This perpetual motion machine she made today is a joke! It just keeps going faster and faster!
May 30, 2012 6:00 PM   Subscribe

As they become more readily available to consumers, LEDs will undoubtedly replace CFLs as the primary light source for residential and commercial, inside and out, due to their dramatic efficiency gains. In an unexpected turn of events, however, MIT researchers have developed an LED with 230 percent efficiency. Previously

Unpossible, you say? Supposedly , the Law of Thermodynamics is not violated because the device converts ambient heat into photons. Cue the skeptics!
posted by CynicalKnight (70 comments total) 15 users marked this as a favorite

 
So, it functions as an upconverter of photons? Pretty neat trick.
posted by IAmBroom at 6:03 PM on May 30, 2012 [1 favorite]


A bad time to be a light bulb manufacturer I would say.
posted by Defenestrator at 6:06 PM on May 30, 2012 [1 favorite]


Also previously (The Light Bulb Conspiracy)

I guess LED manufacturers aren't members of Phoebus?
posted by carsonb at 6:15 PM on May 30, 2012 [1 favorite]


> the device converts ambient heat into photons.

So instead of a refrigerator with a light inside it, they've made a light with a refrigerator around it. Neat.
posted by benito.strauss at 6:17 PM on May 30, 2012 [45 favorites]


I guess LED manufacturers MIT Researchers aren't members of Phoebus?
posted by carsonb at 6:18 PM on May 30, 2012 [1 favorite]


Would be interesting to use these to cool CPUs, but I don't know how efficient it is at cooling, etc.
posted by empath at 6:19 PM on May 30, 2012


When it gets more than 100 percent electrically-efficient, it begins to cool down, stealing energy from its environment to convert into more photons.

Well played, well played.
posted by the jam at 6:24 PM on May 30, 2012 [1 favorite]


Climate change = solved!
posted by BobbyVan at 6:24 PM on May 30, 2012 [1 favorite]


Supposedly , the Law of Thermodynamics is not violated because the device converts ambient heat into photons.

So they absorb ambient heat? Like, leave 'em on too long in an enclosed area, they'll start freezing up? Gives a new meaning to the term "frosted bulb". Or, use them in a Easy Bake Oven to make ice cream sandwiches. The future is like Bizzaro-world when light bulbs make things colder the brighter they get.
posted by AzraelBrown at 6:25 PM on May 30, 2012 [7 favorites]


I'm gonna be honest: this freaks me out.
posted by OmieWise at 6:26 PM on May 30, 2012 [18 favorites]


Don't peltiers do this already at about the same efficiency but a lower wavelength?
posted by teppic at 6:30 PM on May 30, 2012


Make a trillion of em and beam global warming into the Sun.
posted by seanmpuckett at 6:31 PM on May 30, 2012 [2 favorites]


69 picowatts of light, of course, is a very small amount -- so you're not likely to be able to read in bed with one of these LEDs.

I knew there had to be a catch.
posted by crapmatic at 6:32 PM on May 30, 2012 [1 favorite]


Yeah, they're microscopic.
posted by empath at 6:33 PM on May 30, 2012


Look, I don't know about you, but I'm afraid the result of this discovery is bound to be the singularity that will cause the universe to collapse back in onto itself.

The Big Smoosh, if you will.
posted by mr_crash_davis at 6:36 PM on May 30, 2012


Part of the global socialist conspiracy, no doubt.
posted by dave78981 at 6:36 PM on May 30, 2012


69 picowatts of light, of course, is a very small amount -- so you're not likely to be able to read in bed with one of these LEDs.

Yeah, but put 69,000 of them together.....
posted by lumpenprole at 6:42 PM on May 30, 2012 [2 favorites]


Sadly, the right way to think of this is not as a source of free energy (which would violate the second law of thermodynamics) but as a very strange type of transistor. Instead of a small current controlling a large one, as in your garden-variety transistor, a small current controls the flow of thermal energy, which emits light as a side effect of traversing the device. There still has to be a source of heat and a sink.
posted by drdanger at 6:44 PM on May 30, 2012 [3 favorites]


Turn up the heat, it is getting dark in here!
posted by b1tr0t at 6:45 PM on May 30, 2012 [1 favorite]


Yeah, but put 69,000 of them together.....

