HORTICULTURE

Detailed explanation-1: -Averaged over the entire planet, the amount of sunlight arriving at the top of Earth’s atmosphere is only one-fourth of the total solar irradiance, or approximately 340 watts per square meter.

Detailed explanation-2: -The total power density of the solar radiation at the mean earth-sun distance on a plane perpendicular to the direction of the sun, outside the earth’s atmosphere, is referred to as the solar constant. Its value is 1353 W/m2.

Detailed explanation-3: -Solar energy is incident normally on the earth’s surface at the rate of about 1.4 kW m−2 . The distance between the earth and the sun is 1.

Detailed explanation-4: -The solar constant is the energy which reaches the earth upper surface per second on 1 m2. It is usually taken to be 1, 388 watts per meter square.

Detailed explanation-5: -The amount of solar energy per unit area arriving on a surface at a particular angle is called irradiance which is measured in watts per square metre, W/m2, or kilowatts per square metre, kW/m2 where 1000 watts equals 1.0 kilowatts.