From the solar constant we deduce that

1.4 kW of power is incident upon every 1m2 of area.

i.e the total energy incident in 1 hr over an area of 1 m2 will be = 1.4 kW x 1 hr

(Since P=E/t or E=P x t)

Hence, energy = 1.4 kWh

Solar energy received by 1 m2 area in one hour (or 3600 s) = 1.4 x 3600 = 5040 kJ