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

Given, the power consumption by the family is 8 kW , energy converted into useful electrical energy is 20% and the rate of solar energy received is 200 W/ m 2 .

(a)

Power consumed by the family P is the result of conversion of solar energy hence,

P=20%×solar energy …… (1)

Let A be the area of roof and E be the solar energy. Then

E=A×200

Substitute the values in equation (1).

8000= 20 100 ×( A×200 ) A=200  m 2

Hence, the area needed to supply 8 kW is 200  m 2 .

(b)

The area of solar plate needed is of almost same dimensions as the area of the roof of a building with dimensions 14×14  m 2 .