Question

TABLE 4.1 Energy Comparisons Energy Joules) Item Energy of sunlight at Earth (per m- per second) Energy from metabolism of a cand 1.3 x 103 Energy needed to walk for 1 hour of a candy bar 1 hour 100 km/hr Kinetic energy of a car going 100 kr 1 X 106 1 x 106 1 X 106 1x10² Daily food energy need of average adult Energy released by burning 1 liter of oil Thermal energy of parked car Energy released by fission of 1 kilogram of uranium-235 1.2 x 10? 1 X 108 5.6 X 1013 Energy released by fusion of hydrogen 7 X 1013 in 1 liter of water Energy released by 1-megaton H-bomb4 X 1015 Energy released by magnitude 8 earthquake ergy 2.5 X 1016 Annual U.S. energy consumption Annual energy generation of Sun Energy released by a supernova 1020 nservation 1034 1044-1046 Eling with, same stan- of enn Therm

Answer 1

Sunlight energy hits the earth per m2 per second = 1300 m2/s

so sunlight energy hits the earth per m2 per year = 1300 x 365 x 24x 60 x 60 = 40996800000 = 4.0997x1010    ---- (1)

Solar cell efficiency = 4.0997x1010x 0.20 = 8.1994x 109   ---- (2)

US energy consuption per year = 1020 ---- (3)

Dividing 3 by 2 we get area of US in m2 required to consume this energy = 1.20x1010     ---- (4)

Percentage of US land required to power this grid = 1.20x1010x 100/ 9.834x1012 = 0.124 %