Solar Power. In space, outside the atmosphere, some 1360 Watts of radiant power

Question

Solar Power. In space, outside the atmosphere, some 1360 Watts of radiant power pass through every square meter (at normal incidence).

a) What total amount of power does the Earth intercept from the Sun? (The projected area of the Earth is ?RE2, where RE is the radius of the Earth, 6.38 million meters.)

b) Compare this figure to the total amount of power produced by all of human civilization, currently some 40 trillion (1012) Watts. What conclusions about solar power can you draw from this comparison?

Explanation / Answer

( a )

projected area = 4 r^2 = 4 * ( 6.38 e 6 ) ^2 = 5.115 e 14 m^2 ;

so power = 1360 * 5.115 e 14 = 6.956 e 17 W <-------ans

( b )

power by all of civilization = 40 e 12 W ,

this is still less than the power by sun by a factor of 6.956e17 / 40e12 = 17391 ,

that means the power by sun is nearly 17,000 times more than the power produced by all

of civilization <---------ans

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