Available solar energy is 50,000 times our energy need.
At least 100 watts of energy strike each square foot of the earth’s surface in a fully sunlit hour. Most areas of the U.S. receive the equivalent of 4 hours’ full sunlight per day, translating into about 1.5 trillion TWh (terawatt hours) of energy per year—many times the 28,000 TWh used in the U.S.
However, solar cells today can capture only about 20% of the sun’s energy that strikes them and are subject to a theoretical maximum of about 33%. And as the percentage of land that feasibly can be covered with solar collectors is small, it is difficult to meet all our energy demands through solar power. At present levels, the U.S. would need a continuous field of solar collectors covering the entire land area of Indiana. If the world used energy at the per capita rate of the U.S., a field the size of Venezuela would be required.
