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Displays Power Hardware

UCLA Engineers Create Energy-Generating LCD Screen 108

An anonymous reader writes "Engineers at UCLA have developed technology that allows gadgets like smartphones and laptops to convert sunlight, ambient light, and their own backlight into energy. Equipping LCD-enhanced devices with so-called polarizing organic photovoltaics will recoup battery loads of lost power, and enable smartphone users to scour Yelp, scan Twitter, and update their Facebook page without fear of draining the charge before a real communication crisis arises."
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UCLA Engineers Create Energy-Generating LCD Screen

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  • by msauve ( 701917 )
    "their own backlight into energy"

    I thought perpetual motion was settled a long time ago.

    The only way converting backlight to energy works is by stealing photons (effectively dimming the display), and putting it through a level of inefficiency. Better to just adjust the display backlight to the appropriate level.
    • it isn't perpetual motion... it is energy recapture. You really think that all the light generated by the LCD backlight is
      1) transmitted through to your eye
      2) used at 100% efficiency

      • by mirix ( 1649853 )

        It would be more efficient to only light the pixels that need lighting, like say, OLED. Need more work in that dept.

        But I guess recovering some amount of power is superior to not recovering anything, it's just never going to be as efficient as using less power in the first place.

        • OLED is certainly the way to go, but they need to pick up the production and make larger screens cheaper.

          This will be really good for lowering the power requirements of an LED TV even more.

          • But it's so dark. I can barely see anything on the screen.

            Really, it probably would save more power by turning down the brightness of the internal light source than whatever power was generated by reconverting some of it's light output back to electricity.

        • But I guess recovering some amount of power is superior to not recovering anything, it's just never going to be as efficient as using less power in the first place.

          Were it not for the added entropy from generating heat, recapturing energy from the display would be exactly as efficient as using less energy in the first place. However if they implement this technology well, they could have it capturing energy from external sources as well as the screen. Efficiency wouldn't need to be terribly high for it to actually extend battery life better than decreased expediture would. It could even go as far as to recharge your device provided your device saw enough downtime.


          • by Adriax ( 746043 )

            Say 100 lumen per watt backlight, 10% capture on the solar layer with 20% conversion efficiency.
            Starting with a 1 watt draw, the final transmitted light is 90 lumen.
            Of the 10 lumen caught, 2 actually get converted to energy. Since 683lumen/watt is max efficacy (of lighting, assuming going in reverse is true), that 2 lumen equals a whopping 0.003 watts.
            Bringing the final total to 0.997 watt net draw for 90 lumen.

            Dimming the display 10% on the other hand, gives 90 lumen for .9 watts.

            The solar option is a net

            • by danlip ( 737336 )

              There may not be much in the way of non-display areas to line with cells. The front of my iPhone is all display, and the back is covered by a case.

              Your calculations are right if it's only capturing it's own light, but it can also capture sunlight/ambient light.

            • Of course having read the other comments it becomes apparent that they are capturing the photons that are normally not emitted anyway due to being absorbed by the polarizing filters. So both our comments are rather moot. :-/
    • by eyenot ( 102141 )

      I think you have a good point. Anything that captures the photons by necessity is going to filter said light and therefore what reaches you is going to appear darker for that "setting" than it would without the filter. It is highly, highly, HIGHLY unlikely that there is somehow a way to get more energy out of "recouping" the backlight through that filter than would have been reserved simply by running the battery at the lower light level that corresponds to the diminished level of light reaching the user.

      • by blair1q ( 305137 )

        There's probably a lot of waste light that could be scavenged.

        Otherwise, yes, this thing ignores the fact that right now the back of every LCD is highly reflective to get the most brightness out of the screen.

        But most of us turn the brightness down, so maybe there's an excess. But in order to get the brightness and the energy scavenging, we'd have to turn it up. Thus generating more energy just to boost a line on a graph, one that's probably less efficient a method of saving energy than just turning the b

        • Speaking of watches that is something I've always wondered...why not put one of those devices that turn your movement into power into a laptop? Sorry I can't think of the tech term but its 4AM here and I have a monster cold but I always thought if it works on a watch, why not size it up for a laptop? if you are gonna be lugging the thing around in a bag all day might as well turn some of that foot power into energy. you wouldn't be able to power the thing directly with it but it could probably help keep the
          • by Ptolom ( 2191478 )
            There's quite a big difference between the power requirements of a watch, and those of a laptop. On the order of 10^7 times worth of difference. You'd be jiggling your bag pretty hard to get that kind of power out of it.
      • Except that the capture device is BEHIND the screen not in front of it. Was that really a difficult leap for you guys to make?
    • Except it's doubling as a polarizing filter which is fundametally needed by LCDs and hence you already have the energy loss.

      • by msauve ( 701917 )
        Since this is based on organic technology, why not just use an OLED display, and avoid wasting that energy in the first place? (assuming that this would add costs similar to the LCD/OLED delta, or greater).

