ReuniWatt data

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ReuniWatt data

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ReuniWatt ( provides hourly solar radiation and meteorological data derived from 5 satellites, worlwide, in the form of time-series and TMY files.
Data covers useful information for PVSyst:

Global horizontal irradiance (GHI or GlobHor)

Diffuse horizontal irradiance (DiffHor)

Direct normal irradiance (DNI or BeamNor)  

Wind Speed


Aerosol Optical Depth (AOD) - to be used in the future by PVSYST

Precipitable water (pw)  - to be used in the future by PVSYST


In the ReuniWatt irradiance dataset, please note that :

the effect of far shadings from mountains at sunrise and sunset is not included, which means that in mountaneous regions an horizon mask must be further applied in the project area of PVSyst.

the diffuse circumsolar radiation is included in the DNI component (direct normal), which means that the data is not compatible with the use of the Perez-transposition model.


ReuniWatt data are available for pay.


Details of the Method


ReuniWatt retrieves up to 15 years of data from the following geostationary meteorological satellites : Meteosat-10, Meteosat-8, GOES-E, GOES-W, Himawari-8.
The processing chain - developed internally- is based on the Heliosat-2 method, which was co-developed in 2004 by Reuniwatt’s Chief Scientific Officer, Dr. Sylvain Cros. Images from geostationary meteorological satellites’ broadband visible channel are used to retrieve solar irradiance at a world scale with a high spatial resolution going up to 1 km at nadir, with a sample time of 15 min. The general principle of such algorithms consists in comparing the reflectance observed at a given pixel with the reflectance from the same pixel under clear sky (cloud-free) conditions. A cloud index is computed from this difference. This cloud index is used as a linear attenuation factor of the simulated irradiance under clear sky. An internal clear-sky model is used during the post-processing chain. Processed data are recalibrated against ground stations.