What is your source for this claim. It sounds bogus to me.
The Solar constant is 1366 Watts / square meter.
The Earth's radius is 6400 kilometers.
The population is around 5 billion I think.
1366 x 3.14 x 6.4e6 x 6.4e6 / 5e9 = 35 megawatts per person
Relative to most people, I lead an extremley affluent life style,
but still only probably consume perhaps 10 kilowatts.
Even at 10% efficiency, 1 thousandth of the Earth's surface should
thus be able to provide sufficient energy for all current needs.