lumens vs voltage; incandescent

[oldy...@yahoo.com]

How does voltage effect lumens in a incandescent bulb?

A bulb rated 420 lumens at 130VAC will output how many lumens at 115VAC?

[Jeff Liebermann]

On Sat, 28 Mar 2015 08:00:50 -0700 (PDT), oldy...@yahoo.com wrote:

>How does voltage effect lumens in a incandescent bulb?
>A bulb rated 420 lumens at 130VAC will output how many lumens at 115VAC?

This directly addresses your question:
<http://blog.1000bulbs.com/why-buy-130-volt-light-bulbs/#.VRbGao7i_EA>

Also, Fig 4:
<http://www.ilo.org/iloenc/part-vi/lighting/item/262-types-of-lamps-and-lighting>

and Fig 2:
<http://www.mendipcavinggroup.org.uk/sections/news/occpub2.html>

--
Jeff Liebermann je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[oldy...@yahoo.com]

Thanks Jeff. Looks like 130VAC bulb operating at 115 looses about 30%.

[piglet]

On 28/03/2015 15:00, oldy...@yahoo.com wrote:
> How does voltage effect lumens in a incandescent bulb?
>
> A bulb rated 420 lumens at 130VAC will output how many lumens at 115VAC?
>

Light output is reckoned to vary with the power 3.5 against rated
voltage. Lifetime inversely to the 12th power. So intensity will be a
bit lower, lamp lifetime will be much greater.

So 115 vs 130VAC is 65% light reduction or 273lumens to answer your
question. (Lifetime at 115v will be more than four times 130V life.)

piglet

[piglet]

On 28/03/2015 16:36, piglet wrote:
> So 115 vs 130VAC is 65% light reduction or 273lumens to answer your

Correction. Please forgive sloppy language: meant reduced *to* 65% of
rated output not reduced *by* 65%. IOW 420 * 0.65 = 273

piglet

[Phil Hobbs]

30% lower light and three times the life is the usual rule for 10% lower voltage.

Cheers

Phil Hobbs

[Syd Rumpo]

On 28/03/2015 15:24, Jeff Liebermann wrote:
> On Sat, 28 Mar 2015 08:00:50 -0700 (PDT), oldy...@yahoo.com wrote:
>
>> How does voltage effect lumens in a incandescent bulb?
>> A bulb rated 420 lumens at 130VAC will output how many lumens at 115VAC?
>
> This directly addresses your question:
> <http://blog.1000bulbs.com/why-buy-130-volt-light-bulbs/#.VRbGao7i_EA>

<snip>

<quote>
130 volt Halogen and incandescent light bulbs are manufactured with a
thick filament designed to withstand a theoretical 130 volts. I say
“theoretical” because almost all homes in the US operate on only 110-120
volts. The thicker filament in a 130 volt bulb, when operated on typical
110-120 line voltage, has a higher resistance to the electrical current
flowing through the filament, decreasing the amount current across the
filament. As a result, the bulb burns cooler, uses less energy (watts),
and lasts longer; however, as a trade-off, the bulb is also slightly
dimmer and has a lower (more yellow) color temperature.
</quote>

Thicker filament in a 130V bulb? Riiight.

Cheers
--
Syd

[Phil Hobbs]

Not thick wire, right. Tungsten bulbs working ar mains voltage use coiled-coil filaments, so a fatter coil of the same wire gauge will have a higher resistance.

Cheers

Phil Hobbs

[John Larkin]

Low voltage bulbs, like 12 volts, seem to last a long time. Maybe a
thick filament has more metal to boil off.


--

John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

[k...@zzz.com]

On Sat, 28 Mar 2015 14:12:28 -0700, John Larkin
<jla...@highlandtechnology.com> wrote:

>On Sat, 28 Mar 2015 12:24:42 -0700 (PDT), Phil Hobbs
><pcdh...@gmail.com> wrote:
>
>>Not thick wire, right. Tungsten bulbs working ar mains voltage use coiled-coil filaments, so a fatter coil of the same wire gauge will have a higher resistance.
>>
>>Cheers
>>
>>Phil Hobbs
>
>Low voltage bulbs, like 12 volts, seem to last a long time. Maybe a
>thick filament has more metal to boil off.

