Location and Resource#
The Location and Resource page is where you choose a weather file for the simulation. It provides access to the solar resource library and tools for downloading files from the National Solar Radiation Database (NSRDB).
The solar resource library is a list of CSV files with valid and correctly formatted solar resource data. SAM builds the library from the folders that you identify as containing weather files. When you first install SAM, it comes with a few default weather files stored in the <user>/SAM Downloaded Weather Files folder that are automatically added to the library. As you use SAM for your own projects, you can add and remove folders to manage the library.
There are two ways to add weather files to your solar resource library:
Use the Download button or the Advanced NSRDB Options window to download files from the NSRDB and add them to your library.
Use the Add/remove weather file folders button to add files that are on your computer.
Tip
You may want to model your system using weather data for several different locations around your project site, and if available, from different data sources to understand how sensitive your analysis results are to the weather assumptions, and how much variation there is in the data from the different weather files.
You can compare results for a system using more than one weather file in a single case by using SAM’s parametric simulation option.
For a list of sources of solar resource data other than the NSRDB, see the Weather Data page on the SAM website.
For a helpful discussion of weather data and power system simulation, see the Best Practices Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications.
See also
Download Weather Files#
The Download Weather File options are for downloading weather files from the National Solar Radiation Database (NSRDB). For information about other sources, see the Weather Data page on the SAM website.
- Type an address or coordinates to download latest NSRDB data
Choose this option to download files from the latest available dataset for one location or for a list of locations. You can download a TMY file, a file for a specific year, or files for all available years.
- Use Advanced NSRDB Options window to access all available data
Choose this option to download 5-minute or 15-minute data for a specific year, or to download files from a specific NSRDB dataset. The Advanced NSRDB Options window displays a list of files from all available datasets for a given location that you can choose from to download. You can also download files directly from the NSRDB using the NSRDB Viewer.
- Download
The Download button is available when you choose Type an address or coordinates to download NSRBD data. Click the button to start the download after typing an address.
- Advanced NSRDB Options
The Advanced NSRDB Options button is available when you choose Use Advanced NSRDB Options window to access all available data. Click the button to open the Advanced NSRDB Options window.
The following inputs are only visible for the Type an address or coordinates to download latest NSRDB data option.
- Address or coordinates
Type a street address, city and state or country name, zip code, or latitude longitude pair. For example:
Golden, Colorado
golden, co
15013 Denver West Parkway, Golden CO 80401
80401
thimpu, bhutan
- File options
Choose the files you want to download from the NSRDB.
Default TMY file downloads a typical meteorological year weather file for the location or locations you specified. TMY data is appropriate when you are using simulation results for a single year to make cash flow calculations over a multi-year period.
Choose year displays a list of available years when you click Download so you can choose a single-year file to download. Single-year files are appropriate when you want to see how the system would perform in a particular year. For example, for a residential or commercial system, if you have measured building load data for a given year, you could use weather data for the same year to see how the system’s power output compares to the load.
Download files for all years (P50/P90) downloads a set of files for all available years. When you click Download, SAM creates a folder in your weather file download folder to store the single-year files based on the location address or latitude-longitude pair you typed. It also downloads the typical meteorological year (TMY) file for the location and stores it in your weather file download folder. SAM appends an underscore with the year to the single-year file names so that the P50 P90 simulations work correctly. See P50/P90 Simulations for details. If you choose to download files for all years with Multiple locations, SAM downloads a set of files for each location, and puts the files for each location in a separate folder.
- One location, Multiple locations
Choose One location to download a weather file for a single location. Choose Multiple locations to download weather files for more than one location.
- List of locations
The list of locations for the Multiple locations option. The button is disabled for the One location option. Click Edit data to open the Edit Data window where you can enter the list of locations. When the window opens, click Number of Values to enter the number of locations in the list, and then type or import a list of addresses and/or coordinates.
- 60-minute, 30-minute
Choose 60-minute to download weather files with hourly time steps or 8,760 data records. Choose 30-minute to download files with 30-minute time steps or 17,520 data records. This option is disabled for the Default TMY file option because TMY files contain hourly data. (To download 5- or 15-minute data, click Use Advanced Options window to access all available data).
- Show Download Log
Click this button to open the <user>/SAM Downloaded Weather Files/sam_nsrdb_download_log.txt file. This file is a running log of your NSRDB downloads and provides information that can be helpful for troubleshooting weather file downloads.
