# 40% efficinent Incandescent bulb!



## jharkin (Jan 13, 2016)

My wife found this on one of her old house blogs.  Really cool idea.

http://www.telegraph.co.uk/news/sci...Echobox&utm_medium=Social&utm_source=Facebook


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## iamlucky13 (Jan 13, 2016)

The website says I have to disable my ad blocker to read the article. I disabled and it still won't let me read it.

However, I saw the article from MIT itself the other day:
http://news.mit.edu/2016/nanophotonic-incandescent-light-bulbs-0111

It's a pretty clever idea - incandescent bulbs work by simply heating them enough to glow. They effectively trap heat that would otherwise be wasted in the filament to get the same temperature with less power. Figuring out how to trap that heat without also blocking the light was the key.

The prototype lamp they made is 6.6% efficient, not 40%. ~40% efficient is the highest possible for white light (our eye's optimal sensitivity at green light factors into the efficiency calc for any light that isn't pure green), so they're going to shoot for that target, but it will take further research to see how far they get.

Lighting almost never gets talked about in terms of efficiency (%), but rather of efficacy (lumens/Watt).

6.6% efficiency works out to 45 Lumens per Watt. This is much better than a standard 60W, 800 lumen bulb at 13.3 lumens/W, or a halogen equivalent at 18.6 lumens/W. The maximum possible efficacy for an ideal white light is around 300 lumens/W.

One of the other big drawbacks of incandescents - short lifespan - isn't fixed by this technology, but I could definitely put up with that in a few places like the bathroom to have the high color quality of an incandescent without the historically high power consumption. I hope their progress continues.


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## jebatty (Jan 14, 2016)

The article states "In comparison LED or florescent bulbs manage around 14 per cent efficiency." Based on lumens/watt, my LED's have about twice the lumens/watt as CFL's.


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## woodgeek (Jan 14, 2016)

I don't care how they make my light, I just want lumens per watt, CRI and cheap.  

But I don't think this thing has a chance to catch LEDs. 

The article is also misleading re the performance of modern LED lights.


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## jebatty (Jan 14, 2016)

The next project of these MIT researchers is Swiss watches that use new high tech gears made out of coal. Rumor is that coal is abundant and the market for coal has collapsed due to the demise of incandescent lighting.


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## jharkin (Jan 14, 2016)

Ok guys, got it.... I'll stop posting about interesting scientific discoveries that are not on the hearth approved list.


Disregard I mentioned it.


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## Jags (Jan 14, 2016)

jharkin said:


> that are not on the hearth approved list.


I added this to the list.  Please continue....


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## iamlucky13 (Jan 14, 2016)

woodgeek said:


> I don't care how they make my light, I just want lumens per watt, CRI and cheap.
> 
> But I don't think this thing has a chance to catch LEDs.
> 
> The article is also misleading re the performance of modern LED lights.



I'm not going to lay odds on whether they can catch LED's, but tripling the normal efficiency on one of their first tries is really fast progress. We'll see.

I think they updated the LED numbers in the MIT article. Looking again this morning, the percentages given work out to be 34 to 137 lumens/W. That's pretty accurate (I've seen some as low as 40 lm/W in specialty bulbs). I'm pretty sure yesterday I calculated just over 100 lumens/W on the high end, which is still close. Not many lamps get much more than 100 lm/W.



jebatty said:


> The next project of these MIT researchers is Swiss watches that use new high tech gears made out of coal. Rumor is that coal is abundant and the market for coal has collapsed due to the demise of incandescent lighting.



This hardly seems to merit mocking. The mere fact that incandescents are old technology like coal and gears* is not relevant. The fact that they're inefficient is. Bring the efficiency up to par with newer lighting technologies and we can have more options, potentially with a appreciably higher color rendering index than LED's. The high efficacy (100+ lm/W) LED's are mostly around 80 CRI. Pretty decent in my opinion, but less than ideal. The high CRI LED's top out in the low 90's CRI, but they trade off efficacy to achieve that (usually 60-70 lm/W). If they can hold the high-90 CRI of incandescents AND get high efficacy, then they'd have a pretty awesome product.

* Especially since gears are still one of the best ways we have to translate rotary motion to different speeds, locations, or directions.


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## woodgeek (Jan 14, 2016)

Its ok Jeremy. 

Any photonics lab worth its salt could have done this expt.   They are basically making a planar, high-temperature, custom optical filter with a wide passband, by using a stack of thin films of different dielectric materials.  When I buy simpler dielectric filters for my lab, they are usually ~$100/cm^2.  Making these stacks well is a slow vacuum process, in my understanding.

And there is still the whole burning out thing, i.e. tungsten evaporation.

I would think to get higher eff, they would need to go to a cylindrical geometry, and fill it with halogen gas.

Their 'proof of concept' is 3x more efficient than the bare filament, presumably ~30 lum/W.

I have been following this guy Joannopoulos since I was a student...he wrote my textbooks.  That said, the 40% may be difficult to fabricate.


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## jebatty (Jan 15, 2016)

I will apologize for the levity, but I do ask to given a break to be a bit flippant once in awhile. Usually I'm pretty objective and experience oriented. I did not mean to offend jharkin or anyone else. 

The MIT technology may be important. Market forces and price points rule the entry of new products to consumers. The ability of a new tungsten light bulb to have a price point to achieve sufficient market penetration to be a viable product will remain to be seen.


