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THE Lighting Thread (merged)

How to save energy through both societal and individual actions.

LED Lighting

Unread postby BabyPeanut » Wed 24 Nov 2004, 07:56:12

Hi World,

I just found this web site

http://www.optiled.biz/faqs/faqs.html

Seems LED lighting can't quite replace conventional home lighting but it's starting to be a reasonable alternative for outdoor lighting (think security) and at 2 watts, instant-on, long life, ability to turn on and off without degrading the bulb life it's clearly the lighting of the future.
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LEDs

Unread postby EnviroEngr » Wed 24 Nov 2004, 20:05:58

Add to that:

http://www.sunbriteleds.com/
http://www.ledtronics.com/

So far, they are getting promising enough to be affordable for simple applications such as Flashlights and the like.
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Unread postby lowem » Wed 24 Nov 2004, 21:03:21

Yeah, I've got some LED flashlights. They work pretty well. Much purer white than conventional light bulbs or flourescent. Haven't used them that long yet but according to the blurbs they're supposed to last longer (over 100,000 hours?) and consume much less power compared to the conventional bulbs.
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Unread postby smallpoxgirl » Thu 25 Nov 2004, 02:33:16

I looked into this a couple of years ago. Was ready to light my whole house with LED's. Turns out LED's aren't really very efficient. The properties that make them usefull in certain situations are A: they can be a relatively efficient way of producing colored light for applications like street lights. B: they are very directional, so they can be useful in applications like spot lights or flashlights. When it comes to lighting a living space where you need to light the whole area, they are very expensive and have about the same efficiency as incandescents. They are about 1/3 as efficient as a flourescent or worse. Useful in certain specialized applications, but definitely no panacea.

See: http://www.otherpower.com/otherpower_lighting.html

32 watt T8 fluorescent--85 to 95 lumens/watt
standard F40T12 cool white fluorescent--60-65 lumens/watt
compact fluorescents--low 30's to low 60's lumens per watt, usually 48-60
T3 tubular halogen--20 lumens/watt
white LED--15-19 lumens/watt
standard 100 watt incandescent--17 lumens/watt
incandescent night light bulb (7w)--6 lumens/watt
incandescent flashlight bulbs--dismal, less than 6 lumens/watt
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Unread postby BabyPeanut » Thu 25 Nov 2004, 22:25:00

Don't forget about car and bike headlights. Over 300,000 hits:

http://www.google.com/search?q=led+head ... headlights
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Unread postby BabyPeanut » Thu 25 Nov 2004, 22:32:12

smallpoxgirl wrote:they are very directional, so they can be useful in applications like spot lights or flashlights.

There are LED spot lights with 80 degress of beam spread which may be enough for a desk lamp. Track lighting would also be a consideration.
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Unread postby KiddieKorral » Fri 26 Nov 2004, 10:32:34

Aroound here, they have LED stoplights.
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Unread postby lowem » Fri 26 Nov 2004, 18:24:23

Ah, same here in Singapore. They've converted all the traffic lights to LED's. I'd say they're much brighter than the old bulbs which had to have filters to turn them into red/yellow/green lights.
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Unread postby Bytesmiths » Sun 05 Dec 2004, 06:33:20

smallpoxgirl wrote:Turns out LED's aren't really very efficient.
Well, yes and no...
smallpoxgirl wrote:they are very directional, so they can be useful in applications like spot lights or flashlights.
Or desk lights, or kitchen lights, or any time you need light "here" instead of "everywhere."

One key aspect of efficiency is lighting no more of an area than you need to light. In this case, LED lighting <b>is</b> more efficient than fluorescent lighting! If you need to light your desktop, why light up the entire room?

Fluorescent lights, conversely, are <b>not</b> able to be tightly focused, because their brightness comes via relatively low areal intensity.

So, LED, or fluorescent? One is a screwdriver, the other is a hammer. Pick the proper tool for the task at hand!
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Unread postby BabyPeanut » Sun 05 Dec 2004, 12:52:19

Well I got my bulb. It has a beam spreader that is rated at 80 degrees. I put it in the kitchen poarch light fixture which has no glass around the bulb anymore. I turned it on and left it that way. At 2 - 2.5 watts it will take all day to use a fraction of the energy a compact fluorescent would use overnight on a timer plus there's no timer using electricity.