And you still have a light output of only 0.000004761W.
posted by Talez at 6:59 PM on May 30, 2012 [14 favorites]


Yeah, that line in the Wired article saying that you're not likely to be able to read in bed with one is a SEVERE understatement. If these gave off a green light at the optimal wavelength for detection by the human eye, it would only take, oh, 9,898,550,724,639 of them for a single lumen of light. You'd need 460ish times that many to equal the light put off by a 40 watt incandescent bulb.

But, how small are these leds? Empath said microscopic, and if that's the case you could do a heck of a lot with some crazy (probably massively unlikely?) material science breakthrough that allows these to be painted onto a surface.
posted by jason_steakums at 7:10 PM on May 30, 2012 [3 favorites]


I really hope this scales up.
That's what she said.
posted by exogenous at 7:12 PM on May 30, 2012 [5 favorites]


So instead of a refrigerator with a light inside it, they've made a light with a refrigerator around it. Neat.

So you'll keep opening and closing the door trying to see if the cold goes off.
posted by condour75 at 7:17 PM on May 30, 2012 [11 favorites]


Living in Canada, I look forward to even colder evenings.
posted by arcticseal at 7:22 PM on May 30, 2012


This is incredibly cool.

But, as others have already pointed out, there's no free energy in this discovery, and it's not at all obvious that it can be applied to nightstand reading lights. (And, the use of the word ambient in some of the above comments seems a poor choice.)

The abstract of the PRL paper has a great one-sentence summary of the big-picture here. They say, "A heated semiconductor light-emitting diode at low forward bias voltage V < kB T=q is shown to use electrical work to pump heat from the lattice to the photon field."

It only works if it's in a hot oven, and keeping the oven hot sure isn't free.

For some sense of the scale of the thing - the blackbody radiation from the 280 micron diameter LED itself at 135C is around a million times brighter than the 69 pW LED emission. Even within the 1.9 to 2.4 micron band of the experimenters' detector, the thermal emission is 200 times brighter. So, if you were going to build a broad-band light bulb using this thing, you wouldn't bother turning it on, 'cause you'd never notice the extra light it adds to the thermal emission from the oven it's sitting in.

But, as a demonstration of very cool and non-obvious semiconductor physics, and possibly as a useful way to generate useful, narrow-band, coherent radiation in specialized environments, it sure is neat.
posted by eotvos at 7:23 PM on May 30, 2012 [5 favorites]


In dim conditions, human eyes are more sensitive to blue light than green light. Rods vs. cones.
posted by ryanrs at 7:26 PM on May 30, 2012


Crap, didn't mean to say "coherent" in the above comment. Also didn't mean to say "useful" so many times. Grr.
posted by eotvos at 7:27 PM on May 30, 2012


I switched from incandescent to CFL bulbs but I can't see the effect on my energy bill. I think most of the electricity I use is from the computer, fridge, heating, and cooling.
posted by gyp casino at 7:36 PM on May 30, 2012 [1 favorite]


gyp casino, I switched because the incandescents on the outside of my house (porch, garage) kept burning out every three weeks or so and I got tired of changing them. I've put it one set of CFLs and haven't changed a bulb in over a year.
posted by mr_crash_davis at 7:48 PM on May 30, 2012


The Big Smoosh, if you will.

I will not.
posted by Tomorrowful at 7:56 PM on May 30, 2012 [4 favorites]


Drawing heat energy to power a light bulb? No, that doesn't violate the First Law of Thermodynamics, but it does violate the second. Either this is another one of those 'oops, we were wrong about that' things, or there will be a revolution in physics. This is Maxwell's Demon we're talking about. It shouldn't be possible.
posted by thatnerd at 8:03 PM on May 30, 2012 [4 favorites]


In the meantime, until this technology becomes commercialized, I have glued several hundred peltier 130W peltier coolers with heatsink/fan units to the window of my house. It's getting very frosty on one side, but the other side is approaching the temperature of the sun.
posted by thewalrus at 8:04 PM on May 30, 2012


This is how Mr. Freeze got started.
posted by Saxon Kane at 8:05 PM on May 30, 2012


So, it's too dim for any practical application as a light.

