{"id":1775,"date":"2024-10-11T10:06:32","date_gmt":"2024-10-11T09:06:32","guid":{"rendered":"http:\/\/guemisa.es\/?post_type=documentos-pdf&p=1775"},"modified":"2026-11-03T13:42:35","modified_gmt":"2026-11-03T12:42:35","slug":"magnitudes-of-solar-radiation","status":"publish","type":"documentos-pdf","link":"https:\/\/guemisa.es\/en\/documentos-pdf\/magnitudes-radiacion-solar\/","title":{"rendered":"Measurement of solar radiation: magnitudes, pyranometers and pyrheliometers"},"content":{"rendered":"
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Technical tutorial \u00b7 GUEMISA<\/p>\n

Irradiance W m-2<\/span>Pyranometer<\/span>Pyrheliometer<\/span>Direct, diffuse and global radiation<\/span>Heliograph<\/span><\/div>\n
Quick response<\/b>Global solar radiation is the sum of the radiation direct, diffuse and reflected<\/b>. It is measured with pyranometers (global and diffuse, spectral range of 0.3 to 3.0 \u03bcm) and pyrheliometers (direct, on solar tracker); the recommended unit of irradiance is W m-2<\/sup><\/b>.<\/div>\n

Magnitudes of solar radiation<\/h2>\n
Magnitude<\/th>Definition<\/th>How is it measured?<\/th><\/tr><\/thead>
Direct radiation<\/td>It comes directly from the solar disk.<\/td>With systems to track the movement of the Sun<\/td><\/tr>
Diffuse radiation<\/td>It comes from reflections in the atmosphere<\/td>With solar disk shading systems<\/td><\/tr>
Reflected radiation<\/td>Radiation reflected by the surroundings of the receiving surface that strikes an inclined surface; its average value is 20% of the global radiation on a horizontal surface<\/td>It is not usually measured<\/td><\/tr>
Global radiation<\/td>Sum of direct, diffuse and reflected radiation received per unit area<\/td>It is usually measured on a horizontal surface; sometimes in the arrangement of the panels<\/td><\/tr><\/tbody><\/table><\/div>\n

95% of extraterrestrial solar radiation is between 0.2 and 3 \u03bcm. Terrestrial radiation is longwave: at 300 K, 99.99 percent of its energy has a wavelength greater than 3 \u03bcm.<\/p>\n

Units and spectrum<\/h2>\n
Magnitude<\/th>Recommended unit<\/th><\/tr><\/thead>
Irradiance (power)<\/td>watts per square meter (W m -2<\/sup> )<\/td><\/tr>
Radiant exposure (energy)<\/td>joules per square meter (J m -2<\/sup> )<\/td><\/tr>
Spectral irradiance<\/td>W m -2<\/sup> nm -1<\/sup><\/td><\/tr>
Spectral radiant exposure<\/td>J m -2<\/sup> nm -1<\/sup><\/td><\/tr><\/tbody><\/table><\/div>\n
Band<\/th>Interval<\/th><\/tr><\/thead>
Visible light (99% of visible radiation)<\/td>400 nm to 730 nm<\/td><\/tr>
GRAPE<\/td>315 to 400 nm<\/td><\/tr>
UV-B<\/td>280 to 315 nm<\/td><\/tr>
UV-C<\/td>100 to 280 nm<\/td><\/tr>
Shortwave extraterrestrial solar radiation (97%)<\/td>0.29 \u03bcm to 3.00 \u03bcm<\/td><\/tr><\/tbody><\/table><\/div>\n

Accuracy, precision, and integration period<\/h2>\n

Accuracy expresses the uncertainty in the agreement between the measured value and the true value. The precision of the instrument is determined by:<\/p>\n