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## begreen (Jan 15, 2016)

Another article on the topic
http://www.sciencemag.org/news/2016/01/how-get-old-fashioned-light-bulb-glow-without-wasting-so-much-energy


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## Ashful (Jan 15, 2016)

As I sat below the warm (literally) glow of twenty R38 reflector bulbs in my great room the other night, I wondered... what's the real advantage of going LED in an environment where our heating degree days outstrip our cooling degree days seven to one?  Seems to me every bit of wasted luminary efficiency is at 100% heating efficiency... in other words, nothing truly lost.

Our average cooling costs, as a national population, are such a small fraction of our heating costs that I really don't understand this aversion to the waste heat produced by incandescent bulbs.  In fact, I wonder if the net lifetime (including all manufacturing processes) energy loss of the LED might be higher than an incandescent, when you scale the incandescent bulb's assumed efficiency by this ratio of cooling degree days to heating degree days.


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## begreen (Jan 16, 2016)

Multiply your home times millions. It's not about heating the house, it's about increasing efficiency and reducing waste on all fronts. Same reason you are now burning more efficient stoves. Conservation is our best resource and the cheapest path to energy self-sufficiency we have.


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## Blowingsmokeupyourchimney (Jan 16, 2016)

Heat your home with electricity and see what your power bill is(using space heaters, not heat pump), on the other side of that heat your home with wood and see what your power bill is.  It is not efficient to convert electricity into heat. I.E. mine coal, transport coal, burn coal to turn turbine, power travels over electric grid to power substation, power goes to your home.


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## Ashful (Jan 16, 2016)

begreen said:


> Multiply your home times millions. It's not about heating the house, it's about increasing efficiency and reducing waste on all fronts. Same reason you are now burning more efficient stoves. Conservation is our best resource and the cheapest path to energy self-sufficiency we have.


You missed my point, begreen!  It's 100% efficient, with zero waste during heating season for everyone, not just me.  My local clime is 5600 heating degree days, and 800 cooling degree days, so one might say the average annual efficiency is really 88%.  Either way, I don't understand how LEDs are cutting down on waste, when we consider the increased manufacturing costs, given that the national population average climate is probably not far from my own.

And, yes, I have had a home heated with electric.  Worked out great for me, since I was only heating the rooms in which I was sitting at any time, so it ended up being very inexpensive and efficient for me.  Sort of like the lights also only heating the room in which you have them on.


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## jebatty (Jan 16, 2016)

Ashful said:


> Either way, I don't understand how LEDs are cutting down on waste, when we consider the increased manufacturing costs, given that the national population average climate is probably not far from my own.


 If you research this issue you will find that the life cycle cost of LEDs (manufacturing, transportation, and energy from using) is much lower than incandescent bulbs.


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## jatoxico (Jan 16, 2016)

Ashful said:


> You missed my point, begreen! It's 100% efficient, with zero waste during heating season for everyone, not just me.


I think it's efficient to use but not very when considering generation not to mention transmission. More efficient overall to heat with oil/gas (wood!) and not with a bunch of tiny electric heaters . It would be cost prohibitive for me as well since our price per kw/hr are high.


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## woodgeek (Jan 16, 2016)

Ashful said:


> You missed my point, begreen!  It's 100% efficient, with zero waste during heating season for everyone, not just me.  My local clime is 5600 heating degree days, and 800 cooling degree days, so one might say the average annual efficiency is really 88%.  Either way, I don't understand how LEDs are cutting down on waste, when we consider the increased manufacturing costs, given that the national population average climate is probably not far from my own.
> 
> And, yes, I have had a home heated with electric.  Worked out great for me, since I was only heating the rooms in which I was sitting at any time, so it ended up being very inexpensive and efficient for me.  Sort of like the lights also only heating the room in which you have them on.



With modern heat pumps in our climate, >200% average efficiency is easy, 250% is attainable.  With geo, you can get over 300%.  So 100% IS practically 'wasteful'.


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## Ashful (Jan 16, 2016)

woodgeek said:


> With modern heat pumps in our climate, >200% average efficiency is easy, 250% is attainable.  With geo, you can get over 300%.  So 100% IS practically 'wasteful'.


Thank you!  I should have expected if there were a good answer, it would come from you, woodgeek.


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## iamlucky13 (Jan 17, 2016)

Heat pumps are one example of a price disadvantage. Similarly, if you have natural gas, the heating cost is roughly equivalent to $0.05/kWh currently. The effective cost of heat from your bulbs is likely 2-3 times that cost, depending where you live. And then, of course, there's the wood alternative for our demographic in particular. Oil or propane will generally come out close to a similar price to electricity.

And yes, your cooling costs in the summer are lower than your heating costs in the winter in most places, but it's still a cost you can avoid.



jebatty said:


> If you research this issue you will find that the life cycle cost of LEDs (manufacturing, transportation, and energy from using) is much lower than incandescent bulbs.



Another metric aside from life cycle cost sometimes used for that kind of comparison is the energy return on investment.

I looked at life cycle cost of LED's a little while back and confirmed they are significantly positive. There was enough info in the analysis I read to surmise the energy return on investment probably starts to favor LED's pretty quickly. If I remember right, net positive energy return on investment occurred within 1000 hours of use - roughly speaking, by the time an incandescent has lasted its rated life, it's used more extra energy than it took to make the LED. Meanwhile, the LED bulb still has 9000+ hours worth of probably use left.

As bulbs have gotten lighter and more efficient, and production more streamlined, that energy return on investment period has probably dropped further.


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