h a l f b a k e r yWhat's a nice idea like yours doing in a place like this?
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Sun to Rain
Redirect sun to increase rainfall in California | |
This may be applicable elsewhere, but California definitely
has the right conditions:
Put a huge solar diffuse solar mirror in geostationary orbit
over the desert southwest. This mirror intercepts say
maybe 10% of the sunlight that would otherwise fall on this
area. A lot of energy, but
not enough to shade any one
area completely.
This sunlight is not blocked, but redirected slightly to a
patch of ocean somewhere off the coast of California.
That portion of the ocean warms, increasing the
evaporation. The correct level of concentration is to be
determined, but I'm thinking you'd only want to increase
total insolation by a factor of 1.1-1.2, so it could be close
to 1:1.
At the same time, the desert southwest cools, producing a
low pressure area. This causes the extra moisture to be
sucked in from the ocean and over California, increasing
rainfall.
(And yes, I know there are massive issues with potentially
warming the oceans, and killing wildlife, and so on. Deal)
[link]
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How does a geostationary orbit that isn't above the
equator work? |
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I'll be honest, I didn't think this idea out that
much,
but... |
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You cheat. You use a geostationary altitude that
moves north and south of the equator by the
lattitude of your northernmost point, and is at the
peak around noon. That leaves it in the target
area
for a significant chunk of the daylight (and maybe
you increase the intercepted light to offset the
decreased time). Also you possibly play with an
elliptical orbit such that you've got a slightly
longer, slower portion in the daylight. Details to
be worked out if I find something that lets me
model orbits easily. |
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Another question to refine this... When you
redirect the light to the ocean, is there any
advantage to keeping it concentrated? Even if you
spread the light over a larger area than you are
shadowing, all that solar energy still goes into the
water. It seems like it would be linear up until you
got the water hot enough to start bubbling.
Speaking of which, you could make an offshore
concentrated solar generator if you made the
reflectors accurate enough. |
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I'm really not sure on the concentration. It feels like
some would be desirable, just from a controlling
where the energy goes standpoint, but it may not be
needed. |
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Concentrated solar from orbit requires very
concentrated sunlight, and suffers from atmospheric
distortion, so you're going to have your plant
generating power, and boiled fish around it. |
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All other considerations aside, if you focused your efforts far enough offshore, you'd kill a minimum of fish - they tend to collect near structures and shallows, with some exceptions of course. |
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And after the initial heatup, they'd learn where not to hang out. This would of course affect currents, which affects feeding and other phenoms. |
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Hmmm... I think there's a problem here. Unless we're
doing one of those biblical "the sun was standing still"
things, it seems like the the shadow is going to be headed
that-a-way (points off in direction of lessening
longitude)... OK. Calculator out. |
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I look at my little diagram which represents the earth,
the sun (in this reference frame, stationary at the top of
the diagram) and the mirror array (travelling around the
earth in 24 hours, give or take a few minutes of
siderialness).
Geosync orbit radius = 42,164 km (you think, "that's not
right!" - but the number you're more used to seeing is
altitude above earth's surface, which is not of interest
here)
Distance moved by mirror array in 24 hours: 0 km (oops,
useless result, it went back to where it started from)
Distance moved by mirror array in 12 hours: 84,328
km (the sun sees it moving back and forth along a line,
not around in a circle)
Average speed of eastbound shadow: 84,328km/12hr =>
7,027 km/hr
Since that's the average of a sinusoidal curve, peak
velocity (which will hit at precisely the point you'd rather
have it stationary) will be 7,027 * sqrt(2) = 9,938 km/hr.
Just slightly over Mach 8. I'm thinking that
could be an issue. ;) |
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What [lurch] said. Plus, unless you're controlling the angle of the mirror, the hot spot is going to travel, too, as the angle between the sun's rays and the mirror changes due to the mirror's orbit. |
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//is there any advantage to keeping it
concentrated?// |
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Ultimately, this is just a heat engine. So, you'll get
the most bang for your bucks if you keep the hot side
as hot (and therefore as concentrated) as possible. |
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I was definitely figuring on a controllable mirror array. |
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Lots of little mirrors, each with a driving motor. This also
allows for correction of the aiming point for the
north/south wandering, and adjustments to where the
rain
forms relative to the points that need it most. |
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Yeah, the shade is going to drift, but you've got it
overhead when it's in the desert, anyway. And once
again, an elliptical orbit might allow you to improve that
a bit by causing the mirror array to apparently drift
backward and forward over the earth, but I still haven't
found a way to simulate that. |
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After some quick math, however, it looks like the mirror
array will only shade the earth at all for about an hour
each day. After that, you're missing to either side.
Which sort of defeats the advantage of producing the
desired low pressure area (and the unstated desire to
keep the total idea insolation neutral). |
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Which means the idea might work better as a
constellation of LEO arrays. More expensive to build,
cheaper to launch. |
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I think you need to beat the cost of desalinization plants. How about large tethered balloons with cleverly designed reflective surfaces? |
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I think this is achievable on a much larger scale than de-sal
plants, and the operating cost is essentially zero once the
plant cost is dealt with, unlike de-sal. |
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Water already costs more than gasoline. Why don't they
just start mining antarctic glaciers. They can
simultaneously fix the drought and reduce worry about
rising sea levels. Not to mention opening up an entire
continent. |
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Plankton and other green things would surely grow more. |
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( We have had unusual winter rains locally in San Diego. A second generation of weeds when usually only one by now. Gophers and other things that eat weeds have had population explosions. Now knee deep in weeds that are shading out and killing the ice plant. The ice plant is one of the few that can survive the hot dry summer. Looking forward to barren hills due to critters and shading. Kinda of ironic.) |
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Just cranking up one major variable in an ecosystem, is not magically going to make it all come up roses. |
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This should make for a healthy raptor population this year. |
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// Water already costs more than gasoline // You're
talking bottled water. That costs about 2000 times
as much as tap water according to Google. Of
course that utility price is probably regulated which
is why it has to be rationed. |
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And if it wasn't regulated, people in the US wouldn't eat so
well. California exports water to the rest of the world one
tomato, one head of lettuce, or one orange at a time. |
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Perhaps California should just require all exports to be
dehydrated. |
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//Perhaps California should just require all exports to be
dehydrated// |
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All the grape juice I import form California is dehydrated by
10-13%. |
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[lurch], that's displacement. |
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A possible improvement: Two satellites. The first reflects the
sunlight to the side (or back up at an angle) and the second
down to the ocean. That eliminates the necessity for a mirror
much larger than the area*amount that it shades because it
has to be so oblique. |
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