Duplicatting the Sun

[John Taylor]

If I install a 3 inches piece of plastic of the type used to
manufacture fiber optics with an inverted L shape through my roof and
concentrate on it a light from the Sun using a parabolic reflecting
dish into it, can I have a duplicate of the Son in my house.
Will it melt the plastic? What efficiency may I expect?

I have the parabolic dish on the northerly side of my house that can
be modified to track the Sun and it can have a new parabolic surface
done with a reflective material.

This way, can I have one Sun on the South side of the house and
another on the North side?

Opinions please. Including the nasty ones.

John

 

[John S]

If I install a 3 inches piece of plastic of the type used to
manufacture fiber optics with an inverted L shape through my roof and
concentrate on it a light from the Sun using a parabolic reflecting
dish into it, can I have a duplicate of the Son in my house.
Will it melt the plastic? What efficiency may I expect?

No, it will not duplicate the Son in your house. It might burn him, though.

 

[John Taylor]

No, it will not duplicate the Son in your house. It might burn him, though.

If the transmission efficiency of the plastic is 100% , no heat is
generated and consequently will be safe.

 

[John S]

If the transmission efficiency of the plastic is 100% , no heat is
generated and consequently will be safe.

Then his eyes may be damaged by the intense light. How old is your Son?

 

[Taylor]

Actually, if you're trying to duplicate the Son then the Father and the
Holy Ghost may have issues with you.

The ignorant jokers had a good time . They can place the replies
where the Sun doesn't shine.

I can communicate in 4 different languages , what about you?

John

 

[tm]

The ignorant jokers had a good time . They can place the replies
where the Sun doesn't shine.

I can communicate in 4 different languages , what about you?

John

We thought you were a bit slow.



tm

 

[Rich Grise]

Actually, if you're trying to duplicate the Son then the Father and the
Holy Ghost may have issues with you.

Not to mention the Mother.
http://www.godchannel.com/expguide.html

And no, it's probably not a good idea to concentrate sunlight into
a house. There are off-the-shelf skylights that light up a room quite
well, when the sun's out. On the north side, a flat reflector
should be more than enough.

The Sun is quite bright, you know.

Good Luck!
Rich

 

[John Taylor]

Without wishing to detract from the lovely flame war you seem to have
started, there's a physical principle called the conservation of
radiance that governs this sort of thing. (It's deducible from
Maxwell's equations, so it isn't a separate principle on its own like
universal gravitation, but it's widely useful in helping prevent folks
from trying recreational impossibilities unintentionally.)

Radiance is light intensity in watts per square meter per steradian,
which corresponds roughly to the subjective concept of the brightness of
an image. We know by experience that when something gets further away,
it looks the same brightness, only smaller.

For instance, a star in the night sky has about the same radiance as the
Sun, but since it appears so very small (about 250,000 times smaller in
angular diameter), it doesn't give us much light. However, if there
were a very large number of stars similar to Alpha Centauri, so that
they occupied the same fraction of the sky as the Sun, they'd be about
equally bright and hot as well. (Alpha Centauri is a bit hotter than
the Sun, so the comparison isn't exact, but you get the idea.)

If you could form an image of the Sun such that the light came in from
all directions equally, and none was lost in the process, then an object
placed in that image would heat up to the temperature of the surface of
the Sun. In real life you don't get all that close.

For instance, AFAIK the world's record for a concentrator solar
photovoltaic device is held by my friend Ted van Kessel of IBM, and it's
about 2500 suns, i.e. the Sun magnified so that it covers the equivalent
of about 1.2% of the sky. (*)

Cheers

Phil Hobbs


(*) angular radius of the Sun = 0.25 degrees = 4.4 mrad,
Solid angle of the Sun = pi*(4.4 mrad)**2 = 6E-5 steradians
Solid angle of a sphere = 4*pi

=> 2500 suns = (0.15 steradians)/(12.5 steradians) = 0.012 of a sphere

Now that I have attracted the attention of the smart people of the
group, let me give you details of my small projects.

I have a large living room with 10 feet plants located at the corners.
Those plants like to have sunlight. Since I have access to the
sunlight I designed a platform supporting 10 flat mirrors of 4feef by
6 inches installed by a sunny window facing South.
The panel could be moved vertically and the mirrors could be moved
horizontally but in a synchronous movement.
I learned that if more than one mirror illuminate the same area the
consequences could be disastrous. I have burned a plant but projecting
the light on the white ceiling gave the amazing look of having the
room on the outside.

I am some what of a fanatic on the energy field. So much that I am at
the present biding on a roof of a 10 floor building in a very sunny
country. I am offering $140k for the exclusive use of the roof and if
accepted will support a penthouse, as many solar panels I can on the
available space , rain water collection etc.
The central room will have a large sky light and I am considering the
installation of mirrors on the inside walls of that box in order to
increase the light on the referred room .
Also being considered is the use of the pipe rails of a large veranda
to heat the water and since the temperature never goes below 5 degrees
C there is no need for antifreeze but some rust inhibitor is a must.

