A family uses 8 kW of power, (i) Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square metre. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW? (ii) Compare this area to that of the roof of a typical house.
(i) Power used by family, P = 8 kW = 8000 W
As only 20% of solar energy can be converted to useful electrical energy, hence, power to be supplied by solar energy
8000 W/ 20%= 40000 W
As solar energy is incident at a rate of 200 W,
hence the area needed
A = 40000 W/200 W = 200
(ii) The area needed is comparable to roof area of a large sized house.