Question #1: Solar Energy

I saw this graphic about solar energy on your facebook page: http://boingboing.net/2014/06/12/the-total-area-of-solar-panels.html Having a little experience with renewable electricity generation, this graphic seemed overly optimistic. So I dug into the numbers a bit more. Apparently this graphic comes from a diploma thesis (http://www.dlr.de/…/Ecobalance_of_a_Solar_Electricity… ). On page 11 she takes 250GWh/km^2 as an assumed base yield. This would work out to 250kWh/m^2. But according to Wikipedia (http://en.wikipedia.org/wiki/Sun#Sunlight ) we only receive about 1kW/m^2 of energy at the surface of the earth. Where are those extra 249kw/m^2 coming from? I then looked up numbers for an existing solar generation plant- the 354 MW SEGS solar complex in northern San Bernardino County, California (http://en.wikipedia.org/wiki/Solar_Energy_Generating_Systems ). This plant can generate up to 354 MW but covers 1,600 acres or 6.475 km^2. This suggests a yield of approximately 55 MW / km^2 or 0.055 kW / m^2. Am I making a silly mathematical mistake or is this graphic in error by three orders of magnitude? Paul LaMar United States