Do you ever wonder about that claim that the energy flux of sunshine on the Earth is 10,000 times the projected energy use of civilization? Well, I do. I decided to drill down a bit into this number, to find out what the real bottom line potential of solar energy is. There are a lot of caveats to that number:
- 3/4 of the Earth’s surface is ocean, so the energy flux on land, right off, is on 2,500 times the projected energy use of civilization. I’m not saying we can’t collect solar energy off the ocean, but to the layperson, “Earth’s surface” means “land surface,” and that should be clarified
- The sun’s energy is not just going to waste as it hits the Earth – it drives climate, for example. Most importantly, it drives photosynthesis. How much of the sunlight dropping on the earth used for photosynthesis? Interesting question.
- The amount of solar energy hitting one square meter at noon is about one kilowatt, which is a handy metric to remember
- For a roof-mounted solar photovoltaic system today, you can expect to get 20% or less efficiency – meaning that you need 5 square meters for one kilowatt
But, as it turns out, there’s actually a cool map (shown above) that shows not only where the sun shines across the Earth on average, but also provides a visual clue about how much area it would take to provide all the energy demand of the entire world using solar power. The map is presented in this paper from Matthias Loster, and has been shown in various places around the web.
Solar power systems installed in the areas defined by the dark disks could provide a little more than the world’s current total primary energy demand (assuming a conversion efficiency of 8%, [and for the year 2006]).
Now all we have to do is string some (big) wires over to those desert-y places with the big black dots, and we’re made in the shade … er… sun.
By the way, while researching this post, I came across one from Robert Rapier at R-Squared Energy blog, focusing on the insolation just in the United States, and comparing it to Germany’s. Interesting reading.
What questions do you have about solar energy and its potential either in the US or around the world? Let me know what you’re wondering about in the comments section and I’ll do some more research.