Very grateful for the pass and future help

John Taylor

 

[Tom Del Rosso]

Now that I have attracted the attention of the smart people of the
group, let me give you details of my small projects.

Maybe a better way to say thank you would be "thank you".

I am some what of a fanatic on the energy field. So much that I am at
the present biding on a roof of a 10 floor building in a very sunny
country. I am offering $140k for the exclusive use of the roof and if
accepted will support a penthouse, as many solar panels I can on the
available space , rain water collection etc.

If you have that much money to throw at the problem you should have said
so. Offer a few $k and then you'll get lots of serious help.

I can offer one free suggestion though. Where you focus light on the
end of the light pipe, have the end of the pipe extend some distance
from the house in any direction. That way if the assembly shifts and
the light misses the pipe, it will be out of focus where it hits the
house, and hence won't set it on fire. If the focal point is halfway
between the reflector and the house then the radiation at the house
should be the same as at the reflector, so will be no worse than
exposure to direct sunlight.

 

[A Monkey]

No, this would not work as a kind of Star Trek replicator for your
Son.

He asked for it. He got it.

Typically, high energy solar setups for this type of light gathering or
concentration, etc. only follows a very low number of bends. The fewer
the better. ("replicating the Sun"). But for general room lighting, it
would be easy to gather enough with some fiber bundles and light shafts.

They have far more serious uses for it now though.

Modern solar thermoelectric generators are a field of mirrors which all
reflect upward to a mirror at the top of a tower, where it gets reflected
down the tower shaft to the base (or further), to heat a mass of
liquefied Sodium which is used to make steam and turn steam turbine
driven electrical power generator sets for huge, multi-megawatt outputs.

Long before this was a reality, say back in the early to mid sixties,
there was an early version of such a tower and the mirror array down in
the base focused the beam onto a 6 inch thick steel plate, and proceeded
to punch an 8 inch hole through it like a laser would (probably not as
fast).

But that was the predecessor to what is currently in use in the
Southwest to make power as described above. There are also fields of
mirrors the track the sun which reflect directly onto Sodium filled heat
pipe right there on the mirror, so it had a far shorter focal length than
the tower pointed arrays. These mirrors looked curled. Those systems do
not perform as well (per acre maybe?) as the tower pointed variety. The
Sodium get a more direct (more efficient in the final analysis) solar
heat infusion, I guess.

 

[Winston]

Maybe a better way to say thank you would be "thank you".



If you have that much money to throw at the problem you should have said
so. Offer a few $k and then you'll get lots of serious help.

I can offer one free suggestion though. Where you focus light on the
end of the light pipe, have the end of the pipe extend some distance
from the house in any direction. That way if the assembly shifts and
the light misses the pipe, it will be out of focus where it hits the
house, and hence won't set it on fire. If the focal point is halfway
between the reflector and the house then the radiation at the house
should be the same as at the reflector, so will be no worse than
exposure to direct sunlight.

Apparently it works a treat:
http://goo.gl/xVRSd

--Winston

 

[VioletaPachydermata]

Deep underground.

 

[Martin Brown]

Plastic fiber has a lot of attenuation with distance. You'd probably
melt it. And the focussed image of the sun will still be pretty big
for coupling into a reasonably sized chunk of plastic. Aiming, as the
sun moves, will be a problem too.

Err. No it won't the sun subtends an angle of about 0.01 radians so
unless he has a 100m parabolic dish the image of the sun won't even come
close to the size of his waveguide. The heat load on the front surface
will probably melt it though but that is another matter.

Having said that I once burnt a line along the inside of a dome with a
0.5m f5 mirror uncapped as the sun came in around through the slit.
Imaging concentrators can be dangerous and capable of starting fires if
they are more than about 4" in diameter.

Tracking the sun can be done, but the kit tends to be expensive.

The OP probably wants to build a non-imaging flux concentrator of the
type that are used for HEP scintillators. They will give a gain of
roughly 10x incident light onto the target area but at wild angles.

The canonical simplest design is a half parabolic reflector y = x^2 with
the second half of the curve displaced along so that it goes through the
focus. Any ray incident on the front aperture will after a finite number
of reflections hit the detector area at the back. eg.

http://en.wikipedia.org/wiki/Non-imaging_optics

I haven't read the page carefully to be sure what it says is accurate.

Actual ones used in buildings tend to be flat mirror approximations to
this ideal (and also work reasonably well when it isn't sunny).

Regards,
Martin Brown

 

[Jon Kirwan]

http://en.wikipedia.org/wiki/Non-imaging_optics

Thanks, Martin. I was aware of fresnel, but not this. It
expands my thinking in this area and I appreciate being made
aware. More study to do, though.