It's also mechanically stronger.

[Phil Hobbs]

Yes, plus the filament is more nearly isothermal. 220V bulbs are quite a bit more fragile than 120V ones.

Cheers

Phil Hobbs

[Lasse Langwadt Christensen]

back when all stage lighting was incandescent I saw a lot of companies using
PAR64 lamps with 120V bulbs in series pairs on 240V

-Lasse

[Phil Hobbs]

That fit function doesn't apply across the whole range though,
especially towards higher voltage. Once the tungsten melts, it's all over.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

[Bill Sloman]

On Sunday, 29 March 2015 11:51:09 UTC+11, Phil Hobbs wrote:
> On 3/28/2015 12:36 PM, piglet wrote:
> > On 28/03/2015 15:00, oldy...@yahoo.com wrote:
> >> How does voltage effect lumens in a incandescent bulb?
> >>
> >> A bulb rated 420 lumens at 130VAC will output how many lumens at 115VAC?
> >
> > Light output is reckoned to vary with the power 3.5 against rated
> > voltage. Lifetime inversely to the 12th power. So intensity will be a
> > bit lower, lamp lifetime will be much greater.
> >
> > So 115 vs 130VAC is 65% light reduction or 273lumens to answer your
> > question. (Lifetime at 115v will be more than four times 130V life.)
>

> That fit function doesn't apply across the whole range though,
> especially towards higher voltage. Once the tungsten melts, it's all over.

Tungsten halogen lamps are complicated beasts. The halogen gas inside the silica envelope reacts with evaporated tungsten vapour to produce a volatile tungsten halide, which doesn't condense on the inside of the silica envelope (if the lamp is being run hard enough to keep the envelope warm), and eventually circulates past the hot filament, which is hot enough to decompose the tungsten halide, which decomposes into tungsten - which condenses onto the filament - and halogen gas, which is recycled.

The cute bit is that the hottest bits of the filament decompose more halide, so that the wire thickness remains sensibly uniform along the filament - no hot spots.

--
Bill Sloman, Sydney

[Phil Hobbs]

It's actually the high gas pressure (requiring the strong quartz
envelope) that retards hot spot formation, by slowing down diffusion of
vapour/halide away from its point of origin.

The hot spots aren't enough hotter for there to be a significant
difference in the sticking probability of an incident molecule. This is
especially true in the early stages of hot spot formation, which you
want to slow down as much as possible.

Also the redeposited tungsten tends to form largish crystals, so the
redeposited metal is nonuniform.

The halide mechanism is thus sort-of regenerative, but its main purpose
is to keep the very small envelope clean. Normal low pressure bulbs
reduce darkening by spreading the condensed tungsten over an area ~100x
larger, but a bulb that big with the kind of internal pressure required
to reduce diffusion would be very dangerous, and the internal convection
loss would be gigantic.

[mako...@yahoo.com]

>
> The halide mechanism is thus sort-of regenerative, but its main purpose
> is to keep the very small envelope clean. Normal low pressure bulbs
> reduce darkening by spreading the condensed tungsten over an area ~100x
> larger, but a bulb that big with the kind of internal pressure required
> to reduce diffusion would be very dangerous, and the internal convection
> loss would be gigantic.

Question.... does operating a halogen bulb on a lower voltage with a dimmer for example, offer the same lifetime advantages vs efficency tradeoffs as does a conventional incandescent?

or are the low voltage tradeoffs significantly different?

Mark

[Martin Brown]

Tends to ruin them with tungsten plating out on the quartz envelope
preventing light escaping and not being recycled properly as the
volatile halogen compound back to the filament where it decomposes into
metal and releases the halogen again. Run too cold the stuff plates out
on the cooler envelope and never makes it back to the filament again.

Lifetime and light output both potentially compromised.

