irradiance

The term irradiance is used equally in solar and radio technology. It is the total power ofRF radiation, light radiation, or solar radiation incident on a surface. It is expressed in watts per unit area (W/m2).

Solar irradiance is affected by air mass, Air Mass( AM), and is dependent on location, time of day, and season because the angle of incidence of the sun's rays depends on latitude and changes with the time of day and season.

Direct Normal Irradiance (DNI)

The highest irradiance is when the light rays strike the surface vertically and perpendicularly. This is the case at the equator when the sun is at its zenith. If it is at a different angle to the earth's surface, then the irradiance is reduced by the air mass of the atmosphere. Direct Normal Irradiance( DNI) is the solar radiation that radiates perpendicularly onto a surface regardless of the position of the sun.

The irradiance itself, the irradiance, is the product of irradiance and time, or the time integral of irradiance. For example, an irradiance of 50 W/m2 over 10 seconds results in an irradiance of 500 J/m2.