But what a fantastic heat sink - small enough to be strategically placed within a VLSI circuit to dissipate thermal energy from neighbouring components, and amazingly efficient at it's job. This could significantly push back thermal design constraints.
posted by ceribus peribus at 8:18 PM on May 30, 2012 [3 favorites]


This is incredibly cool.

Ba dum bum pshhhh!
posted by nanojath at 8:47 PM on May 30, 2012 [1 favorite]


Thanks for going there before me, nanojath.

It's nice to know that Metafilter sinking to my level of humor is a constant I can depend on, since, apparently my understanding of thermodynamics is not.
posted by MCMikeNamara at 9:11 PM on May 30, 2012


Now it's not commonly known but LEDs do work as photodiodes. One could in theory set up a pair of LEDs that take electricity plus heat to make light, and then convert it back to get more electric out than went in.

Can I patent that idea? ;-)
posted by MikeWarot at 9:16 PM on May 30, 2012


ceribus peribus: "But what a fantastic heat sink - small enough to be strategically placed within a VLSI circuit to dissipate thermal energy from neighbouring components, and amazingly efficient at it's job. This could significantly push back thermal design constraints."

Yeah, but I'm curious: Don't those extra photons turn right back into heat once they're absorbed by the nearest sufficiently-opaque object? (Of course, if the critical parts of the circuits are transparent at the wavelength that the LEDs emit, this isn't an issue, but I somehow doubt that they're throwing off x-ray or building clear transistors)
posted by schmod at 9:31 PM on May 30, 2012 [1 favorite]


CynicalKnight: "dramatic efficiency gains"

So, I hear this line a lot when LEDs are discussed, and it's not exactly quite true for current technology. The Wikipedia article on Luminous Efficacy gives some examples of real-world efficiency figures for various light sources.

Incandescent bulbs are approximately 2-3% efficient, with Halogens doing slightly better. Current mass-market LEDs clock in at around 8-15% efficiency (with a likely-unattainable theoretical maximum around 40%). CFLs will do 8-12% efficiency, and straight tubes can go up to 15%. Note that the efficiency of current LED is (at best) roughly on par with what current fluorescent technology has to offer.

The big surprise, though, comes from discharge lamps. Those nasty yellow low-pressure sodium lamps that you see used as streetlights have a whopping 30% efficiency. Nearly twice that of the nearest viable alternative (unless you count high-pressure sodium, which is only a bit less efficient than the low-pressure variety, and offers the tradeoff of much whiter light). Replacing these lamps with LEDs (as many cities are doing as part of "green initiatives" actually doubles energy usage if the lighting level is kept the same*.

*But it often isn't kept the same, so LEDs might actually help save some energy, since it's far easier to dim or cycle an LED than a discharge lamp. Motion sensors are practical with LEDs, and completely impractical with gas discharge. However, everything else being held equal, nothing even approaches the efficiency of a low-pressure sodium lamp.
posted by schmod at 9:40 PM on May 30, 2012 [4 favorites]


schmod: sodium vapor more efficient? Here is the head of Seattle City Light:

“We are entering a new era in street lighting,” Superintendent Jorge Carrasco said. “LEDs use 40 percent less energy and last three times longer than the high-pressure sodium lights that have been the standard for the past 30 years. That means better reliability, less maintenance, a longer life cycle, and lower operating costs for our customers.”

What would account for the difference between the Wiki claim you mention of LED's being 15% less efficient than sodium vapor and his 40% more efficient?
posted by Mei's lost sandal at 9:52 PM on May 30, 2012


mr_crash_davis: "gyp casino, I switched because the incandescents on the outside of my house (porch, garage) kept burning out every three weeks or so and I got tired of changing them. I've put it one set of CFLs and haven't changed a bulb in over a year."

