Video on planned obsolescence.

[David Hess]

Operating life ratings for LED bulbs are disingenuous at best.  The operating life of the LEDs is 10s of thousands of hours to half brightness but failure is complete when the ballast fails, which in my experience often happens before an incandescent bulb would fail.

So how much energy is saved by using a bulb which costs more in energy to manufacturer (as measured by cost which is a good proxy), when it does not last as long?  None.  NONE!

[SilverSolder]

Have you noticed that after the Phoebus cartel was shut down standard incandescent bulbs are still rated for only 1000h? Business as usual - it doesn't need a cartel.

If you increase longevity, you will decrease lumens per consumed power, as I already mentioned. You will make more durable product but much worse overall.

I don't understand the science behind that assertion - why would increased lifetime correlate with light output as a percentage of power consumed?

As you decrease filament temperature to increase it's lifetime, bulb becomes less efficient as it's spectrum shifts more towards IR, thus more energy is spent on heating ambient rather than usable light. And light no longer will be "white" and will have a strong yellow/red tint.

OK but there is an unspoken assumption here -  that lowering the filament temperature is the only way to improve bulb life.  It is one way, and it is an easy way - but is it really the only way?  For example, you could make the filament thicker, so it could withstand "boiling off its surface" for longer?

[james_s]

I don't understand the science behind that assertion - why would increased lifetime correlate with light output as a percentage of power consumed?

Lifespan is determined largely by filament temperature. The hotter the filament, the more rapidly tungsten evaporates off it and the sooner it fails. The ratio of visible light to IR (heat) produced by the filament is also determined by temperature, the cooler the filament, the more of its radiation occurs as heat instead of visible light. There is a sweet spot right around 700-1000 hours where the lamp delivers reasonably good efficiency (in incandescent terms) while lasting an acceptable lifespan.

There are some extreme examples, like photoflood lamps that produce a very bright white light around 3200k and are quite efficient, but this is accomplished by overdriving the filament and the result is a rated life of 6 hours. Lifespan decreases exponentially as voltage is increased.

[SilverSolder]

Operating life ratings for LED bulbs are disingenuous at best.  The operating life of the LEDs is 10s of thousands of hours to half brightness but failure is complete when the ballast fails, which in my experience often happens before an incandescent bulb would fail.

So how much energy is saved by using a bulb which costs more in energy to manufacturer (as measured by cost which is a good proxy), when it does not last as long?  None.  NONE!

The switch to more advanced bulbs that have less "real world" life and at higher cost might be considered related to Planned Obsolescence:    basically, needlessly increase the complexity of a product so you can charge more for it.

This works best of all if you can lobby to have laws passed that bans the simple and inexpensive solution that you don't think is making you enough money...  especially if you think the public would not accept price rises on the existing, simpler product!

[SilverSolder]

I don't understand the science behind that assertion - why would increased lifetime correlate with light output as a percentage of power consumed?

Lifespan is determined largely by filament temperature. The hotter the filament, the more rapidly tungsten evaporates off it and the sooner it fails. The ratio of visible light to IR (heat) produced by the filament is also determined by temperature, the cooler the filament, the more of its radiation occurs as heat instead of visible light. There is a sweet spot right around 700-1000 hours where the lamp delivers reasonably good efficiency (in incandescent terms) while lasting an acceptable lifespan.

There are some extreme examples, like photoflood lamps that produce a very bright white light around 3200k and are quite efficient, but this is accomplished by overdriving the filament and the result is a rated life of 6 hours. Lifespan decreases exponentially as voltage is increased.

Understood.  What happens if we make a thicker and longer filament to maintain the same resistance - will it burn longer before it breaks?

[james_s]

OK but there is an unspoken assumption here -  that lowering the filament temperature is the only way to improve bulb life.  It is one way, and it is an easy way - but is it really the only way?  For example, you could make the filament thicker, so it could withstand "boiling off its surface" for longer?

You can. But what else happens when you make the filament thicker? It requires more current to reach the same temperature, so either your lamp wattage increases, or you need the supply voltage to be lower. This precisely why low voltage incandescent lamps are more efficient than high voltage lamps of the same wattage. A 240V 60W incandescent produces close to the same light output as a 120V 40W lamp. Everything is a compromise, you can gain in one area but it will cost you in another.

