Thread: LED light output

Here you can see the difference between regular incandescent bulbs and sunlight:
lightspectrum2.JPG

As you can see, sunlight is a wide full spectrum hump centering on yellow light. Incandescent light is also full spectrum, but gives off much more "warm-colored" light (red, orange, yellow) and not as much blue light. Here again, you can see the comparison between incandescent and white LED:
123.jpg
Incandescent has much more red-orange light than LED.

Halogen bulbs give off similar light to incandescent, but because of the higher temperature the distribution is shifted a little more towards the bluer side the spectrum. For this reason, halogen bulbs appear "whiter" than incandescents.
halogenspectrum.JPG


The point of all these spectral graphs is to show that one type of light source can never really substitute for another type of light of light source. Each light source gives off its own unique spectrum. It is much more complicated than just "color temperature".

Putting it in a nutshell: In most cases both LED and CFL bulbs are a bad deal for the consumer.

Thanks for jamming a bad deal down our throats, government.

And the spectrum for fluorescent lights (including CFL's) is just awful. It is not continuous at all, which means colors often look wierd under fluorescent light, and it also has an eery pink or greenish tint.



This graph does not even show all the harmful UV that leeks out of the spiral bulbs. All this UV actually causes yellowing of the plastic base over time.





Here's the spectrum from an incandescent light bulb for comparison:


As you can see, light produced by incandescence is full spectrum, and thus does not have any sharp lines, just like natural sunlight.

One of the other environmental considerations for LED lighting is the aluminum used in the cooling fins.
Some of these heat sinks / cooling fins can be quite heavy, especially for higher output LED lights.

This aluminum heat sink is for an 80 Watt LED chip, and weighs 1.8 kg:


This aluminum heat sink for a 100-120 Watt LED chip weighs 3.8 kg:
http://www.made-in-china.com/showroo...W-120W-1-.html
while this one (100 Watts) weighs 3.4 kg:
http://www.made-in-china.com/showroo...100W-B-4-.html

So how much energy does it take to produce the aluminum for these heat sinks?
Because aluminum smelting involves passing an electric current through a molten electrolyte, it requires large amounts of electrical energy. On average, production of 2 lb (1 kg) of aluminum requires 15 kilowatt-hours (kWh) of energy. Just the cost of electricity represents about one-third of the cost of smelting aluminum. All these heat sinks are made in China, where most of the electricity comes from dirty coal fired powerplants.

The other major ingredient used in the smelting operation is carbon. Carbon electrodes transmit the electric current through the electrolyte. During the smelting operation, some of the carbon is consumed as it combines with oxygen to form carbon dioxide. In fact, about half a pound (0.2 kg) of carbon is used for every pound (2.2 kg) of aluminum produced. This carbon is released as carbon dioxide into the atmosphere. For every one pound of carbon consumed, 3.6 pounds of carbond dioxide is created.

This is why it would be so important to recycle the aluminum heat sinks for LED lighting.

Originally Posted by Anders Hoveland

Halogen bulbs give off similar light to incandescent, but because of the higher temperature the distribution is shifted a little more towards the bluer side the spectrum. For this reason, halogen bulbs appear "whiter" than incandescents.
halogenspectrum.JPG


The point of all these spectral graphs is to show that one type of light source can never really substitute for another type of light of light source. Each light source gives off its own unique spectrum. It is much more complicated than just "color temperature".

The spectrum shift also provides twice the visible light per watt. This requires high temp glass (the quartz in quartz halogen), and replacing the vacuum with a halogen gas that allows the tungesten vapor to return to the filiment, extending it's life (regular incandescent bulbs plate the glass resulting in a black film).

I understand that T12 fluorescent bulbs (the most common kind) get the incandescent bulb treatment next year as well. Hence the "sales" being held to unload inventory.

Ain't Big Government grand?

Originally Posted by Not Amused

The spectrum shift also provides twice the visible light per watt.

