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.

Answer 1

(a) 200 $m^2$: Power used by the family, P = 8 kW = 8 × 10 $^3$W
Solar energy received per square metre = 200 W
Efficiency of conversion from solar to electricity energy = 20 %
Area required to generate the desired electricity = A
As per the information given in the question, we have:
8 × 10$^3$= 20 % × (A × 200)

= $\frac{20}{100}$ × A × 200

∴ A = $\frac {8 \times 10^3}{40} = 200 \ m^2$

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.