That's why I went with LED bulbs. (New) CFLs don't last very long in my house, for whatever reason. I have one in my upstairs hall that I bought in late 2000 or early 2001 that is still burning. The other one I have from that time frame died a few months ago. I bought 8 when I moved into this house for many of the other lights and zero of those still work.

Both LED bulbs are still going strong nearly a year on, though. Too bad the 60W equivalent was 40 bucks when I bought it. (and the 40W was 20!) Still worth it. The only downside relative to incandescent is that they don't help heat the room in the winter.
posted by wierdo at 9:59 PM on May 30, 2012


What would account for the difference between the Wiki claim you mention of LED's being 15% less efficient than sodium vapor and his 40% more efficient?

The sodium lamps are brighter.
posted by empath at 10:02 PM on May 30, 2012


Let me know when they're suitable for an indoor grow room that doesn't alert the law due to the heat profile.
posted by PeterMcDermott at 11:20 PM on May 30, 2012 [2 favorites]


thatnerd, this is not Maxwell's demon, and doesn't violate any laws. This is an LED being made to lead a secret double life as a crime fighter on the streets of Gotham thermoelectric generator. Those aren't terribly efficient, but if you count the output from both that and the electricity, while only counting the input of the electricity, you can make it look miraculously efficient.

(which is not to say it doesn't have applications -- it does, just not in producing light bulbs that draw their energy from the air around them)
posted by ubernostrum at 11:38 PM on May 30, 2012


PeterMcDermott: we're already there. The LED systems are much more expensive, but due to a neat trick of optics you can get the same amount of growing power for far less electrical power and therefore far less waste heat. Plants, you see, tend not to absorb green light - they reflect it, which is why they appear green to our eyes - and yet green light is exactly the range that we perceive most readily. It is relatively straightforward to design an LED system which puts all of its power into sections of spectrum in red and blue, which the plants will absorb, and little or none in the green area.

A friend of mine was a big fan of fresh, organic, home-grown.... uh... tomatoes, and turned her spare bedroom into a greenhouse. I built a custom LED-based lighting panel for her, and it reportedly worked well in the closet she used for starting sprouts.
posted by Mars Saxman at 11:44 PM on May 30, 2012 [2 favorites]


Mei's lost sandal:: What would account for the difference between the Wiki claim you mention of LED's being 15% less efficient than sodium vapor and his 40% more efficient?

empath: The sodium lamps are brighter.
Living in Seattle, I can say that the new LED streetlights are both noticeably brighter and a much more neutral white color.
posted by JiBB at 12:39 AM on May 31, 2012


However, while MIT's diode puts out more than twice as much energy in photons as it's fed in electrons, it doesn't violate the conservation of energy because it appears to draw in heat energy from its surroundings instead. When it gets more than 100 percent electrically-efficient, it begins to cool down, stealing energy from its environment to convert into more photons.
Yeah, that actually does violate the laws of thermodynamics, at least the way it's described in the article. Turning heat into light reduces entropy.
posted by delmoi at 1:23 AM on May 31, 2012


In dim conditions, human eyes are more sensitive to blue light than green light. Rods vs. cones.

Learn something new about color science every day. Our "blue" cones really peak in what we traditionally call violet, and we don't have nearly as many of them.
posted by effugas at 1:26 AM on May 31, 2012


At the moment manufacturers are loudly promoting their launch of LED replacements for the 100W Incandescent light bulb (example). And we have LED versions of most other light-bulb form factors. Great. But wouldn't it be better to have an LED bulb design with a shape optimised for LED lights - presumably something more like a flat sheet rather than a spherical cluster? Do such designs exist?
posted by rongorongo at 1:41 AM on May 31, 2012


delmoi: Yeah, that actually does violate the laws of thermodynamics, at least the way it's described in the article. Turning heat into light reduces entropy.

