lumens vs voltage; incandescent

And here's another one, showing tungsten crystals growing on the reflector and support wires:

Cheers

Phil Hobbs

Great, for those of us who have access to incancescent bulbs?

Dave in the non-incandescent USA

Well, I have 200 of them in the closet. ;)

You can still get them here, just not in the supermarket. See e.g.

Cheers

Phil Hobbs

This is not what you asked, but have you calculated the cost of the electri city to run that bulb? A 40 watt bulb rated at 420 lumens at 130 volts has an average life of 1000 hours. So at 130 volts you get 420,000 lumen hour s and consume 40,000 watt hours. If the power is 0.10 per kilowatt hour th en the cost of electricity is $4. or 105,000 lumen hours per dollar for the electricity.

At 10 % lower voltage you get about 294 lumens . so for 1000 hours of oper ation you will get 294,000 lumen hours and assuming 10% less wattage, that would cost in electricity 3.60. Or 82,000 lumen hours per dollar of electr icity.

A high efficientcy 4 watt LED will put out about 400 lumens and consume abo ut forty cents of electricity per 1000 hours.

Dan

I have at least 300 (100-100W clear, 100-60W clear, 100-60W frosted and miscellaneous others) in the basement. I did buy a few LED "vintage style" because the incandescent versions were rather dim. These are going in pendant lights over the sink, so wanted more light.

That's where I bought my stash, a few years back.

Another way of looking at it is that if I'm reading a book by an slightly dim CFL or an ugly LED (they're all ugly at some level), I can have it the way I like it for about one cent per hour, if some bloody officious bureaucrat doesn't have a hard-on about it.

Cheers

Phil Hobbs

I posted that mostly because many people think they are saving money by using 130 volt lamps because they last longer. But most of the cost is in the electricity not the cost of the lamp. Cheaper to use lower wattage 120 lamps.

Here in the winter using incandescent bulbs helps keep the house warm. In the summer not as good an idea.

Dan

the electricity not the cost of the lamp. Cheaper to use lower wattage 120 lamps.

Right y'are, guv. The 130V ones are good for places that are hard to reach, like stairwell ceilings, but are otherwise a bad idea.

Cheers

Phil Hobbs

It's not "iodide vapour" that interesting, but tungsten iodide vapour (whic h may have been what you meant) and that doesn't decompose "everywhere".

Tungsten chloride doesn't decompose below 1200C. Tungsten iodide still seem s to form at 800C

In reality, there's an equilibrium between tungsten and iodine and tungsten iodide which is heavily biased towards tungsten iodide at low temperatures and towards the elements at high temperatures do a degree that's controlle d by the enthalpy of formation

only lists the bond energy for W-F and W-Cl (548 and 4323 kjoule/mole). The entropy involved is obvious.

The point is that WI2, WI4 etc form away from the filament, and come apart close to the filament. The processes of formation and decomposition are fas test where the temperature is higher - closest to the filament.

Both processes may be going on "everywhere", but decomposition is a lot fas ter close to the filament, and even faster closer to hot spots on the filam ent. I did do my Ph.D. in chemical kinetics so I may be more conscious of t he importance of reaction rates than you seem to be.

If they stick out, they'll be cooler than the body of the filament - no res istance heating - and the tip won't grow as fast as surfaces closest to the filament.

You couldn't find it, so my chances would be worse.

Further reading says I got it wrong - the first tungsten halide bulbs were developed for aircraft beacon lights, and they moved into project lamps ver y early on.

The advantage of coarser gauge filaments can't be all that great - with tra nsformer drive you can use pretty much any voltage you want, but while ther e are lower voltage bulbs available (for bicycle lights, for instance) nobo dy seems to be selling lower-than-12V bulbs for interior lighting.

My 240V halogen lamps for indoor lighting last two years - twice as long as the regular bulbs they replace, as well as delivering appreciably more lig ht per watt consumed.

Run the dimmer at 100 % occasionally for minutes or hours to restore the cycle, this seems to help.

Going too much lower takes a lot of copper, and probably risks dumping a lot of heat into the sockets due to the contact resistance and much larger conduction loss from the filament, which could be bad. (I haven't calculated the size of any of those effects.)

Also there's the issue of the glass-metal seal, which is usually made of Dumet wire. The larger you make the pins, the more stress the residual CTE mismatch causes.

Cheers

Phil Hobbs

I suppose it is inevitable with diffusion limited slow growing crystals

- we should give thanks that it doesn't form dendrites.

BTW do you have any more info on the new graphene based light bulbs.

This picture of the UK Chancellor (aka Mr Bean) marvelling at one has a press release repeated on the BBC that makes no sense at all.

"Filament shaped LED inside a graphene cylinder" WOT!?!

It does, but they burn off when they short out. There's patent literature on that.

Haven't seen them. Sounds like a gimmick, but I'd be glad to be wrong about that.

People have been trying to use things like tungsten photonic crystals to improve incandescent lights for ages, and nobody has managed to solve the diffusion problem. The photonic crystals have so much internal surface area that they just fuse together, like a snowball in the deep freeze.

Cheers

Phil Hobbs

ding ding ding

we have a winner

yes..... when I have the old fashion incandescnet light on near me in the winter, i can actualy turn the whole house heat down a bit..

so which is better for my carbon foot print

officious bureaucrats are not very good at science

Mark

Hmm maybe the graphene is being used for it's heat conduction, get's the heat out of the led faster, keeping it cooler. (?)

At the latest APS show there was a company that will sell you graphene on different substrates. I think Si was the cheapest ~ $50 per sample. From a little reading it's not all that hard to make.

George H.

In the summer not as good an idea.

he winter, I can actualy turn the whole house heat down a bit..

Officious bureaucrats are probably aware that you'll have the same light-bu lb in place in summer, and have to turn the air-conditioning up higher to g et rid of the extra heat it is producing. Air-conditioning systems seem to eat up more energy that home heating - reverse cycle air-conditioning is an efficient way of heating a house in winter but can rarely shift enough hea t to cope with a Northern European or US winter.

They are probably better at science than you are - which isn't saying much.

Sellotape (TM) natural graphite and a bit of patience.

Crossed polars will show when you are down to a single layer. Back in my physics days we did theoretical calculations of 2D trapped electron states and now they can actually make real systems to play with.

Same with buckminsterfullerenes they had been lurking in soot since forever waiting for someone to extract them with xylene. Also had been seen in space by astronomers as dark "dust" with curious absorbtion features not previously seen in any terrestrial compounds...

The people I talked with are all using CVD (chemical vapor deposition) on copper substrates. (You can search for CVD Graphene and get lots of stuff.) Copper is a good "catalyst" for some reason.

George H.

--- The reason is that - at the start of the reaction - Copper's affinity for its valence electrons isn't high enough to keep them bound, and they move over to the "other side".

Then, when the reaction is complete, there are leftover electrons which find copper more alluring than what was made, fill its outer shell, and free it, leaving the work it did behind. John Fields