The LED light is a dim greenish gray but it's brighter than no light which is what was there before.
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Unread postby Bytesmiths » Sun 05 Dec 2004, 15:11:12

BabyPeanut wrote:Well I got my bulb. It has a beam spreader that is rated at 80 degrees... At 2 - 2.5 watts it will take all day to use a fraction of the energy a compact fluorescent would use overnight on a timer plus there's no timer using electricity.
Your case sounds like area lighting (vs task lighting), and I might have recommended a 3W compact fluorescent bulb. They are available, and probably put out considerably more light over the desired area than your LED with a spreader.

IMHO, putting a spreader on a LED is not the best thing to do. You lose it's biggest advantage -- tight focus, without gaining the advantage of fluorescent lighting -- high efficiency over a wide area. And mimicking fluorescent's wide angle with a spreader comes at considerable financial penalty, as well.

The 3W CFBs I use came from China via Home Depot (unfortunately) and have a miniature, "christmas bulb" base, which would probably have to be adapted to your fixture, which is another consideration.

If someone bugs me, I'll go in the lab and make some actual measurements to report. (I've done this before to my satisfaction, but can't find the back of the envelope where I put the data... :-)

Efficiency ratings in lumens is deceptive. For task lighting, illumination should be compared in lux, which is illumination over a given area. "Luminance" is measured in lumens, and measures the light given off by a light source. "Illuminance" is measured in lux, and measures the light falling on an area.

For example, if one device produces 100 lumens, uniform over an entire sphere, and another device produces 10 lumens, but directs it all to 1/10th the area of a sphere, they produce the same illumination over that 1/10th of a sphere, but 90% of the output of the 100 lumen source is being wasted. This is why fluorescent bulbs seemingly have greater luminous efficiency than LEDs, but may actually have far less illuminous efficiency over the desired area to be illuminated.

At first glance, <i>samllpoxgirl's</i> figures appear to give fluorescent light up to a 6x improvement in efficiency, but in reality, concentrating a fluorescent's total lumination into 1/6th of a sphere illumination is not trivial, and as the desired beamwidth narrows beyond that, LEDs hold increasing advantage.

<b>Summary:</b><i> area lighting, think fluorescent; task lighting, think LED, or halogen with integrated reflectors.</i> A single 20W reflector-halogen illuminates my desk with more light than a four-tube, 200W fluorescent fixture mounted on the ceiling in the center of the room.

Hope this clarifies things a bit!
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Unread postby gg3 » Mon 06 Dec 2004, 03:25:41

But then comes the question of direct v. indirect lighting, and the issue of contrasts and shadows.

I'm dyslexic and I can tell you for certain that hard, high-contrast shadows in a work area make it basically unusable for me. And for "normals" there is probably a similar though more subtle effect (issues of degree rather than kind).

Task lighting is fine in theory, but in practice it needs to have a way to reflect it off some surface and thereby break up the shadows and contrasts.

Conventional fluorescents suffer from 60-hz flicker, which is known to interfere with concentration and memory (yes).

I use CFs throughout the house with a couple of exceptions, and at my desk I have three smaller CFs pointed in different directions to break up the shadows, rather than one larger CF.
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Unread postby Bytesmiths » Mon 06 Dec 2004, 14:11:27

gg3 wrote:I'm dyslexic and I can tell you for certain that hard, high-contrast shadows in a work area make it basically unusable for me...

Task lighting is fine in theory, but in practice it needs to have a way to reflect it off some surface and thereby break up the shadows and contrasts.
There's more than one way to deal with this.

Task lighting that is bounced off a ceiling becomes area lighting, and is less efficient. Two or more task lights aimed at the same work surface can simulate low-contrast lighting to some degree, but at improved efficiency.

I'm not saying you're wrong for wanting low contrast lighting, but we were talking efficiency here. Low contrast area lighting will always be less efficient than high contrast task lighting. This is not a value judgment on your needs; it's simply physics -- you inevitably illuminate more area than needed.

If you work at it, you can combine some of the best features of low contrast lighting and directional lighting. You reduce the contrast of a light source by increasing its angular size with respect to the illuminated area. Reflecting it off a white ceiling is one way that is not particularly efficient.

