Suppose the average solar energy incident on the green canopy (leaves) of a tree is 10⁸ J per day. The calorific value of the wood obtained from the tree could convert 1% of incident solar energy as wood, how many days will it take to produce 10 kg of wood?

Calorific value of wood = 15KJ/g Conversely the same energy (15KJ) is required to form 1g of wood. Energy required to form 10Kg of wood = 10 × 1000 × 15 = 15 × 10⁴ KJ of energy The average solar energy received per day = 10⁸J day^-1 But 1% of incident energy that is useful for the formation of wood = = 10⁶ J day^-1 No of days required to form 10kg of wood = = 15 × 10 = 150 days.