question_answer 23)

A large family uses 8 kW of power, (a) Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square meter. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW ? (b) Compare this area to that of the roof of a house constructed on a plot of size 20 m x 15 m with a permission to cover upto 70%                                  

Answer:

(a) Let the area needed to supply Energy incident per unit area = 200 W Energy incident on area Energy converted into useful electrical energy = 20% of But 40 AW = 8 kW = 8000 W or              (b) Area of the roof of the given house,  of   Required ratio .