[Miyuki]

I once saw some "special long life" incandescent with a rating of 5000h it had super thin and long fillament with a complicated support structure (230V one)

[james_s]

There exist incandescent lamps rated for 50k hours, I doubt they're made anymore but they were for indicator use where long life is more important than efficiency. For most applications though, lamps are optimized for efficiency. There is another factor that affects this, an inert gas fill. The increased pressure of a gas fill reduces the evaporation rate of tungsten which allows increased life at a given filament temperature. The cost is an increase in thermal losses from convection, which becomes more pronounced with thinner filaments and this is why most line voltage lamps below about 40 watts are vacuum filled while almost all larger lamps are gas filled.

[james_s]

Operating life ratings for LED bulbs are disingenuous at best.  The operating life of the LEDs is 10s of thousands of hours to half brightness but failure is complete when the ballast fails, which in my experience often happens before an incandescent bulb would fail.

So how much energy is saved by using a bulb which costs more in energy to manufacturer (as measured by cost which is a good proxy), when it does not last as long?  None.  NONE!

That does not reflect my experience at all. I have numerous LED bulbs that have been in service for at least 10 years so far. Some of them I replaced due to technological obsolescence, the original ones still worked fine but the newer ones bring almost double the efficiency and better quality light. I've had a couple of early failures but even the cheapest ones have lasted longer than incandescent lamps. Even just eliminating the "flash & pop" failure mode which usually seemed to happen when I turn on a light in the middle of the night made it worthwhile to change.

[SilverSolder]

So the best bet for a long life incandescent - if we lived in a cartel-free world - might be:

1) Longer, thicker filament to maintain same output while tolerating evaporation for longer (con: more complex support structure)
2) Gas fill, to suppress tungsten evaporation

and

3) Always run them on dimmers, so they only get cranked up to the max when actually needed


(point 3 is probably why I have many bulbs in this house that are >20 years old and still working!)

[james_s]

So the best bet for a long life incandescent - if we lived in a cartel-free world - might be:

1) Longer, thicker filament to maintain same output while tolerating evaporation for longer (con: more complex support structure)
2) Gas fill, to suppress tungsten evaporation

and

3) Always run them on dimmers, so they only get cranked up to the max when actually needed


(point 3 is probably why I have many bulbs in this house that are >20 years old and still working!)

If electricity was free then yes, that would work nicely. In the real world, you pay much more for the electricity than you do for the bulb, so while running a big high wattage bulb at lower power will give you very long life, it will also give you abysmal efficiency. It would be much cheaper to run a lower wattage bulb at full power and turn on an additional higher wattage bulb in those occasions where you need more light. The cost of the more frequent bulb replacements is trivial compared to the energy savings in doing so.

Using a longer, thicker filament for the same light output is just another way of saying "using a less efficient bulb optimized for long life". A thicker filament means higher current, a longer filament means higher voltage. A longer, thicker filament means higher wattage, ie more power consumed. The same light output from that longer, thicker, long lived filament means lower efficiency.

You can already buy exactly what you are proposing, at least you could. They are sold as "long life" lamps and often are simply 130V rated bulbs for use on 120V. They were intended for applications where changing bulbs is difficult and do last a very long time, however they are dim for the rated wattage (inefficient) and produce a yellowish light. You can also connect two identical bulbs in series so each gets half the rated voltage and they will easily last many decades of continuous use, but again there is a cost, the light output is a fraction of what you would get by giving each lamp full rated voltage. Using a dimmer is another option, but again with the same penalty. Try sometime dimming a lamp while watching the consumption on something like a Kill A Watt. Drop it down to where it looks perhaps half of full brightness and see that the energy consumption is around 80% of full power. Drop it down to half of rated power and it will be a dull reddish glow. It will last a very, very long time though.

You can optimize for lifespan or efficiency, increasing one will always cost you the other, there is no free lunch. Technologies like inert or halogen gas fill shift the entire scale but you still get the same compromise between long life or high efficiency and whiter light. It's still always true that in terms of commodity bulbs, the cost of the bulb itself is a small fraction of the total cost of ownership, the majority being the cost of energy it consumes over its life.

[SilverSolder]

[...] A longer, thicker filament means higher wattage, ie more power consumed. [...]

This is the part I am having difficulty understanding.  We can make the filament thicker:  lower R.   We can also make the filament longer: higher R.   If we do this just right, we can make a filament of any size ranging from very small to very large for a given target R.  The R is what controls the power ( P = E^2/R ) since we are keeping voltage constant.   The only difference between a small and a large filament of a given R will be how much metal it takes to make it (and therefore how long it will last before burning through).