        The whole point being, it's always better to reduce energy use, than to try to inefficiently recapture otherwise wasted energy.
        • Because it also captures ambient light from external sources into energy. (Outdoors, energy from sunlight would vastly outweigh anything recaptured from the backlight). Perhaps you could make an e-reader that *never* needs recharging under typical usage patterns. The Kindle already lasts a long time, but dispensing with the charging apparatus altogether would be pretty cool.
          • Problem is, such devices typically have a cover protecting their screen, or in the case of phones, are buried in your pocket when not in use. Unless you specifically leave it out/uncovered, it won't be able to trickle-charge from ambient light.

          • You could put a puny calculator solar charger on a Kindle and it would keep it powered forever. I have no idea why there's no solar powered e-readers in the US market. I saw a Korean prototype once, but why not in the West befuddles me.
    • Re:Huh? (Score:4, Interesting)

      by artor3 ( 1344997 ) on Wednesday August 17, 2011 @08:04PM (#37124722)

      LCDs work by creating a whole bunch of light, and then filtering out the light that isn't needed. That's why black isn't truly black on LCD screens -- the backlight is still on, the screen is just filtering out as much light as it can. If they have a way to recapture that light, which otherwise goes to waste, then it will provide substantial energy savings, especially considering that the screen often consumes as much energy as the rest of the phone combined.

      • by msauve ( 701917 )
        There's nothing in the article to indicate that the energy capture on this technology is variable. If you can't control how much dimming these provide by capturing photons, on an individual basis, then your point is moot.
        • by dissy ( 172727 )

          > There's nothing in the article to indicate that the energy capture on this technology is variable.
          > If you can't control how much dimming these provide by capturing photons, on an individual basis, then your point is moot.

          Liquid crystals naturally work variable. The amount of current through the crystal determines how bendy it gets. If it's bent out straight, it lets basically all the light through and you see a colored dot. The more current, the more bendy it gets blocking more of the light, unt

        • If you can't control how much dimming these provide by capturing photons, on an individual basis, then your point is moot.

          You can control that. This is a polarizing filter, just like the one that's there now. The polarizing filter is there to filter out the light that has had it's polarization rotated by the LCD layer. LCD layers themselves are very transparent, they do not block light themselves. They get polarized light, rotate the polarization and send it through another polarization layer. If the polarization of the light is rotated (the LCD layer is "on") the light is absorbed by the filter (or just a part of it. Dependin

          • Hmm, I should have previewed that. It's a bit of an abstract matter, but my explanation is clear as mud. Read the wikipedia, it's much better.
      • by msauve ( 701917 )
        Being generous, and assuming polarizers consume 75% of the available light, and the light-voltage conversion is 30% efficient, aren't OLEDs already more energy efficient?
    • Re:Huh? (Score:5, Interesting)

      by An Ominous Coward ( 13324 ) on Wednesday August 17, 2011 @08:04PM (#37124726)

      LCD forms images when the crystals align in a particular way to block the backlight. Now in addition to forming an image, those crystals blocking photos are tapped to recoup a charge.

      • The crystals aren't being tapped to recoup charge. The polarizing filters that the crystals are sandwiched between are being tapped. The benefit in that is that you can recoup energy regardless of the image being displayed, since the filters are the same regardless of the image on the screen. Plus, they're likely blocking significantly more photons than the crystals themselves.

    • As soon as I read the (crappy) summary, I knew there would be posts like this:)

      The way LCDs work is that you have a constant back-light (halogen, LED, whatever), and then the LCD matrix blocks light for pixels that should be dark, while allowing light to pass for pixels that should be bright. This modifies the LCD itself to have photovoltaic properties, thus recapturing (some of) the energy from blocked photons in dark pixels, rather than wasting it as heat.

      • by ceoyoyo ( 59147 )

        Not to mention there's a polarizing filter that ALWAYS blocks roughly half the light.

      • From what I understand, that's not strictly correct. It actually captures the energy regardless of what's on the screen, since they're replacing the polarizing filters with their own photovoltaic polarizing filters, rather than the LCD matrix, as you suggest. The polarizing filters are independent of the image displayed on the screen, but everything else you said sounds right.

        • Well, the standard LCS works as follows:
          First, there's a polarizer which absorbs the light of the wrong polarization (so that the remaining light is polarized).
          Next. there are the liquid crystals. They don't absorb light (well, they surely also absorb a bit, but that's just losses). What they do it to change the direction the light is polarized depending on the electric field applied to them. In other words, by themselves, they don't produce black pixels. Now after the light has passed the liquid crystals,

    • Re:Huh? (Score:5, Interesting)

      by Anubis IV ( 1279820 ) on Wednesday August 17, 2011 @08:59PM (#37125076)

      The only way converting backlight to energy works is by stealing photons (effectively dimming the display), and putting it through a level of inefficiency.

