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The Dubai Lamp

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james_s:

--- Quote from: MK14 on April 11, 2022, 01:01:29 pm ---Are you sure that 120V incandescent bulbs, are more efficient than 240V directly equivalent bulbs ?
Do you have any sources for that information ?

It doesn't make a lot of sense. Because a 60 Watt bulb, with the tungsten filament, suitably adjusted for operation on 120V AC or 240V AC, should have roughly the same energy consumption (60 Watts), roughly the same life expectancy (1,000 hours seemed to be a common standard), and as far as I know, the same light output at 60 Watts of heat, assuming the filaments, are broadly compatible.

--- End quote ---

Absolutely, it's a simple matter to look at the specifications on the package. A 120V 60W incandescent lamp produces about 800 lumens for example, while the 240V version is only about 700 lumens. You can see the same effect by looking at the lumens per watt of different wattages of lamps. All else being equal, the higher the wattage, the more efficient. A single 150W lamp produces significantly more lumens than a pair of 75W lamps.

It actually makes a lot of sense when you consider what needs to happen for a bulb of the same wattage to be higher voltage. The current has to be lower, so the filament has to be longer and thinner. A longer and thinner filament has greater thermal losses due to having a much greater surface area. Both lamps consume 60 watts of electrical input, both produce a lot more heat than visible light but the 240V lamp with its longer and thinner filament produces a significantly greater ratio of heat to visible light. This is one reason low voltage halogen lamps are (were) so popular, a low voltage lamp has a compact and relatively thick filament so it is considerably more efficient even when transformer losses are factored in.

The lowest voltage flashlight (torch) bulbs are more efficient than the higher voltage bulbs, but higher voltage has an advantage when you look at the whole system. Higher voltage means you can have greater wattage (so a brighter bulb) while the percentage of losses in the switch, terminals, internal resistance of the batteries, etc is lower. When you only have 1.5V to work with it doesn't take much resistance to result in a significant percentage of loss. If you start with 6V the same resistance is a lot less significant.

MK14:

--- Quote from: james_s on April 11, 2022, 06:51:19 pm ---Absolutely, it's a simple matter to look at the specifications on the package. A 120V 60W incandescent lamp produces about 800 lumens for example, while the 240V version is only about 700 lumens. You can see the same effect by looking at the lumens per watt of different wattages of lamps. All else being equal, the higher the wattage, the more efficient. A single 150W lamp produces significantly more lumens than a pair of 75W lamps.

It actually makes a lot of sense when you consider what needs to happen for a bulb of the same wattage to be higher voltage. The current has to be lower, so the filament has to be longer and thinner. A longer and thinner filament has greater thermal losses due to having a much greater surface area. Both lamps consume 60 watts of electrical input, both produce a lot more heat than visible light but the 240V lamp with its longer and thinner filament produces a significantly greater ratio of heat to visible light. This is one reason low voltage halogen lamps are (were) so popular, a low voltage lamp has a compact and relatively thick filament so it is considerably more efficient even when transformer losses are factored in.

The lowest voltage flashlight (torch) bulbs are more efficient than the higher voltage bulbs, but higher voltage has an advantage when you look at the whole system. Higher voltage means you can have greater wattage (so a brighter bulb) while the percentage of losses in the switch, terminals, internal resistance of the batteries, etc is lower. When you only have 1.5V to work with it doesn't take much resistance to result in a significant percentage of loss. If you start with 6V the same resistance is a lot less significant.

--- End quote ---

Thanks for the detailed explanations. I'm somewhat fascinated, because I didn't realize there was any appreciable incandescent efficiency difference, between differing mains voltage countries.

The nearest thing to a definitive link I've been able to find, is here:
https://en.wikipedia.org/wiki/Incandescent_light_bulb#Electrical_characteristics

From the link (wiki) above, it seems to give the respective Efficacy (lm/W)'s as 14.2 for 120V 60W Filament bulbs, and 230V 60W as 12.2, agreeing with what you are carefully explaining.

