Question
A 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 typical house.
Solution
(a)
Power used by the family, P = 8 kW
= 8 × 103 W
Solar energy received per square metre = 200 W Power used by the family, P = 8 kW
= 8 × 103 W
Efficiency of conversion from solar to electricity energy = 20 %
Area required to generate the desired electricity = A
We have
8 × 103 = 20% × (A × 200)
= (20 /100) × A × 200
∴ A = 8 × 103 / 40 = 200 m2
(b)
The area of a solar plate required to generate 8 kW of electricity is almost equivalent to the area of the roof of a building having dimensions 14 m × 14 m. (≈ √200).