      You're assuming they're stealing it from the final output. What they've actually done is replace the standard polarizing filter that LCDs use with their own filter that captures the filtered photons. Those photons are already being lost by design [wikipedia.org], so capturing them is entirely beneficial. For a quick car analogy, think of it as a flywheel for your LCD. You're going to be doing something that consumes energy anyway, and most of that energy would be wasted otherwise, so you might as well make a point of capturing some of it for your use. Plus, the article indicates that as much as 75% of the energy is lost to polarization, so there's plenty of light to grab there.

    • I thought perpetual motion was settled a long time ago.

      I believe that the law of conservation of energy will be repealed in my lifetime. Seriously, I believe that.

      But then, I believe I'll live another 400 years.

    • I thought perpetual motion was settled a long time ago. The only way converting backlight to energy works is by stealing photons (effectively dimming the display),

      An LCD display works like this:
      - The back light emits light.
      - The rear polarizer eats the half of it that isn't polarized a particular way, letting the other half through as polarized light
      . - A color filter eats the 2/3s of the light that is the wrong color for each dot.
      - Liquid crystals in each dot rotate the polarizatio

  • It seems rather silly to go from battery discharge -> LCD -> recover the light in a photovoltiac -> charge the battery, with some loss of efficiency at all steps. Isn't there reflective stuff behind there to make it so all the light goes where it's needed, and only enough power is supplied to the LCD to make it sufficiently visible?

    • The step where the light goes through the LCD isn't perfectly efficient (in fact its a lot inefficient) so this step just helps recover some of that waste light and convert it back to power. If the LCD didn't emit lots of waste light this wouldn't do anything, and the batteries on these devices wouldn't bet as hard hit.

  • Wouldn't any benefit be lost in the amount of energy required to overcome the tint of even a polarized photovoltaic? It'd also add yet another layer of glass to the already sandwiched LCD (backlight pane, that plastic lense thing, the LCD pane, SURPRISE NOW A SOLAR PANE, the digitizer & yet another pane for the faceplate...this might actually work in conjunction with OLED's though...
    • If I read this right, this new tech would replace the existing polarizer. As it stands, a normal LCD polarizing layer is just throwing away lots of energy-- this accomplishes the same polarization, but recovers some percentage of the light energy that's ordinarily lost. Additionally, it can apparently absorb some of the light energy coming in from outside as well.

  • by drobety ( 2429764 ) on Wednesday August 17, 2011 @08:23PM (#37124854)
    Couldn't they also invent a device that convert the kinetic energy of the wrist while in front of the computer screen?
  • by PJ6 ( 1151747 )

    ... without fear of draining the charge before a real communication crisis arises.


    • by Eskarel ( 565631 )

      What he means is that one of the reasons you have your phone is so that you can, at least in theory, get in contact with people in case of an emergency or be contacted by others. If you drain your battery playing angry birds, you won't be able to make said call. IE "without draining the charge before a real communication crisis arises".

  • Why not put a solar panel on the back of the cellphone, where its not going to interfere with the display and to charge it you flip it on its back.

  • I somehow think that the point was NOT to convert the backlight into energy. But rather to convert external light sources, such as the sunlight into extra battery. I almost thought it was obvious.
    • No. Read up on LCD's [wikipedia.org]
      They replaced the polarization layers (which absorb wrong-polarized photons and convert them into heat) with energy generating polarization layers (which absorb wrong-polarized photons and convert them into electricity).
      To do this they had to create an energy generating polarization layer, which is a great feat.
      • Which raises the interesting question as to whether you could somehow ensure that only correctly polarised photons are generated in the first place....

        OMG I'm going all Trekkie...

  • by umbrellasd ( 876984 ) on Thursday August 18, 2011 @01:27AM (#37126382)
    Come on. You can't power a phone from the energy of the phone's own display. That would be like living off your own...*OK--that is so gross I can't even make the joke in a feeble attempt at /. Karma* Wait, I just made the joke, while not making the joke andapologizing for not making it. I guess you can make something from nothing.

    Skepticism withdrawn.
  • we are one step closer to making contact lens with built in HUDs and/or cameras. now we just need to (significantly) miniaturize the technologies.

  • saw a video from a tradeshow (thought it was CES, but can't find the video right off the bat) about two years ago of a transparent overlay for any media screen. the demo showed a VERY rigged version of the product over an iphone and coupled to a multimeter displaying its active voltage as the reporter checking it out moved it with respect to a light source. and it was completely transparent. does anyone remember this??
  • Ok people, as stated before...

    This is the same thing as regenerative braking in cars. It isn't generating energy from nothing, it's recapturing and reusing energy already spent.

    This component replaces one of the components already in charge of wasting photons generated by your LCD screen (polarizing filter). Not in addition to it.

    This isn't perpetual motion, it's energy reclamation.

    My only concern is that the batteries and phones do not like to be left in sunlight (a proposed alternate use of this component
  • It's "energy-capturing".

"I may kid around about drugs, but really, I take them seriously." - Doctor Graper