Question

(a) What is solar constant ? What is the value of solar constant ?
(b) If the energy received by 5 $m^2$ area in 10 minutes is 4200 kj, calculate the value of solar constant.

Answer 1

a) - The solar constant is a flux density measuring mean solar electromagnetic radiation (solarirradiance) per unit area. It is measured on a surface perpendicular to the rays, one astronomical unit (AU) from the Sun (roughly the distance from the Sun to the Earth).

The approximate average value cited, 1.3608 ± 0.0005 kW/m², which is 81.65 kJ/m² per minute, is equivalent to approximately 1.951calories per minute per square centimeter, or 1.951 langleys per minute. Solar output is nearly, but not quite, constant.

b) -

i

E = 4200 kJ

t = 10 min = 600 sec

P = E/t = 7 kJ/sec

Area = 5 m²

P/A = 7/5 = 1.4 kJ/sec m²

This is the value of the solar constant.

This means that 1.4 kJ of solar energy reaches the surface of the earth in 1 second over an area of 1m².