SAM's solar resource library displays information from weather files in your solar resource data folders. The default solar resource library that comes with SAM contains weather files for a few locations around the United States for the default configurations. 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 full file name and information about the selected file appears under Weather Data Information. To see the data in the file, click View data.

Add/remove weather file folders

Use the folder settings to tell SAM what folders on your computer it should scan for weather files 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 will only add 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 may need to manually refresh it.

SAM can download weather files from the National Solar Radiation Database (NSRDB) Physical Solar Model (PSM) datasets:

•Type an address and click Download and add to library to download TMY (typical meteorological year) data.

•Check Advanced download and click Download and add to library to choose from all files available from the NSRDB for your location, including file with subhourly data, files for different years, and files from different datasets.

To download a TMY weather file for a single location:

1.Replace the text "Type a location name, street address or latitude and longitude" with 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

2.Click Download and add to library.

For more instructions to download multiple files, see Weather File Download Instructions below.

SAM converts the address you type to a latitude and longitude pair for the location, and submits that information to the NSRDB along with your email address. If the location is in the region covered by the NSRDB, it returns a weather file in the SAM CSV format, and adds it to your weather file download folder. Otherwise, it displays a message telling you the location is not covered by the NSRDB.

When you first install SAM, it creates the SAM Downloaded Weather Files folder and assigns it as your weather file download folder. You can change the weather file download folder by clicking Add/Remove weather file folders. See Folders and Libraries for details.

When the download finishes, SAM displays a prompt asking you if you want to open the weather file download log. This prompt is the indication that the download finished. During the download and before that prompt appears, SAM may become unresponsive. If it does, wait for the prompt to avoid interrupting the download.

The weather file download log is a text file that SAM creates in your weather file download folder, and serves as a record of all of the files you download from the NSRDB. For each download, it lists the date and time of the request, the information you provided, the URL SAM generated, the name of the file returned by the NSRDB, or error messages it returns if the download fails. This information is useful for troubleshooting weather file download problems.

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.

One location, Multiple locations

Choose One location to download a weather file for a single location.

Choose Multiple locations to submit a list of locations and download a file or files for each location. For Multiple locations, click Edit data to open the Edit Data window where you can enter the list of locations and click Number of Values to enter the number of locations in the list.

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. Thirty-minute data is not available for the NSRDB SUNY International dataset.

Download options

Default TMY file

Download a typical meteorological year weather file for the location or locations you specified.

Typical year 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

Choose a single year file to download. After you click the Download button, SAM prompts you with a list of available years for each location you requested to choose a year.

The single year option is 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.

If you use both Choose year and Multiple locations, SAM prompts you for a year for each location.

SAM queries the NSRDB to generate the list of available years. The list of available years varies between regions.

Download files for all years (P50/P90)

Download a set of single-year files covering the range of historical data (nineteen files for 1998 through 2017 as of October 2018 for PSM data). 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 file name 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. Note that this may take a long time.

Weather File Download Instructions

Examples of valid street address or latitude-longitude pairs:

•golden colorado

•golden, co

•15013 Denver West Parkway, Golden CO 80401

•80401

•39.75, -105.15

•Super Market, F-6 Markaz, Islamabad, Pakistan

•New Delhi, India

Note. When the download finishes, SAM displays a prompt asking you if you want to open the weather file download log. This prompt is the indication that the download finished. During the download and before that prompt appears, SAM may become unresponsive. If it does, wait for the prompt to avoid interrupting the download.

To download an hourly typical-year (TMY) weather file from the NSRDB (use this option for most situations):

1.Click One location.

2.Type either a street address or latitude-longitude pair.

3.Click 60-minute.

4.Choose Default TMY File.

5.Click Download and add to library.

To download files for more than one location:

1.Click Multiple locations.

2.Click Edit data.

3.In the Edit Data window, click Number of Values and type the number of locations to create a table with a row for each location.

4.Type a street address or latitude-longitude pair in the table for each location.

5.Click OK.

6.Choose a time step, 60-minute for hourly, or 30-minute for 30-minute data.

7.Choose the type of file(s) you want to download as described below.

8.Click Download and add to library.

Weather File

The path and name of the active weather file SAM will use for simulation. Download a different file from the NSRDB, or click a different file name in the library to change the file.

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 from Weather File

Header data is information in the weather file that describes the location and type of data in the file. SAM uses the time zone, elevation, latitude and longitude to calculate the sun position during simulations. It does not use the city, state, country, and other descriptive information.

Annual Values Calculated from Weather File

When you add a weather file to the solar resource library, SAM reads weather data from the file and calculates the annual values to display for your reference. It does not use annual values during simulations.

Global horizontal, Direct normal (beam), Diffuse horizontal

The sum of solar irradiance data (W/m2) 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. For information about where to find weather files with snow depth data, see the note on the Weather Data page of the SAM website.

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.

The NREL National Solar Radiation Database (NSRDB) is an online database of weather files containing solar resource data in the SAM CSV format. Files are available both as typical-year files and single-year files. The database covers the parts of the world shown in the map below. The current data is called PSM (Physical Solar Model).

Important Note for CSP Modelers! SAM's CSP models assume that each DNI value in the weather file represents the average irradiance over the time step, and calculate sun angles for the midpoint of the time step. For hourly weather files from the NSRDB, the irradiance data for each time step is measured instantaneously at the time indicated by the minute column. For hourly data, minute = 30, so the irradiance data is measured at midpoint of each hour. For subhourly data, the irradiance data is measured at the beginning of each time step. As a result, if you use an NSRDB weather file with a CSP model with subhourly data, the sun angle for each time step will be for a different time than the time for the instantaneous irradiance values. See Time Convention and Sun Position for additional details.

Notes.
 
The NSRDB 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. NREL uses your email address to determine how many people are using the NSRDB. It does not share email addresses.
 
SAM uses the Google Maps API Geocoding Service service 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.
 
For information about downloading weather files and data from other sources, see the Weather Data page on the SAM website.

SAM downloads weather files with the following hourly data from the NSRDB:

•Direct normal (beam) irradiance, DNI (W/m²)

•Diffuse horizontal irradiance, DHI (W/m²)

•Dry-bulb temperature (°C)

•Dew-point temperature (°C)

•Relative humidity (%), for single-year files only

•Atmospheric pressure (mbar)

•Wind speed at 2 meters above the ground (m/s)

•Wind direction (°E of N)

•Albedo

Note. Weather files with snow depth data for the Detailed Photovoltaic model are not available from the NSRDB PSM dataset. They are available for 239 locations in the United States from the legacy MTS1 (TMY2) files in the original format, which cover the period 1961 - 1990. See Snow Losses for details.