are there any templates, which follow the required order of rows/columns in the weather data, for different file types (TM2, SRW, EPW, CSV, DDY, STAT, etc) ?

Thanks

Hi Michael,

The format of the EPW file you attached is fine, but there may be a problem with the atmospheric pressure values in the file. You can use a couple of SAM macros to confirm that (click Macros under the Simulate button):

• The "Solar Resource File Checker" macro works with files in the SAM CSV, EPW and the old TMY2 and TMY3 file formats and runs some checks on the data to help identify problems.
• The "Solar Resource File Converter" macro converts files from EPW, old TMY2 and TMY3, SolarAnywhere, PVsyst CSV and PVGIS V5 CSV formats to the SAM CSV format, which can be a little easier to work with than the other formats.

The EPW file format is described in the EnergyPlus documentation "Auxiliary Programs" PDF.

The SAM CSV format is described in SAM's Help system, under Weather Data, Weather File Formats.

SAM's CSP models generate a simulation warning if there is a problem with a calculation in each time step. If there are only a handful of warnings for the 8,760 hourly time steps, you can usually ignore them.

Best regards,
Paul.

Hi Paul,

Thanks for your reply. The EPW weather file (attached to my 1st post and downloaded from energyplus.net/weather) is the same as the weather file used for the case using SAM 2013.1.15 in your website. Can you explain why the atmospheric pressure hourly values "DO NOT" affect the model results in SAM 2013.1.15 but "DO" affect the results in SAM 2018.11.11 ?

Michael

Hi Michael,

We made some changes to the Physical Trough model in SAM 2018.11.11 SSC 198 that are listed in the SAM release notes under that version name that involved pressure calculations.

I'll ask the CSP model developers if they can provide any additional insight.

Best regards,
Paul.