The author of this column wrote:
"Sunlight on average, at sea level, bombards the earth with about 1.3 KW per square meter. In one hour, that means that one square meter of sunlight generates 1.3 KWh. Pretty straight forward."
This does NOT seem straight forward. The amount of energy at the equator is much more than in the latitudes far away from the equator. By averaging, you vastly underestimate the energy to be harvested in the places where solar energy devices would likely be located. Thus, you could easily be off by quite a large factor.