permaculture

[Toby Hemenway <toby@patternliteracy.com>]

Laurence Gaffney wrote:
>     "amount of total solar energy hitting the Earth is meaningless"
>
> I am not exactly sure what you mean here Toby but I don't think it is 
> meaningless.
Sorry; careless writing. I meant that if all life on the planet can 
capture only 0.05% of solar input hitting the Earth, we shouldn't get 
too excited about how big that total input number is (see below for 
why). It would be a mistake to say, "wow, there's so much energy out 
there--we'll never run out!"

And you're right, Laurance. Odum's energy quality idea is very useful 
here. The 1/170,000 yield for solar electricity is quite revealing.
> Question:- How does the current Solar Emergy consumption of humans in the USA 
> per annum compare with the annual input of Solar Energy over its Land 
> Mass/Boundaries?.
Thanks, Nathan, for doing the quick calculation. To follow Laurance's 
"Joules ain't joules" argument, you then need to multiply by some 
enormous factor to account for quality of energy. In other words, if all 
the energy used by the US were derived via solar conversion to 
electricity, the 0.4333% (US energy use/solar input) would be multiplied 
by 170,000, the conversion inefficiency factor for solar electric. That 
comes out to 735%.

Thus the US uses 735%, or 7-fold, more usable energy each year than 
falls on the entire country as solar energy. Bingo. That should suggest 
the nature of our problem. Energy conversion is the killer.
> PS:-     What is the source of your figures Nathan? 
The numbers Nathan used seemed to have been taken from Wikipedia, as 
they have that exact list at http://en.wikipedia.org/wiki/Solar_powe

Toby
http://patternliteracy.com


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