X-Message-Number: 29442
Date: Tue, 17 Apr 2007 20:17:16 -0400
From: Francois <>
Subject: Re: Small musing about global oil reserves

David's and Kennita's comments are indeed quite true. The problem is not in 
the availability of alternate energy technology, the problem is in the time 
we need to switch from oil to its replacement. Lets shine a few numbers on 
the problem. To begin with, how much oil do we need to replace? This little 
website provides data about this. http://www.solcomhouse.com/Energy.htm

From its many graphs, it appears that we consume about 160 quadrillion BTUs 
worth of oil every year worldwide. In metric, that converts to 1.688x10E20 
joules. That's the minimum quantity of energy we must find to completely 
replace oil as an energy source.

Solar energy is usually considered the best long term candidate for the 
source of that energy. According to this webside 
http://www.solarserver.de/lexikon/solarkonstante-e.html the Earth gets 1.37 
kw per square meter from the Sun. That's above our atmosphere. We get 
somewhat less energy on the ground because of clouds, dust and other 
factors. Lets choose favorable locations and say that we can get 1.1 kw per 
square meter as indicated on the website. This number does not take into 
account the day-night cycle, which cuts the available energy further, down 
to about 500 watts per square meter. Lets further assume a very good 
conversion rate of about 50%, which means we have 250 wats per square meter 
to work with.

1.688x10E20 joules per year turns out to be about 5.35 trillion watts, so to 
completely replace oil with solar, according to these numbers, would take 
21400 square kilometers of solar gathering surface. That's a lot, and that's 
only to replace oil. Triple that for the entire energy consumption of the 
world. Increase it even more to take into account the rising energy needs of 
China, India, Africa, and other nations who are in the process of catching 
up with American and European energy needs. That's at least another tenfold 
increase. And I did not take into account the need to replace the existing 
energy distribution infrastructure with the new solar based one. After all 
that, we easily need 700000 square kilometers of solar gathering surface. 
That's really a lot.

It is not, however, impossible to achieve. After all, this is a square of 
about 836 x 836 kilometers, and our deserts are much larger than that, so we 
have plenty of room to build it. But, assuming we still have a century's 
worth of usable fossil fuel reserves, it means we would have to bring online 
7000 square kilometers of solar gathering area per year, starting right now, 
in order to make the transition. And lets not forget all the energy 
distribution infrastructure that goes with it. I'm not sure we can 
realistically expect this to happen. Our prehistoric ancestors did not run 
out of stone before bronze was ready to take its place, but we may very well 
run out of oil before its replacement is ready to come online.


Francois

Good health is merely the slowest
possible rate at which one can die. 

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