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Efficient Lamp: Newsletter Challenge (06/01/11)

Posted June 01, 2011 11:15 AM
Pathfinder Tags: challenge questions

This month's Challenge Question:

Comparing fluorescent vs incandescent lamps, a fluorescent lamp emits mostly ultraviolet (UV) light and a very small amount of visible light, whereas an incandescent lamp produces mostly visible light. And even though UV light can't be used to "see" anything (unless you want to damage your eyes), a fluorescent lamp is more efficient in producing visible light than an incandescent one - how is this possible?

And the answer is:

In a fluorescent lamp the lamp tube is coated with a special powder that absorbs the UV light; once the UV light is absorbed, the powder fluoresces producing light in the visible spectrum. There is almost no heating produced, so the electrical energy used by the lamp is used to produce the UV light which in turn is converted to visible light.

On the other hand, an incandescent lamp is nothing more than a resistor (filament) that heats up to high enough temperature (over 2,000 degrees Celsius) so that its thermal radiation emits visible light. If all the electrical energy can be converted to illumination, the incandescent lamp can produce a maximum of 250 lumens per watt; its actual output is only around 20 lumens per watt with an efficiency of less than 10%

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#1

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/01/2011 11:43 AM

The answer is in the question: Efficiency.

From LUMIVERSAL:

Fluorescent lamps are relatively efficient at converting input power into visible light. For purposes of comparison, incandescent lamps convert 2% of their input power into visible light, while typical fluorescent lamps convert 22%.

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#2
In reply to #1

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/01/2011 9:35 PM

If that is true. Fluorescent lamps only convert 22% of their input power into visible light, we are wasting a tremendous amount of power. How then can we design lamps that are more efficient? If we could even double it to 44%, would that not then be a huge savings? Would it be possible to achieve say 60, 75 or maybe even 80% efficiency? The genius of man has solved so many incredible problems over the years, how have we let this one get past us? Have we just become complacent because electricity (Power) has been relatively cheap, Lamps plentiful and cheap, so we just haven't bothered to seek a solution to the inefficiency of yesterdays lighting? Is the future in LED lighting? or is there some other, better way?

Just a few random thoughts to get you thinking.

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#4
In reply to #2

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/01/2011 10:37 PM

Great idea, I'm surprised no one has thought of this before.

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#5
In reply to #1

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/01/2011 10:38 PM

LED lamps are 80% efficient. That's quite an improvement.

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#3

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/01/2011 10:32 PM

An incandescent lamp does not produce 'mostly visible light'. Nor does it produce a measly 2 or 3 %.

Of the energy an incandescent light bulb consumes, about 10% to 15% is emitted as visible light, not 3%. [Whereas about 85% to 90% is emitted as heat.] (I calculated 15% using my spectral analysis program; Wikipedia says 10%). The '3%' figure is the luminous efficacy compared to a theoretically perfect emitter that emits at exactly 555 nm, where the eye's spectral response is at it's maximum -- but there is no such emitter. This is merely a figure-of-merit used for comparing different types of lighting.

Nor does a fluorescent lamp emit 'mostly ultraviolet (UV) light and a very small amount of visible light'. The mercury gas inside the fluorescent produces UV, but the lamp as a whole produces mostly visible light, along with some infrared (around 810 nm and 910 nm) mainly due to the argon gas used to moderate the energy transfer to the mercury gas, and a small amount of the 256 nm UV emission from the mercury that leaks through the glass tube. There is also a fair amount of infrared emitted by the cathodes at the ends of the lamp which get quite warm while the lamps are operating. The majority of the energy is visible light emission from the rare-earth phosphors coating the inner wall of the tube. The phosphors use the principal of fluorescence (and to some extent phosphorescence) to convert the 256 nm energy from the Hg to visible light.

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#6

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/01/2011 10:50 PM

Neither of these lamps directly produces much visible light. The incandescent lamp emits whatever it doesn't emit as visible light, as heat, which is then wasted.

The fluorescent lamp creates a continuous ark in a gas which produces a considerable quantity of uV light. The trick is coating the surface of the inside of the lamp with a fluorescent phosphor coating which is very efficient at absorbing the uV light and re-emitting it in the visible spectrum, i.e. 'fluorescing'.