Some discussions about that subject area, show a wide range of diverse, disagreeing comments. Such as here:
https://www.quora.com/Are-100w-bulbs-in-America-brighter-than-in-the-UK-The-American-version-would-draw-more-amps-with-the-lower-voltage-outlet-than-the-220v-counterpart-If-not-why-would-bulbs-with-2-different-amperages-give-off

Some say that 60 watts of heat energy is 60 watts of heat energy, so it must (should) make the same amount of light, due to the laws of Physics.

Others still seem to say that it could be because of differences, between the real life, life expectancy of the real life bulbs (as opposed to what the American bulb manufactures are claiming, is the expected life expectancy (burn life), of those bulbs). I.e. European Bulbs are expected to generously outlast the stated 1,000 hour lamp burn life, whereas greedy big business USA bulb manufacturers, want a shortened life expectancy, so they can sell more bulbs and hence make a bigger profit.
TL;DR
The real reason for the difference, might be that the USA bulbs (claimed perhaps 1,000 hours), are really 750 hours, and hence more efficient, but the European 1,000 hours, really last for 1,250 .. 1,500+ hours, and hence are less efficient.

Also, although on the one hand you are right:

--- Quote from: james_s on April 11, 2022, 06:51:19 pm ---A single 150W lamp produces significantly more lumens than a pair of 75W lamps.

--- End quote ---

Another way of looking at it, is that the two 75W lamps, could be separated out into optimised lighting positions, giving a more even and bigger spread of light, than a single 150W lamp, in a single position, in a room. I.e. in real terms, the pair of 75W lamps, may give better lighting, overall. Even though they are less efficient, than a single 150W lamp.

TL;DR
To be clear, I'm NOT trying to disagree with you here. I'm just trying to confirm, an interesting/new (to me, at least), fact about these increasingly obsolete incandescent bulbs.

james_s:

--- Quote from: MK14 on April 11, 2022, 09:37:11 pm ---Some say that 60 watts of heat energy is 60 watts of heat energy, so it must (should) make the same amount of light, due to the laws of Physics.

--- End quote ---

But they don't put off 60 watts of heat energy. An ordinary 60W 120V A19 lamp puts out about 57 watts of heat and 3 watts of visible light. Now it's true that if you put a 60W bulb inside an opaque box that box is going to put out 60 watts of heat no matter what type of lamp (or indeed no matter what device) is inside that box consuming 60 watts of electricity but in most applications the lamp is used to produce light and the heat emitted directly from it is a byproduct. If you removed the glass from a 60W lamp and immersed the filament in a cooling fluid (and ignored the fact that in the real world the resistance would drop dramatically) the filament would still consume 60 watts of energy, but it would produce 60 watts of heat and no visible light, so the efficiency is then 0%.

Remember that when speaking of a lamp, efficiency means only the amount of visible light emitted relative to the energy consumed. It's always going to give off as much energy as it consumes, but we ignore output that is not in the desired form, ie visible light.

MK14:

--- Quote from: james_s on April 11, 2022, 10:08:05 pm ---
--- Quote from: MK14 on April 11, 2022, 09:37:11 pm ---Some say that 60 watts of heat energy is 60 watts of heat energy, so it must (should) make the same amount of light, due to the laws of Physics.

--- End quote ---

But they don't put off 60 watts of heat energy. An ordinary 60W 120V A19 lamp puts out about 57 watts of heat and 3 watts of visible light. Now it's true that if you put a 60W bulb inside an opaque box that box is going to put out 60 watts of heat no matter what type of lamp (or indeed no matter what device) is inside that box consuming 60 watts of electricity but in most applications the lamp is used to produce light and the heat emitted directly from it is a byproduct. If you removed the glass from a 60W lamp and immersed the filament in a cooling fluid (and ignored the fact that in the real world the resistance would drop dramatically) the filament would still consume 60 watts of energy, but it would produce 60 watts of heat and no visible light, so the efficiency is then 0%.

Remember that when speaking of a lamp, efficiency means only the amount of visible light emitted relative to the energy consumed. It's always going to give off as much energy as it consumes, but we ignore output that is not in the desired form, ie visible light.

--- End quote ---

Sorry my fault/mistake. I poorly reported back on that thread, I linked to, earlier. I meant that the 60 Watts of heat, then emits visible light, from that heat energy, regardless of if 115V or 230V, generated the 60W, in the first place.