Another way is to diffuse it -- something as simple as a white sheet between your work area and the high-contrast light. But by doing so, you are still reducing the illumination efficiency by spreading the light out more. Also, using long fluorescent tubes reduces contrast by increasing the luminous source angle. You can get high-efficiency electronic ballasts if the flicker bothers you.

If you can afford to waste energy, you can make the trade off between comfort and efficiency. If not -- for example, if you have limited PV electricity -- whatever discomfort comes from efficient task lighting trumps having no light at all! For many, it may well come down to simple energy budgeting.
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Unread postby lotrfan55345 » Mon 06 Dec 2004, 17:44:11

They use LED lights in Tokyo. They are VERY energy efficient, electricity load just PLUMMETED after they used them for street/traffic/parking lights. For affect the city used pink, green and white LED's.


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THE Lighting Thread (merged)

Unread postby PhilBiker » Thu 16 Dec 2004, 10:45:22

Hey I have changed out most if the light bulbs in my house from incandescent to fluorescent.
However, I was thinking...
Maybe in the winter incandescants are more efficient?
One of the big knocks on incandescents is that they give off so much heat. Well, in the winter I want that. Sure they're not as efficient as my gas furnace, but hey when I use them in the winter time I'm getting "double duty" from the energy expended. I'm getting both light and heat from one device.
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Unread postby VMA131Marine » Thu 16 Dec 2004, 14:41:29

PhilBiker wrote:Hey I have changed out most if the light bulbs in my house from incandescent to fluorescent.
Maybe in the winter incandescants are more efficient?

True, flourescents convert a much higher fraction of input power to light and thus require less power to generate the same amount of light as an incandescent bulb. However, ultimately all the power input to both types of fixture ends up as heat in your house (assuming your windows are shaded). There is no "double-duty"as you put it, light is just another form of energy that gets converted to heat when it's absorbed by the walls, floor, ceiling and furnishings of your house.
The thing is, that to get 1 Watt-hr of heat from electricity at your house takes 3 to 4 Watt-hours of energy at the power plant that generates it. Most likely, that energy comes from natural gas or coal. Meanwhile, your gas furnace puts 80-90% of the heat it generates into your house. Taken as a complete system, it's much more efficient to create the heat you need by burning it at your house than by burning it at the power plant .
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Unread postby skateari » Thu 16 Dec 2004, 15:37:24

Good post VMA.. I was kinda wondering the same thing myself, thanks
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Unread postby MonteQuest » Sun 19 Dec 2004, 21:26:33

VMA131Marine wrote:
The thing is, that to get 1 Watt-hr of heat from electricity at your house takes 3 to 4 Watt-hours of energy at the power plant that generates it. Most likely, that energy comes from natural gas or coal. Meanwhile, your gas furnace puts 80-90% of the heat it generates into your house. Taken as a complete system, it's much more efficient to create the heat you need by burning it at your house than by burning it at the power plant .


This is spot on, and something everyone needs to have down. Consider for a moment how we heat water for our shower in most homes:

LNG is used to heat water/to produce steam/the water is used to turn a turbine/the turbine spins a generator/the generator produces electricity/the electricity is sent to a step-up transformer/ it is converted to high voltage/ this is transferred over power lines to a substation/then sent to a step-down transformer/and transferred to your house/where it heats a coil/ to heat your water.

Every / bar represents energy being transferred from one form to another with a loss of available energy (entropy) at each point.

If we used LNG at our home to heat water, we would have only one conversion. LNG to hot water. While this is certainly “technology,â€
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Unread postby PhilBiker » Mon 20 Dec 2004, 09:48:41

I don't think gas fired water heaters are as rare as you seem to think Monte. My current house and my previous one both had gas fired water heaters, they're the norm around here.
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Unread postby MonteQuest » Mon 20 Dec 2004, 18:26:21

PhilBiker wrote:I don't think gas fired water heaters are as rare as you seem to think Monte. My current house and my previous one both had gas fired water heaters, they're the norm around here.

I guess it depends on where you live. In Socal, where I just moved from, "all electric" is the the rage in the homes I was working on. But I was more focusing on the inefficiency of centralized energy production and lost over power line transmissions and energy conversions.
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