The correct answer is 1,368 MW/km2:

1,000,000 W = 1 MW, so 1,368 W/m2 = 0.001368 MW/m2

1,000 m = 1 km

But 1,000,000 m2 = 1 km2: One square kilometer is the area of a square one kilometer on a side. That is a square 1,000 meters by 1,000 meters, or an area of 1,000,000 square meters. So 0.001368 MW for each m2 times 1,000,000 m2 = 1,368 MW for each km2.

Question 2.

We will work in W/m2. About 22% of the flux (1,368 W/m2) is absorbed or reflected by the Earth's atmosphere before it reaches the ground (even ignoring clouds). How much power per square meter is left?

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© 2001-2002, 2005 by Wm. Robert Johnston.
Last modified 11 January 2005.
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