
A nanophotonic comeback for incandescent bulbs? - skybrian
http://news.mit.edu/2016/nanophotonic-incandescent-light-bulbs-0111
======
jrapdx3
This development was discussed on HN about 3 days ago. On that thread I
commented that a merit of the incandescent is its continuous output spectrum.
The newer lamp technologies produce discontinuous spectral output, CFL having
prominent green, and LED blue emissions.

The difference is reflected in the CRI (Color Rendering Index) where 100
represents natural daylight. Incandescent lamps are generally very close to
100, but most fluorescent and LED sources are much lower, 90 or less. CRI is
crucially important in the visual arts (museum/gallery lighting, photography,
etc.) and other industries (color matching).

There are fluorescent and recently LED lamps that have high CRI ratings. These
are relatively expensive items different from the "bulbs" sold at the hardware
store. For the future, "remote phosphor" LED lamps look promising, though
likely there will be a market for improved incandescents as described in the
article.

Looks like advancements in LED, and now incandescent, technology could produce
lamps that provide the best of both worlds: high CRI along with significantly
extended durability.

~~~
jacobolus
Note that by definition incandescent bulbs have a CRI of 100.

The CRI is calculated by looking at the colors reflected by a particular set
of 14 paint chips under the lamp being analyzed, and comparing it to either
illuminant D65 (representing daylight) or to an incandescent bulb, depending
on the lamp’s color temperature. The color from the paint chips undergo an
outdated type of chromatic adaptation transform, and are then compared to the
colors under the reference illuminant, using colorimetric distance in the
outdated 1964 CIEUVW color space. To find the final CRI take the arithmetic
mean of all the distances, scale it, and subtract from 100. Most of the
choices in this process are somewhat arbitrary.

CRI numbers are an okay first approximation to judge how much a particular
lamp will muck with color relationships, but when you get to the precise
details it gets pretty arbitrary, and the spec is heavily gamed by lighting
vendors, because it’s one of the main values they report. Take CRI numbers
with a big pinch of salt, and try looking directly at a chart of emission
spectrum if you can, or ideally get a bulb and try looking at various objects
under it for better understanding.

~~~
bettercri
I've studied lighting tech on and off since getting into planted aquariums in
2006 and remember that some researchers at Philips also lamented the issues
with CRI as a metric of light quality and presented their own system which I
remember as being a color wheel with a lot of (possibly 100+) marked points.
For each point, they'd present a vector as the difference from "actual" (as
represented by the appearance in midday sun on a clear day) for a light
source, so you could easily see how much a particular light skewed particular
colors with fairly fine granularity. I neglected to save the source and
haven't been able to find it in subsequent searchings though.

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prewett
Cool idea, but these sound difficult to manufacture efficiently, given that
you need to grow precise layers of crystal on the filament. On the other hand,
you know are living in the high-tech future when even your light bulbs require
a clean room!

~~~
jjoonathan
In the age of $0.35 16MHz ARM cores (I'm sure you can get them much cheaper,
that's just what I found on digikey) a bit of process complexity might not be
so prohibitive. What a time to be alive!

~~~
SwellJoe
Why doesn't everything have a supercomputer (circa 1985) built into it? At
$0.35, why not!?

~~~
driverdan
Because it's completely pointless in most cases. The "Internet of Shit"
Twitter account[1] may be satire but it highlights this unnecessary use of
technology.

1: [https://twitter.com/internetofshit](https://twitter.com/internetofshit)

------
donatj
I've always wondered how efficient are traditional bulbs as an actual heat
source? I live in Minnesota and its -17°F outside, and would it be more energy
efficient to heat the room I am currently occupying with the light bulbs of
the room, keeping the rest of the house cooler than pumping a higher level of
heat to the entire house?

I feel like the switch to CFLs may have increased my energy bills overall.

~~~
repsilat
They're somewhere in the vicinity of 100% efficient as heat producers. Even
the energy that goes into producing light just decays into heat after bouncing
off a couple of walls.

