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air mass (AM)

In photovoltaics, solar radiation is affected by the azimuth

of the sun. The more obliquely the sunlight falls, the more atmosphere it has to pass through, which attenuates it. The air mass is called Air Mass (AM). In photovoltaics, the air mass is a dimensionless value that is calculated from the angle of incidence at our latitudes to the perpendicular irradiation at the equator. At perpendicular irradiation at the equator, the Air Mass is 1. At our latitudes, the value for the Air Mass changes with the seasons.

Air Mass (AM) at an angle of incidence of 90° and 41.8°

Air Mass (AM) at an angle of incidence of 90° and 41.8°

In summer, the angle of incidence for sunlight is up to 60°, which corresponds to an Air Mass of 1.15. At an angle of incidence of 41.8°, the Air Mass is 1.5. In winter, the angle of incidence is very shallow and is up to 15°. The Air Mass is then 14. The light must pass through an atmosphere 14 times thicker than with an Air Mass of 1.

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Englisch: air mass - AM
Updated at: 09.11.2013
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Translations: DE