API field
Direct normal irradiance
Sunlight from the sun's disc on a surface facing the sun, per interval
Unit W/m²
What it is
The sunlight arriving straight from the sun, measured on a surface that faces the sun, averaged over each interval, in watts per square metre.
Typical values and how to get it
Up to about 1,000 W/m² at ground level under a clear sky, a little more at high altitude. The values come from the uploaded file. When the file has none, the parser derives it as the global minus the diffuse value, divided by the sine of the sun height at the middle of the sunlit part of the interval, with the sun height held at 5° or more. A PVsyst hourly export is rebuilt from its horizontal beam column and its own sun height, capped at 1,500 W/m² as a sanity limit.
References
- Sengupta, Xie, Lopez, Habte, Maclaurin & Shelby 2018, The National Solar Radiation Data Base (NSRDB), Renewable and Sustainable Energy Reviews 89 51–60
API
weather.dni