If turning heat into light violates thermodynamics, how does blackbody radiation or radiative cooling work?
posted by Mitrovarr at 1:49 AM on May 31, 2012 [2 favorites]


LEDs are slowly taking over. They are the standard now for bicycle lights, with serious amounts of light available for night-time off-road biking. Cheap Chinese lights are becoming very popular, although their (often) simpler electronics and heat-sinking means that they don't output anywhere close to their stated lumens (LEDs dim when they get too hot). They're still more than bright enough, though.

Luxury cars are beginning to use LED lighting for all external lights, including headlights. One interesting detail is that halogen and HID lights defrost the headlights automatically since they're essentially big heat lamps. LEDs, though, chuck most of their heat back into the engine bay so designers have to make sure that the lights will still clear themselves in winter.
posted by milkb0at at 3:52 AM on May 31, 2012


This is an LED being made to lead a secret double life as a crime fighter on the streets of Gotham thermoelectric generator.

I thought you could only draw energy from a temperature gradient, not from ambient temperature.
posted by DarkForest at 4:48 AM on May 31, 2012


They've got it all wrong. LEDs and bulbs are not sources of light, their sinks for darkness - dark-suckers, if you will.

So, they suck in darkness. And you've all heard of "dark energy", right?

WELL THAT'S WHERE THE "EXTRA" ENERGY COMES FROM!
posted by kcds at 5:35 AM on May 31, 2012 [1 favorite]


A bad time to be a light bulb manufacturer I would say.

American and European light bulb manufacturers lobbied heavily for energy efficiency standards because they're better at making highly efficient lighting than their Chinese competitors and they were being destroyed by Chinese competition in the incandescent market.
posted by atrazine at 5:51 AM on May 31, 2012


LEDs are awesome.

I worked for a Member of Congress for a while, about a decade ago now, the 107th I think. I drafted legislation to provide federal grants for municipalities to convert their traffic signals from incandescent to LED. I had CRS come up with the figures for how much energy and money it would save and when it would pay for itself - its was pretty significant. Having a company that made LEDs appliances in the district was also an attraction.

The majority Republican staff laughed in my face and killed it.
posted by RandlePatrickMcMurphy at 5:54 AM on May 31, 2012 [1 favorite]


RandlePatrickMcMurphy: "I had CRS come up with the figures for how much energy and money it would save and when it would pay for itself - its was pretty significant. "

LED streetlights pay for themselves in about a year in maintenance costs alone. If you're not rolling a truck to replace burned-out bulbs every 6 months, you end up saving a lot of money very quickly, not to mention the city's liability if a burned-out streetlight causes an accident.

For this reason, most cities have been refitting their incandescent traffic lights to LEDs as the old ones burn out. The up-front cost is a bit higher, but it's pretty much a slam-dunk from a financial perspective. They're not ubiquitous quite yet, but the rate of adoption has been nothing but impressive.
posted by schmod at 6:02 AM on May 31, 2012 [1 favorite]


Haitz's Law says that sodium lamps won't have much time on top.
posted by plinth at 7:25 AM on May 31, 2012


It seems like these (if they scale up and/or can be made to produce more light) could be a good supplement to an LED bulb design. IIRC, LED light bulbs put off a fair amount of heat. They could replace the heat sinks that are used now and convert that heat into light to supplement the main LED.

As a heat sink, it seems to me that you could use it to convert heat to light and then "beam" that light somewhere else where it could get converted back to heat to do something useful. Basically, it would act as a heat pump but instead of using air and ducts, you use light and...I guess fiber optics or something?

I could get rid of the big heat sinks and noisy fans in my desktop computer and use these instead to take the heat from the CPU and GPU and keep my pizza warm.

I have an idea for a combination quiet PC case/heat lamp/slow cooker.
posted by VTX at 7:31 AM on May 31, 2012


rongorongo: "But wouldn't it be better to have an LED bulb design with a shape optimised for LED lights - presumably something more like a flat sheet rather than a spherical cluster? Do such designs exist?"