Less "efficient" than using a "heat pump," and possibly more expensive than
using gas (I don't know anything about energy in Minnesota). If you're using
electricity to heat your home, though, you might as well use something like
SETI@home and put it to use :-)

~~~
tempestn
Unfortunately you can't use a heat pump (at least a normal one) below about
-8C (17F), so -17F would definitely be out.

I also don't know anything about energy in Minnesota, but here in BC, gas
heating is still cheaper than electric, especially if you use an efficient gas
furnace (that doesn't exhaust too much heat), but not as much as it used to
be. (Technically though it will always be less "efficient" than electric due
to that exhaust, but that's really comparing apples to oranges.)

~~~
lscharen
That's true for air heat pumps, but many people (myself included) have ground
water heat pump systems; either open- or closed-loop.

My unit is fairly old (mid 1980 Tetco) and provide all of our heating and
cooling. It uses the most electricity in January/February for heating and
July/August for cooling, but my total electric bill is usually never more than
$200/mo and that included all of the home's "normal" electricity use.

------
jacobolus
I sure hope so. Incandescent bulbs are much more pleasant than any
fluorescents and the vast majority of LEDs on the market.

------
wyldfire
Aren't LEDs and CFLs significantly more durable than incandescent? Certainly
they're more durable than tungsten-filament incandescent bulbs. Hopefully they
can do better than just parity with LED/CFL power consumption otherwise it
wouldn't seem worthwhile.

~~~
Spooky23
Supposedly they last forever, but they don't seem to deliver on the supposed
10+ year lifespans -- I have no bulb older then 3 years in my house.

~~~
mrbill
Out of 12 bulbs, I've had three of the CREE LED bulbs from Home Depot fail in
a "disco strobe" mode in less than six months :(

~~~
Spooky23
I actually gave up and bought a bunch of incandescent bulbs at a clearance
sale.

Even accounting for wasted energy, financially I'll be in the black for 5-7
years based on my experience with CFL/LED fail.

------
jhallenworld
My LED bulbs work well (Philips), but have one flaw: they do not redden when
you dim them. I would like the color temperature to be much lower than 2700K
when they are dim- to more approximate an oil lamp.

Anyway, perhaps this work will lead to efficient incandescent bulbs that
provide nicer light when dimmed.

------
kup0
Does this address the short lifespans of incandescent bulbs? Since the
filament portion is essentially the same, wouldn't these new bulbs suffer from
this same issue, and wouldn't that make them less efficient overall due to
replacement costs and waste?

------
CountHackulus
Interesting technology, and it'll be fun to see how they market the technology
since people just started understanding that incandescent = lots of energy =
money. I wonder if LED technology will be able to keep up.

~~~
Animats
They've developed a photonic crystal [1] which reflects IR while passing
visible light. That should be useful. Using it to to try to reflect IR back to
the filament of an incandescent bulb is probably not going to be cost-
effective. Photonic crystals have detailed structure like an IC, with
waveguides and cavities, and are made by similar methods. That's a lot to make
just to get an IR mirror for a light bulb, since you'd need a large surface
area of the material. Probably more expensive than fabbing LEDs.

This sounds like an interesting development overhyped by the PR staff. Again.
See [2].

[1] [http://ab-initio.mit.edu/photons/](http://ab-initio.mit.edu/photons/) [2]
[https://news.ycombinator.com/item?id=10916894](https://news.ycombinator.com/item?id=10916894)

~~~
neltnerb
Nah, I bet this can be done with a 1D photonic crystal where they can get away
with simply using alternating layers of uniform thin film thickness. I forget
exactly but I'd think all that's needed is alternating dielectric constant
materials with a periodicity ~700nm which isn't that crazy. More expensive
than glass sure, but it's not like it'll need special etching to get
microlenses.

~~~
Animats
That sounds like an ordinary bandpass interference filter.[1] Those have film
layers and only pass a specific wavelength of light. Unlike ordinary filters,
the angle at which the light hits the filter affects the passband, because
it's the spacing of the layers that makes it work. The receive side of LIDAR
systems use those. But those absorb the light they reject; they don't reflect
it, much.

[1] [http://www.edmundoptics.com/optics/optical-
filters/bandpass-...](http://www.edmundoptics.com/optics/optical-
filters/bandpass-filters/infrared-bandpass-interference-filters/3430/)

~~~
neltnerb
Gotcha, that makes sense. I suppose most of it will come from a narrow solid
angle so if it were perfectly spherical you'd be okay but that would only work
for the first reflection unless it was all reflection and no emission...

