Q23 (a) A family uses 8 kW of power. 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?
It is given that the efficiency of energy conversion is 20 per cent.
According to question, we can write (equating power used by family) :
(Here A is the area required.)
or
or
Thus required area is 200 m2.