Are all irradiance databases the same?

☀️ You've probably heard phrases like "The best irradiance database for Europe is PVGIS!" or "The best database is NASA's because no one knows more about satellites than Americans!".

The first thing we need to know is that both PVGIS, NSRDB, and NASA offer access services to their databases. These databases are calculated from satellite images from different sources and apply different validated models to infer the irradiance reaching the Earth's surface.

This means that even though they all "do the same thing," they all do it differently.

So... What's the best database?

To answer this question, we conducted a study comparing the annual global insolation of different databases with the insolation recorded by 37 ground-based meteorological stations throughout Spain (AEMET).

According to these results, PVGIS offers meteorological databases with the lowest average error in Spain.

Furthermore, both NASA and NSRDB do not take into account the distant horizon for direct irradiance calculation, so for locations with geographic features that create shadows, it is necessary to calculate and include that profile in the simulations.