Comments on: Let there be light, optical cables included

New company Sunlight Direct looks to commercialize a system for piping daylight into buildings through fiber optic cables.
Photos: Sunlight's system

[Mark Shapiro]

Daylight in buildings is good for everyone

An important note in the story is that ordinary daylight is the most
pleasing kind of light for people, making them more productive.
It's better for employees, customers, and whoever pays the electric
bill and breathes the air.

There are probably less expensive, more effective ways to bring
daylight in though. Reflective awnings teamed with internal
reflectors on ceilings can bring daylight deep into offices. But let's
see how this complex system stacks up.

[beardedfish]

MAN!

I had this exact idea! Its a good one as well. Especially for big
buildings like the hospital I work in. The area I work in has no
windows at all and i can go for an entire shift with out seeing the
daylight.

[littlejon2]

Vitamin D benefits?

Natural sunlight helps/causes the body to produce vitamin D. Will the piped sunlight do the same?

[NocturnalCT]

Probably not

They probably filter out the UV to appease skin cancer fear mongers. So vitamin D benefits will probably be limited. If they do filter out all the UV then it would not be fair to extrapolate skylight effects on mood to lightpipes like this.

I have no doubts that the light 'color' itself is beneficial but the UV stimulating the skin to produce D is one of the major factors to being 'happy' outside.

[NocturnalCT]

Sorry

Meant to reply to the Vit D. question

[DeusExMachina]

Probably, but it won't make much difference

First, Vitamin D production is stimulated by UVB, skin cancer is
predominantly caused by UVA, so there is no reason why
cancer-causing spectra can not be filtered out with no effect on
Vitamin D production.
Second, there is no evidence that ingested vitamin D in the diet
is not equivalent to that manufactured in the skin, and a wealth
of evidence to the contrary, so that particular benefit is
negligible.
Third, while studies DO show that Vitamin D has an effect on
mood, they are also quite clear that this is not the primary
vector by which light exposure affects mood. In fact, the
majority of the mood elevating effect is stimulated by light
impinging on the eye and stimulating the production of
hormones, including melatonin from the pineal, that have little
or nothing to do with Vitamin D levels.
All in all, the benefit of endogenous Vitamin D production in
modern society is overblown.

[NocturnalCT]

Why GPS?

Do buildings move a whole lot? I realize GPS receivers are cheap these days but clocks that receive time signals via radio are even cheaper. At least I assume the GPS unit is used to get accurate time information?

Simply initialize the location when installing the unit and take the GPS with you. Then use accurate date/time information to calcuate the position of the sun to aim your collector.

[DeusExMachina]

Why time signals?

Simpler still, why not just a light intensity tracking circuit. All the
thing has to do is track the sun across the sky. All it needs to do
that is two photocells and a voltage comparator.

[BobAIA]

heat gain

I toyed with this in 74 @ VPI. This would also bring in the light without the associated heat gain of windows & skylights. Great concept, but mine also included a 'view' of the outside. We're still not there yet! Congratulations!

[thmst30]

This really isn't gonna work that well

Am I the only one who realizes this will only work if it is a completely clear day outside. The fact is that anytime a cloud passes over, and early in the morning and at night when its dark, you still have to have electrical lights. I don't believe the cost for this stuff is worth how very little use you can actually get from them. Definitely needs some more innovation and work to be useful.

[jasonemanuelson1]

Not completely true

Actually, there is a good deal of light in the natural sky without
direct sunlight. It won't be as bright, but as a supplement to indoor
lighting, it would indeed be a benefit. It would also act to tone the
light temperature. Obviously, dreary days would not offer anything,
but to a large building, this does offer some promise.

[kieranmullen]

Why no shielding

I see from the photos that alot of light is escaping in the ceiling because the cable has no reflective shielding. Why?

KieranMullen

[internetdog]

Not really that much loss

The photo is misleading in that it is looking at the light cables in near total darkness and exposing to emphasize the leakage from the fibers. An optical fiber works on the principle of total internal reflection, so the amount of light the "leaks" out the sides is extremely small. And external reflective shielding would not get the light back into the fiber in a way which would aim it toward the destination.

To be transmitted, light must enter the fiber through an end and leave it through an end. The only exception is when a fiber is deliberately made more leaky by changing the surface, so that it can serve as its own diffuser at the destination end.