What am I overlooking?

[BrokenYugo]

You're overlooking that this resistor has to get white hot, more mass/area=lower temperature=lower luminous efficiency.

[tooki]

Surprisingly many people will argue there is no such thing as planned obsolescence...

And people will argue that it exists where it doesn't, or where it's just incompetence or cost-cutting.  "Yeah, maaaaan, they had a carburetor back in the 70's that got 100MPG maaaaaan.  But they don't want you to know."

Sure, but that's not what was being discussed in the video:   we are talking about hard-core planned obsolescence.

I can see it could be hard for e.g. an Apple fan-boi to admit they are being taken advantage of this way, but nevertheless, that is what is happening to them.

Or maybe it’s because it’s actually not. The useful lifespans of Apple products is well above average, and this has been the case since the 80s.* Apple provides OS updates for its phones and tablets for 5+ years, far above the 0-2 years typical in the Android world. (My iPad is from 2014 and still gets OS updates, and is still more than snappy enough for daily use. My 2015 iPhone 6S running the current iOS is nearly as snappy as my year-old SE. I only upgraded because I couldn’t get replacement parts quickly enough due to COVID delays, and my screen was cracked.)

*Through the mid 2000s, researchers continuously found that Windows PCs were replaced after an average of 3 years, while the average Mac was replaced after 4-5 years. Between the longer lifespan and the dramatically higher resale value, the higher up-front cost was more than compensated. Since then, the average useful lives of both PCs and Macs has risen a lot, but the much higher resale value of used Macs is still the case.

[wraper]

What am I overlooking?

More filament for the same power = lower temperature = lower efficiency.

[tooki]

You're overlooking that this resistor has to get white hot, more mass/area=lower temperature=lower luminous efficiency.

Not to mention that the resistor would rapidly grow in size, to where it wouldn’t fit inside the bulb.

People forget just how long the filament is: it’s not a coiled wire. It’s a coiled coil of insanely thin wire, so it’s far longer than it appears. If we increased its diameter, we’d have to increase its length too...

[SilverSolder]

If a filament is suspended in a perfect vacuum, do we agree that the only way it can lose heat is by radiation?  (IR + light)

[Wolfram]

If a filament is suspended in a perfect vacuum, do we agree that the only way it can lose heat is by radiation?  (IR + light)

Radiation is by far dominant, and there will also be some conduction down the lead-in wires. Part of the IR from the filament is re-absorbed by the outer glass envelope, some of which is re-radiated and some of which is conducted to the socket. An energy balance diagram for gas-filled lamps can be found at http://lamptech.co.uk/Documents/IN%20Operation.htm , along with other relevant info.

[james_s]

There were a few incandescent lamps that employed an IR reflective coating on the inside of a specially shaped capsule to reflect radiated heat back at the filament. The challenge is that it requires extremely precise placement of the filament in the focal point for that to work, and that means that it has to be relatively rigid. The early attempts used a filament that was extremely brittle and often did not survive shipping from the manufacture. More recently around 12 years ago I got a few 60W equivalent lamps that used something like 38W. They used a small quartz capsule with a compact tightly wound filament. They worked well, but still couldn't compete with even the early LED bulbs.

They really did make attempts to push incandescent as far as possible. There were long life lamps, vibration resistant lamps, high efficiency lamps, low cost lamps, lamps optimized for heat output, lamps optimized for high color temperature, lamps optimized for any one characteristic for specific applications. With over 100 years of development it is a very mature technology, at some point there just wasn't much further it could be taken.

[tooki]

Tangent about IR reflection: did you know that halogen reflector bulbs come in two kinds? One uses an aluminum reflector coating, and reflects all the IR energy. This means the fixture doesn’t get hot, but the object lit by the bulb does. The other kind uses a dichroic mirror coating, which reflects visible light, but lets IR pass through, keeping the lighted object cooler, but requiring a fixture that can handle the heat.

[james_s]

Yes I remember when the dichroic ones first started appearing in the 80s, they were expensive and were used in high end track lighting in places like jewelry stores. I think one of the first applications was film and slide projection, as it was always a challenge to have a bright enough light source that would not melt your slides if you left one up on the screen for too long.

