 Solar irradiance

Solar radiant power incident per unit area. Horizontal, beam-normal and tilted-plane irradiances are different quantities: for a direct beam on a horizontal plane, $I_h=I_n\sin \alpha$, where $\alpha$ is solar elevation.

Solar irradiance is the power per unit area received from the Sun's radiation, measured in watts per square meter (W/m²). It quantifies the intensity of sunlight hitting a surface at a specific location and time. Solar irradiance varies based on several factors, including the angle of sunlight, atmospheric conditions, and the time of year.