The correct answer is **179,000 km ^{2}**.

Use the formula (area) = (power)/(flux): the answer is 1.38x10^{7} MW divided by 77 MW/km^{2}.

This is about the area of the state of Missouri (you may have come up with other choices).

**Question 12.**

Finally, suppose (as currently suggested by the U.N.) that world population stabilizes at about 9.2 billion late in the next century. Assume that we want to use solar power exclusively to provide everyone with the same standard of living enjoyed by Americans now. Recall than in 2003 the total power consumption by the U.S. was 3.29x10^{6} MW. This was for a population of 291,000,000. Find the total world energy needs, at this same rate per person, for a population of 9.2 billion. Then find the collecting area now required.

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© 2001-2002, 2005 by Wm. Robert Johnston.

Last modified 11 January 2005.

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