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?

Explanation

Converted energy from electric energy
= 20 % of 200
` = 20/100 xx200`
` = 40 W/(m^(2))`
Power consumed by a family = 8000 W
Area required to genrate the derived electric
`A = (8000)/40 = 200 m^(2)`
(b) Suppose , the length of roof is l ,
` :. ` Area of roof `A =l^(2)`
` :. 200 = l^(2)`
` :. l = 10sqrt(2) m = 14.14 m `
The roof should have large dimension of `(14 m xx14 m)`