A large family uses `8KW` of power. Direct solar energy is incident on the horizontal surface at an average rate of `200Wm^-2`. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply `8kW`?

Explanation

If `Am^2` is the area, then power `=200xxAW`
Useful electrical energy produced per second is
`200/100(200A)=40xxAW`
But `40A=8000` or `A=200m^2`