A typical halogen bulb only puts out 21% more lumens than a typical incandescent bulb, although this can go up to 40% for certain high power types of halogen bulbs.

Well, part of the reason for this (more vissible light per watt) is simply that the human eye is more sensitive to yellow-green light than red light. When the color distribution gets shifted more towards the blue side of the spectrum, a higher ratio of the light is yellow, green, and blue. In other words, the lumen rating is being increased by shifting the light color. For incandescent lights, this is usually a good thing, since normal filaments tend to be a little orange-yellowish and halogen gives a whiter light. But some people prefer the oranger "softer" color of light, and it may also be more desirable for certain places where a "cozy" feel is desired. While halogen filaments are a little more efficient at producing orange-red light, most of their "efficiency" comes from producing more of other colors of light. This is why it is not always really fair to use the lumen ratings when discussing efficiency. The most "efficient" light possible, for example, would produce all green-colored light. Indeed, many manufacturers of fluorescent lights actually "cheat" by incorporating more green phosphor to give the tube a higher lumen rating, but this results in an ugly greenish tinge to the light.

And the "warm white" LED's are deficient in far red frequency light, not because red phosphors do not exist, but because incorporating more of this light would lower the lumen rating because the human eye is not as sensitive to it as orange-red light. But the absence of this far red light decreases the LED's CRI index, certain red colored objects are not illuminated as well, and the color rendering seems more "off". The latest high-CRI technology LED's incorporate a separate red LED chip, because it is more efficient to directly produce this light than to produce it through a phosphor. But this adds complexity and expense. The 10 Watt Phillips L Prize LED light, incorporates this far-red color light, but is currently being sold for 50 US dollars each.



Although the Phillips L prize has a has a better spectrum distribution than normal white LED's, it is still far from perfect:

Here are the spectrum distributions for the latest technology of high-CRI LED's:

fullspectrumLED.jpg
(click on the picture to expand)


They are the closest things to full spectrum from an LED light currently available, but right now are very very expensive. These are already being used in a few televission studios. We will have to wait to see if the prices eventually drop, and whether these will ever become widely used in offices and schools to replace the unpleasant fluorescent lighting.

The current LED technology and state of commercial development is just not ready to replace incandescent lights in people's homes. I support the government funding research, but a ban on incandescents is just ridiculous, especially at this point in time. If people are all forced to use LED lighting instead of incandescent, the quality of lighting in their homes is going to suffer.

But LED's are not any worse than fluorescent, so maybe the government should focus more of its energy getting workplaces to use LED instead of fluorescent if they want to reduce energy consumption. Although incandescent consumes more energy than fluorescent, the fact still remains that far more energy is consumed powering all the fluorescent lights everywhere than the few incandescents in people's homes.

Originally Posted by livefree

The first phones, computers and cell phones did not consume four or five times as much electricity as the newer alternatives. The extra electricity being used did not scale up with the whole population of America to amount to millions of extra barrels of oil being burned every day to provide the juice. The use of older phones and computers did not negatively affect our balance of trade or adversely affect the climate.

As usual, you have no idea what you're talking about.

LOL, no, you have no idea what you are talking about.

The first computers used thousands of vacuum tubes, which are simple brute force devices that use a huge amount of power. When tubes were replaced with transistors, computers still used a tremendous amount of power. When tubes were replaced with transistors, memory was cabinet after cabinet filled with tens of thousands of these 08897B8CDF0442EC9DEFAAD2FF16AD64.jpg. On a one-to-one basis, every generation of computer uses less and less power.

Same for telephones. Try powering an old style 1970's type phone on the little tiny battery in your cell phone. Or power a 1990's cell phone with that battery.

The free market drove the development of phones. People wanted a portable phone - so the cell phone was invented.
Then people wanted a smaller cell phone, and one that would run longer - so batteries were improved.

The great improvements in battery technology over the past 20 years are not from "green" energy or govt mandate, its from the cell phone industry. Thats a cell phone industry driven by billions of customers in a free market.