Jon

 

[John Taylor]

Apparently it works a treat:
http://goo.gl/xVRSd

--Winston

Thank you Winston. That's what I was looking for .

 

[John]

This Taylor guy must already have a history... my filters snagged him.

From your discussion above, it appears we have yet another
Slowman-Larkin emulator on our hands... snotty ignorant.

...Jim Thompson

"This Taylor guy" is new to this group so obviously it isn't the one
you are referring to. I just pick a name that you people can easily
pronounce.
I think that is about time some people realize that just because some
aren't fluent in their language they aren't necessarily stupid.

Vladimir

 

[Winston]

(...)


Thank you Winston. That's what I was looking for .

And thanks to Tom Del Rosso for stirring my memory
of the neat Japanese 'Sunflower' concept.

You can shrink some HIX tubing around these pipe
strands to make your prototype, for cheap:

12 ft long, total 6.25 sq mm area for $35
http://www.surplusshed.com/pages/item/m4109.html

Fresnel Lens. 8 for $2.95:
http://www.sciplus.com/singleItem.cfm/terms/16938
(You may want to cut these down on a lathe!)

Gear motors for your altazimuth mechanism.
$13.50 per axis
http://www.surplusshed.com/pages/item/m3029.html


--Winston <-- Post your prototype to YouTube!

 

[John Taylor]

He asked for it. He got it.

Typically, high energy solar setups for this type of light gathering or
concentration, etc. only follows a very low number of bends. The fewer
the better. ("replicating the Sun"). But for general room lighting, it
would be easy to gather enough with some fiber bundles and light shafts.

They have far more serious uses for it now though.

Modern solar thermoelectric generators are a field of mirrors which all
reflect upward to a mirror at the top of a tower, where it gets reflected
down the tower shaft to the base (or further), to heat a mass of
liquefied Sodium which is used to make steam and turn steam turbine
driven electrical power generator sets for huge, multi-megawatt outputs.

Long before this was a reality, say back in the early to mid sixties,
there was an early version of such a tower and the mirror array down in
the base focused the beam onto a 6 inch thick steel plate, and proceeded
to punch an 8 inch hole through it like a laser would (probably not as
fast).

But that was the predecessor to what is currently in use in the
Southwest to make power as described above. There are also fields of
mirrors the track the sun which reflect directly onto Sodium filled heat
pipe right there on the mirror, so it had a far shorter focal length than
the tower pointed arrays. These mirrors looked curled. Those systems do
not perform as well (per acre maybe?) as the tower pointed variety. The
Sodium get a more direct (more efficient in the final analysis) solar
heat infusion, I guess.

Thank you again
In conclusion, I am going to use the dish to heat water. It already
has a 350 degrees span and another motor that controls the vertical
axis.

John

 

[John S]

"This Taylor guy" is new to this group so obviously it isn't the one
you are referring to. I just pick a name that you people can easily
pronounce.

"You people?" What makes you think we people can't pronounce Vladimir?
And why would we want to pronounce it?

I think that is about time some people realize that just because some
aren't fluent in their language they aren't necessarily stupid.

It works both ways, Vladimir.

 

[John Devereux]

Without wishing to detract from the lovely flame war you seem to have
started, there's a physical principle called the conservation of
radiance that governs this sort of thing. (It's deducible from
Maxwell's equations, so it isn't a separate principle on its own like
universal gravitation, but it's widely useful in helping prevent folks
from trying recreational impossibilities unintentionally.)

Radiance is light intensity in watts per square meter per steradian,
which corresponds roughly to the subjective concept of the brightness
of an image. We know by experience that when something gets further
away, it looks the same brightness, only smaller.

For instance, a star in the night sky has about the same radiance as
the Sun, but since it appears so very small (about 250,000 times
smaller in angular diameter), it doesn't give us much light. However,
if there were a very large number of stars similar to Alpha Centauri,
so that they occupied the same fraction of the sky as the Sun, they'd
be about equally bright and hot as well. (Alpha Centauri is a bit
hotter than the Sun, so the comparison isn't exact, but you get the
idea.)

If you could form an image of the Sun such that the light came in from
all directions equally, and none was lost in the process, then an
object placed in that image would heat up to the temperature of the
surface of the Sun. In real life you don't get all that close.

That brings back memories of an essay I read a long time ago as a
teenager, I think it was by Isaac Asimov. It was a proof that you cannot
have an infinitely old, infinite universe unless it is expanding.

Otherwise, if you draw a line from your eyeball in any direction, it
will eventually terminate on the surface of a star. Essentially every
part of the sky is the temperature of the surface of the sun, as would
we be. The only reason this does not happen is that really distant stars
are red shifted to nothing,i.e. the universe must be expanding. (Or not
infinite, or not infinitely old - so the light from distant parts hasn't
reached us yet).

[...]