The calorific value of fuel: Amount of heat energy liberated on the burning of a fuel = (mass of fuel) × (calorific value of fuel)
or, Heat = mass x Calorific value
Solar constant :
Heat energy produced by incident solar radiation = (solar constant) × (Area) × (time) where solar constant
= 1.4 kJ m-2s-1 = 1.4 kWm-2.