Yes. There is LED tape that you can slap onto a surface. There are LED can lights that completely replace ordinary can lights with screw-in sockets. The problem, obviously, is that houses don't get technology upgrades very regularly. A more subtle problem, perhaps, is that our whole idea of lighting is oriented around point sources of light, and so LED bulbs are not only technologically compatible, they're culturally compatible. We do see indirect lighting that creates a sort of sheet of light effect, but it's less common and with incandescent lighting, kind of a PITA to build. I expect that kind of thing will become more common, as it would be really easy to nail up a strip of moulding with a recess for LED tape. I wouldn't be surprised if eventually we even started seeing 12 V DC wiring in walls alongside 120 V AC—you could save a lot of copper (and money) if you wired your house for 12 V DC lights, and I'm guessing that one big AC/DC converter near the electrical panel could run more efficiently than a bunch of little ones at the points of use.
posted by adamrice at 8:06 AM on May 31, 2012 [2 favorites]


LED light bulbs put off a fair amount of heat

Nope.

Incandescent bulbs release 90% of their energy as heat.

A CFL releases about 80% of its energy as heat.

Halogen - I couldn't find the number quickly but they're always hot.

LEDs are basically cool to the touch. In a well-designed product a small amount of heat is released backwards, into a heat sink.

schmod - thanks. Ten years ago, with that audience, it was harder to make the case.
posted by RandlePatrickMcMurphy at 8:18 AM on May 31, 2012


In dim conditions, human eyes are more sensitive to blue light than green light. Rods vs. cones.

The peak absorption for the rod is 500 nm which is a bluish green. Our rods are actually sensitive enough to detect individual photons of light. And they have to be, because during starlight there just aren't enough photons around to have to wait for two or more to hit simultaneously.

Amazingly, the experiment demonstrating this was performed 60 years ago and is still referenced today.

However this extreme sensitivity comes at a cost. Because individual photons have so little energy the rod needs to have what is essentially a hair trigger response. This means that occasionally, the molecule that detects photons, rhodopsin, will signal that it caught one due to random thermal noise. This happens about once every 420 years. But because there are about 10^8 rhodopsin molecules in each rod, each rod says that it saw a photon, even in absolute darkness, every ~100 seconds. This false light signal from the rods and other sources of noise downstream is referred to as the "Eigengrau" or darklight.

One can show that this effect is temperature dependent by taking the rod from a cold blooded animal, such as a toad (Bufo bufo), and measuring the number of responses in complete darkness over a range of temperatures.
posted by euphorb at 8:35 AM on May 31, 2012 [6 favorites]


My understanding is that the discrepancy between the efficiency of HPS and LED lights is not so much due to the luminous efficiency at the source, but rather the total efficiency of the system. This overview from My LED Lighting Guide makes the case for slightly increased total system efficiency after including energy losses and light losses from the luminaires. According to EERE data on that site, HPS delivers about 61 lumens/watt and LED delivers 67 lumens/watt. In general, it seems to me that LEDs, HPS, and fluorescent are all pretty much in the same ballpark right now. It is generally more useful to look at a a given light's function in a given situation than trying to determine an ultimate lighting champion. Theory is nice, but real-world performance is where it's at.

Physics World addresses the concerns over the Second Law of Thermodynamics:
At first glance this conversion of waste heat to useful photons could appear to violate fundamental laws of thermodynamics, but lead researcher Parthiban Santhanam of the Massachusetts Institute of Technology explains that the process is perfectly consistent with the second law of thermodynamics. "The most counterintuitive aspect of this result is that we don't typically think of light as being a form of heat. Usually we ignore the entropy and think of light as work," he explains. "If the photons didn't have entropy (i.e. if they were a form of work, rather than heat), this would break the second law. Instead, the entropy shows up in the outgoing photons, so the second law is satisfied."
posted by nTeleKy at 8:52 AM on May 31, 2012


LEDs are basically cool to the touch. In a well-designed product a small amount of heat is released backwards, into a heat sink.

I don't mean the LED itself but the whole assembly does put out some heat (from the AC/DC conversion maybe?). A review of a Philips dimmable LED blub on amazon.com claims that they get up to 145 degrees F but I haven't been able to find a better source than that.
posted by VTX at 9:28 AM on May 31, 2012


I thought you could only draw energy from a temperature gradient, not from ambient temperature.

