Bright lights, big energy

Hybrid solar lighting: a solar retrofit for hot climates

Posted by Gar Lipow (Guest Contributor) at 2:08 PM on 03 Jun 2008

Read more about: energy | renewable energy | green building | solar thermal power

A fascinating commercial application for solar energy in clear (or semi-clear) hot climates seems to not be getting the attention it deserves: hybrid solar lighting.

You take a parabolic concentrator and focus some sunlight, optically split with plastic fiber into visible light and heat. Pipe the visible light through diffusers throughout the building. It saves lighting electricity, of course, but unlike skylights or conventional T8s, it adds almost no heat to the building. In a cooling climate it saves about a third as much in air-conditioning energy as it does in light.

You still need electric lighting supplementation, but in office buildings you get most of the light when you need it. And the advanced diffusers means you have only one hole to cut into the building. That gets you better odds of decent installation that avoids leaks or thermal bridges.

Unlike solar PV, which typically turns 15 percent of sunlight into electricity, this system saves the energy equivalent of about 50 percent of the energy striking the collector. Solar heating can do better, of course, but in cooling climates you don't have much call for that, and hot water demand is a much smaller percentage of total demand in office buildings than in residential ones. Originally the intent was to convert the other 50 percent of energy not used for lighting into electricity. Apparently the added capital costs were too high for deployment in actual commercial use.

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7 Comments | Post a Comment

should be able to route it, right?

simple switches to liberate light from unoccupied rooms? kinda tricky i guess.

by hapa at 4:50 PM on 03 Jun 2008

How About Just Going Outside...

Yeah, it's really cool that on a hot sunny day, you can build some Dexter's Laboratory gadget with a parabolic mirror and fiber optics to bring in the sunlight and run you air conditioner...but how about this: take your laptop and go sit on a park bench.

Seriously, why are we still getting in our cars, driving 50 miles and going into a big building and sitting at a cubicle. We have WiMax. We have Clearwire. We can go anywhere we want. Too hot? Put on some swim trunks. And so on...how about an open air deck with roof made of palm fronds and some light breezes from big metal fans while you sketch away on Auto-Cad.

by jabailo at 6:08 PM on 03 Jun 2008

Feeding the troll

Sitting outdoors in Houston when its 90 degrees out and 95% humidity? I'll pass (Not where I am now, but I lived in Houston for a number of long, long years.) Los Vegas, OK at least it is a dry heat. And there is T-Shirt that spread from New Mexico with a picture of a skeleton under a cactus saying that. Of course all the people in Houston, and Phoenix and Las Vegas could move to Seattle. I'll bet that would just thrill you.

by Gar Lipow at 6:22 PM on 03 Jun 2008

Hapa and switches

Since the capital expenses continue regardless, I suspect you just leave the rooms lit by diffuse sunlight whether anyone is in them or not. If you need darkness for a presentation or something there are probably shutters to close.

by Gar Lipow at 6:24 PM on 03 Jun 2008

"people" being relative

isn't it nice that the 20% of the population that is riding the upswing of today's economy is in a line of work where telecommuting has some relevance. it allows for such wonderful generalizations.

by hapa at 7:49 PM on 03 Jun 2008

Infrared PV

These would accept the waste heat from the solar lighting system. I'm not sure how far along they are towards mass production, but with concentration they should get pretty good efficiency.

These could work on a lot of high temp waste heat sources, or even on hot lava, yikes.

http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin

by amazingdrx at 8:50 PM on 03 Jun 2008

Loosening The Barnacle

Of course all the people in Houston, and Phoenix and Las Vegas could move to Seattle. I'll bet that would just thrill you.

Given that the average home price here is still $500,000 and about 25 cents in those other places...not gonna happen.

by jabailo at 9:42 PM on 03 Jun 2008

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