What's Solar Irradiance in solar power system?

Solar irradiance in photovoltaic power system refers to the amount of solar radiation power projected onto a unit area of surface per unit time, measured in watts per square meter (W/m ²). As a core indicator for measuring the strength of solar radiation, it directly determines the real-time output power and overall power generation of photovoltaic modules, and is a key basic data for the design, operation, and revenue evaluation of photovoltaic systems. From the core definition, irradiance is essentially the radiation flux density of the illuminated surface, which is the total amount of solar radiation received per unit area and unit time. The mathematical expression is

(where dΦ is the radiation flux element and dA is the area element); In practical application scenarios, under standard test conditions (STC), the irradiance is fixed at 1000 W/m ² (the benchmark value for component performance testing). The ground irradiance on sunny days at noon usually reaches around 1000 W/m ², while on cloudy and cloudy days, it is often lower than 200 W/m ², and the radiation intensity significantly decreases.

In the photovoltaic power generation scenario, irradiance is mainly divided into three categories, and the characteristics and application values of each type of radiation differ significantly: Direct irradiance (DNI) specifically refers to the direct radiation power from the solar disk and its surrounding 8 ° semi-circular cone angle range. On sunny days, it accounts for the highest proportion of total radiation and is the core dependence of efficient power generation in concentrated photovoltaic technology; Scattered irradiance (DHI) refers to the diffuse radiation power from the entire sky dome after excluding direct radiation, which is significantly increased in cloudy, hazy, or building obstructed environments. Conventional photovoltaic panels can achieve partial power generation through non direct absorption; The total irradiance (horizontal plane, GHI) is the sum of direct irradiance and scattered irradiance. As the core basic data for photovoltaic power plant site selection planning and accurate evaluation of power generation, its measurement accuracy directly affects the accuracy of project calculation in the early stage and the expected future benefits.