--
Regards,
Martin Brown

[Phil Hobbs]

The primary evaporation rate will still basically set the life of the
bulb, so I'd expect the life to improve at about the same rate as with
normal argon-filled bulbs, for sufficiently small voltage reductions.
(How's that for physics weaselling?) ;)

At some point the halogen mechanism shuts down and bulb darkening sets
in, though. IME that's generally reversible if you crank it up to full
brightness for awhile.

[Bill Sloman]

You've got to decompose your tungsten halide molecule before you've got an an incident tungsten atom to stick onto anything.

The decomposition is going to happen close to the filament, and it's going to happen faster where the filament is hottest - convection currents are going to be faster there too, delivering more tungsten halide into the hot zone.

> This is
> especially true in the early stages of hot spot formation, which you
> want to slow down as much as possible.
>
> Also the redeposited tungsten tends to form largish crystals, so the
> redeposited metal is nonuniform.

Got any pictures? "Largeish" in the context of a coiled-coil tungsten filament would probably only show up in an electron-microscope photograph.

>
> The halide mechanism is thus sort-of regenerative, but its main purpose
> is to keep the very small envelope clean.

True.

> Normal low pressure bulbs
> reduce darkening by spreading the condensed tungsten over an area ~100x
> larger, but a bulb that big with the kind of internal pressure required
> to reduce diffusion would be very dangerous, and the internal convection
> loss would be gigantic.

The halide regeneration was developed to beat that particular limit - with the halogen in the gas mix you can get away with running the filament hotter, and in a more compact envelope. If memory serves, the scheme was originally developed to make better bulbs for car head-lights and it was a while later before you could get tungsten halogen bulbs for domestic lighting - and the first generation of them showed their automotive origins by needing step-down transformers to let them run at 12V.

--
Bill Sloman, Sydney

[Phil Hobbs]

A little bit more, but not nearly _enough_ more, especially in the early
stages, as I say. Iodide vapour decomposes everywhere, and so
redeposits everywhere. To retard hot spot growth, you need a lot of
extra vapour right there, and the only way to get that is by slowing
down diffusion.

>> This is especially true in the early stages of hot spot formation,
>> which you want to slow down as much as possible.
>>
>> Also the redeposited tungsten tends to form largish crystals, so
>> the redeposited metal is nonuniform.
>
> Got any pictures? "Largeish" in the context of a coiled-coil
> tungsten filament would probably only show up in an
> electron-microscope photograph.

Largish in the sense of "comparable to the wire radius".

Someplace on the web, there was a great picture of a well-used BMW
headlamp filament, but I couldn't find it again in a quick search. It
had tungsten crystals comparable in size to the filament radius, which
was _big_. You can probably find it in a few minutes if you look.

>> The halide mechanism is thus sort-of regenerative, but its main
>> purpose is to keep the very small envelope clean.
>
> True.
>
>> Normal low pressure bulbs reduce darkening by spreading the
>> condensed tungsten over an area ~100x larger, but a bulb that big
>> with the kind of internal pressure required to reduce diffusion
>> would be very dangerous, and the internal convection loss would be
>> gigantic.
>
> The halide regeneration was developed to beat that particular limit
> - with the halogen in the gas mix you can get away with running the
> filament hotter, and in a more compact envelope. If memory serves,
> the scheme was originally developed to make better bulbs for car
> head-lights and it was a while later before you could get tungsten
> halogen bulbs for domestic lighting - and the first generation of
> them showed their automotive origins by needing step-down
> transformers to let them run at 12V.

I remember "high intensity" desk lamps back in the '60s that used
halogen bulbs. I think slide projectors had them very early too. Most
bulbs used in projectors are low voltage to this day, because the
coarser gauge filaments last a lot longer at the same temperature--lots
more metal available per unit area.

