Types of Solar Radiation
The solar radiation reaching the Earth's surface, known as global radiation, consists of three main components:
- 1 . Radiation directe – L'énergie solaire qui atteint la surface de la Terre sans dispersion.
- 2 . Radiation diffuse – La lumière solaire qui est réfléchie ou dispersée par l'atmosphère.
- 3 . Radiation réfléchie – L'énergie solaire réfléchie par le sol ou les obstacles environnants.
In clear sky conditions, solar radiation reaches its maximum level, which is crucial for modeling photovoltaic production in PVGIS.COM.
Estimating Solar Radiation: Ground Measurements vs. Satellite Data
Ground Measurements: High Accuracy but Limited Coverage
The most accurate way to measure solar radiation is through high-precision sensors , but this requires:
- Regular sensor calibration and maintenance
- Frequent measurements (at least once per hour)
- Data collection over at least 20 years
However, ground measurement stations are limited and unevenly distributed, making satellite data a more reliable alternative.
Satellite Data: Global Coverage and Long-Term Analysis
Weather satellites like METEOSAT provide high-resolution images covering Europe, Africa, and Asia , with historical records spanning over 30 years.
Advantages of Satellite Data
- Available even in areas without ground measurement stations
- Data updates every 15-30 minutes
- Reliable estimations based on cloud, aerosol, and water vapor analysis
Limitations of Satellite Data
Possible inaccuracies under certain conditions:
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- Snow may be misinterpreted as clouds
- Dust storms can be difficult to detect
- Geostationary satellites do not cover polar regions
To compensate for these limitations, PVGIS.COM also integrates climate reanalysis data for regions not covered by satellite observations.
Methods for Calculating Solar Radiation in PVGIS.COM
PVGIS.COM uses advanced algorithms to estimate solar radiation based on the following data sources:
- PVGIS-CMSAF and PVGIS-SARAH – Data for Europe, Africa, and Asia
- NSRDB – Solar radiation database for North and Central America
- ECMWF ERA-5 – Climate model data from global reanalysis
Calculation Process
- 1 . Analyzing satellite images to determine cloud cover
- 2 . Modeling solar radiation under clear-sky conditions , considering the effects of aerosols, water vapor, and ozone
- 3 . Computing total solar radiation using cloud reflectivity data and atmospheric models
Potential Sources of Error
Snow may be mistaken for clouds , leading to underestimated radiation values
Sudden changes in aerosol levels (e.g., dust storms, volcanic eruptions) may not be immediately detected
Data Sources and Availability in PVGIS.COM
METEOSAT Satellites – Provide hourly data for Europe, Africa, and Asia.
ECMWF ERA-5 – Global climate data reanalysis.
NSRDB – Solar radiation database for North and Central America.
These data sources allow PVGIS.COM to offer near-global coverage for solar radiation estimates and enhance photovoltaic simulations.
Conclusion
Advancements in satellite remote sensing and climate modeling enable PVGIS.COM to provide highly accurate solar radiation estimates, helping solar energy professionals optimize their PV installations.
Benefits of PVGIS.COM
Reliable data from satellite and climate models
Accurate simulations for each region to estimate solar energy production
Advanced tools for researchers and engineers in solar energy analysis