Your calculations are out by several orders of magnitude (don't forget that 1 km^2 = 1,000,000 m^2). 200MW at 10% efficiency and 800W/m insolation is 2.5 km^2

Your calculations are out by several orders of magnitude (don't forget that 1 km^2 = 1,000,000 m^2). 200MW at 10% efficiency and 800W/m insolation is 2.5 km^2 (I believe their claimed efficiency is considerably lower than that, though).