[Phil Hobbs]

This wasn't it, but you can see the process beginning.
<http://upload.wikimedia.org/wikipedia/commons/8/82/TungstenFilamentHalogenH1Lamp.JPG>

[Phil Hobbs]

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

<http://techno-fandom.org/~hobbit/cars/maint100k/2315oldfdet.jpg>

[DaveC]

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

Dave
in the non-incandescent USA

[Phil Hobbs]

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

You can still get them here, just not in the supermarket. See e.g.
https://www.1000bulbs.com/product/114013/SYLVANIA-12902.html

[dca...@krl.org]

On Saturday, March 28, 2015 at 11:01:00 AM UTC-4, oldy...@yahoo.com wrote:
> How does voltage effect lumens in a incandescent bulb?
>
> A bulb rated 420 lumens at 130VAC will output how many lumens at 115VAC?

This is not what you asked, but have you calculated the cost of the electricity 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 hours and consume 40,000 watt hours. If the power is 0.10 per kilowatt hour then 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 operation 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 electricity.

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

Dan

[k...@zzz.com]

On Mon, 30 Mar 2015 15:54:23 -0400, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>On 03/30/2015 03:47 PM, DaveC wrote:
>> 30% lower light and three times the life is the usual rule for 10% lower
>>> voltage.
>>>
>>> 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. ;)

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.

>You can still get them here, just not in the supermarket. See e.g.
>https://www.1000bulbs.com/product/114013/SYLVANIA-12902.html

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

[Phil Hobbs]

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.

[dca...@krl.org]

On Monday, March 30, 2015 at 9:00:29 PM UTC-4, Phil Hobbs wrote:

> >
>
> 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

[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.

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

[Bill Sloman]

On Tuesday, 31 March 2015 01:26:00 UTC+11, Phil Hobbs wrote:
> On 03/30/2015 10:12 AM, Bill Sloman wrote:
> > On Monday, 30 March 2015 23:29:02 UTC+11, Phil Hobbs wrote:
> >> On 3/30/2015 1:51 AM, Bill Sloman wrote:
> >>> On Sunday, 29 March 2015 11:51:09 UTC+11, Phil Hobbs wrote:
> >>>> On 3/28/2015 12:36 PM, piglet wrote:
> >>>>> On 28/03/2015 15:00, oldy...@yahoo.com wrote:

<snip>

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

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

http://www.digipac.ca/chemical/mtom/contents/chapter3/halogenlight.htm

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 controlled by the enthalpy of formation

https://labs.chem.ucsb.edu/zakarian/armen/11---bonddissociationenergy.pdf

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 fastest where the temperature is higher - closest to the filament.

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

<snip>

> > Got any pictures? "Largeish" in the context of a coiled-coil
> > tungsten filament would probably only show up in an
> > electron-microscope photograph.
>
> Largish in the sense of "comparable to the wire radius".

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

> Someplace on the web, there was a great picture of a well-used BMW
> headlamp filament, but I couldn't find it again in a quick search. It
> had tungsten crystals comparable in size to the filament radius, which
> was _big_. You can probably find it in a few minutes if you look.

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

> >> The halide mechanism is thus sort-of regenerative, but its main
> >> purpose is to keep the very small envelope clean.
> >
> > True.
> >
> >> Normal low pressure bulbs reduce darkening by spreading the
> >> condensed tungsten over an area ~100x larger, but a bulb that big
> >> with the kind of internal pressure required to reduce diffusion
> >> would be very dangerous, and the internal convection loss would be
> >> gigantic.
> >
> > The halide regeneration was developed to beat that particular limit
> > - with the halogen in the gas mix you can get away with running the
> > filament hotter, and in a more compact envelope. If memory serves,
> > the scheme was originally developed to make better bulbs for car
> > head-lights and it was a while later before you could get tungsten
> > halogen bulbs for domestic lighting - and the first generation of
> > them showed their automotive origins by needing step-down
> > transformers to let them run at 12V.
>
> I remember "high intensity" desk lamps back in the '60s that used
> halogen bulbs. I think slide projectors had them very early too. Most
> bulbs used in projectors are low voltage to this day, because the
> coarser gauge filaments last a lot longer at the same temperature--lots
> more metal available per unit area.

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

The advantage of coarser gauge filaments can't be all that great - with transformer drive you can use pretty much any voltage you want, but while there are lower voltage bulbs available (for bicycle lights, for instance) nobody 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 light per watt consumed.

