How many Lu/watt is a Naked Flame? Efficiency

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xiaowenzu

xiaowenzu

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Okay, I know it's a weird question and honestly I'm not sure if I am posting it the right location. Well, I've been thinking.... about when you light a match to get a flame right? Well does anyone know how much watt it's using? because I'm not sure how to assertain the wattage of something like this! I think, even though it's Lumen count is not as High as LEDs or HIDs, it could be MUCH more efficient because of low operating current.

Currently the best LEDS can do 115Lumens/WATT (latest Cree)
The best HID may achieve ~ 100 Lu/Watt

Anyone have any ideas now? Well, I'm currently having a bath by candlelight - my room now is very bright with 10 flaming candles! I guess it's about 70 Lumens. :party:
 
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T

Trekmeister

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It is usually said that a candle gives of about 100W of heat. Let us say that 100W includes any light turned into heat when hitting walls, the cieling etc. (since pretty much any light is turned to heat sooner or later anyway. If you are correct in that 10 candles using a total of 1kW gives about 70 lumen you have an efficiency of 0.07 lumen/watt, a pretty crappy number...

Addition:
Wikipedia claims a candle gives of about 13 lumens of visible light while burning 40W of energy. That would give us 0.325 lumen/w, quite a lot better than my aproximation but still bad.
 
xiaowenzu

xiaowenzu

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Thanks for the reply! 0.325 lumen/w is still pretty crappy!:laughing: I'm going back to my Novatac 120t now. Lol. Well, if they could convert 100W heat of candlepower into PURE light, that would be something I'd like to put into my flashlight. :D
 
rizky_p

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you must admire the candle being low on efficiency they last for hours and unfortunately come with 1 mode only no strobe or SOS :) :naughty:
 
Marduke

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rizky_p said:
you must admire the candle being low on efficiency they last for hours and unfortunately come with 1 mode only no strobe or SOS :) :naughty:
Click to expand...

Candle, yes. Naked flame, well my oil lamps would have to say otherwise on 1-mode only. They were the first "infinitely variable" brightness lights on the market!!! And if I tune my oil candles just right, I can even get them to strobe as they periodically suck in air.
 
Burgess

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This is indeed a very proper question for

CandlePowerForums. :wave:

_
 
A

AzN1337c0d3r

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A candle is more like a battery than an LED. It stores its energy for use later. We don't really measure the power efficiency of a battery do we?

Efficiency is a measure of output compared to input. In the case of a candle, what do we take as the input?

The energy it took to ignite the candle? That seems unreasonable since it took a lot of energy to manufacture the candle.

The physical energy that is stored in the solid state of the wax? Also unreasonable. The candle would burn out in seconds if it was just a physical change.

The chemical energy store in the bonds holding the molecules together? The most reasonable assumption, since burning is a chemical process.

The atomic energy stored in the nucleus of the atoms that make up the candle?
Atoms don't split when we burn a candle, so this is unreasonable too.

However, note how all the above examples are energy, not power. You can't directly relate the power output of a candle (measured in lumens, a unit of power) to the input (because well we're not inputting anything in the same timeframe)

However, if we are interested in the efficiency of which we can extract energy from the candle. We can burn the candle, and integrate the light output over time, so that we get the luminous energy (measured in lumen-seconds). Once we know that, and assuming we know how much total chemical energy is in the candle. We can get a ratio of output energy to input energy, which will be in lumen-second/joules.

To get the total energy in a candle is fairly simple. Just measure the heat lost and add it to the light output and you have total output. Integrate that over time and you have total energy.

lumen-second/joules is the same thing as lumens/watt (divide top and bottom by seconds) from a mathematical standpoint, but physically it's not really.
 
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Marduke

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AzN1337c0d3r said:
A candle is more like a battery than an LED. It stores its energy for use later. We don't really measure the power efficiency of a battery do we?

Efficiency is a measure of output compared to input. In the case of a candle, what do we take as the input?

The energy it took to ignite the candle? That seems unreasonable since it took a lot of energy to manufacture the candle.

The physical energy that is stored in the solid state of the wax? Also unreasonable. The candle would burn out in seconds if it was just a physical change.

The chemical energy store in the bonds holding the molecules together? The most reasonable assumption, since burning is a chemical process.

The atomic energy stored in the nucleus of the atoms that make up the candle?
Atoms don't split when we burn a candle, so this is unreasonable too.

However, note how all the above examples are energy, not power. You can't directly relate the power output of a candle (measured in lumens, a unit of power) to the input (because well we're not inputting anything in the same timeframe)

However, if we are interested in the efficiency of which we can extract energy from the candle. We can burn the candle, and integrate the light output over time, so that we get the luminous energy (measured in lumen-seconds). Once we know that, and assuming we know how much total chemical energy is in the candle. We can get a ratio of output energy to input energy, which will be in lumen-second/joules.

To get the total energy in a candle is fairly simple. Just measure the heat lost and add it to the light output and you have total output. Integrate that over time and you have total energy.

lumen-second/joules is the same thing as lumens/watt (divide top and bottom by seconds) from a mathematical standpoint, but physically it's not really.
Click to expand...