[helius]

You'll hear endless repetitions of the concept that filament life is a function of temperature, a convenient explanation that is both true (you can change the life by changing the voltage, which affects temperature) and false (not all filaments at the same temperature have the same life). That is because temperature is not the only independent variable in the life equation.

since we are keeping voltage constant.
What am I overlooking?

Most of the design space, if you think in terms of constant voltage. The higher the voltage, the longer and/or thinner the filament must be to get the same power dissipation. This reduces luminous efficacy and life, since the power is spread over a larger area (in a relation of length and cross-section to surface area, length dominates) (longer and thinner means more fragile). Automotive bulbs have much longer lives compared to house bulbs, and 120V bulbs much longer lives than 240V bulbs. And higher luminous efficacy!

There are more blind spots in this discussion, but the biggest one is the steady state assumption. If temperature corresponded with life, we would expect that bulbs of the same design would cluster around the same life time in terms of "on hours". But what actually happens is that a significant number last for 0 hours! If you've ever had a motion-activated "security" light, you know that they burn out bulbs at a ferocious rate. It's almost as if life should be counted in switching cycles rather than on hours...

What mechanism can explain the frequent (nearly universal) observation that burnout coincides with switching? The filament has a temperature coefficient. When turned off, it is at room temperature (or colder for exterior lamps; generally, ambient temperature). The temperature coefficient of resistance is positive, so as temperature increases, so does resistance. That makes cold resistance much lower than operating resistance. Say that a 240V lamp has a power dissipation of 60W. That means that its operating resistance should be around 1K ohms. Suppose it operates at 3000 °C. Then its cold resistance (from the tungsten tempco of 0.0045) is just 75 ohms. So during the first few milliseconds after it switches on, its power consumption is over 750 watts! And the wiring etc has no difficulty delivering that much current.

When such a large amount of power is focused in a small object, heating is also rapid. Unfortunately, the filament does not have uniform cross-section at the atomic level, so there will be some regions where heating happens first. Metal will boil away faster in these areas, thinning them down further, and the local heating becomes progressively more intense. These are the places where the filament will eventually, on one of these switch-on events, break and end its useful life.

There are also ways to mitigate this process, and they have been known for a very long time. This is really basic stuff, nothing fancy that you could patent or build a company on. It was probably known by Edison a hundred years ago.

[james_s]

They do usually fail at turn-on, however in typical usage patterns I don't think a light would last that many more hours when left on continuously, eventually you will still get a thin spot that burns hotter and thins even more quickly until it fails, and I have had lamps burn out a few times while they were on steady state. I suspect a lot of the rapid failures in motion sensor lights involve halogen lamps, which most of the later incandescent PAR lamps are too. You can kill a halogen lamp pretty quickly by running it in short cycles, or on a dimmer at too low brightness because the envelope temperature never reaches a point where the halogen cycle works effectively. This happens in laser printers too which typically use a tubular halogen lamp to heat the fuser roller. I remember replacing one once that was completely black, and back when those halogen torchier lamps were popular I killed a bulb once when I accidentally left it on at low brightness overnight, by the time I noticed it was on, the bulb had turned black and it burned out soon after I tried turning it up to see if the bulb wall would clean up.

Certainly some bulbs tolerate cycling well, the small vacuum filled sign lamps used to frequently be used on chasers and scintilators that would turn a bulb on and off thousands of times in a single evening.

[SilverSolder]

I was thinking about the implications of a coiled filament.  It seems to me that by coiling the filament, it cannot radiate from half its surface (the IR radiation on the inside of the coil is balanced by the IR radiation coming in from the opposite side).  So a coiled filament will run hotter than the same length of filament that has not been coiled.  -  Which in turn means that a coiled filament could be made from thicker wire, and might therefore last longer...  ?

[NiHaoMike]

Most of the design space, if you think in terms of constant voltage. The higher the voltage, the longer and/or thinner the filament must be to get the same power dissipation. This reduces luminous efficacy and life, since the power is spread over a larger area (in a relation of length and cross-section to surface area, length dominates) (longer and thinner means more fragile). Automotive bulbs have much longer lives compared to house bulbs, and 120V bulbs much longer lives than 240V bulbs. And higher luminous efficacy!

There were some incandescent bulbs with built in diodes to allow the use of a shorter and thicker filament for a given wattage, often marketed as "solid state enhanced". They did not achieve much popularity since they appeared around the time CFLs became affordable.