Note
Downloading multiple weather files from the NSRDB can take a long time. If you download files for multiple locations or years, be prepared to wait for the files to download. The download log file reports the time it takes for each file to download. Download times depend on your internet connection and computer. For a new computer with a fast connection, downloading and processing a single file takes about 10 seconds.
The NSRDB API on the NLR Developer Network that SAM uses for weather file downloads requires an email address to download weather file. When you download a weather file from SAM, SAM submits the email address that you used to register SAM.
When you download a file using the Type an address or coordinates to download latest NSRDB data option, SAM uses the NSRDB Data Query API on the NLR Developer Network to identify available NSRDB datasets for a the requested location, and then downloads a file from one of the following datasets depending on the location. For TMY files:
GOES TMY PSM v4.0.0
Himarawi TMY PSM v3
NSRDB Polar Typical Meteorological Year v4.0.0
Meteosat Prime Meridian TMY PSM v4
And, for single-year files:
GOES Aggregated PSM v4.0
Himawari 2016-2020 PSM v3
METEOSAT IODC Region PSM v3
NSRDB Polar v4.0.0
GOES Full Disc PSM v4 (only if files are not available for the location in GOES Aggregated PSM v4).
SAM uses the Mapquest geocoding service through a private NLR Developer Network API to identify the geographic coordinates (latitude and longitude) of a location when you type a street address or city and state name to identify the location.
Choose Weather File#
You can choose a weather file from the solar resource library, or you can disable the library and choose a file directly from a folder on your computer.
- Solar Resource Library
SAM’s solar resource library displays information from weather files in your solar resource data folders. As you use SAM, use Add/remove weather file folders to build a library of files for locations you frequently use as described in Folders and Libraries.
To choose a file from the solar resource library, click the location name in the list. You can type a few letters of the file name in the Search box to filter the list.
The solar resource library is disabled when you check Choose weather file.
Note
SAM comes with a few weather files that it loads when you create a new .sam file. These files are always in your library and are required for SAM to work properly.
- Weather file from library
The full path and file name for the currently selected file in the library.
- Add/remove weather file folders
Click the button to open the Solar Resource Data Folder Settings window where you choose folders on your computer that SAM scans to build the solar resource library. SAM adds any files it can identify as valid weather files in each folder you specify to the library.
Before adding a file to the library, SAM checks the data in the file displays a message if it finds any problems with the data in the file.
SAM only adds valid weather files to the library. If you add a folder that contains CSV files that are not in the SAM CSV format, it will not add those files to the library.
The list of solar resource folders are the folders that SAM scans for weather files to build the solar resource library.
- Refresh library
Refresh the library after adding files to the weather file folder. In most cases, SAM should automatically refresh the library as needed, but you do not see files you just added to the library, click the button to refresh it.
- Choose a weather file
Check this box to disable the solar resource library and enable the Browse button.
- Browse
When the library is disabled, click Browse to choose a weather file directly from your computer. SAM checks the file and displays a message if it finds problems with the data in the file.
Weather Data Information#
The weather data information variables display information about data in the current weather file.
- Weather File
The path and name of the weather file SAM will use for simulation.
- View data
Display weather file data in the time series data viewer.
Note
You can also see the data after running a simulation on the Results page data tables and time series graphs.
Header data is information in the weather file that describes the location and type of data in the file. SAM uses the following information from the header to calculate the sun position during simulations:
Latitude
Longitude
Time zone
Elevation
Time step is the temporal resolution of the weather file in minutes.
Location and Data Source are optional items that provide information about the source of the data that SAM does not use.
When you add a weather file to the solar resource library, SAM reads weather data from the file and calculates annual values to display for your reference. It does not use these annual values during simulations.
- Global horizontal, Direct normal (beam), Diffuse horizontal
The sum of solar irradiance data (W/m 2 ) in the weather file converted to kW and divided by 365 days/year.
- Average temperature
The sum of temperature data (°C) in the weather file divided by the number of records in the file (8760 for hourly data).
- Average wind speed
The sum of wind speed data (m/s) in the weather file divided by the number of records in the file (8760 for hourly data).
- Maximum snow depth
If the weather file contains snow depth data, the maximum value of snow depth data (cm) in the weather file. NaN indicates the file does not contain snow depth data. Snow depth data is required for to model snow losses for the Detailed Photovoltaic and PVWatts models.
Note
If your weather file does not contain snow depth data, and you are using the Detailed Photovoltaic model, you can download data from the Soiling Shading Snow page.
- Annual albedo
If the weather file contains albedo (ground reflectance) data, the average value of albedo values in the weather file. NaN indicates the file does not contain albedo data.