Not really comparing the stored energy. Efficiency of a flame to LED is about the energy consumed, not what a battery/candle hold. We can measure how much spectral energy either gives off, which includes visible light, heat, and energy not visible to the human eyes. If you compare the amount of total energy being emitted to the amount which is visible light, you get your comparison.
 
asdalton

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For a candle, the relevant energy is the heat of combustion for wax. The power emitted by the candle can be calculated from this if you know the rate of wax consumption. Or you can use the candle flame to heat up a small container of water, and then determine the power from the temperature increase of the water over time.

Hydrocarbons (oil, wax, propane, etc.) have similar heats of combustion on a per-weight basis.

However, the thermal power from a flame is not the proper basis for comparison of efficiency against electrical lights of any kind--not if the electrical lights' efficiency is being calculated based on electrical power consumed. For that, you need to first determine how much thermal power has to be expended to generate the electricity from a combustion source such as oil or gas. This quantity will always be considerably greater than the electrical power itself. Therefore, a correct analysis will end up penalizing the electrical light source for this initial % energy loss.
 
TorchBoy

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asdalton said:
Therefore, a correct analysis will end up penalizing the electrical light source for this initial % energy loss.
Click to expand...
But then you're assessing a system efficiency, not the device efficiency of the electric lightbulb, LED, fluoro tube etc. That may be an interesting thing to do (I imagine the lighting efficiency of a burning lump of coal is quite low) but it's really a quite different thing. Why not calculate the thermal energy that was used making the candle, melting the wax into its candle shape? Where do you stop? :tinfoil:
 
Marduke

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All you need is a spectrographic analysis, and set some point as a reference for comparison (ie. compare equivalent lumens of visible light). A little integration and you have a A-B comparison of efficiency. It would be interesting to compare the differences between different types of wax candles.
 
asdalton

asdalton

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TorchBoy said:
But then you're assessing a system efficiency, not the device efficiency of the electric lightbulb, LED, fluoro tube etc. That may be an interesting thing to do (I imagine the lighting efficiency of a burning lump of coal is quite low) but it's really a quite different thing. Why not calculate the thermal energy that was used making the candle, melting the wax into its candle shape? Where do you stop? :tinfoil:
Click to expand...

It is easy: You pick the standard that, from a practical human standpoint, represents the conversion of a raw energy source into useful output. More importantly, you have to compare technologies on a consistent basis that doesn't "cheat" by using a raw energy source (combustible fuel) for calculating one efficiency, while using a human-produced intermediate energy source (electricity) for calculating another.
 
TorchBoy

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asdalton said:
It is easy: You pick the standard that, from a practical human standpoint, represents the conversion of a raw energy source into useful output.
Click to expand...
Why? :shrug: I want to know how efficient a lightbulb is, not an electrical generation system. Why would calculating that be cheating when that is what I want to calculate? :party:
 
A

Any Cal.

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Just depends on what you are trying to measure. Is a steam engine that runs off a boiler powered by wood picked up along the road more or less efficient than an internal combustion engine that burns gasoline? It really depends on how many systems and supports that you choose to include in the equation.

Does an LEDs efficiency change if a person is using rechargeable batts? It is all semantics if a person is simply trying to measure the efficiency of the end product, i.e. the candle or the flashlight.

Also, does the candle's efficiency change if you are using it's energy wasted as heat for another purpose? If it is giving off heat as wasted energy, but that heat is being used to help warm the room, does that mean the candle is 100 percent efficient?

Just playing around. Have fun everyone.
 
asdalton

asdalton

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TorchBoy said:
Why? :shrug: I want to know how efficient a lightbulb is, not an electrical generation system. Why would calculating that be cheating when that is what I want to calculate? :party:
Click to expand...

It's not wrong, per se, to calculate the electricity-to-light conversion only. And for comparing technologies that use the same derived energy source, such as electrical incandescent versus LED, then it doesn't really matter whether you use the intermediate or the raw energy source as the basis for the efficiency--since the preceding energy losses are shared by all technologies and therefore don't affect the ranking.

But more widely ...

The need for an apples-to-apples comparison of energy sources, and the consequences of not doing this--has real-world consequences. For example, there is a lot of stuff in the news about using hydrogen as a fuel for cars and other things, as an alternative to fossil fuels. Governments, universities, and private companies are drinking up this hype like, well, Kool-Aid.

The problem is that the whole concept is undiluted, 200-proof poppycock. Hydrogen is not an energy source at all--not unless you have a ready-made repository of hydrogen to extract. There isn't one. You either make it from fossil fuels, or else use electricity (a lot of electricity) to electrolyze water.

At best, hydrogen might be used as an energy storage medium that allows vehicles to indirectly be run indirectly from a wider array energy sources than just oil. But it's not an energy source that can replace oil, coal, nuclear, hydroelectric, etc. The failure of people to understand this fact is leading to billions of dollars being wasted due to a giant false premise.
 
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