--
Bill Sloman, Sydney

[upsid...@downunder.com]

On Mon, 30 Mar 2015 06:12:38 -0700 (PDT), mako...@yahoo.com wrote:

>
>>
>> The halide mechanism is thus sort-of regenerative, but its main purpose
>> is to keep the very small envelope clean. Normal low pressure bulbs
>> reduce darkening by spreading the condensed tungsten over an area ~100x
>> larger, but a bulb that big with the kind of internal pressure required
>> to reduce diffusion would be very dangerous, and the internal convection
>> loss would be gigantic.
>
>Question.... does operating a halogen bulb on a lower voltage with a dimmer for example, offer the same lifetime advantages vs efficency tradeoffs as does a conventional incandescent?

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

[Phil Hobbs]

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.

>
> 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 light per watt consumed.
>

[Martin Brown]

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.

http://www.bbc.co.uk/news/science-environment-32100071

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

--
Regards,
Martin Brown

[Phil Hobbs]

On 03/31/2015 08:27 AM, Martin Brown wrote:
> On 30/03/2015 15:40, Phil Hobbs wrote:
>> On 03/30/2015 10:34 AM, Phil Hobbs wrote:
>>> On 03/30/2015 10:25 AM, Phil Hobbs wrote:
>>>> On 03/30/2015 10:12 AM, Bill Sloman wrote:
>>>>> On Monday, 30 March 2015 23:29:02 UTC+11, Phil Hobbs wrote:
>>>>>>
>>>>>> Also the redeposited tungsten tends to form largish
>>>>>> crystals, so the redeposited metal is nonuniform.
>>>>>
>>>>> Got any pictures? "Largeish" in the context of a coiled-coil
>>>>> tungsten filament would probably only show up in an
>>>>> electron-microscope photograph.
>>>>
>>>> Largish in the sense of "comparable to the wire radius".
>>>>
>>>> Someplace on the web, there was a great picture of a well-used
>>>> BMW headlamp filament, but I couldn't find it again in a quick
>>>> search. It had tungsten crystals comparable in size to the
>>>> filament radius, which was _big_. You can probably find it in
>>>> a few minutes if you look.
>>>
>>> This wasn't it, but you can see the process beginning.
>>> <http://upload.wikimedia.org/wikipedia/commons/8/82/TungstenFilamentHalogenH1Lamp.JPG>
>>>
>>>
>>
>> And here's another one, showing tungsten crystals growing on the
>> reflector and support wires:
>>
>> <http://techno-fandom.org/~hobbit/cars/maint100k/2315oldfdet.jpg>
>
> I suppose it is inevitable with diffusion limited slow growing
> crystals - we should give thanks that it doesn't form dendrites.

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

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

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

>
> 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.
>
> http://www.bbc.co.uk/news/science-environment-32100071
>
> "Filament shaped LED inside a graphene cylinder" WOT!?!

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.

[mako...@yahoo.com]

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

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

[George Herold]

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.
>
> --
> Regards,
> Martin Brown

[Bill Sloman]

On Wednesday, 1 April 2015 00:23:09 UTC+11, mako...@yahoo.com wrote:
> >
> > Here in the winter using incandescent bulbs helps keep the house warm. In the summer not as good an idea.
> >
> > Dan
>
> ding ding ding
>
> we have a winner
>

> yes..... when I have the old fashioned incandescent 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.

Officious bureaucrats are probably aware that you'll have the same light-bulb in place in summer, and have to turn the air-conditioning up higher to get 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 heat to cope with a Northern European or US winter.

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

--
Bill Sloman, Sydney

[Martin Brown]

On 31/03/2015 14:57, George Herold wrote:

> 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.

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...

--
Regards,
Martin Brown

[George Herold]

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.

[John Fields]

On Tue, 31 Mar 2015 08:08:11 -0700 (PDT), George Herold
<ghe...@teachspin.com> wrote:


>Copper is a good "catalyst" for some reason.

---
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