Weather File Converter Error

Hi Aaron,

SAM's weather file converter macro algorithms for converting TMY3 format files are based on the format used for NREL's National Solar Radiation Database. TMY3 files from other sources may be different from the NREL format and cause the algorithm to fail. The SolarAnywhere "TMY3" format is different from the original NREL TMY3 format.

Please try running the Macro with Weather file to format set to SolarAnywhere instead of TMY3. The macro is designed to detect the SolarAnywhere version of the TMY3 format, so it should work to convert your file.

If that does not work, would you mind attaching a copy of the SolarAnywhere TMY3 file you are trying to convert?

Best regards,
Paul.

Hi Aaron,

I'm glad you found a solution. Please note that it is no longer necessary to download the LK script as described in the older post you linked to -- the Solar Resource File Converter macro in newer versions of SAM should handle that conversion from both the SolarAnywhere format and the "SolarAnywhere TMY3" format. I updated the old post to mention that as well. Sorry you had to go that effort.

As for your questions about file formats, I agree that it would be helpful to have a single standard format for all solar resource data. Even within NREL, the formats have changed over the years as computer and database technology has evolved.

There is a difference between the format of the file and the type of data it contains. Unfortunately, terms like TMY2 and TMY3 are sometimes used to describe a file format and sometimes to describe the data they contain. I will try to describe each below. They are described in more detail on the NSRDB website description of NSRDB versions  and description of typical meteorological year (TMY) .

NREL's National Solar Radiation Database (NSRDB) 1961 - 1990 update included typical meteorological year (TMY) files that were called "TMY2" to distinguish them from the TMY files distributed in the original NSRDB Version 1.1.  The TMY2 files are stored in .tm2 files and use a non comma-delimited text format where data is identified by its column position. The method used to develop TMY files was also different from Version 1. The NSRDB currently refers to this data as Meteorological Statistical Model (MTS) 1.

For subsequent updates to the NSRDB, called the 1991 - 2005 update and  1991 - 2010 update, the TMY files were often referred to as "TMY3". The TMY files for these datasets were stored in .csv files using a comma-separated format that we often call the TMY3 format. The NSRDB currently refers to these updates as MTS2 and MTS3. The method for developing TMY files in these updates was updated from the earlier method.

Finally, the current data from the NSRDB is called the Physical Solar Model (PSM) and is currently at Version 3, hence the name PSM v3. The NSRDB currently uses the same file format as SAM, which is a simple CSV format with column headings identifying the columns. In theory all of the legacy data should be available from the NSRDB in this simple CSV format.

The download tools on SAM's Location and Resource page are intended to give you access to all of the NSRDB datasets, but there are currently some issues with the database, so for now, only downloads for the PSM v3 work reliably.

As for downloading files from the NSRDB website, the PSM v3 tab is for downloading single-year data (as opposed to typical year data). The PSM TMY tab provides access to different typical year files.  Each tmy option has a year indicating the most recent year used to build the typical year file. So, "tmy-2016" is built from 1998 - 2016 data, and "tmy-2017" is built from 1998 - 2017 data. The text wrapping makes it look like the option is tmy-2 016, but it should be read as tmy-2016. By default, SAM downloads the latest TMY year, so the "tmy-2017" file should give you the same file as SAM.

Sorry that is all so complicated!

Best regards,
Paul.