The Wired article is a really bad description, judging from the abstract of the actual paper. But the phrase "lattice vibrations" is the giveaway that what this actually is, is a thermoelectric generator. Which does create and exploit a heat gradient to create electricity, which then -- in this thing -- gets turned into light, apparently.
posted by ubernostrum at 10:28 AM on May 31, 2012


CynicalKnight: "dramatic efficiency gains"

So, I hear this line a lot when LEDs are discussed, and it's not exactly quite true for current technology.


I replaced all twelve of the #1003 bulbs in my camper with LED equivalents from eBay, and the current draw went from 1.0 amp per bulb down to 130ma.

But, everyone complained about the cold white light so I swapped them all out for warm white LEDs, and the current consumption rose to 260ma per bulb.

The newest flat panel SMD LEDs, however, can consume up to 500ma apiece depending on their size.

So, efficiency for LEDs does vary greatly, but at their best I think there's a significant improvement over this CFL at 660ma.
posted by CynicalKnight at 1:08 PM on May 31, 2012


I expect that kind of thing will become more common, as it would be really easy to nail up a strip of moulding with a recess for LED tape.

When we moved into our apartment, the kitchen counter where you'd naturally do food prep was always shadowed - some cabinets hung over it so that it was always dark. We got a cheap strip of LEDs and stuck it underneath the cabinets - hey presto, the entire counter is illuminated with bright, even light. Using a negligible amount of power we get exactly the lighting we need exactly where we want it. This wouldn't really be possible with incandescents.

In fact it worked so well we stuck another LED on the ceiling above the range. This one is brighter, more narrowly focused, and burns a lot more power, but it means that the range is always brightly lit.

We are sort of LED pioneers here because I'm just fascinated with the technology and like to build lots of little LED-based gadgets, but it's easy to see that the Home Of Tomorrow can have substantially more useful lighting at a tiny fraction of the current power required. It's really nice to have a combination of smooth, slightly dim ambient light with little points of bright focused light for specific tasks.
posted by Mars Saxman at 1:19 PM on May 31, 2012


VTX: " A review of a Philips dimmable LED blub on amazon.com claims that they get up to 145 degrees F but I haven't been able to find a better source than that."

I can tell you that my Philips 60W equivalent gets somewhat hot, but it's in a glass luminaire. The heatsink isn't hot enough to burn your skin instantly like an incandescent would, but it's hot enough to be uncomfortably warm.

And yes, some LEDs do draw a lot of power. I have some Cree RGBW modules for my pinball machine. The module can draw around 3A at 12V (each one is around 700mA). That seems like a lot until you see how bright they are.
posted by wierdo at 6:21 PM on May 31, 2012


If turning heat into light violates thermodynamics, how does blackbody radiation or radiative cooling work?

Hmm, that's an interesting question. There is still a thermal gradient, though. If you have two regions of space that are each the same temperature, there's no net transfer of photons between the two regions. Obviously photons are being generated. Anyway, I guess if you think of the light as taking photons out of warm region and blasting them into a cool region entropy is still going up, whereas in an enclosed space, the entropy of the entire system would stay the same.

Interesting.
posted by delmoi at 6:50 PM on May 31, 2012


CynicalKnight: "So, efficiency for LEDs does vary greatly, but at their best I think there's a significant improvement over this CFL at 660ma."

That's not a CFL, and a few specifics of fluorescent bulbs on low-voltage power supplies make it difficult to make an apples-to-apples comparison, since the power supply ends up sucking down a lot of juice. LEDs are clear winners in these applications (and, really, for anything battery-powered). You wouldn't use a sodium vapor lamp in your RV (or really anyplace other than a streetlamp), and I somewhat doubt that you even could....
posted by schmod at 8:57 PM on May 31, 2012 [1 favorite]


I sometimes joke that "This coffee is too hot - better pop it into the anti-microwave for a minute!", but I'm unclear whether this micro-LED cooling effect is something that could be used in such a manner...
posted by Philofacts at 3:08 AM on June 1, 2012


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