Solar Resources
Use this section to load solar resource data to be used in energy yield calculation. Multiple datasets can be loaded though only one can be used at a time for an individual energy yield calculation.
You can import solar data from one of various supported file formats. Or download the data using one of the online APIs that we currently support.
Importing Solar Data from a File
File Formats
The following file formats are currently supported by SolarFarmer:
- Meteonorm PVsyst Hourly TMY (
*.dat
) - NSRDB TMY3 (
*.csv
) - SolarAnywhere TMY3 (
*.csv
) - SolarGIS database TMY (
*.csv
) - SolarGIS database multi-year (
*.csv
) - Tab separated variable, free-format file (
*.tsv
) - Tab separated variable, Date | POA | Temp | (WS) (
*.tsv
) - Tab separated variable, Date | DHI | Temp | (WS) (
*.tsv
) - Tab separated variable, Date | GHI | DHI | Temp | (WS) (
*.tsv
) - Vaisala TMY and long-term formats (
*.csv
)
Terminology
The following table defines the acronyms used on this page:
TMY | Typical Meteorological Year |
NSRDB | National Solar Radiation Database |
POA | Plane of Array (W/m²) |
DHI | Diffuse Horizontal Irradiance (W/m²) |
GHI | Global Horizontal Irradiance (W/m²) |
Temp | Temperature (°C) |
WS | Wind Speed (m/s) |
Site Meta Data
When you select a file with one of the known formats, the latitude and longitude are displayed along with the time zone. You can adjust the time zone which is used to help SolarFarmer adjust the time stamps if necessary so it is valid for your site location. This is especially useful for tab separated variable files that do not contain latitude and longitude.
Solar Resource Resolution
You can use sub-hourly resolution for the energy calculation - you are not limited to hourly resolution.
Warning
The thermal model used in the energy calculation assumes steady state and may lose accuracy when it is less than 5-minute resolution. It is therefore recommended that you use at least 5-minute resolution.
This restriction will be addressed in future releases.
Be aware that using sub-hourly resolutions will also take the calculation longer to complete as the number of time-steps is greater than if you used an hourly resolution.
Validation Warnings
You will be notified of any validation issues after the import is complete.
Tab Separated Variable Files
There are four options to upload tab separated variable files. Read the directions in the upload window for required format and units. Here is a quick summary:
- Header rows are ignored
- IMPORTANT - Use the ISO 8601 date-time format YYYY-MM-DD hh:mm:ss (for example 2019-12-17 11:16:01)
- Use hyphens between the year, month and day
- Use colons between the hour, minutes and seconds
- Timestamps should correspond to the beginning of the interval
- The order of the columns must be one of the following:
- Date-time, POA, ambient temperature, (wind-speed)
- Date-time, GHI, ambient temperature, (wind-speed)
- Date-time, GHI, DHI, ambient temperature, (wind-speed)
- GHI and DHI are in W/m²
- Ambient temperature is in Celsius
- Wind speed is optional (use units of metres per second)
- Only use tabs as delimiters between the data columns; no commas or spaces
- Use a full-stop period for a decimal point; do not use commas
- You can specify the timezone after the file selection to make sure that the data, sunrise, solar noon, and sunset, are within expected tolerance
- It there are any anomalies in the data, such as diffuse greater than global, then they will be reported and/or corrected
How to use Excel to reformat your date time column
If your date times are in a different format to the expected one you can use Microsoft Excel to reformat them.
Load your text file into Excel
Highlight the data in the date/time column (select the column header to select them all)
Select 'Home' from the menu bar and then 'Number' from the ribbon:
Expand the Number Formats pull down menu and select 'More Number Formats...'
Select Custom and enter Type as
yyyy-mm-dd hh:mm:ss
Now use 'Save As' from 'File' in the menu bar to save the data as tab-separated:
Downloading Solar Data from Online Sources
You can download solar resource data from various online sources directly into your SolarFarmer workbook.
Note
Online sources that we support are currently a bit limited. Please let us know which other sources you would like to be supported and we'll do our best to add them soon.
Currently supported sources
Source | Description |
---|---|
Solar Resource Compass | This is a DNV service (running in a web browser) that accesses and compares irradiance data from multiple data providers and allows you to see how they compare for your project location. See https://src.dnv.com for more details. Once you purchase and download your chosen data (currently in Meteonorm PVsyst Hourly TMY ( *.dat ) format) you can import the downloaded file into SolarFarmer via the Import button. |
PVGIS TMY | PVGIS is a free online source of solar data that now covers all of the world. It is implemented by the JRC (Joint Research Center) from the European Commission's in-house science services. See their main website for more details: https://ec.europa.eu/jrc/en/pvgis and a map of areas of the world that they support: https://re.jrc.ec.europa.eu/pvg_tools/en/#TMY A new version (5.2) was released in March 2022. This contains updated databases and coverage for the whole world. However, there is still a known issue for version 5.2 that some coastal areas can show values of zero (or close to zero) for variables such as temperature, wind speed, wind direction and humidity (see PVGIS 5.2 and scroll down to 'Known Issues'). It is recommended to use the latest 5.2 version. But if you see the above problems, use version 5.1 (if it is available) for your site. |