A very similar technique is used to dope a uV LED with fluorescent material to make it a 'white' led, with the added bonus it gives a continuous light output running from a DC source, compared with fluorescent tubes which being AC driven have instants when they emit no light.

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#20
In reply to #6

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

11/03/2011 9:12 AM

Regards.

I add to:

<< compared with fluorescent tubes which being AC driven have instants when they emit no light. >>

It is stroboscpic effect.

You can see in every day life if you ve Flouro lamps lighting and a cieling fan running, try to vary the speed and you will feel it running in reverse.

Or on tv you note the direction of car wheels; changing direction or running in reverse to the car direction.

Speed of Auto-engines was measured by Strobometers and Timimg also was set.

Is in use to measure RPMs .

Stroboscope

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#7

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/02/2011 12:07 AM

USBport is right on. The question is defective and should be pulled to avoid further blushing of those who know what is intended and to avoid giving out bad information to those who are yet unaware of the facts and who may gullibly repeat the error.

This question would have been instructive if asked 50 years ago, but today it is counterproductive to limit the subject to vacuum fluorescent lamps and tungsten incandescent lamps because they are a technological precursor of the lighting sources we will be using in the next 50 years, many of which are now available.

My apologies if this is negative. I usually am very positive in replies and subtle because of the needs of the questioners who are in the dark, but in this case our mentors should know better.

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#8

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/02/2011 1:40 AM

Hello, I have the privalage to share some information regarding the question at hand. See the discussion on LPCS, Light Power Cell system.

So in the world of LPCS or Light Power Cell System, the light produced from incandescent and Cfl maybe reused and redistributed. All light fixtures or at least almost all light fixtures has some waste due to design or restrictions of design and LPCS can and does convert that back to usable elctricity. This aplies to LED as well.Of all light that is used on a large scale incandescent is by far the most potent when it comes to converting light to useable electricity. Led's have the same problem as incandescents of heat mangement, if Led's get too hot they burn out. Cfls are the coolest of all the light producers and can produce large amounts of useable electricity by converting the light to useable electrical energy.

Thought I would enter my two cents for your info.\

LPCS /Gary

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#9

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/02/2011 1:59 AM

This shows the way a fluorescent lamp Emits light

The essential component in the process of making light is the inter-conversion of energy. Different types of lamps and lighting devices convert energy in different ways and with differing efficiencies.

In the tungsten lamp, electrical energy heats a filament to a white-hot glow; thus, thermal energy is converted into light energy. Light emission from the solid filament is a continuum and gives a visible spectrum, much like a rainbow. Unfortunately the efficiency with which electrical energy is converted to visible light energy is only about 5-12%.

In the fluorescent lamp, electrical energy is converted into atomic excitation energy (UV) in the mercury vapour atoms inside a tube. The UV is then converted into visible light using phosphors. In this case, the energy conversion efficiency is about twice that of a tungsten bulb at around 22%. However, the spectrum of light emitted by these lamps (when the electrons return to their non-excited state) is not continuous; instead, light is emitted at specific wavelengths and colours corresponding to the electrical energy levels of the mercury atoms.

Replacing the mercury vapour with other gases, such as neon (which gives an orange light) or other inert gases, allows the production of many different coloured fluorescent lamps, used for luminous displays and signs (see image). Different phosphor coatings also change the colour of the light from the lamp.

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#10

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/02/2011 6:45 AM

The question is faulty (I am not the first to say that either) and shows a complete lack of any formal knowledge about any of the current forms of light producers. This in itself is not a bad thing, but the question is posed as though he has some GREAT new question that will help all the scientists and engineers working on future lighting.

Most of the posts (with a couple of notable exceptions) are just as faulty/incorrect.

Anyone wishing to learn something useful would be better off looking at one of the many other CR4 blogs that have already covered this subject to death....and accurately too.

This is just a collection of rubbish (mostly!).

Techart`s comment is as though nobody in the last 50 years has done anything to improve the situation, I personally would be completely ashamed if I had so posted a question without informing myself as best I could beforehand.

But there again, I do know the subject a little as I have read many of the previous blogs covering this on CR4, though I am still no expert. Now wasn't that easy?

Why cannot such people do a few simple searches on CR4 and read up first before posting such childish "questions"?

