Tungsten bulbs on the World Service.

Was listening to the car radio on the way home last night at about 1 am. When The World Service takes over from R4.

And they mentioned an improvment to tungsten bulbs - some form of crystalline coating which reflects the IR back into the filament and improves efficiency. Anyone got more details?

Reply to
Dave Plowman (News)
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see thread "Torygraph: MIT develops incandescent lamp that is more efficient than LED" Robin reply to address is (meant to be) valid

Reply to
Robin

I heard that broadcast too and was surprised to hear that a typical incandescent bulb is only 2% efficient.

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I looked up light bulb efficiency on Wikipedia and it said LED and fluorescent bulbs are both about 10% efficient. I thought LED was much more efficient but Wikipedia's figure suggest otherwise. See this table.

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Reply to
pamela

I might have got the wrong end of the stick, but the other day I was reading that the very best commercially available LEDs now run up to 200 lumens per watt. E.g. in very expensive torches. With 240 in the labs. Too expensive to be in our run of the mill pond shop specials. Yet.

Reply to
polygonum

The obvious thing to do, having looked that table, is to tackle the efficiency of the candle. With a luminous efficiency quoted as 0.04%, there is loads of room for improvement!

Reply to
polygonum

Depends what you mean by typical. Seems to be the fashion to quote the very worst possible they can find as 'typical'

Think with LEDs many judge the brightness by looking at it - rather than measuring the light from it.

Reply to
Dave Plowman (News)

Thanks for posting that link. It's the best comparison table I've seen so far. However, you must have missed the LED lamp figures if you think the current best examples are only 10% efficient. There's a 5.4W 100v screw base lamp showing 14.9% efficiency (nothing said about its CRI so it might be s**te) but that is less than half what Cree and Philips managed with laboratory examples almost 2 years ago when they suggested such lamps take about 18 to 24 months to be realised as saleable product.

If their timetable on this promise hasn't seriously slipped, we might reasonably expect to see 250 to 300Lm per watt lamps on the shop shelves by the end of the first quarter (some 2 1/2 to 3 times better than the best 91 Lm per watt examples I've seen on sale during the last 6 months or so.

The impending release of these lamps may simply be the reason the retail chain is only now offering the current crop at seemingly reasonable prices - clearing out what is destined to become unsaleable product from off the shelves. No doubt the new lamps will carry the same premium pricing the existing product had when that first hit the shops but they will represent a much better investment this time around.

If you're looking to upgrade existing lamps in fittings designed for incandescent lamps, it's well worth hanging on for a 200Lm per watt lamp simply to avoid the overheating hazard of (say for example) a 120v 100W

750 hour equivilent lamp with a 91 Lm per watt rating since, as well as using the same input energy of the older 75W equivilent, there's an even smaller fraction of that input energy going to waste heat (70% instead of 85% of the input energy).

It's not *all* about efficiency. If we could safely ignore the overheating issue, the current best of 90 to 100 Lm per watt would be efficient enough. Doubling the efficiency to 200 Lm per watt will make very little impact on most users' electricity consumption. The major savings in electricity on lighting costs took place when the electronically ballasted CFL was first introduced some twenty(?) years ago.

Reply to
Johnny B Good

You're over 2 years late with that news regarding laboratory examples. Both Cree and Philips announced, some 23 months back, 303 and 267 Lm per watt samples respectively. Their spokespersons both reckoned on an 18 to

24 month timetable to translate this into saleable product.

We're now only a month away from the end of that 24 month promissory period when we might expect to see such higher efficiency lamps on sale. Unless you're in desperate need to upgrade, I'd hold off any heavy investment for now (i.e. don't go mad buying several packs of 5 to completely relamp your house and restock your 'spares cupboard').

Reply to
Johnny B Good

About the only way I could see to achieve such a laudable goal might be to use the candle to energise a thermoelectric generator and use the output from that to drive a high efficiency LED lamp. :-)

Checking out thermoelectric generator efficiency figures (which range from 5 to 8 percent for existing TEGs right up to the 15 to 20 percent promises being made with the latest telluride semiconductor materials) it seems this might be the way to bump up a candle's light output by a factor of anywhere from 125 to 750 times! There may of course be other practical issues which reduce the overall improvement suggested by the raw figures but, even so, it does suggest the possibility that a modest four to tenfold improvement might actually be readily obtained, a not insignificant improvement over a naked candle alone.

