On 28 February 2014 06:43, John Clark <[email protected]> wrote: > On Wed, Feb 26, 2014 at 4:50 PM, LizR <[email protected]> wrote: > > > Why bother with all these other power sources when you have a fusion >> reactor in the astronomical backyard? >> > > Because the energy density decreases with the square of the distance and > the fusion reactor is 93 million miles away, and because the energy drops > to zero for at least half the time. > > It still delivers thousands of times more energy to earth than human civilisation uses. Let's do a quick back of the envelope calculation.
Human civilisation uses approx 150 x 10^15 watt/hours per year according to wikipedia The Sun delivers about 1000 W/m^2 on average at Earth's orbital distance (1360 actually but obviously some is scattered, etc) So treating the Earth as a disc for purposes of intercepting sunlight, the total possible insolation available is around 40 x 10^15 W Or around 320 x 10^18 watt/hours per year That's about 2000 times the energy requirements of our civilisation. It can be knocked down a lot by clouds, falling on the sea, running the weather, inefficiencies in collection, etc, of course, but I'd say there's still a bit of room for ramping up how much solar we use. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
