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How much power does the sun give us?

Our solar technologies are still new and increasing in efficiency all the time. So how much power we can get from the sun is one thing, but how much power is available from the sun is another.

At any moment, the sun emits about 3.86 x 1026 watts of energy. So add 24 zeros to the end of that number, and you’ll get an idea of how unimaginably large an amount of energy that is!

Most of that energy goes off into space, but about 1.74 x 1017 watts strikes the earth. (ie: 174,000,000,000,000,000, or 174 quadrillion watts).

If there are no clouds in the way, then one square meter of the earth will receive about one kilowatt of that energy. So for the six hours in the middle of a sunny day, an area the size of a small backyard swimming pool (48 m2) will receive about 288 kilowatts of energy. That’s nearly 10 times what the average US household uses in an entire day! (In the United States, the average daily electricity use is around 30 kilowatt hours per household).

Even on an overcast day, that same area will receive about 28 kilowatts of energy in the same six hour period. And best of all, solar power is extremely clean, with zero greenhouse gas emissions.

One big challenge is simply finding more efficient ways of harnessing solar power. Another is how to store it for when we need it. But the technology is advancing all the time. In 2011, a solar thermal power plant near Seville, Spain, used cutting edge molten salt technology to generate electricity for over 24 hours straight. By storing the sun’s heat in the molten salt, they could use the heat to run turbines even in the middle of the night. This advanced technology, pioneered in the US but not initially brought to market there, may be one key solution to the challenge of harnessing solar energy more effectively.

The fact is, we have a huge incentive to solve these problems: there is more clean energy coming our way from the sun every day, cloudy or not, than we can possibly use!

Wikipedia has a section on the “solar constant”, or the amount of energy the sun emits and the earth receives, which goes into more technical detail about those numbers.