Reply to
Johnny B Good

They're over 300 lm/W in the labs now, but I don't see high power, high efficiency devices yet, e.g. Cree offer their XP-L with a headline 200 lm/W efficiency but that's only when driven at 350mA, if you want the other headline 10W output, it drops to 150 lm/W, granted that's 50% higher than bog standard BC22s on the shelves.

Reply to
Andy Burns

5% is the figure I've heard.

Yes, I did. Odd.

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Well, not in a domestic setting I'd have thought. And then there's the 'candle effect':

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Reply to
RJH

I think most of the LED figures are old one - a couple of random click on the reference links takes you to pages a few years old. .

Are we going to have a party when they finally arrive :-)

Reply to
Chris French

I've no idea how accurate it is, but it confirms my findings here. That the best LED commonly available is no better than the best fluorescent. And of course most of the cheap LEDs are nowhere near state of the art.

It also suggests that for a GLS replacement, LED equates to about 3 times the light of decent halogen, watt for watt. And the problem being there are simply no LED replacements available that give the same amount of light as say a 100w halogen.

My problem is I first need the lighting level I want. Cost savings are secondary.

Reply to
Dave Plowman (News)

I was very surprised at the Wikipedia values for LEDs vs fluorescents. In the last two days I have replaced 10 screw-in CFL bulbs with LED bulbs of lower wattage (according to info on the bulbs). All the bulbs, LED and CFL, were purchased from Ikea.

In every case, the LED bulbs were markedly brighter (as well as becoming bright instantly). The only cases where there was near-equality were two tubular CFL bulbs in ceiling globes. The other CFL bulbs were of the classic "incandescent" shape.

Reply to
Timothy Murphy

CFLs may be fluorescent, but generally nowhere as good as a proper tube one.

This is the main problem. Within any principle of operation - be it filament, fluorescent, LED, etc, there is a wide range of efficiencies. And the marketing boys simply choose the ones which suit their sale pitch best.

Reply to
Dave Plowman (News)

A proper tube one is useless as a screw-in replacement bulb though, so in that context, comparing CFL with LED makes sense though.

Even for proper tubes, LED replacements can make sense:

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Reply to
Alan Braggins

Neither is ideal. A normal pendant fitting means the power supply to the bulb is at the top so gets all the heat from the bulb, which shortens its life. Not a problem with most weedy output 40 watt equivalents - but is with larger ones.

Reply to
Dave Plowman (News)

In message , "Dave Plowman (News)" writes

True, but not much point in comparing an LED bulb with a fluorescent tube. Anyway, as I said, the LED figures in the wiki page are on the low side generally, as some are referring to bulbs a few years old.

My general experience here is that for mid sized bulbs (40-60W equivalent) you need about half the rated consumption for an LED to replace a CFL, about 6 times for it to replace a halogen.

But as you said elsewhere, it's hard to get LED lamps in GLS size packages for more than about 75W equivalent. Heat dissipation issues I guess.

'Twas ever thus :-)

Reply to
Chris French

I too was surprised at the Wikipedia figures too especialy as they seem to contradict what many sites say about LED bulbs being significantly more efficient than CFLs

I was hoping someone might explain this. However when I take a look at more sites, it seems some are not as bullish as others about the benefit of LED bulbs.

For example

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efficient/

However my own experience is that LED bulbs are, in fact, more efficient. They certainly seem to warm up less which is presumably a measure of wasted energy.

Reply to
pamela

Actually most of the marketing around LED's seems to be comparing them to incandescent bulbs, comparing them to CFL sounds much less compelling

In part it is because some of the LED figures are way out of date. I think you would struggle to find LED lamps on sale with such low efficiencies as some of them now. Also bulbs vary quite a bit. But also the benefit over a CFL is much more limited compared to over an incandescent

About right, though a bit pessimistic on the LED front I think.

And old article (2011). Things are a bit better now.

LED bulbs are in general more efficient than a comparative CFL, though there is quite a bit of variation, and as the wattage of LED's goes up they seem to get less efficient. Probably between at best 50 - 25% more efficient depending

But the benefit going from CFL to LED is limited, as most of the savings have been made going from incandescent to CFL. Replacing a 40W bulb with an 11W CFL saves you about 30W, replacing that CFL with say a 6W LED saves you 5W - the percentage saving might be good, the actual saving is small.

The improvements in LEDS though over the last few years have been as much is design of the lamps , improvements in light quality and spread etc. nothing much is going to happen efficiency wise until more efficient LEDs make it onto the market

Reply to
Chris French

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