Here is a quote (for the exact wording) from the actual link, repeated here, for convenience:

https://www.quora.com/Are-100w-bulbs-in-America-brighter-than-in-the-UK-The-American-version-would-draw-more-amps-with-the-lower-voltage-outlet-than-the-220v-counterpart-If-not-why-would-bulbs-with-2-different-amperages-give-off


--- Quote ---Bob Siegerdt says 100 watts is 100 watts. The filament for either bulb would be emanating the same amount of heat & light regardless of the input parameters.

I agree but the proportion of heat and light may differ. According to Wiki a 100 W, 230 V bulb puts out 13.8 lumens/watt but a 110 V version, 17.5 lm/W.

The difference might be due to the geometry of the filament. The higher voltage bulb needs to have very thin wire so it is usually of coiled coil construction. Maybe this affects the light output.

Another factor could be the longevity of the bulbs. Longer life bulbs run at a lower temperature but have lower efficiency. It could be that the US bulbs run hotter at the expense of bulb life. Thus they provide more profit to the manufacturer.

For more on this topic see The Great Light Bulb Conspiracy Full Page Reload
--- End quote ---

Also, someone saying things, very similar to what you are saying:


--- Quote ---Seems awfully many incorrect answers. For reasons I do not exactly know light bulbs work better at lower voltages. Therefore a 100 W bulb at 120 volts gives more light than on 230 volts, about 23% more assuming both are rated to 1000 hours. To get same amount of light at 230 volts one might have to cut the life to about 250 hours.

In Finland trams run at 1000 volts. Because that works badly with bulbs older trams had four 250 volt bulbs in series. Newer ones have have separated the voltage for internal lighting from the driving voltage.
--- End quote ---

More examples of similar disagreements:


--- Quote ---Its the power that makes light’s intensity. Although the voltage and current would be different in the US, a 100 W bulb in either country is still a 100 W bulb.
--- End quote ---


--- Quote ---The wattages are the same.

The temperatures of the filaments are the same.

Therefore the surface areas of the filaments are the same, and the amount of light emitted is the same.

What is different is that the 110 Volt filament is shorter and fatter than the 220 Volt filament, to keep everything above the same despite the lower voltage and higher current.

No, the brightness is the same ( or it would be if you could still buy 220 volt 100 watt bulbs).
--- End quote ---


The following is what I really should have said:


--- Quote ---100 watts is 100 watts. The filament for either bulb would be emanating the same amount of heat & light regardless of the input parameters.
--- End quote ---

Then it goes back to agreeing with you:


--- Quote ---For the same wattage a thicker wire is used and it is more rigid and can be run at a higher temperature giving more light without burning out.

I use LEDs for every thing except the oven light and that is only used for a few minutes a month.

--- End quote ---

MK14:

--- Quote from: james_s on April 11, 2022, 06:51:19 pm ---A 120V 60W incandescent lamp produces about 800 lumens for example, while the 240V version is only about 700 lumens. You can see the same effect by looking at the lumens per watt of different wattages of lamps.

--- End quote ---

TL;DR
Just to be clear. I somewhat agree with you, and your explanation as to why the 120V 60W lamps, are more efficient than the 240V versions.

It's deceptively difficult to properly/accurately interpret the situation. Because, changes to the filament design parameters, have to take place to restore the 1,000 hour life, between the 120V and 240V versions. Also, the exact definition/quality of the 1,000 hours burn life, might vary between the US and Europe/UK. Which could also confuse/complicate the issue. Because any genuine increase in burn life, the Europe/UK versions gain. Would be expected to respectively reduce the efficiency, between the 120V/240V lamp types.

I wonder if there is much difference between 120V and 240V LED bulb, efficiencies and burn life expectancy.

It can be tricky when trying to directly compare things between the US and Europe/UK, because standards, laws, and other things are different. E.g. Even the size of Gallons is in disagreement between the US and UK, and measurements are not necessarily done in the same way.
E.g. Is a 1,000 hour burn life or 800 Lumens, truly identical between the US and UK ?

Anyway, it does make a fair bit of sense. That a 120V lamp filament would be thicker, and hence take longer to thin out, intuitively speaking.

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