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#11

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/02/2011 7:04 AM

I'm surprised that no one has mentioned the research that is being put into bio-luminescence. Although it is in the early stages of research it would seem to be something that has a promise of working.

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#12

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/02/2011 3:27 PM

fluorescent lamps have a fluorescent coating, of various composition, possibly zinc sulfide?, that converts the ultraviolet light emitted by the primary excitation by absorbing photons, then quickly transfering energy to a lower energy state by fluorescing from the excited electronic state produced to a lower energy state, resulting in an emitted photon of a visible wavelength. If the resulting electronic state of the fluorescent material is still sufficiently energetic relative to the molecular ground state, then it is possible that a second photon of visible light will be emitted, otherwise this energy will likely be converted to infrared (heat). The materials used generally have a high quantum efficiency of conversion of ultraviolet to visible.

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#13

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/15/2011 12:39 AM

if the given statement is right, than:

10% visible light of 90% emitting light is more visible light than 5% of 100% emitting light!

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#14

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/17/2011 7:27 PM

One relies on heat to cause an item not made to emit light ... to emit light. For example if you heat metal enough (or anything really) it begins to glow.

The other electrically excites gasses that emit light in specific wavelengths because of the specific energy difference between two electron energy states within the atom.

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#18
In reply to #14

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

11/02/2011 1:01 AM

It's possible because in addition to light (EM radiation), the bulb is producing heat. And since an incandescent light relies on heat to create the light, there is a lot more heat loss. This is where the extra wasted energy goes.

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#24
In reply to #18

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

12/03/2011 9:00 PM

Maybe if I put this in numbers instead of words it'll make more sense.


Efficiency is in Watts of visible light/Watts of electricity.

So, in the below examples I'm going to make up some numbers, just to show how it's possible starting with input of energy = sum of the output energies.

An incandescent light relies on heat to produce light. So there is a lot of heat loss. Let's say:100 Watts of electricity = 94 Watts of heat + 5 Watts of visible light + 1 Watt of UV light.

A florescent light relies on changing electrons energy level to create light. So there isn't much heat loss. Let's say:20 Watts of electricity = 1 Watt of heat + 5 Watts of visible light + 14 Watts of UV light

So the efficiency of the incandescent and florescent lights are 5/100 (5%) and 5/20 (25%) respectively.

So while the florescent light in my example produces more UV light then visible light it's still more efficient due to the lack of heat loss.

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#19
In reply to #14

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

11/03/2011 8:36 AM

In tool shops when tools were hardened or Tempered by heat the colour of temperature was identified and the tool dipped in water or the chemical for a time then again the colour indicated the temprature and dipped again.

With advancement of technology the temperature now is measured by Spectrometer.

The incandescent bulbs and Carbon rod Arc [was used in Cinema machines] are the source of white-light.

Of course these white colour sources are in efficient in convertion.

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#15

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/20/2011 12:09 AM

Well it appears that the patience & persistence of members has been exhausted by the current puzzle. In order to fill the remaining time here is something to consider: I have a large jar full of pocket change. I also have a rack with three grooves that I know can hold no more than US$150. I put pennies ($.01) in one groove, nickles ($.05) & Dimes ($.10) together in the second groove, & Quarters ($.25) in the remaining groove. I also note that there are 3 times as many nickles as there are Dimes. Also the length of each stack of coins is exactly the same.. The thickness of Pennies is 1.40 mm, Nickles is 1.80 mm, Dimes is 1.00 mm & Quarters is 1.70 mm.. What is the total US$ value of the coins from the jar???.

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#16
In reply to #15

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

06/20/2011 12:41 AM

What you should perhaps consider is sending this in to Admin as a new challenge entry.

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#21
In reply to #15

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

12/02/2011 7:16 AM

The total US value of the coins are:

dimes are 10 cents

nickes are 5 cents

quarters are 25 cents

and pennies are 1 cent

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#22
In reply to #15

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

12/02/2011 8:57 AM

Not challenging enough... $147.19

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#17

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

11/01/2011 10:34 AM

Regards

<

The answer to this challenge will be posted later this month, right here on CR4.>

from 1st June to today. ?

Answer still not visible.

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#23

Re: Efficient Lamp: Newsletter Challenge (06/01/11)

12/03/2011 3:54 PM

Reply to the challange still due.

Posted June 01, 2011 8:15 PM

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