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Piping in sunlight question?

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Posted by David O'Daniel on April 28, 2010, 10:27 am
 


Hi, me again. I posted several things a while back. Got another
idea/question, if it could work.

A. For solar energy, including focusing lenses & mirror arrays (that
Spain & also Israel now, HAVE made work), someone is always shooting
them down, saying it can't work, it is not always daylight.

B. Fiber-optics have been around now for years even decads, including I
believe, piping in light from outside, by I assume some lens, then
through fiber-optics through a pinhole or straw at least sized hole down
through the building & then expanded back out into room lighting at lest
on a limited scale. I assume that this idea never caught on for some
reason & ppl are still using electricity to run lights in the day time,
maybe too expensive to build such systems through a building?

C. So then shouldn't lenses & maybe also mirror arrays focusing
sunlight, send light from one part of the country/globe through a
fiber-optic cable or a simple straight hole through a pipe (maybe a
mirrored/polished interior pipe), to then provide light to areas during
night?

It seems that a network could be set up of such systems to then use the
light to heat water at night to make steam & turn turbines & make
electricity. And of course in day, use the direct sunlight to do it.
while other systems ship other sunlight to other parts of the globe
still in darkness?

Any flaw in this idea? Other than resistance to new technology & cost of
building it?

Thanks in advance for any help.


Bo


Posted by John B. Slocomb on April 28, 2010, 11:25 am
 


On Wed, 28 Apr 2010 05:27:51 -0500, Bojutsu1@webtv.net (David
O'Daniel) wrote:


My guess is capacity of the fiber optic cable limits the amount of
power that can economically be transported.

If you are going to use light energy to make steam you are talking
about substantial amounts of energy.

According to a very quick search:

At atmospheric pressure (0 bar g), water boils at 100C, and 419 kJ of
energy are required to heat 1 kg of water from 0C to its saturation
temperature of 100C. An additional  2 257 kJ of energy are required
to evaporate 1 kg of water at 100C into 1 kg of steam at 100C.

So to turn 0 degree water into 0 psi(gage) steam requires some 2,676
kj of energy. About 743 watt-hours of energy.

see:
http://www.spiraxsarco.com/resources/steam-engineering-tutorials/steam-engineering-principles-and-heat-transfer/what-is-steam.asp
for more complete calcs.

John B. Slocomb
(johnbslocombatgmaildotcom)

Posted by David O'Daniel on April 29, 2010, 8:40 am
 

Thanks for responding.

Wouldn't it be a material thing then? If today's fiber optics are
limited, melt or deform maybe, then maybe the idea of a mirror/polished
internal surface high-temp resistent steel or whatever material pipe
instead.

I always go on the assumption that you can use vast areas, with the use
of lenses, focusing into such pipes (if not fiber optics), so amount of
light shouldn't be a problem.

From when I was first googleing mirror arrays & solar furnaces & fresnel
lenses, back maybe a decade ago now, it seemed that it didn't take that
much of an area of sunlight to concentrate, to melt steel. The 3X3'
Fresnel lens story where they were blasting holes in the sidewalk trying
to melt a dime & burning holes in steel stop-signs, as an example. So if
you had the area say over a parking lot or just the roof of a house,
much less a mall, gathered & focused to shine down a pipe, maybe a
vacuum filled (aka empty) pipe, then there should be plenty of energy to
make steam for electricity when it is night on the other end. When it is
day, just use the focused light on site.

Arguably, the reducing of at least some of the sunlight shining down on
a parking lot could help reduce skin cancer from sun exposure. Discussed
that idea though with my parking lot covered by a canopy of solar
panels, before.

Just that shoppers would have to avoid the point where the light is
being focused to, down into the pipe or whatever system, lest they melt
their shopping carts, toast their groceries & fry themselves along with
it. Cost would probably be prohibitive to build the lenses of mirror
arrays but IF the investment were made & regular maintenance of cleaning
kept lenses & mirrors clear, there should be little to no other further
costs. Unless a car crashes into some section perhaps. Probably some
cost-cutters will use cheap glass rather than lexann or pressure glass
or whatever & thus be vulnerable to teen vandalism of throwing rocks, I
suppose.

Recently, there was some suggestion of putting up floating giant
sports-stadium-sized discs or umbrellas (I assume inflated) to block out
(rather than make use of) sunlight, as a suggestion for the global
warming scare. That will also never be built but I thought that it was
less likely than my idea and that idea made the news. Granted, I had
only "heard" of it & hadn't personally seen the news story on it at the
time.


Bo


Posted by harry on April 29, 2010, 5:27 pm
 

On 28 Apr, 11:27, Bojut...@webtv.net (David O'Daniel) wrote:

I have a suntube in my house. It's a tube about a foot in diameter
with a mirror finish inside. It stretches from the roof where there is
a plastic clear dome to a windowless room where it finishes with a
Freznel lens.
They are common in the UK. It works well.
Bit about them here:-
http://en.wikipedia.org/wiki/Light_tube

Posted by David O'Daniel on April 30, 2010, 3:44 am
 

<Harry wrote>:
"I have a suntube in my house. It's a tube about a foot in diameter with
a mirror finish inside. It stretches from the roof where there is a
plastic clear dome to a windowless room where it finishes with a Freznel
lens.
They are common in the UK. It works well. Bit about them here:-
http://en.wikipedia.org/wiki/Light_tube"

<Bo>: Thanks Harry. I'll check it out. I've only seen such a sky-light
system in 1 building at a local Jr. College. It was to light stair-wells
in just a 3 story building but the light under the middle stairs/over
the bottom floor, was just as bright as that over the 3rd floor steps,
as I recall.

This probably helped inspire my current strange alternative idea just on
a much larger scale. 12 hr differences with maybe the tubes shining
light for street lights as well for the time-zone currently in
night-time darkness, thus saving electricity.

To then make electricity with a simple light tube grid & send the
electricity out over the current complex electrical grid with wire
resistance OR build direct lighting with a complex branching network of
light tubes & skip the electricity making, if the tubes would preserve
the light strength more. Just a side thought, which would reduce the
energy from focusing/collecting end, to the 12 hr difference time zone
usage of it?

Also then comparing startup cost between the use end making steam, cost
of the turbine system, hooked to an existing electric power grid of
wires, and no generator but newly building, probably running
underground, a new tube network out to street lights & eventually
building light fixtures or whatever else on-site use.


Bo


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