[ RadSafe ] BUT solar energy just doesn't cut it .....
Ted de Castro
tdc at xrayted.com
Wed Oct 5 00:13:46 CDT 2011
Or more precisely PROMPT solar energy gathered over a technologically
I posted a calculation here a few months ago that demonstrated the
enormity of utilizing enough solar energy just to replace fossil fuel
use in the US. Doable but not easily. All energy, whole world - I
Realize however that ALL the energy we use is solar (or maybe stellar)
energy - in one way or another. The difference is the time and area
over which it is integrated.
Solar panels (PV) are prompt solar energy x collection efficiency
integrated over 0 time and the area of the panel. Same for solar
Solar dissociation to produce hydrogen and integrate over a large area
and time for use in a short time and space - but how much area?
Bio fuels are delayed solar energy integrated over the growing season
and the area of cultivation x collection efficiency.
Wind energy is solar energy integrated over the area over which the air
is heated and the time it heats - times absorption efficiency of course.
Fossil fuel energy is integrated over an epoch or two and over the area
that the "donors" grew and fed in, times many efficiency factors.
Hydro is of course solar energy integrated over the area of evaporation
and the time that process takes until condensation and deposition.
Wave energy is solar energy either by wind blowing or orbital mechanics.
And of course nuclear is solar - or more likely stellar energy
integrated over billions of years and the volumes of the sun or stars
that produced the source material from cosmic hydrogen.
So the issue is time and space - mostly space. We are using the energy
in a shorter time and smaller space than the time and space it was
integrated over which when used up (or not used due to political
restrictions) will leave us only with prompt solar energy which we will
need to integrate over a LARGE area to supply our concentrated use.
It was said here that more than enough solar energy falls on the earth
each day to meet our usage - but that is only true if we can intercept
and use all that shines on the entire surface.
Looking at the calculations I did just to replace fossil consumption
with solar would use a massive amount of land and we don't really have
the technology to harvest much solar energy over the seas. From those
calculations - the combination of solar energy and our technology to use
it just can't meet the need.
I did not attempt a wind energy calculation as I couldn't come up with
determination of the area/time over which the solar energy is integrated
and harvested. HOWEVER it is clear that even enormous wind farms can
intercept but a very small percentage of the total airflow - in other
words - the total solar energy imparted to the winds.
Its just a back of the envelope calculation - that got no comments here
BTW - but its very clear that no form of short term integration or small
area collection or harvesting of solar energy can meet the need.
Ted de Castro
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